'■ X * =*£- ** _h--'^;«.-; C'ft'i * X NATIONAL LIBRARY OF MEDICINE Bethesda, Maryland cess of lower animals. 52 THE SKELETON. presents just above its centre the external occip'ital protu'berance. From this a ridge, the occip'ital crest,1 descends to the occipital fora- men and gives attachment to the nuchal ligament. From the protuber- ance there extends outwardly the superior curved line,2 so called in contradistinction to another lower down, the inferior curved line.3 These lines, which are only well marked in well-developed muscular indi- viduals of mature age, together with the surfaces between and below them, give attachment to the muscles which sustain the erect position of the head. The inner surface, of the expanded portion of the bone, is divided by ridges, forming the occip'ital cross, into four broad, shallow fossae, of which the lower two accommodate the hemispheres of the cerebellum, and the upper two the posterior lobes of the cerebrum. The prominent centre of the cross is the internal occip'ital protu'berance, which is situated a little lower than the external one. The upper limb of the occipital cross is marked by a groove indicating the course of the terminal portion of the longitudinal sinus; and it has attached to it the posterior extremity of the cerebral falx of the dura mater. The lower limb, extending to the occipital foramen, has the cerebellar falx attached to it. The lateral limbs are marked with grooves indicating the course of the lateral sinuses and the attachment of the tentorium. The superior borders of the bone are dentated, and converge to form the occip'ital angle, which is received between the parietal bones. The lateral borders inferiorly articulate with the mastoid portions of the tem- poral bones. The upper extremity of the occipital bone is occasionally found to be separated from the other portion by a transverse suture at any position down to the superior curved line. Such an anomalous piece corresponds with the interparietal bone of certain of the lower animals, as many rodents and ruminants. Occasionally the anomalous human inter- parietal bone is divided in the median line into two parts. THE SPHENOID BONE. The Sphe'noid bone* is situated across the base of the cranium, and extended up on each side, just in advance of the middle. It contributes 1 Occipital spine. 2 Superior semicircular ridge. 3 Inferior semicircular ridge. * Os sphenoideum; os sphecoideum; os cuneiforme; os vespiforme; os basil- are ; os baxilare ; os papillare; os mul- tiforme; osazygos; os inconjugatum; os alatum; osalaeforme; os polymorphon; os pterygoideum; os colatorii; os cuneo comparatum; sphenoidal part of the os spheno-basilare, or of the os spheno- occipitalis. THE SKELETON. 53 Fig. 32. to the formation of the cranial cavity, the orbits, and the temporal, spheno-maxillary, and nasal fossae. From its complex form we may examine in succession its body, its small and great wings, its pterygoid processes, and its foramina. The body1 or central portion of the bone is irregularly cuboidal, and articulates posteriorly by a rugged surface, in the manner previously men- tioned, with the.occipital bone. Its upper surface presents a deep excava- tion, the pitu'itary fos- sa,2 which lodges the pi- tuitary body of the brain. Posteriorly the fossa is bounded by an oblique plate, the decliv'ity,3 which continues the slope Front view op the sphenoid bone. 1, 2, sphenoidal crest and rostrum for joining the nasal plate of the ethmoid bone and the vomer; 3, entrance of the sphenoidal sinuses; 4, sm;ill wing; 5, of the basilar process Of 0ptic foramen piercing its base; 6, sphenoidal foramen; 7, rotund foramen; 8, orbital surface of the great wing; 9, temporal sur- face of the same; 10, ridge separating the temporal and spheno- maxillary fossae; 11, position of the pterygopalatine canal; 12, pterygoid canal; 13, internal pterygoid process, ending in a hook 14; 15, external pterygoid process; 16, spinous process; 17, oval foramen; 18, spinous foramen. the occipital bone, and supports the pons. The convex prominence in front, is the ol'ivary proc'ess,4 upon the slight- ly depressed surface of which the „ commissure of the optic nerve rests. In advance of this, is a smooth surface inclining toward the ethmoid bone, with which it articulates by its anterior border. The prominent angles of the declivity are called the posterior cli'noid proc'esses,5 in contradistinction to the obtuse, backward projections, of the small wings, called the anterior cli'noid proc'esses.5 On each side of the body, below the pituitary fossa, there is a shallow groove,6 for the accommodation of the internal carotid artery, which curves from a notch at the back of the bone to the interval between the anterior clinoid and olivary processes. The inferior surface of the body, which overhangs the posterior nares, 1 Basisphenoidbone; posterior or prin- cipal sphenoid bone ; basis sive corpus partis sphenoidalis ossis spheno-occipi- talis. 2 Sella turcica; s. equina; ephippiura. 3 Dorsum ephippii; clivus; clivus Blu- menbachii. 4 Tuberculum ephippii. 5 Processus clinoidei posteriores et an- teriores; apophyses clinoides. 6 Sulcus caroticus. 54 THE SKELETON. presents a median acute ridge, the ros'trum,1 with which the expanded border of the vomer articulates; and on each side is a thin projecting plate, which joins the reflected margin of the same bone. The anterior surface, directed toward the nasal fossae, presents a median ridge, the sphe'noidal crest,2 which articulates with the nasal plate of the ethmoid bone! NOn each side of the crest is an opening communicating with the sphe'noidal sinuses,3 which are two large cavities hollowed in the interior of the body, and separated by a usually unsymmetrical par- tition. In infancy the sphenoidal sinuses do not exist; and the body then presents inferiorly a thick median ridge, with a triangular space on each side. These spaces receive a pair of hollow cones,4 projecting from the ethmoid bone, which subsequently coalesce with the sphenoid bone and detach themselves from the former, thus producing the sphenoidal sinuses. The small wings5 of the sphenoid bone are two sabre-like processes, which extend horizontally outward from the antero- lateral portion of the body. Their anterior rugged bor- der articulates with the orbital plates of the fron- tal bone; and their pos- terior smooth and curved border is received into the fissure'separating the an- terior and middle lobes of the cerebrum. Their outer end is sharp pointed; and their posterior end forms the blunt anterior cli'noid process. The great wings6 pro- ject laterally from the body, curve outward, for- ward, and upward, and present three important surfaces. The superior Upper view op the sphenoid bone. 1, pituitary fossa; 2, olivary process; 3, declivity; 4, anterior clinoid process; 5, pos- terior clinoid process; 6, posterior border of the body; 7, cerebral surface of the great wing; 8, articular surface for the frontal bone; 9, articular border for the temporal bone; 10, spinous pro- cess; 11, small wing; 12, border articulating with the orbital plate of the frontal bone; 13, border joining the ethmoid bone; 14, optic foramen; 15, sphenoidal foramen; 16, rotund foramen; 17, oval foramen; 18, spinous foramen; 19, groove for the internal carotid artery. 1 Processus azygos. 2 Crista or spina sphenoidalis. 3 Sinus sphenoidales. * Ossicula Bertini; cornua sphenoi- dal; pyramids of Wistar; ossa triangu- laria. 5 Alae minores; processus enciformes; apophyses Ingrassii. 6 Alae magnae, temporal wings. THE SKELETON. 55 or cer'ebral surface1 is a crescentic concavity contributing to form the middle cerebral fossa. The anterior or orb'ital surface2 is an oblique quadrate, vertical plane, forming part of the outer wall of the orbit. The external or tem'poral surface3 is divided by a ridge into two parts, of which the upper, slightly concave and directed outwardly, forms part of the temporal fossa, while the lower division directed downward forms part of the spheno-maxillary fossa. From the back part of the great wing projects the thick, angular, spinous process,4 which is received in the interval between the squamous and petrous portions of the temporal bone. Upon the broad rough surface inclining from the summit of the great wing forward, rest the anterior prolonged angle of the parietal bone and the orbital plate of the frontal bone. The anterior border of the orbital surface articulates with the malar bone, and its lower border forms the upper boundary of the spheno-maxillary fissure. The posterior concave border of the great wing joins the squamous portion of the tem- poral bone. ,, , , The pter'ygoid proc'esses5Aproject vertically downward from the junc- tion of the great wings with the body. They consist of a pair of plates united at an angle anteriorly, and diverging posteriorly, so as to inclose an angular groove, the pter'ygoid fossa.6 The external pter'ygoid pro- cess is broad and thin, and directed outward and backward. The inter- nal pter'ygoid process is longer and narrower than the other; and it forms the lateral border of the posterior nares. At its upper part behind is a fossa7 for the origin of the tensor muscle of the palate; and its lower part is prolonged into a hook8 around which the tendon of the latter muscle turns in its course to the palate*. A The pterygoid fossa at its lower part presents a deep angular notch,9 which is occupied by the pyramidal process of the palate bone.1* The foramina of the sphenoid bone are numerous and important. The op'tic fora'men10 pierces the base of the small wing from the side of the olivary process outward and forward. It transmits the optic nerve and ophthalmic artery from the cranial cavity to the orbit. The sphenoidal fora'men11 in the separated bone is open at its outer end, but is closed by the apposition of the frontal bone. It is club- 1 Superficies cerebralis; s. interna. 2 S. orbitalts; s. anterior. 3 S temporalis; s. externa. * Lamina triangularis; spina angu- laris. 5 Processus pterygoidea ; alae inferi- ores; a. palatinae; processus aliformes. 6 Fossa pterygoidea. 7 Scaphoid fossa. 8 Hamulus pterygoideus; hamular pro- cess. 9 Incisura pterygoidea; fissura ptery- goidea. 10 Foramen opticum. 11 F. sphenoidalis; f. orbitalis superior; f. lacerum superius. 56 THE SKELETON. shaped, with the broad end internal, and separates the small and great wings. It opens into the orbit and transmits the occulo-motor, pathetic, ophthalmic, and abducent nerves, and the ophthalmic vein. The rotund' fora'men1 pierces the great wing from behind forward, just below the inner extremity of the preceding foramen. It opens from the cerebral surface into the pterygo-maxillary fossa, and transmits the superior maxillary nerve. The oval fora'men,2 larger than the last, and less than half an inch behind it, pierces the great wing vertically, and transmits the inferior maxillary nerve, v *'*^_'J »"■'" ^ ' -* : "' " ,Jt The spinous fora'men,3 quite near the preceding, pierces the spinous process vertically, and transmits the great meningeal artery. The pter'ygoid canal4 penetrates the root of the pterygoid processes from before backward, and transmits the pterygoid nerve. The pter'ygo-pal'atine canal5 is a small groove situated internally to the former, and converted into a complete canal by the apposition of the palate bone. THE ETHMOID BONE. The Eth'moid bone6 is situated at the anterior part of the base of the cranium, between the cavity of the latter and the nasal fossae, and between the orbits. It is cuboidal in form, and is exceedingly light, in conse- quence of its excavated character. We may consider, separately, its vertical lamina, its cribriform plate, and its lateral masses. / The vertical lamina occupies the median line. Its upper' portion, pro- jecting into the cavity of the cranium, is the ethmoid'al crest,7 which is thick and prominent in front, and rapidly declines posteriorly. It sepa- rates the ethmoidal gutters, and has attached the anterior extremity of the cerebral falx. From its front project the ethmoid'al wings,8 two small processes resting against the frontal bone. The lower four-fifths of the vertical lamina form the na'sal plate,9 which contributes about one-third to the extent of the nasal partition.?: Its posterior border joins the sphenoidal crest; its inferior, the vomer; and its anterior below, the triangular cartilage; and above, the nasal process of the frontal bone. Its superior border on each side is pierced by vertical canals, for the passage of branches of the olfactory nerves. 1 F. rotundum. 2 F. ovale. 3 F. spinosum. * Canalis pterygoideus; c. Vidianus. 5 Canalis pterygo-palatinus. 6 Os ethmoideum ; os cribrosum; os spongiosum; os cristatum; os cubicum; os colatorium; os foraminulentum ; os coliforme; os multiforme. T Crista ethmoidalis; crista galli. 8 Processus alares. 9 Lamella nasalis. THE SKELETON. 57 Fig. 34. Upper view of the ethmoid bone 1, orbital surface of the lateral mass; 2, posterior extremity of the cribri- The crib'riform plate1 is the horizontal perforated portion connecting the lateral masses with the vertical lamina, and occupying the interval of the orbital plates of the frontal bone. It separates the cavity of the cranium from the nasal fossae, and is depressed on each side of the ethmoidal crest, so as to form the ethmoid'al gutters, for the lodg- ment of the olfactory bulbs. Its numerous orifices2 transmit the nerves from the latter, except the larger .anterior one, which gives passage to the, nasal branch of the ophthalmic nerve. The lateral masses consist of an aggrega- tion of thin walled cavities, the ethmoid'al si'nuses,3 which are usually separated into three sets: the anterior, middle, and pos- terior. They are bounded externally by the form plate, which unites the lateral ■L'ii - j. i. \.' \. c j.pj.1 • masses, and is depressed and perfo- orbital plate,4 which forms part of the inner rated with numepr0lls foraminpa on Wall Of the Orbit. The plate is Square, but each side of the ethmoidal crest 3; the not being sufficiently extensive to close all the ^^J^Z^S^ Sinuses, this is done in front by the lachrymal 4, anterior extremity of the nasal and maxillary bones, above by the borders of fte; 5>the ethmoidal 8i™- the orbital plates of the frontal bone, and behind by the sphenoid and palate bones. The inner or nasal surface of the lateral masses presents two oblique, scroll-like laminae, the superior and inferior tur'binated proc'esses.5 The former is posterior, shorter than the other, and is thin and narrow. The latter extends the length of the lateral mass, and presents a convex surface toward the nasal partition, a concave surface toward the eth- moidal sinuses, and a convoluted and rough border downward. Between the turbinated processes is an oblique fissure, the superior mea'tus6 of the nose, into which opens the posterior and middle ethmoidal sinuses. Above the processes, the surface is perforated by branches of the olfactory nerve. The inferior turbinated process forms the upper boundary of the middle mea'tus7 of the nose, into which opens the anterior, and sometimes the middle ethmoidal sinuses. 1 Lamina cribrosa. 2 Foramina cribrosa. 3 Cellulae ethmoidales. * Os planum; lamina papyracea. 5 Superior and middle turbinated bones; concha sup. et inf.; c. minor et major; ossa spongiosa sup. et medius; superior and middle spongy bones. 6 Meatus narium superior. 7 M. n. medius. 58 THE SKELETON. From the lower portion of the lateral mass, where it rests upon the maxillary bone, one or two small irregular plates1 project downward so as to diminish the size of the aperture of the maxillary sinus. THE FRONTAL BONE. The Front'al bone2 is situated at the anterior part of the cranium, and forms the basis of the forehead, the FlG- 35- root of the nose, and the roofs of the orbits. Externally it is convex and smooth, and presents on each side the front'al eminence,3 usually the most prominent part of the fore- head, and especially well marked in the young. At the lower border of the bone on each side is an arching ridge, the supra-orb'ital margin, the ex- tremities of which terminate in the external4 and internal angular processes. At the, inner part of the ridge is a foramen, or a notch converted into one by a ligament, the supra-orb'ital fora'men, which transmits" an artery and nerve to the forehead. Above the supra-orbital margin is an arching prominence, the super- cil'iary ridge,5 which is situated just above the eyebrow, and varies in degree of development in different individuals. The prominence between the ridges of the two sides is the nasal eminence,6 the width of which has much influence in the intellectual expression of the face. Below, it terminates at the root of the nose,7 which is a rough surface, for articu- lating with the nasal and maxillary bones. From this surface projects the nasal spine,8 which serves as a point of support to the nasal bones, and joins behind the nasal plate of the ethmoid bone. External view op the frontal bone. 1, situa- tion of the frontal eminence; 2, situation of the superciliary ridge; 3, supra-orbital margin; 4, 5, external and internal angular processes; 6, supra- orbital notch or foramen; 7, nasal eminence; 8, temporal ridge; 9, nasal spine. 1 Processus uncinatus; p. Blumen- bachii. 2 Os sincipitis; os coronale; os prorae; os puppis; osrationis; os inverecundum. 3 Tuber frontalis; frontal protuber- ance. 1 Processus zygomaticus. 5 Arcus superciliaris. 6 Nasal tuberosity ; glabella; inter- cilium; metopium; mesophryon. 7 Pons nasalis. 8 Spina nasalis superior. THE SKELETON. 59 Fig. 36. At the side of the bone, curving upward and backward from the external angular process, is the tem'poral ridge, which includes the anterior part of the temporal fossa. The internal surface of the frontal bone is generally concave and impressed by the convolutions of the cerebrum. In its middle below is a ridge, the front'al crest,1 which gives attachment to the cerebral falx, and disappears above at the sides of a shallow groove for ac- commodating the longitudinal sinus. At the bottom of the crest is a blind-pit,2 or a canal,3 transmitting a vein from the nose to the latter sinus. From the lower part of the in- ternal surface project the two broad, arching orb'ital plates,4 which form the roofs of the orbits. They are separated by a wide interval, the ethmoid'al fissure.5 Above, they are convex, and strongly marked by the inferior convolutions of the anterior cerebral lobes. Below, they are concave and smooth, and are deeply depressed within the position of the external angular process for the accommodation of the lachrymal gland.6 Just above the internal angular process, on the same surface, is a small impression,1 made by the fibro-cartilaginous pulley of the superior oblique muscle of the eyeball. The outer border of the orbital plate and the external angular process articulate with the malar bone; and the posterior border of the former joins the small wing of the sphenoid bone. Its inner border exhibits several superficial excavations, which form the upper boundary of the ethmoidal sinuses, and in front of them is the communication with the Internal view op the frontal bone. 1, com- mencement of the groove for the longitudinal sinus, formed by the divergence of the frontal crest; 2, is placed in the ethmoidal fissure, and points to a small venous canal; 3, superior dentated border, articulating with the parietal bones; 4, pos- terior border of the orbital plate 5, which joins the small wing of the sphenoid bone; 6, irregular inner border of the same plate which covers the upper part of the ethmoidal sinuses; 7, points, to the posi- tion of the ethmoidal foramina; 8, nasal spine; 9, thick rough border articulating with the great wing of the sphenoid bone; 10, refers to the black spot which indicates the position of a fossa for the trochlea of the superior oblique muscle; to its outer side is the supra-orbital notch; 11, internal angular process, and entrance to the frontal sinus; 12, external angular process. 1 Crista frontalis. 2 Foramen coecum. 3 Porus cranio-nasalis. 4 Partes orbitales or horizontales. 5 Incissura ethmoidalis. 6 Fovea glanduloe lachrymalis. 7 Foveola trochlearis. 60 THE SKELETON. front'al si'nus.1 This cavity extends upward and outward within the position of the superciliary ridge, and varies in size in different individ- uals. Very rarely it does not exist; but not unfrequently it extends as high as the frontal prominence, and backward into the orbital plate. It is separated from the other by a partition, and communicates through the anterior ethmoidal sinuses with the nose. The upper thick dentated border2 articulates with the parietal bones, and the lateral beveled and roughened border with the sphenoid bone. THE PAEIETAL BONE. The Pari'etal bone3 forms the upper part of the cranial vault between the frontal and occipital bones, and is united with its fellow in the median line. It is square, with the external surface convex and smooth, Fig. 37. Fig. 38. Outer view op the left parietal bone. 1, upper border; 2, beveled lower border, which ar- ticulates with the squamous portion of the tempo- ral bone; 3, anterior border, joining the frontal bone; 4, occipital border; 5, temporal ridge; 0, venous foramen; 7, prolonged anterior inferior angle joining the summit of the great wing of the sphenoid bone; 8, posterior inferior angle articu- lating with the mastoid portion of the temporal bone. Inner view op the left parietal bone. 1-4, borders corresponding with same numbers in for- mer figure; 5, groove for the longitudinal sinus, and communication with it. of a venous foramen, 6; 7, 8, anterior and posterior inferior angles; the groove on the latter accommodates the lateral sinus. The arborescent lines on the inner concave surface of the bone indicate grooves produced by the great meningeal artery. , incisive for- amen; 27, posterior palatine for- amen ; 2S, spheno-maxillary fis- sure ; 29, posterior naris; 30, oval foramen ; 31, spinous foramen; :;2. lacerated foramen; 33, Eustachian tube; 34, entrance of the carotid canal; 35, jugular foramen; 36, stylo-mastoid foramen; 07, pit with a posterior condyloid foramen; 38, mastoid foramen. MECHANICAL CONSTRUCTION OF THE CRANIUM. A sphere is best adapted to resist pressure equally applied on all sides, and therefore of all abstract forms is the strongest. It or its modi- fications into the oval and ovate forms are constantly employed in the organic kingdom in the construction and protection of delicate structures, as instanced in the organic cell, the eggs of animals, etc. Under special circumstances the oval or ovate forms are better adapted to the preservation of delicate structures than the perfect snhere. THE SKELETON. 71 The human cranium, especially adapted to the protection of the brain, is ovate, with the narrow end strongest and situated forward, where it is most liable to violence. The cranium of the infant varies, from the more mature ovate form, in presenting a number of prominent points in positions liable to receive pressure during birth, or subsequently to receive the first impression from falls or blows. Prior to co-ossification of the bones of the cranium, they are so inti- mately and admirably articulated, that it requires considerable force to separate any one of them, but after this is done the connection of the whole becomes more or less enfeebled. The sphenoid bone is the most important agent of connection of the bones of the cranium; extending transversely across the base of the latter it articulates with all the other bones and its body appears to be a central point of support for the whole of them. If sections are made in different directions through the cranium, they will exhibit the intimate rela- tionship existing in the con- nection of the bones by which so many pieces are enabled to preserve the integrity of the cranium. Thus a vertical anteropos- terior section of the cranium exhibits a connection of its segments, as represented in figure 44. The upper border of the frontal bone rests upon the beveled contiguous bor- der of the parietal bones, these behind abut against the occipital bone, and the circle, after bifurcating and surrounding the occipital foramen, terminates in the basilar process, which is firmly supported against the body of the sphenoid bone. The latter by its lesser wings affords a support to the orbital processes of the frontal bone, and thus the circle is completed. A horizontal circle of the cranium, as represented in figure 45, exhibits the borders of its frontal segment overlapped by the parietal segments, and these likewise slightly overlapped by the occipital segment. A circle lower down will exhibit the frontal segment overlapped by the great wings of the sphenoid bone, and these by the squamous portions Fig. 44. Antero-posterior section of the cranicm, exhibiting the mode by which the connection of the different bones con- tributes to preserve its integrity. 1, parietal bone; 2, front- al bone; 3, its orbital plate; 4, frontal sinus; 5, body of sphenoid bone; 6, sphenoidal sinus; 7, occipital bone; 8, marginal ridge of the occipital foramen. 72 THE SKELETON. of the temporal bones, which likewise behind inclose the parietal bones, also slightly overlapped by the occipital bone. A vertical transverse circle at the front of the cranium, as represented in figure 40, exhibits a frontal arch inter- locked by the sphenoid bone. A second circle a short dis- tance behind the preceding, as represented in figure 47, exhibits the parietal bones dove-tailed above, and in- terlocked by the sphenoid bone below. A third circle further back, as represented in figure 48, exhibits the parietal bones articulating as in the pre- ceding instance, and interlocked below by the temporal bones, which abut against the sphenoid and occipital bones. Horizontal section of the cranium. 2, parietal bone; 3, occipital bone. 1, frontal bone; Fig. 46. Fig. 47. Transverse section through the front of the cranium. 1, transverse arch formed by the frontal bone; 2, great wing of the sphenoid bone, includ- ing or overlapping the abutments of the frontal arch; 3, body of the sphenoid bone, with its sinuses. Transverse section in advance of the middle of the cranium. 1, parietal bono forming with its fellow an arch; 2, great wing of the sphenoid bone; 3, horizontal portion of the wing; 4, body, with the sphenoidal sinuses. A fourth circle at the back of the cranium, as represented in figure 49, exhibits the parietal bones joined as in the two preceding instances, and fitting into a notch below, between the squamous and mastoid portions of the temporal bones, which, as before stated, abut against the sphenoid and occipital bones. THE SKELETON. 73 Fig. 48. Fig. 49. Transverse section posterior to the middle Transverse section through the middle of of tbe cranium. 1, back part of the parietal the cranium. 1, parietal bone; 2, squamous por- bones; 2, mastoid portion of the temporal bone; tion of the temporal bone; 3, petrous portion; 4, 3, mastoid process with the sinuses; 4, petrous por- body of the sphenoid bone. tion of the temporal; 5, sphenoidal body, or the basilar process of the occipital bone. DEVELOPMENT OF THE CRANIUM. The occipital bone is developed from seven distinct centres of ossifica- tion : four for the expanded portion, and three for the lower portion. At birth it consists of three pieces: the upper expanded portion,1 the two condyloid portions,2 and the basilar portion.3 They usually become united into one piece by the fifth or sixth year. The sphenoid bone is developed from twelve ossific centres, including the formation of the sphenoidal sinuses from the ethmoidal pyramids. At birth it consists of three pieces: the body and small wings as one, and the great wing and pterygoid processes making one on each side. Subsequently, during the first year, the three pieces are united into one. The ethmoidal pyramids become the sphenoidal sinuses on the approach of puberty. The ethmoid bone is developed from five centres of ossification, exclu- sive of the pyramids. At birth, its two lateral masses only are ossi- fied, but during the first year the vertical and cribriform plates ossify and become united with the former. The frontal bone is developed from two ossific centres, which corre- spond with the supra-orbital ridges. At birth it consists of two halves united at the median line. They usually co-ossify before the third year; but occasionally the suture remains as one of the least disposed to obliteration. 1 Supra-occipital bone; inter-parietal - Exoccipitals; lateral occipitals. bone ; squama occipitalis. s Basioccipital bone ; basilar bone ; inferior occipital bone. 74 THE SKELETON. The parietal bones are each developed from a single centre of ossifica- tion, corresponding with the parietal protuberance. The temporal bones are each developed from four ossific centres : one for the squamous portion, one for the combined petrous and mastoid portions, one for the auditory process, and one for the styloid process. At birth it usually consists of three pieces : the squamous portion as one, the petrous and mastoid portions as a second, and the auditory process as a third, which then appears as a ring of bone, incomplete at j its upper part, and encircling the tympanic membrane. The three pieces speedily unite after birth, and the ring of bone encircling the tympanic membrane gradually elongates outward into the external auditory meatus. The styloid process subsequently ossifies, TWO PIECES OF THE TEMPORAL BONE, ...... e. t -, . ^ as observed about the period of VarleS m lts deSree °f development, and birth; the third piece corresponding sometimes never unites with the temporal with the petrous and mastoid por- •. tions, not represented. 1, the squa- mous portion of the temporal bone; The tabular bones of the vault of the cra- 2, the auditorj- process, in the form • __ , ,i • j r> i • , i , ., of anim erfect rin<* mum, at the period of birth, present the ap- pearance of depressed cones; being conspicu- ously prominent at their centres, which correspond with the frontal, parietal, and occipital protuberances. From the summits of the cones the ossific structure radiates in well-marked lines to the borders of the bones, which overlap instead of interlocking with each other, as they do subsequently. The parietals overlap both the frontals and the occipital. From this arrangement of the vault of the cranium, compression may reduce its diameters, which is an important provision in the passage of the head of the child through the pelvis of the mother. The bones at the base of the skull meet at their borders without overlapping so as not to permit diminution from pressure, which is not only unnecessary from the small size of the base compared with the vault, but which would prove inju- rious to the parts of the brain concerned in this position. At or near the period of birth, there are several membranous spaces left in the line of the sutures, through which ossification has not extended, and which are named font'anels.1 The largest of these interspaces, the anterior font'anel,2 is situated at the contiguous angles of the two frontals with the two parietal bones. It is quadrangular, with the anterior angle much prolonged and acute, and the posterior short and 1 Fontanellae ; fonticuli; lacunae. fons pulsatilis; vertex palpitans; fonti- 2 Great, sincipital, or frontal fontanel; cuius quadrangularis. THE SKELETON. 75 obtuse. It remains unossified for several months after birth; and at the membranous space, the pulsations of the brain may be felt. The posterior font'anel,1 situated between the parietal bones behind, is usu- ally closed at birth by the summit of the occipital bone. The anterior fontanel, and the posterior one, or the three sutures which lead to its position, afford important means to the midwife in determining the relative position of the head of the child while within the pelvis of the mother. At the sides of the cranium are the lateral font'anels, of which one is situated between the frontal, temporal, parietal, and sphenoid bones,2 and the other is placed between the occipital, temporal, and parietal bones.3 The bones of the foetal cranium consist of a single layer of compact substance; the spongy substance being developed in them subsequent to birth. The frontal and mastoid sinuses are developed by a resolution of the spongy substance. SUPERNUMERARY BONES OF THE CRANIUM. Not unfrequently there are found in the course of the sutures of the cranium supernumerary, islet-like bones,4 which have originated from distinct centres of ossification. They rarely occur in any other than the sutures of the vault of the cranium, and of these are most frequent in the course of the occipito-parietal suture. These bones vary much in number and size ; and in hydrocephalic cases are often numerous and large. Frequently they may be found on the two sides of the cranium, alike or symmetrical in position. Occasionally one5 is found occupying the former position of the anterior fontanel. BONES OF THE FACE. Of the fourteen bones of the face, twelve are in pairs: the superior maxillary, palate, lachrymal, nasal, turbinated, and malar bones; the remaining two arc single and symmetrical: the vomer, situated in the par- tition of the nose, and the inferior maxillary bone. 1 Small, brcgmatic, or occipital font- anel. 2 Sphenoid fontanel. 3 Mastoid fontanel; fonticulus mas- toideus ; f. Casserii. i Ossa intercalaria; o. suturarum; o. Wormiana; o. triquetra; o epaotalia; o. rapliogeminantia ; o. triangularia Blasii; claves calvarite. 5 Os antiepilepticum. 76 THE SKELETON. THE SUPERIOR MAXILLARY BONE. The Superior Max'illary bone1 forms with its fellow the upper jaw, and contributes in the construction of the roof of the mouth, the nasal fossae, the orbits, the cheeks, and the spheno-maxillary fossa?. Fig. 51. Superior maxillary bone of the left side, outer view. 1, body; 2, tuberosity; 3, alveolar border; 4, orbital plate; 5, nasal process; 6, nasal notch; 7, nasal spine; 8, lachrymal groove; 9, en- trance of the infra-orbital canal; 10, infra-orbital foramen; 11, orifices of the posterior dental canals; 12, malar process; 13, articulation for the internal angular process of the frontal bone; 14, incisor teeth; 15, canine tooth; 16, premolar teeth; 17, large molar teeth. Superior maxillary bone of the left side, inner view. 1, nasal surface of the body; 2, sur- face for the palate bone; 3, alveolar border; 4, orb- ital plate; 5, nasal process; 6, ridge for the articu- lation of the turbinated bone; 7, nasal spine; 8, groove contributing to form the lachrymo-nasal duct; 9, maxillary sinus; 10, palate plate, its ar- ticulating border for the right maxillary bone; 11, incisive foramen continuous with the naso-palatine canals; 12, tuberosity ; 13, articular extremity for the internal angular process of the frontal bone; 14, incisor teeth; 15, canine tooth; 16, premolar teeth; 17, large molar teeth. The body of the bone, independent of its processes, is wedge-shaped, and is hollowed into a large cavity, the max'illary si'nus,2 which com- municates, by a large irregular orifice, through the inner wall, with the nasal fossa. Above the orifice just mentioned, the inner surface of the body articulates with the lachrymal and ethmoid bones, and behind it, with the palate bone. The anterior surface of the body, forming part of the cheek, is depressed3 and is bounded above by the infra-orbital margin. Just 1 Os maxillare superius; upper jaw- bone ; maxilla sup.; mandibula sup.; maxilla syncrania. 2 S. maxillaris; antrum Higbmoria- num; antrum of Highmore; genyan- trum; gnathantrum; sinus genaj pitui- tarius; antrum gense. 3 Fovea maxillaris; canine fossa. THE SKELETON. 77 below the latter is the in'fra-orb'ital fora'men,1 which transmits the infra-orbital nerve and blood-vessels. The posterior convex surface of the body constitutes the tuberosity,2 and contributes to form the spheno-maxillary fossa. It presents a per- forated surface; and several of the larger orifices are the commencement of the posterior dent'al canals',3 which are narrow passages transmit- ting nerves and arteries to the molar teeth. The upper surface of the body, or orb'ital plate,4 forms the floor of the orbit, and terminates behind in an obtuse border, which is the lower boundary of the spheno-maxillary opening. From the latter border, the infra-orb'ital canal'5 proceeds forward in the orbital plate, and term- inates at the corresponding foramen. From the canal two fine passages, the anterior dent'al canals',6 descend in the outer wall of the body, and conduct arteries and nerves to the anterior teeth. Both the anterior and posterior dental canals are partially visible within the maxillary sinus. At the lower part of the superior maxillary bone is the thick pyra- midal ridge, called the alve'olar border,7 which arches from behind for- ward and inward, and projects obliquely downward and outward. The free margin presents the orifices of a number of deep conical pits, the alve'oli,8 or sockets for the insertion of the teeth. The outer surface of the border is marked by alternating vertical ridges and depressions, cor- responding with the alveoli and their intervals. The posterior extremity of the border is rough, and abuts against the pyramidal process of the palate bone. The anterior extremity is likewise rough, and articulates with the corresponding border of the opposite bone. Above the anterior extremity of the alveolar border is a pointed process, the na'sal spine,9 prolonged backward into a ridge, to which the cartilage of the partition of the nose is attached. To the outer side of the spine is a concave notch, which forms part of the anterior nasal orifice. The margin of the na'sal notch in the white race is usually acute, but is rounded off to the anterior surface of the alveolar border in the black race. Above the notch just mentioned is a plate of bone, the na'sal proc'ess,10 1 F. infra orbitale. 7 Processus, or limbus alveolaris. 2 Tuberositas maxillaris. 8 Alveoli dentis ; cavernoe dentium ; 3 Canales, or canaliculi alveolares, or odontobothria; mortarioli. dentales posteriores. 9 Spina nasalis; s. nasalis anterior. * Planum orbitale. 10 Processus nasalis; p. frontalis ; p. 5 Canalis infra-orbitalis. ascendens. 6 Canalis alveolaris, or dentalis medius et anterior. 78 THE SKELETON. which extends upward to join the internal angular process of the frontal bone. Its outer surface forms part of the side of the nose; and its inner surface, directed toward the cavity of the latter, is concave and bounded below by a ridge for the attachment of the turbinated bone. Its ante- rior border is thick and rough for junction with the nasal bone. Its pos- terior border joins the lachrymal bone, and is grooved to form part of the naso-lachrymal canal. From the internal part of the base of the alveolar border there pro- jects horizontally inward, the pal'ate plate,1 which contributes to form the roof of the mouth and the floor of the nose. Its nasal surface is smooth and concave ; and its oral surface, continuous with the inner one of the alveolar border, is vaulted and rough. Its inner border rises into a ridge which articulates with the vomer, and forms a thick rough surface for junction with that of the opposite bone. The posterior border is thin and rough, and joins the palate bone. From the outer part of the body there projects a strong protuberance, the ma'lar proc'ess,2 which presents a large trilateral roughened surface for the support of the malar bone. Between the anterior extremity of the alveolar border and the palate plate of the superior maxillary bone, the na'so-pal'atine canal'3 descends from the nasal fossa, and, converging, forms with that of the opposite bone, in the intermediate suture, the anterior pal'atine fora'men.4 From the canal and foramen a fine fissure may be traced a short distance outwardly, which is a vestige of the separation, existing in other mammals, of that portion of the bone containing the incisive teeth, and called the intermaxillary bone. The representative of the latter is ob- scurely indicated in the human embryo prior to the third month; the line of its separation dividing off the incisive portion of the alveolar border and the lower third of the nasal process. THE PALATE BONE. The Pal'ate bone5 is situated at the back part of the superior max- illary bone, between it and the sphenoid bone. It contributes, with its fellow, to form the mouth, nasal fossae, and orbits. It has the outline of the letter L, consisting of a horizontal and vertical plate, together with smaller processes. 1 P. palatinus. 2 P. zygomaticus. 3 Canalis, or ductus naso-palatinus, or incisivus. * F. palatinum anterius; f. incisivum ; f. alveolare anterius; f. coecum. 5 Os palatinum; o. palati. THE SKELETON. 79 The horizontal or pal'ate plate1 is square, and contributes a smooth concave surface to the floor of the nose, and a smaller surface to the hard palate. Its inner border rises into a crest2 and articulates with that of Fig. 53. Fig. 54. Posterior view of the right palate bone. 1, palate plate; 2, nasal plate; 3, pyramidal process; 4, articular border for the left palate bone; 5, palate spine; 6, ridge for junction with the turbi- nated bone; 7, spheno-palatine notch, between 8, the orbital, and 9, the sphenoidal process; 10, groove for the internal pterygoid process of the sphenoid bone; 11, position of the posterior palatine fora- men. Exterior view of the right palate bone. 1, rough surface articulating with the superior maxillary bone, and diminishing the aperture of the maxillary sinus; 2. posterior palatine canal; completed by the tuberosity of the superior max- illary bone; 3, spheno-palatine notch; 4, 5, 6, orb- ital process; 4, surface directed toward the ptery- go-maxillary fossa; 5, orbital surface; 6, maxillary border; 7, sphenoidal process; 8, pyramidal process. the opposite side; the crests of the conjoined palate plates aiding in the support of the vomer, and projecting backward into a pointed process, the palate spine.3 The anterior border of the palate plate articulates with that of the superior maxillary bone; and the posterior crescentic border has the soft palate attached to it. The vertical or na'sal plate* is thinner than the other, and extends from it to the base of the cranium. Its inner or nasal surface is divided into two parts by a horizontal ridge,5 with which the turbinated bone articulates. Its outer surface is divided by a vertical ridge bounding a groove,6 which, by the approximation of the sphenoid and superior max- illary bones, is converted into the posterior pal'atine canal',7 descend- ing from the pterygo-maxillary fossa to the hard palate. The posterior portion of the outer surface of the nasal plate articulates with the in- ternal pterygoid process, and the anterior portion with the maxillary bone, partially closing the entrance of the maxillary sinus. 1 Pars palati; p. horizontalis. 2 Crista nasalis. 3 Spina palatina ; s. nasalis posterior. * Pars nasalis ; p. perpendicularis. 5 Crista turbinalis ; c. t. inferior. 6 Sulcus pterygo-palatinus. 7 Canalis palatina posterior ; c. ptery- go-palatina. 80 THE SKELETON. At the upper border of the nasal plate is a large, round notch, which, in conjunction with the under part of the body of the sphenoid bone, is converted into the sphe'no-pal'atine fora'men1 communicating from the pterygo-maxillary fossa with the nasal fossa. Behind the notch just mentioned is the sphenoid'al proc'ess,2 which articulates with the under part of the body of the sphenoid bone. In the upper border of this process is a groove, which, in conjunction with the latter bone, is converted into the pter'ygo-pal'atine canal'.3 In advance of the notch indicated, is the orb'ital proc'ess,4 which is received between the orbital plates of the superior maxillary and ethmoid bones at the posterior inferior part of the orbit, where it closes the poste- rior ethmoidal sinuses. At the posterior angle of conjunction of the nasal and palate plates of the palate bone, there projects the pyramidal proc'ess,5 which occu- pies the notch of the pterygoid processes of the sphenoid bone. Some- times it completely incloses the lower part of the posterior palatine canal; and not unfrequently it is pierced by one or two branches from the latter descending in the same direction. THE LACHRYMAL BONE. Fig. 55. The Lach'rymal bone,6 the smallest of those of the face, is situated one at the fore part of the inner wall of each orbit. It contributes to form the latter, the lachrymo-nasal duct, the nasal fossa, and the anterior ethmoidal sinuses. It consists of a thin, oblong square plate, articulating above, behind, and below with the orbital plates of the frontal, ethmoid, and maxillary bones, and in front with the nasal process of the latter bone. The outer surface forms part of the inner wall of the orbit, and in advance contributes a fossa or groove7 to the lach'rymo-na'sal duct.8 The outer surface closes in the anterior eth- moidal sinuses. External view of the right lachrymal bone. 1, orbital sur- face; 2, lachrymal fossa; 3, small process bounding the latter infe- riorly; 4, frontal border; 5, eth- moidal border; 6, maxillary bor- der; 7, process articulating with the turbinated bone. 1 F. spheno-palatinum. 2 Processus sphenoidalis; apophysis pterygoideus. 3 C. pterygo-palatina. * P. orbitalis. 5 Pterygoid process; apophysis sphe- noidalis. 6 Os lachrymale ; os unguis ; ungui- form bone. 7 Lachrymal fossa. 8 Ductus ad nasum. THE SKELETON. 81 From the anterior inferior angle a process1 projects downward, which joins with one from the turbinated bone, and serves to prolong the lach- rymo-nasal duct. THE NASAL BONE. The Na'sal bone2 projects from the root of the nose downward and forward, and with its fellow, together with the nasal processes of the superior maxillary bones, forms the bridge of the nose. It is irregularly quadrate, and thicker and narrower above than below, and not unfrequently is so narrow as to assume a fan-like shape. In its length FlG' 56, it presents a sigmoid curve, though occasion- ally it is simply concave in this direction. The outer surface is smooth, transversely con- vex, and generally presents a small but con- spicuous foramen3 near its middle. The inner surface, directed toward the corresponding na- sal fossa, is transversely concave, and presents a longitudinal groove for the accommodation of a branch of the nasal nerve. An™ ^ew of the left na- sal bone. 1, frontal border; 2, na- The Upper border Of the nasal bone is thick sal border; 3, maxillary border; and roughened for articulation with the frontal *'lower border; 5'nasal foramen- bone; the lower border is thin and notched, and forms the superior boundary of the anterior nasal orifice. The inner border is thick above, narrows off below, and conjoins with that of the opposite bone. The outer border is beveled off and overlapped by the corresponding border of the nasal process of the superior maxillary bone. THE TURBINATED BONE. The Tur'binated bone4 is quite rudimentary in comparison with the corresponding one of most other animals, in which it often acquires an extraordinary degree of development, as the student may observe in any of the common carnivorous animals—the cat, dog, weasel, bear, etc. It projects horizontally from the outer wall of the nasal fossa, and separates the middle and inferior meatus. The bone presents the form of an irregular scroll, with a rough convex surface directed toward the partition of the nose, and a con- 1 Hamulus lachrymalis. * Os turbinatum; 0. t. inferius; spongy 2 Os nasale ; os nasi. bone; 0. spongiosum; concha inferior; c. 3 F. nasalis. veneris ; buccinum. 6 THE SKELETON. cave surface directed outwardly. Its lower part is thick and spongy; its anterior extremity joins the Fig. 57. transverse ridge at the root of the uasal process of the superior max- illary bone; and its posterior nar- rower extremity articulates with a like ridge of the palate bone. From the middle of the upper border a hook-like plate1 overhangs the inferior edge of the entrance to the maxillary sinus; and a small process2 ascending from this plate diminishes the aperture of the lat- ter, and frequently joins a process from the ethmoid bone. In advance of the hook-like plate, another small process3 ascends to join one from the lachrymal bone, and assists in the formation of the lachrymo-nasal duct. External view of the right turbinated bone. 1, anterior extremity articulating with the superior maxillary bone; 2, posterior extremity articulat- ing with the palate bone; 3, hook-like plate over- hanging the lower border of the maxillary sinus. The process in advance of it above joins the lachry- mal bone to contribute in the formation of the lachrymo-nasal duct. 4, inferior, obtuse border. Its lateral surfaces form part Fig. 58. THE TOMER. The Vo'mer4 is a lozenge-shaped plate of bone, situated at the back part of the partition of the nose. of the inner wall of the nasal fossae. The upper border is grooved to re- ceive the rostrum of the sphenoid bone, and its edges5 are reflected to join a thin plate springing out of the root of the pterygoid processes. The lower border articulates with the crest formed at the conjunction of the palate plates of both the superior maxillary and palate bones. The anterior border is grooved to receive the cartilage of the nasal partition, and at its upper part ar- ticulates with the nasal plate of the ethmoid bone. The posterior bor- der is thin and crescentic, and forms' the oblique line of separation of the posterior nasal orifices. Leet side of the vomer. 1,1, broad groove re- ceiving the rostrum of the sphenoid bone; 2, 2, inferior border articulating with the palate plates of the superior maxillary and palate bones; 3, posterior border, the dividing line of the posterior nares; 4, 4, grooved border receiving a narrow slip of cartilage, situated between the vomer and the nasal plate of the ethmoid bone; 5, 5, border for the cartilaginous septum of the nose; 6,6, na- sal surface. 1 Processus maxillaris. 2 P. ethmoidalis. 3 P. lachrymalis. 4 Osvomeris; aratium. 5 Alae vomeris. THE SKELETON. 83 THE MALAR BONE. The Ma'lar or cheek bone1 forms the most prominent part of the cheek, and contributes to the construction of the orbit and temporal fossa. It is quadrangular, and rests by a broad, trilateral, rough surface upon the malar process of the superior maxillary bone. From the upper part a strong front'al proc'ess ascends to articulate with the external angular process of the frontal bone; and from the F,G- 59- back part projects a strong zygo- matic proc'ess to articulate with the corresponding process of the temporal bone. The upper, anterior, concave bor- der forms the inferior and external margin of the orbit. From this border there proceeds backward and inward the orb'ital plate, which separates the orbit from the temporal fossa, articulates with the corresponding plates of the max- illary, sphenoid, and frontal bones, and contributes to the spheno-maxillary foramen. The posterior border of the bone, included between the frontal and zygomatic processes, is sigmoid, and gives attachment to the temporal fascia. The inferior border is convex and rugged, and contributes about one-half to the extent of the lower margin of the zygoma. The fa'cial surface, directed more or less outwardly and forward, is for the most part convex, and pretty constantly presents one or two con- spicuous foramina, which are continuous with canals2 from the orbital and temporal surfaces. The tem'poral surface is concave, directed backward, and forms the anterior part of the temporal fossa. Outer view of the right malar bone. 1, ex- ternal or facial surface; 2, malar foramen; 3, front- al process; 4, 5, orbital border; 6, maxillary bor- der; 7, zygomatic process; 8, temporal border; 9, inferior border. THE INFERIOR MAXILLARY BONE. The Inferior Max'illary, or lower jaw bone,3 is the second of the symmetrical bones of the face, in which it occupies the lower semi- 1 Os malare; o. malae; o. zygomat- icum ; o. jugale; o. suboculare ; o. hypo- pium ; o. pudicum; o. jugamentum; o. genae. C. zygomaticus facialis, or tempo- ralis. 3 Maxilla inferior; os maxillare infe- rius ; inferior maxilla; mandibula. 84 THE SKELETON. Inferior maxillart bone. 1, body; 2, ramus; 3, symphysis; 4, base; 5, angle; 6, mental fora- men ; 7, condyle; 8, coronoid process; 9, semilunar notch; 10, inferior dental foramen, the entrance of the corresponding canal; 11, alveolar border; 12, incisor teeth; 13, canine tooth; 14, premolars; 15, large molars. circumference. It is also the largest and strongest bone of the face, and is the only movable one of the skull. From the other bones of the face it is actually isolated through con- tact of the teeth, and it articulates with the cranium at the glenoid cavities of the temporal bones. It is divisible for description into the body, and rami or branches. The body is the curved portion of the bone supporting the teeth. Its outer surface is convex, and at the middle presents a prominent line, indicating the early separation of the bone into two pieces, and hence called the sym'physis. The prominent portion of the body in front is the chin,1 which in the negro is vertical or even receding. Its lower protuberant part is the men'tal protu'berance,2 on each side of which is the men'tal fora'men,3 the termination of the inferior dental canal. The inner surface of the body presents at the lower part of the sym- physis the men'tal tu'bercle.4 On each side, below the position of the molar teeth, is the oblique mo'lar ridge,5 to which is attached the mus- cular floor of the mouth. Beneath the ridge the surface is slightly im- pressed by the position of the submaxillary gland, and the lower obtuse border of the bone is its base. The upper portion of the body forms its alve'olar border,6 which is constructed on the same plan, and for the same purpose as in the superior maxillary bones. In relation with the corresponding part of the latter, it is usually vertical in position, though in the negro it is generally directed a little forward and upward. The ram'i7 are the quadrate plates ascending from the posterior extremities of the body, reaching as high as the zygomatic arches. Their outer surface forms a nearly vertical plane. Near the middle of 1 Men turn. 2 Protuberantia mentalis. 3 F. mentale ; f. maxillare anterius. * Spina mentalis interna ; spinse men- tales ; internal mental tubercle. 5 Mylo-hyoid ridge ; linea mylohy- oidea; 1. obliqua interna. 6 Processus alveolaris. 7 The name rami is frequently applied by comparative anatomists to the two halves of the jaw. THE SKELETON. 85 the inner surface is the entrance1 of the inferior dent'al canal',2 which descends to the body of the bone and proceeds beneath the alveolar bor- der to terminate at the mental foramen. The entrance of the canal is bounded by a prominent crest,3 which gives attachment to the spheno- maxillary ligament; and below it, there descends a groove for the accom- modation of a small nerve.. ,». ■■■-.<■ *r > The posterior border of each ramus is obtuse, and terminates below in the angle,4 which is more or less obtuse in its relation with the base of the bone. The inner and outer surfaces of the angle are variably rugged, for the attachment of two of the masticating muscles. The anterior border of the ramus is sigmoid in its descent to the outer side of the body, where it terminates just exterior to the last tooth. The upper border of the ramus exhibits a large semilunar notch,5 in advance of which is a flat conical eminence, the cor'onoid proc'ess," into which the temporal muscle is inserted. Posterior to the notch is another process, which supports a transverse articular convexity, the con'dyle,7 and its narrow part below constitutes the neck8 of the jaw, the inner side of which presents a depressed surface, directed forward, for the attachment of the external pterygoid muscle. STRUCTURE AND ARTICULATION OF THE BONES OF THE FACE. The bones of the face are remarkable for their light and laminar char- acter, with the exception of the inferior maxilla, which is the stoutest and strongest bone of the skull, and contains within it, like most of the cra- nial bones, a quantity of spongy substance. All the bones of the face, except the lower jaw, are firmly and immov- ably articulated with one another and with the cranium. The face and cranium together constitute the skull, or bony portion of the head. Across the root of the nose, at the external angular processes of the frontal bone, and at the zygomatic arches, the face articulates by well- marked serrate sutures9 with the cranium. Among themselves the bones of the face generally articulate by the mutual adaptation of more or less 1 Foramen maxillare internum ; infe- rior dental foramen. 2 Canalis maxillaris; c. alveolaris in- ferior. 8 Lingula. 4 Angulus maxillae. 5 Incisura semilunaris; i. sigmoidea. 6 Processus coronoideus. 7 Condylus; capitulum. 8 Cervix; collum. 9 The transverse facial suture. 86 THE SKELETON. roughened borders.1 The different sutures are named from the bones they connect, or from their position, and thus we have a na'so-front'al su'tnre, an intermax'illary su'ture, a middle and transverse pal'ate sn'ture, etc. THE TEMPERO-MAXILLARY ARTICULATION. The movable articulation of the inferior maxillary bone is formed be- tween the condyle of the latter and the glenoid cavity and tubercle of the temporal bone, which are invested with cartilage. The motions of the lower jaw are as follows: 1. the opening and shutting of the mouth, in which the condyles roll on their axes in the glenoid cavities, as in the movement of a hinge; 2. the movement of the lower jaw forward and backward, in which the condyles move forward from the glenoid cavities upon the glenoid tubercles and back again; and 3. the movement from side to side, when the condyles move alternately and obliquely from the glenoid cavities to the glenoid tubercles and back again. The hinge-like or downward and upward movement of the lower jaw is the act of biting; the movements of the jaw forward and backward, and from side to side, are those of mastication or chewing. Fig. 61. Fig. 62. Vertical section of the articulation of the lower jaw. 1. is placed above the glenoid cav- ity ; 2, glenoid tubercle; 3, inter-articular cartilage dividing the joint into two cavities, 4 and 5; 6, an inter-articular cartilage separated from a joint, to exhibit its form. External view of the tempero-maxillart ar- ticulation. 1, zygoma; 2, glenoid tubercle, 3, ra- mus of the inferior maxillary bone; 4. mastoid process; 5, external lateral ligament; 6, stylo- maxillary ligament, a process of the cervical fascia. The articulation of the lower jaw is rendered more movable by an in'terartic'ular fi'bro-car'tilage,2 which is a discoidal plate horizontally dividing the joint into two cavities, each lined with a synovial mem- brane. The margin of the fibro-cartilage is thickened and attached to the capsular ligament; and it is sigmoid in section antero-posteriorly. It follows the movements of the condyle, and reduces the force of its impressions. 1 Suturae harmoniae. Cartilago-interarticularis. THE SKELETON. 87 The cap'sular lig'ament, inclosing the joint, is thin and loose, and is attached above to the articular margin of the glenoid cavity and tubercle, and below to the neck of the lower jaw. The exter'nal lat'eral lig'ament1 strengthens the former on the outer side of the joint. It consists of a short, strong band attached to the root of the zygomatic process, and extending downward and backward to the neck of the lower jaw. GENERAL CONFORMATION AND POSITION OF THE FACE. The Face is placed beneath the fore part of the cra'nium, together with which it forms the skull, as previously stated. In out- FlG- 63- line it has the shape of a wedge-like segment from an oval figure. The rounded portion of the segment is formed by the front and sides of the face; the sectional surfaces are formed by the conjunction of the latter with the cranium and the base of the lower jaw; and the apex, which is truncated, is formed by the back borders of the rami of the lower jaw. The face is mainly consti- tuted of a series of receptacles for the accommodation and protection of the organs of sight, smell, taste, and others belonging to the commence- ment of the alimentary appa- ratus. In relation with the size of the cranium, it is smaller than in other mam- mals. In the white race it forms about one-fifth of the bulk of the skull, but in the inferior races is considerably larger. The greater its size in relation with that of the cranium, the The skull, seen partly in front and on the right side- 1, frontal bone; 2, parietal bone; 3, temporal bone, its squa- mous portion; 4, the sphenoid bone, temporal surface of its great wing; 5, ethmoid bone, its orbital surface; 6, superior maxillary bone; 7, malar bone; 8, lachrymal bone; 9, nasal bone; 10, inferior maxillary bone, a, orbital plate of the frontal bone; b, temporal surface; c, orbital surface of the great wing of the sphenoid bone; d, mastoid portion of the temporal bone; e, orbital surface of the malar bone; /, orb- ital plate of the superior maxillary bone; g, infra-orbital foramen; h,mental foramen; i, symphysis;^', ramus; k, cor- onoid process; I, neck supporting the condyle; m, angle; n. lachrymo-nasal duct. 1 Ligamentum maxillaa laterale externum; membrana articularis ligamentosa. 88 THE SKELETON. less does it project in advance of the latter; and with its proportionate diminution, as its front approaches a line vertical with the forehead, the nearer does it approximate the ideal standard of an intellectual coun- tenance. Hence the advancing forehead and retiring face are most striking features in the white race, especially in its more cultivated fami- lies ; while the prominent face, with large jaws, and receding forehead, are coexistent with the less intellectual character of the inferior races of men. The angle of inclination of the fore part of the skull is viewed to deter- mine the comparative degree of development of the face and cranium, and in some measure to form an estimate of the mental capacity of races and individuals. Though open to many objections, such as variations being produced in the angle, from the presence or absence of teeth, from the different degrees of development of the frontal sinuses, from projection of the forehead in hydrocephalus, or its depression by artificial means, yet independently of these and similar reasons, the fa'cial angle1 is still looked upon, in some measure, as an index of intellectual character. The usual method of estimating the angle, is by drawing a line from the front of the forehead to the front of the upper jaw, and crossing this line by another proceeding from the latter position to the external auditory meatus. In the white race, the facial angle ranges between 15° and 85° ; in the negro, between 10° and 80°. In idiots it is 65°, or even much less ; and in the adult orang-outang it is about 30°. In speaking of the bones which compose the skull, eight were indicated as belonging to the cranium, and fourteen to the face. The ethmoid bone, included in the account of the former, really contributes more to the composition of the latter; and the face, as we usually refer to it, includes the forehead as formed by the frontal bone. x THE SIDE OF THE SKULL. The Tem'poral fos'sa2 occupies a great portion of the side of the skull, and is bounded above by the tem'poral ridge,3 and below by the zygomat'ic arch. The former proceeds from the external angular process of the frontal bone upward and backward upon the parietal bone to the dividing ridge between the squamous and mastoid portions of the temporal bone. The tem'poral surface, which gives origin to the tem- poral muscle, is formed by the frontal, sphenoid, parietal, and temporal bones; and it terminates inferiorly at a ridge proceeding from the root 1 Facial angle of Camper; angulus faciei Camperi. 2 Fossa temporalis. 3 Linea temporalis. THE SKELETON. 89 Fig. 64. of the zygomatic process of the temporal bone, across the great wing of the sphenoid bone to the outer extremity of the spheno- maxillary foramen. The Zygomat'ic arch,1 be- neath which passes the tem- poral muscle to its insertion, is formed by the zygomatic process of the temporal and the malar bone, and gives support to the cheek. The Sphe'no-max'illary fos'sa2 is the space between the bottom of the great wing and the external pterygoid process of the sphenoid bone, and the back part of the View of the right side of a portion of the face and cra- SUpenor maxillary DOne, and nium. 1, frontal bone; 2, malar bone, a portion of its zygo- is OCCUpied by the external matic process removed; 3, zygomatic process of the temporal . bone; 4, glenoid tubercle, and back of it the glenoid cavity; 5, pterygOlCl muSClC At ItS Up- squamous portion of the temporal bone; 6, anterior inferior per part anteriorly is a large anSle of the parietal bone; 7, temporal surface of the frontal , , . . bone; 8, temporal surface of the great wing of the sphenoid aperture, the Sphe nO-maX - bone; 9, inferior surface of the great wing; 10, external illary fora'men,3 Which COm- pterygoid process; 11, internal pterygoid process; 12, superior .,, ,. , .. T, maxillary bone; 13, ptery go-maxillary fossa; 14, spheno-pala- municates with the orbit. It tine foramen. 15j Bphen0.maxillary foramen. X6, oval La- is bounded by the Sphenoid, men! 17, spinous foramen; 18, infra-orbital foramen. Figures Superior maxillary, malar, ^ °<=-py the fore part of the temporal fossa; the space r Jit between 9,10, and 14,15, is the spheno-maxillary fossa. and palate bones; and cor- responds to the free communication, or rather continuation, of the tem- poral fossa and orbit in most of the inferior mammals. The Ptery'go-max'illary fos'sa4 is the deep, wedge-shaped fissure, at the bottom of the former fossa, extending from the inner extremity of the spheno-maxillary foramen downward, between the pterygoid processes of the sphenoid bone, and the superior maxillary and palate bone. It is beneath the apex of the orbit, and has, opening from its upper part backward, the pterygoid canal; and inward, the spheno-palatine foramen 1 Arcus zygomaticus; zygoma ; pons zygomaticus. 2 Fossa spheno-maxillaris; zygomatic fossa. 3 Foramen spheno-maxillare; fissura orbitalis inferior, or spheno-maxillaris; foramen lacerum inferius. 4 Fossa pterygo-maxillaris; f. pterygo- palatina. 90 THE SKELETON. THE BASE OF THE SKULL. Fig. 65. The Base of the Skull, included in the occipital and inferior maxillary outline, is ovate in form, and in- cludes the palatine, gut- teral, and occipital re- gions. The Pal'atine or oral region1 is inclosed by the upper and lower jaws, and is bounded above by the vaulted hard palate. Its depth ordinarily is about two and a half inches, but before the protrusion of the teeth, and sub- sequent to their loss, it is reduced to an inch or less in depth. The hard pal'ate2 presents a roughened surface, divided by the middle and transverse pal'ate su'tures.3 At the fore part of the middle suture is the anterior pal'- atine fora'men,4 which communicates above with the two naso-palatine canals entering the nasal fossae. At the posterior part of the hard palate, on each side, is the posterior pal'atine fora'men,5 from which coarse grooves are directed forward for the accommodation of the pal- atine nerves and blood-vessels. The Gut'teral region,6 so named because it forms the upper boundary View of the right half of the base of the skull. 1. palate plate of the superior maxillary bone; 2, palate plate of the palate bone; 3, vomer; 4. internal ptery- goid process; 5, external ptery- goid process; 6, pyramidal process of the palate bone; 7, under sur- face of the great wing of the sphenoid bone; 8, its temporal surface; 9, zygomatic arch; 10, zygomatic process of the malar bone; 11, zygomatic process of the temporal bone; 12, squamous portion of the temporal bone; 13, glenoid tubercle; 14, glenoid cav- ity; 15, vaginal process, its outer border constituting the auditory process; 16, styloid process; 17, external auditory meatus; 18, mastoid process; 19, digastric groove; 20, basilar process of the occipital bone co-ossified with the body of the sphenoid bone; 21, condyle; 22, occipital protuber- ance ; 23, superior, and 24, inferior semicircular ridges; 25, occipital foramen; 26, incisive foramen; 27, posterior palatine foramen; 28, spheno-maxillary foramen; 29, posterior naris; 30, oval fora- men ; 31, spinous foramen; 32, lacerated foramen; 33, Eustachian tube; 34, carotid canal; 35, jugular foramen; 36, stylo-mastoid fora- men ; 37, 38, foramina for veins. 1 Regio palatina: cavum oris. 2 Palatum durum; p. osseum. 3 Sutura palatina cruciata. 4 F. palatinum anterior ; f. incisivum. f. alveolare anterius; f. coecum. 5 F. palatinum posterior, or descen- dens; f. palato-maxillare; f. alveolare posterius. 6 Kegio gutteralis. THE SKELETON. 91 of the pharynx or throat, has the posterior nares opening into it in front, and is limited behind by the occipital foramen and condyles. On each side are the pterygoid processes, and above, it is bounded by the basilar process of the occipital bone and the body of the sphenoid bone. The Occip'ital region includes that part of the base of the skull pos- terior to the occipital foramen and condyles. THE ORBITS. The Orb'its1 are quadrately pyramidal cavities situated beneath the anterior part of the cranium, with their axes directed forward and outward. The apex of each orbit corresponds with the optic foramen, and the base forms the orb'ital entrance.2 This is situated beneath the forehead, and is transversely quadrate-oval, with a slight obliquity from the median line downward, and a direction forward and a little outward. The roof of the orbit is vaulted, and is formed by the orbital plate of the frontal bone and the lesser wing of the sphenoid bone. The floor is slightly depressed below the infra-orbital margin, and is formed by the orbital plate of the superior maxillary bone and the orbital process of the palate bone. The inner wall is nearly vertical and parallel with that of the other orbit, and is formed by the nasal process of the superior max- illary bone, the lachrymal bone, the orbital plate of the ethmoid bone, and the body of the sphenoid bone. The outer wall is also nearly vertical, but is directed obliquely outward; and it is composed of the orbital plate of the great wing of the sphenoid bone and that of the malar bone. At the bottom or apex of the orbit are the optic and sphenoidal fora- mina, already described, and between the outer wall and floor is the spheno-maxillary foramen, also previously described. At the anterior part of the inner wall of the orbit is the lach'rymo- na'sal duct'.3 Commencing as a fossa4 or groove between the nasal pro- cess of the superior maxillary and lachrymal bones, by the addition of a process of the turbinated bone, its lower half forms a complete tube. It descends with a slight inclination backward, and terminates at the anterior part of the inferior meatus of the nasal fossa. At the upper border of the inner wall of the orbit, in the suture 1 Orbitae; trochiaB; conchi; cavitates, or foveoe, or pelviculce oculorum; orb- itar fossae ; orbitar cavities. 2 Apertura orbitalis. 3 Ductus or canalis lachrymo-nasalis, or naso-lachrymalis ; ductus ad nasum: lachrymal duct; nasal duct; ductus na- salis orbitae. * Fossa lachrymalis. 92 THE SKELETON. between the ethmoid and frontal bones, are the anterior and posterior ethmoid'al fora'mina,1 for the transmission of a nerve and an artery. Fio. 60. THE NASAL CAVITIES. The Na'sal cavities or fos'sse2 are two complicated spaces separated by a thin vertical partition, the os'seous na'sal sep'tum.3 They open on the front of the face by the anterior na'sal or'ifices and communicate posteriorly with the gutteral region by the posterior na'sal or'ifices or na'res. Communicating with them are the frontal, ethmoidal, sphenoidal, and maxillary sinuses, which are accessory chambers. The height and depth of each nasal cavity are about two inches; the greatest width, which is below the turbinated bone, is about half an inch. The anterior na'sal or'ifice* is pyriform, and is bounded by the supe- rior maxillary and na- sal bones. Its border is thin and sharp; in the negro, however, it is rounded off at the bot- tom. From the middle of its base, the na'sal spine5 projects, for the attachment of the column of the nose. The posterior na'sal or'ifices6 are quadrate apertures separated by the vomer, and, in addi- tion to the latter, are bounded by the body and internal pterygoid proc- esses of the sphenoid bone and the palate bones. The os'seous na'sal sep'tum is formed by the nasal plate of the eth- Vertical section of the face, exhibiting the osseous nasal sep- tum. 1, frontal bone; 2, frontal sinus; 3, nasal spine of the frontal bone; 4, nasal bone; 5, nasal spine of the superior maxillary bone; 6, nasal process of the same bone; 7, border of the palate plate of the same; 8, incisive foramen; 9, left posterior naris; 10, palate plate of the palate bone; 11, nasal plate of the ethmoid bone; 12, ethmoidal crest; 13, vomer; 14, left turbinated bone; 15, sphenoidal sinus; 16, internal pterygoid process; 17, external pterygoid process. 1 F. ethmoidale anterius et posterius ; f. orbitale ant. et post. 2 Cavi narium ; nares internse. 3 Septum narium osseum. 4 Apertura narium anterior. 5 Anterior nasal spine. 6 Posterior nares; aperturae narium posteriores. THE SKELETON. 93 moid bone and the vomer, which have between them anteriorly a deep angular notch for the reception of the cartilaginous septum. Frequently the nasal septum is bent to one side, thus increasing the width of one cavity at the expense of the other. The roof of the nasal cavities is antero-posteriorly concave, and is narrower and longer than any other portion. It is formed by the nasal bones, the nasal spine of the frontal bone, the cribriform plate of the ethmoid bone, and the body of the sphenoid bone. The floor of the nasal cavities is a little depressed below the level of the base of the anterior , .-, , . Fig. 67. nasal orifice; and is formed by the palate plates of the maxillary and palate bones. The outer wall is the most complicated portion of the nasal cavities. From it project inward and downward, like three scrolls, the turbinated processes of the ethmoid bone and the turbinated bone; and below these are situated the na'sal mea'tuses.1 The superior mea'tus is the shortest is situated View of the outer wall of the right nasal fossa. 1, frontal ... v> 1 + t k°ne' 2) its orbital plate; 3, its nasal spine; 4, nasal bone; 5, eth- at the Upper back part 01 moid bone. 6; itg upper turbinate(j process; 7, its lower turbinated each Cavity, and is di- process; 8, turbinated bone; 9, process of the lachrymal bone, within , i in. -I -, the position of which is the lachrymo-nasal duct; 10, nasal spine of reCtea ODliquely ClOWn- tho guperior maxjnary bone; 11, naso-palatine canal; 12, palate Ward and backward tO plate of the superior maxillary bone; 13, nasal process of the latter; the Upper part Of the H eternal pterygoid pr^ess; 15, internal pterygoid process; 16, 1 r r nasal plate of the palate bone; 17, its palate plate; 18, posterior pal- COrresponding posterior atine foramen; 19, superior meatus of the nose; 20, middle meatus; niSfll nrifipp Tntfl it 21, inferior meatus ; 22, frontal sinus; 23, sphenoidal sinus; 24, its communication with the upper back part of the nose; 25, spheno- the posterior and middle palatine foramen; 26, orifice of the maxillary sinus. ethmoidal sinuses open; and above its posterior extremity, the sphenoidal sinus communicates with the nose. The middle meatus is situated between the ethmoid and turbinated bones along the middle of the nasal cavity. Into it open the anterior 1 Meatus narium. 94 THE SKELETON. ethmoidal and frontal sinuses and the maxillary sinus. The orifice of the latter is much reduced in size compared with its condition in the isolated maxillary bone; the ethmoid, palate, turbinated, and lachrymal bones all contributing to its diminution. The inferior mea'tus, situated below the turbinated bone, is trans- verse in its direction from before backward ; and it has communicating with its anterior part, the lachrymo-nasal duct. DEVELOPMENT OF THE FACE. In all mammals below man, that portion of the superior maxillary bone which supports the incisor teeth is separated from the principal portion, and is known as the intermaxillary bone. It may be observed in the skull of any domestic animal. As a distinct piece, it is obscurely visible in the human embryo as late as the third month, and may be detached from the superior maxillary bone. It soon becomes co-ossified with the latter, and its line of separation is distinguishable subsequently only for a short distance transversely outward from the incisive fora- men. Occasionally, as in some cases of hare-lip, the intermaxillary bone remains permanently distinct. To the main portion of the maxil- lary bone, the author has not been able to detect more than a single point of ossification, from which the bony rays shoot upward, backward, and outward. The palate bone is developed from a single ossific point, commencing at the angle of conjunction of the vertical and horizontal portions. The lachrymal, nasal, turbinated, and malar bones, and the vomer, are each developed from one centre of ossification. In the development of the inferior maxillary bone, each half appears to originate in a single ossific point, which commences before any other in the skeleton, except that of the clavicle. At birth the lower jaw con- sists of two halves, united at the symphysis by fibro-cartilage, but which, during the first year, subsequently co-ossify. CHANGES OF THE SKULL AT DIFFERENT PERIODS OF LIFE. In the embryo and early foetus the skull has a spheroidal figure, with a comparatively small conical prominence corresponding to the face. At birth, and for some time subsequently, the cranium is still more spher- oidal than afterwards, and at this early period is much larger in com- parison with the face than at maturity. The facial angle also is greater than it is at a later period. The skull is composed of a greater number of pieces at birth than THE SKELETON. 95 afterwards, as already indicated in the account of the individual bones. The texture of these, due to their greater proportion of bone carti- lage, is more flexible, and they are rather disposed to bend than to break. The bones likewise are more readily movable upon one another, so that from this and the preceding circumstance, the head in infancy is readily modified in shape artificially, as instanced in the change of form produced in the cranium, customary among the Flat-head Indians, and other savage tribes. In the infant skull, the bones of the vault of the cranium are more conical than concavo-convex, as they afterwards become. The greatest transverse diameter of the skull is at the parietal protuberances ; but later, is at the temporal fossae. The latter are proportionately small, in accordance with the moderate development of the temporal muscles, which are not yet required for mastication. The face is low, and situated entirely beneath the cranium. The nasal cavities are small, and the various sinuses communicating with them only begin to be developed. The mouth or palatine region in vertical depth is not more than half an inch; and the rami of the lower jaw project comparatively little above its body, and are more oblique than afterwards. As the child grows, the bones of the skull acquire greater hardness, become thicker, and gradually develop their spongy substance and their sinuses. With the development of the teeth and alveolar processes, and the protrusion of the former, the face becomes more prominent and deeper, the facial angle declines, and the spaces occupied by the masticating muscles enlarge. The rami of the lower jaw lengthen downward, and become less oblique; and the mouth increases to two and a half inches of vertical depth. With the advance of the face, there is also a recession of the cranium; and from the development of the frontal sinuses, the superciliary ridges become the most prominent portion of the forehead, instead of the frontal protuberances as in infancy. From puberty to adult age, but little change occurs in the skull, except a comparatively slight and very gradual increase in size and strength. At maturity the sutures gradually disappear; and in old age a sort of retrograde metamorphosis occurs. The bones of the skull become thinner and more brittle, and the spongy substance decreases, though the sinuses enlarge. With a diminution in quantity of the brain, the cranium undergoes an actual reduction in size. The teeth drop out, and the alve- olar borders of the jaws disappear, reducing the depth of the mouth almost to the condition of that in infancy. In consequence of these changes, the face loses much of its vertical extent, and the facial angle is increased. As the body of the lower jaw forms a much larger 96 THE SKELETON. Fig. 68. arch than the upper jaw, it mounts upon and incloses the latter, thus bringing the prominent chin just beneath the nose, as so strikingly observed in the aged. THE HYOID BONE. The Hy'oid bone1 is situated in the front of the neck, at the root of the tongue, and is readily felt just above the larynx. It consists of a median symmetrical body, with a pair of horns on each side. The body2 is the middle piece in front, and is quadrate in outline. Anteriorly it is convex and impressed on each side by muscles, and posteriorly is concave. The greater horns3 project backward from the ends of the body; and are comparatively long, thin processes ending in a tubercle. The lesser horns,4 usually in a cartilaginous condi- tion until late in life, are conical, and project upward and backward from the junction of the body with the greater horns. The lesser horns connect the hyoid bone with the styloid process of the temporal bone, by means of a long, narrow, fibrous cord, the sty'lo- hy'oid liga'ment.5 Generally they are only two or three lines long, and often vary in length and degree of ossification on the two sides. Some- times ossification extends from them up the stylo-hyoid ligament, and rarely, its entire length. The hyoid bone. 1, body; 2, greater horn; 3, lesser horn. THE TRUNK. That division of the skeleton called the trunk6 is composed of the vertebral column, the ribs, the sternum, and the hip bones. Its upper extremity forms the bony axis of the neck; below this is the thorax or chest; then follows the axis of the loins; and the lower part of the* trunk forms the pelvis. 1 Os hyoides; os linguae, or linguale ; os ypsiloides; os gutteris, or gutterale ; os bicorne ; os lambdoides. - Basis; ossiculum medium hyoidis. 3 Cornua majora; branches; rami. 4 Cornua minora; corpuscula, or grana triticea; cornicula; ossa pisiformia lin- gualia; styloid cornua. 5 Ligamentum stylo-hyoideum. 6 Truncus. THE SKELETON. 97 THE VERTEBRAL COLUMN. The Vert'ebral column1 is the axis of sup- port of the body, and is situated along the middle line of the trunk posteriorly. It is composed of twenty-nine symmetrical pieces, named vert'ebrae,2 which are divided into twenty-four true and five false vertebrae. In front, the vertebral column is composed of a series of half cylindroid segments con- joined by fibro-cartilage; posteriorly, of a series of arches supporting processes for mutual ar- ticulation, and others for muscular attachment. From the elongated spine-like character of its posterior median processes, the entire column is ordinarily named the spine.3 THE TRUE VERTEBRA. The True vert'ebrae,4 twenty-four in number, extend from the skull to the pelvis, and gradu- ally increase from the first to the last, which rests on the sacrum. From their relative po- sition] in the trunk they are divided into cer- vical or neck vertebrae, dorsal or thoracic ver- tebrae, and lumbar vertebrae. The true vertebrae are composed of a body and an arch supporting seven processes. The body5 is at the fore part, and usually possesses the form of a transverse segment of a half cylinder, concave posteriorly, and con- stricted at the front and sides. Its broad sur- face above and below is generally flat, with a slightly elevated border; and is conjoined with the contiguous vertebral body by means of a plate of fibro-cartilage.* Fio. 69. The vertebral column, lateral view; exhibiting the curvatures, 1 to 24, true vertebra; 25, 26, false vertebrae; 1 to 7,cervical vertebra-: 8 to 19, dorsal vertebra-: 20 to 24. lumbar vertebral* 25, sacrum; 2ti. coccyx. 1 Columna vertebralis; spinal column; c^jjmna spinalis; columna dorsi; spine; spina dorsi; back bone; rachis; carina; dorsum; tergum; notos; acnestis; acantha; compages vertebrarum; sacra fistula; hiera syrinx. 2 Spondyli; spondles; whetle bones. 3 Spina. 1 Vertebrae verge. 5 Corpus vertebrae; centrum. 98 THE SKELETON. Side view op a dorsal vertebra. 1, body; 2, articular facets for ribs; 3, arch; 4, 5, interverte- bral notches; 6, spinous process; 7, transverse process; 8, 9, articular processes. The arch1 is attached to the sides of the body posteriorly by narrow ped'icles,2 and the passage through it is the spi'nal fora'men,3 forming part of the spinal canal for contain- Fig. 70. ing the spinal cord. In form the arch is angular, and its sides ex- pand below; so that in the verte- bral column the arches together present a somewhat imbricated ap- pearance. From the summit of the arch posteriorly projects the spi'nous proc'ess,4 and from each side, the trans'verse proc'ess,5 all of which serve as points of attachment for muscles. Above and below, the arch supports a pair of artic'ular proc'esses,6 which present smooth discoidal facets for articulation with those of the contiguous vertebrae. Between the position of the articular and spinous processes, the arch is formed of a pair of shelving plates,7 of which the upper border behind and the lower border in front are roughened for the attachment of the elastic yellow ligaments. Above and below the pedicles of the arch, and between the articular processes and body, are the intervert'ebral notches, of which the infe- rior pair is generally the deeper. By the approximation of the notches of the contiguous vertebrae they form the intervert'ebral fora'mina,8 for the transmission of the spinal nerves and blood-vessels. In structure, the body of the vertebrae is composed of a mass of spongy substance covered with a thin layer of compact substance, which is perforated with numerous comparatively large nutritious or vascular fora'mina. At the middle of the body posteriorly there are two of these foramina particularly conspicuous, which communicate with channels for conducting veins from the spongy substance to the vertebral sinuses. The vertebral arch, together with its processes, requiring greater strength 1 Arcus vertebrae; vertebral arch; neural arch. 2 Neurapophyses. 8 Foramen spinale, or vertebrale; ver- tebral foramen. 4 Processus spinosus; neural spine. 5 P. transversus ; diapophysis. 6 P. articulares; oblique processes; p. ascen denies et descendentes; zyga- pophyses. 7 Vertebral plates; laminae; neurapo- physes. 8 F. intervertebralia ; f. vertebralia; f. conjugata. THE SKELETON. 99 than the body, have a predominance of compact substance composing them. The characters, thus given of the true vertebrae, are modified in the three regions to which we have referred; so that the cervical, dorsal, and lumbar vertebrae will now require a special description. In each region, however, the characters are not constant for all the vertebrae, as we find those of contiguous regions assuming more or less the appearance of one another; and in several instances they are much modified, so as to be adapted to some special function, as in the case of the upper pair of the neck. THE CERVICAL VERTEBRJE. The Cer'vical vert'ebrae1 are seven in number, and form the bony axis of the neck, extending from the skull to the thorax. The most striking peculiarity, by Fig. 71. which they may be distinguished from those of the other regions of the trunk, is the large foramen in the transverse processes. The body is widest transversely, and this disposition increases from the first to the last of the series. Its upper surface is rendered transversely concave from the elevation of the lateral borders; and its lower surface is in a less degree concave in the opposite direction upper view of a cervical verte- from the prolongation of the anterior and pos- BRA>from the kiddie of the series. 1, body; 2, 3, arch; 4, spinous proc- terior borders. From this arrangement the ess; 5, transverse process; 6, its fo COntigUOUS bodies interlock, thus affording a ramen; 7, superior articular process: 8, inferior articular process; 9, ele- provision against dislocation where the verte- vated lateral border of the body. brae are smallest. The arch is less deep, but wider than in the dorsal or lumbar vertebrae; and the spinal foramen is trilateral, with rounded angles, and larger than in the other true vertebrae. The upper and lower intervertebral notches are nearly equal in size. The spinous process is comparatively short, and is bifid at the extremity. The transverse processes are also comparatively short, and they consist of two portions. The posterior portion,2 springing from the pedicle of the vertebral arch, corresponds with the transverse processes of the dorsal vertebrae, while the anterior portion corresponds with the ribs.3 The two portions being conjoined by an isthmus, a foramen4 is formed, 1 Vertebrae colli; v. cervicis. 8 Parapophysis. 2 Diapophysis. * F. transversarium; f. vertebrale. 100 THE SKELETON. which, in the case of the upper six vertebrce of the neck, transmits the vertebral artery. The upper articular processes have their facets directed obliquely back- ward and upward; the lower ones, downward and forward. The description thus given of the cervical vertebrae applies especially to those from the third to the sixth inclusive; the remaining three pos- sess peculiarities requiring special notice. The first cervical vertebra is named the At'las,1 from its supporting the head. It is an irregular ring, and is broader than any other of the vertebrae of the neck. The large space included by the ring is divided by the transverse ligament into two parts, of which that anterior is the smallest, and is occupied by the pivot-like odontoid process of the second vertebra; the posterior portion is the true spinal foramen. Anteriorly, the atlas presents a short transverse bridge, with a tubercle in front, and a smooth articular Fl0, l2' facet behind, which moves on the odontoid process. The arch of the atlas is rounded, and its rudimental spinous process is in the form of a small tuberosity. The transverse process is much prolonged beyond that of the other cervical vertebrae, and ends in a rounded tuberosity. The upper articular processes form elliptical concavities inclining inwardly, and having their long diameter directed forward and inward. They articulate with the occip- ital condyles, and are the centre of the backward and forward motion of the head. The lower articular processes have oval, slightly depressed facets, directed downward and inward. The portions of the atlas forming the articular processes are the thickest and strongest of the bone; and they are adapted to sustain the pressure of the skull, which is subsequently transmitted, through the obliquity of the inferior articular processes, to the body of the second cervical vertebra, and thence through all the other vertebral bodies. Between the position of the upper and lower articular processes intern- ally, is a tuberosity, for the attachment of the transverse ligament, which retains the odontoid process in its place. Upper view of the atlas. 1, anterior tubercle; 2, articular facet for the odontoid process; 3, arch, with its rudimental spinous process; 4, groove for the vertebral artery; 5, transverse process; 6, its foramen; 7, superior articular process; 8, tuberos- ity for the transverse ligament. 1 Atlantion; astragnlus. THE SKELETON. 101 The intervertebral notches of the atlas are behind the articular processes, those below being the smaller. The upper ones are continuous with a groove from the foramen of the transverse process, and transmit the ver- tebral arteries in their course to the occipital foramen. Sometimes these upper notches are converted by a bridge of bone into foramina. The second cervical vertebra is called the Ax'is,1 from its supporting the pivot upon which the atlas and the skull together rotate. Fl<>- 73. The body of the axis presents a median prominence in front, and its upper part is pro- longed into the pivot-like odon'toid proc'ess,2 which projects within the circle of the atlas. The process is conical, has a smooth facet in front to articulate with the bridge of the atlas, and another behind, against which the trans- side view of the axis, i, body; verse ligament moves. The summit and sides 2'odontoid Process; 3> articular fa- , cet; 4, arch; 5, spinous process; 6, are also impressed by the attachment Of the transverse process, with its foramen; ligaments which moderate the rotation of the 7>8' suPerior and inferior articular processes. head. The arch of the axis is more robust than in any other of the cervical vertebrae. The spinous process is comparatively very strong; and it has depressed sides, a deep groove below, and a cleft extremity. The transverse process is the shortest in the cervical series, and its foramen ascends at first beneath the upper articular processes, and then turns abruptly outward and backward. The upper articular processes are oval in form and slightly convex, and rest obliquely upon the sides of the body and the pedicles. They are the circle of the rotary movements of the head, while the odontoid process is the centre. The upper intervertebral notches are obsolete ; while those below, and other parts of the bone in this position, correspond with the condition of the other vertebrae of the neck. The last cervical vertebra3 partakes strongly of the characters of the dorsal series, and is particularly remarkable for the length of its spinous process, which is tuberous at the end, instead of being cleft as in the others. 1 Vertebra dentata; epistropheus; 2 P. odontoideus, or odontoides; p. axon; maschalista. dentatus ; p. dentiformis; p. pyrenoides. 3 V. prominens. 102 THE SKELETON. THE DORSAL VERTEBRAE. The Dor'sal vert'ebrae,1 twelve in number, form the bony axis of the thorax, and extend from the neck to the loins. The most characteristic marks by which they may be distinguished from other vertebrae are the articular facets for the ribs. The bodies decrease in breadth from the first to the third, then are nearly uniform in this respect to the fifth, and afterwards gradually increase to the last. They are more demi-cylindroid in form than either those of the neck or loins. Their upper and lower surfaces are flat. The arches are smaller and stronger than in the cervical verte- brae. The spinal foramen is nearly circular, and is smaller than in the neck or loins. The lower intervertebral notches are much larger than the upper ones. The spinous processes are long and narrow, are trilateral, and have a tuberous extremity. They are directed backward and downward, suc- cessively increasing in the latter inclination to the lower ones of the series. The transverse processes2 are long and strong, and terminate in a thick tuberosity. They are directed outward, with a successively increasing inclination backward. The articular processes are nearly ver- tical ; those above being directed backward, those below forward. The articular facets for the ribs are situated one at the upper and lower margin of the body, on each side posteriorly, and another in front of the extremity of the transverse processes. The facets, at the sides of the bodies of contiguous vertebrae, together form pits,3 for the articu- lation of the head of the ribs. The facet of the transverse process articu- lates with the tubercle of the ribs. The bodies of the first and last two dorsal vertebrae present each a complete articular facet for the heads of the corresponding ribs. Side view of a dorsal vertebra. 1, body; 2, articular facets for ribs; 3, arch; 4, 5, interverte- bral notches; 6, spinous process; 7, transverse process; 8, 9, articular processes. 1 V. dorsales; v. thoracis ; thoracic vertebrae. 2 Diapophyses. 3 Foveae articulares. THE SKELETON. 103 THE LUMBAR VERTEBRAE. The Lum'bar vert'ebrae,1 five in number, form the bony axis of the loins, and extend from the thorax to the pelvis. They are the largest of the true vertebrae, and are readily distinguished from the others by the absence of a foramen in the transverse processes and articular facets for ribs. The bodies are oval in transverse section, and successively increase in size to the last. As in the dorsal series, their upper and lower surface FlG- 'u< is flat. The arches are strong, and increase in width from first to last. The spinal foramen is large and trilateral. The intervertebral notches are large, and nearly equal in size above and below. The Spinous process forms a side view of a lumbar vertebra. 1, body; 2. Strong Vertical plate projecting 8ide of the arch; 3, 4, intervertebral notches; 5. , , ■■ ■, j. . ,, . , spinous process; 6, transverse process; 7, 8, artic- backward and ending in a thick- ular proce8seg. ened extremity. The transverse processes2 are narrow, directed outwardly, and suc- cessively increase in length to the middle of the series, and then diminish to the last. They represent ribs; while the part corresponding with the transverse processes of the dorsal vertebra is a tubercle projecting from the outer side of the upper articular process. The articular processes are vertical; the upper ones being directed toward, while the lower ones are directed from each other, by which arrangement those of the contiguous vertebrae interlock, and thus aid in maintaining the articular integrity of the column, where it has no lateral support as in the thorax. THE FALSE VERTEBRiE. The False vert'ebrae3 are so called because they consist of nine seg- ments corresponding with the true vertebrae, which in the mature condi- tion are co-ossified into comparatively few pieces. The upper five pieces, co-ossified, constitute the sacrum ; the lower four pieces form the coccyx. 1 V. lumbales; vertebrae of the loins. - Parapopliyses. 3 V. spuriae. 104 THE SKELETON. THE SACRUM. The Sa'crum1 is a triangular bone, inserted obliquely backward and downward between the hip bones, at the posterior part of the pelvis. Its base is upward, joining the last lumbar vertebra; its apex down- ward, joining the coccyx. Fig. 77. Fig. 76. Front view of the sacrum. 1, transverse ridges, indicating the original separation of the bone into five segments; 2, sacral foramina; 3, promontory; 4, articular surface for the hip bone; 5, sacral bor- der of the sacro-sciatic notch; 6, base of the sa- crum, with its articular surface for the last lumbar vertebra; 7, wing of the sacrum; 8, articular proc- ess ; 9, apex of the sacrum, with its articular sur- face for the coccyx; 10, pedicle of the last verte- bral arch of the sacrum; 11, notch for the last sa- cral nerve. Back view of the sacrum. 1, rudimental spi- nous processes; 2,2, sacral canal, terminating below in a notch between the pedicles, 3, 4, of the last vertebral arch; 3, 3, rudimental articular proc- esses; 5, sacral foramina; 6,6, rudimental trans- verse processes; 7, articular surface for the hip bone; 8, sacral border of the sacro-sciatic notches; 9, articular surface for the last lumbar vertebra; 10, articular processes for the latter bone; 11, apex of the sacrum; 12, rough surface on the wing of the sacrum, for the sacro-iliac ligaments. It is curved forward, and has a broad, smooth, concave surface in front, and an irregular, narrower, convex surface behind. It varies in decree of curvature and relation of length with breadth in different indi- viduals, as well as sexes. As a general rule, it is more curved and longer in proportion with its breadth in the male. The bone corresponds with five vertebrae, whose elements are more or less obscured by co-ossification and feeble development. The front surface of the sacrum exhibits four transverse lines, indi- cating the original separation of the bodies of the sacral vertebrae. The first division of the bone presents an oval articular surface for the 1 Os sacrum; os latum; os clunium; os basilare; os alagas; vertebra magna; lus; luz; clunis; subvertebra; hieron osteon; albagiazi; vetula. THE SKELETON. 105 body of the last lumbar vertebra, and the last division a similar but smaller surface for the first piece of the coccyx. The posterior part of the sacrum is composed of the co-ossified arches of the vertebral segments. The fifth arch is generally incomplete or open at its back part; and sometimes this condition extends to the arch above, or even through the others. The continuation of the spinal canal is called the sa'cral canal',1 and is trilateral. It diminishes in its descent, and terminates in the notch2 produced by the incompleteness of the fifth sacral arch. In front, and behind the sacrum, on each side, are the four sa'cral fora'mina,3 which communicate with the sacral canal, and correspond with the intervertebral foramina. They successively diminish in size from above downward, and transmit the sacral nerves and blood-vessels. The anterior ones are the larger, and lead outwardly into grooves. The spinous processes successively diminish in size. The upper three are in the form of tubercles, and more or less confluent into a ridge. The fourth one is usually cleft into two tubercles, which likewise conjoin with those above. The upper articular processes of the first sacral division form vertic- ally concave facets directed backward and inward. They are separated by a wide notch, which is occupied by the last pair of the yellow liga- ments. The other articular processes are rudimental, and are obscurely distinguishable bounding the inner side of the posterior sacral foramina. The wings4 or lateral portions of the sacrum correspond with the ribs and transverse processes of the dorsal vertebrae, which are here fused together, so as to afford a broad surface of articulation for the hip bones. Below the surface for the latter, the obtuse margin of the bone gives attachment to the sacro-ischiatic ligaments. The rough sur- face behind the articulation gives attachment to the sacro-iliac ligaments. THE COCCYX. The Coc'cyx3 is situated at the lower end of the sacrum, from which it curves downward and forward. It corresponds with four of the true vertebrae, and though described as consisting of as many pieces, it pre- sents a very variable condition of co-ossification of these. The four bones successively decrease in size, and as vertebrae become 1 Canalis sacralis. 2 Hiatus sacralis. 3 F. sacralia. * Alae sacraliae. 5 Os coccygis ; caudal vertebrae ; crup- per bone; rump bone; os alagas ; ossis sacri acumen ; cauda; cuculus; uropy- gion. 106 THE SKELETON. more rudimental. Fig. 78. Posterior view of the coccyx. 1, first piece; 2. 2, pedicles of a ver- tebral arch; 3. transverse processes; 4, 5, 6, lower three pieces of the coccyx, consisting of rudimental vertebral bodies. The first of the series has a compressed body, with oval articular faces for conjunction with the sacrum and the second bone of the coccyx. From each side projects a transverse process. This is not unfrequently co-ossified with the margin of the sacrum, giving rise to a fifth sacral fora- men. Behind the body on each side is another short process,1 which corresponds with the pedicle of a vertebral arch. The remaining three bones present mere flattened bodies successively diminishing in size. The pieces of the coccyx correspond with the caudal or tail vertebrae of lower animals. DEVELOPMENT OF THE VERTEBRAE. Ossification commences in the vertebrae about the seventh or eighth week of embryonic life, and is not entirely completed until near the twenty-fifth year after birth. As a general rule, each true vertebra is developed from three principal ossific points, of which one belongs to the body, and one to each side of the arch with its processes. To these are added five epiphyses, of which three arise at the ends of the spinous and transverse processes, and the remaining two appear as thin plates on the articular surfaces of the body. Fig. 80. Fig. 79. Uevelopment of the vertebra, o, vertebra of a foetus, in a cartilaginous condition, with three centres of ossification; 1, 2, lateral pieces; 3, the body; b, vertebra of an infant. The lateral pieces, 1,2, are co-ossified at the spinous process, and join the body 3, at the sutures 4. The ends of the trans- verse and spinous processes yet in a cartilaginous state. Uevelopmext of the epiphyses to the verte- bra, a, dorsal vertebra, with the epiphysis 4. 5, to the transverse processes; 6, to the spinous pro- cess; and 7, to the body; 6,arch with its processes; and c, body of a lumbar vertebra; 4, 5, epiphyses of the transverse processes; 6, of the spinous pro- cess ; 7, 8, of the body; 9,10, of tubercles of the upper articular processes. Cornua sacralia. THE SKELETON. 107 The atlas is usually developed from three principal points only. The axis has two additional points for the odontoid process. The anterior division of the transverse process of the last cervical vertebra sometimes has a distinct ossific point, and this is occasionally developed into a rudi- mental and movable rib. The lumbar vertebrae have epiphyses at the ends of the transverse processes corresponding with ribs, as well as those upon the tubercles which represent the true transverse processes. The sacrum has three principal points of ossification for each division, as in the true vertebrae. In addition to these, epiphysial plates form on the articular surfaces of the bodies; points originate on each side of the upper three divisions representing ribs ; and subsequently two epiphysial plates originate at each lateral border of the bone. In the coccyx each bone is developed from a single ossific centre. ARTICULATIONS OF THE VERTEBRAL COLUMN. The ligaments which connect the different pieces of the vertebral column together and with the skull are as follows :— Twenty-seven intervertebral ligaments. Twenty-three pairs of yellow ligaments. The anterior vertebral ligament. The posterior vertebral ligament. Twenty-five pairs of capsular ligaments. The supra-spinous ligament. The interspinous ligaments. The nuchal ligament. The anterior and posterior occipito-atloid ligaments. The anterior and posterior atlo-axoid ligaments. The transverse ligament. Three odontoid ligaments. The Intervert'ebral liga'ments1 or disks are plates of fibro-cartilage interposed between the bodies of the vertebrae, except the atlas and axis, constituting a most tenacious but pliant means of connection. They vary in thickness in different parts of the vertebral column ; being thickest in the lumbar region, and thinnest in the coccyx and dorsal region. They also vary in this respect in different parts of themselves; thus, the disks of the cervical and lumbar regions are thickest in front, while those of the dorsal region are somewhat thicker behind. To this 1 Ligmenta intervertebralia; fibro-cartilagines intervertebrales; intervertebral substance, cartilages, or fibro-cartilages. 108 THE SKELETON. arrangement, together with the more or less wedge-like condition of the vertebral bodies, the curves of the vertial column are due, excepting that of the sacrum, which belongs to the bending of the bone itself. Fig. 81. Fig. 82. Upper view of a lumbar vertebra, Vertical section of two lumiiar vertebra, with the in- with a horizontal section of an intervert- tervening intervertebral ligament. The intervening articular ebral ligament. 1, concentric layers of processes, enveloped by a capsular ligament, are also repre- fibrous tissue; 2, pulpy fibro-cartilage. sented. 1,1, concentric layers of fibrous tissue, curving out- wardly; 2,2, concentric layers curving inwardly; 3, pulpy fibro-cartilage in the middle. Each intervertebral ligament is composed at the circumference of con- centric layers of fibrous tissue, and at the centre of a pulp-like fibro-car- tilage. The concentric layers consist of short bundles of fibres extended obliquely between the vertebrae and successively alternating in direction in the different layers, so that if the first proceeds from left to right, the second take their course in the reverse direction, and so on through the series. The concentric layers are not quite vertical, but the more super- ficial ones bend outwardly, while the deeper ones bend inwardly. The interior pulp-like fibro-cartilage appears to be closely compressed in its position ; so that when an intervertebral disk is cut through, the fibro-cartilage rises above the level of the exposed surface. The intervertebral ligaments, while firmly associating the segments of the vertebral column, at the same time give it a decided though restricted flexibility. The exterior concentric fibrous layers strongly attach the vertebral bodies, while their alternately crossing arrange- ment permits a slight degree of torsion or twisting motion ; and at the same time the interior compressed fibro-cartilage gives elasticity to the structure. Under pressure of the body in its erect position, the curvature of the concentric layers of the intervertebral ligaments increases, and the fibrous bundles composing them become more depressed, so that the trunk diminishes in length. In the recumbent position, pressure being removed, THE SKELETON. 109 the condition is reversed ; and in this manner may be explained the fact that a man is slightly taller on rising from bed in the morning than on retiring at night. In the conjunction of the vertebral bodies by means of the interverte- bral ligaments, we may discover some analogy to the ball-and-socket joint, which allows movement in all directions, though in this case it is of a very restricted character. The interior compressed fibro-cartilage of the disks between the resisting vertebral bodies serves the part of a ball, while the exterior concentric layers of alternately crossing fibrous bun- dles act as check ligaments. The entire arrangement is an admirable provision, to give a slight degree of movement in all directions to the vertebral column without endangering the integrity of the delicate nerv- ous cord which it incloses and protects. The Yellow lig'aments,1 of which there are twenty-four pairs, situ- ated between the vertebral arches from the axis to the sacrum, are most distinctly seen within the spinal ca- Fic 83 nal. They are attached to the an- terior surface of the lower part of the arches above, and the posterior surface of the upper part of those below, between the position of the spinous and transverse processes. They are composed of yellow, elas- tic tissue, the fibres of which are extended between the vertebral arches. The Anterior vert'ebral lig'a- ment2 is a strong band extending the entire length of the vertebral column, from the basilar process of the occipital bone to the end of the coccyx. Its upper extremity forms a rounded end, and is usually viewed as a distinct ligament.3 It widens in its descent, is thickest and most obvious opposite the vertebral bodies, thinnest upon the sacrum, and adheres most tightly to the intervertebral disks and the contiguous margins of the vertebral bodies. It is com- posed of closely associated bundles of fibres, of which the superficial Three vertebral arches removed from as many dorsal vertebra, viewed in front, and exhibiting 1, the yellow ligaments; and 2, the capsular liga- ments of the articular processes. 1 L. flava; 1. subflava; 1. intercruralia. 2 Anterior common ligament; liga- mentum longitudinale anterius; 1. cor- poribus vertebrarum commune anterius; fascia longitudinalis anterior. Its lower end, the 1. sacro-coccygeum anterius. 3 Anterior middle occipito-atloid liga- ment. 110 THE SKELETON. extend the length of three or four vertebrae; those deeper, the length of two or three; and the deepest, between the contiguous vertebrae. Fio. 84. Fig. 85. Three dorsal vertebra, with the articulations of the ribs, viewed in front. 1, portion of the an- terior vertebral ligament; 2, radiating ligament; 3, anterior costo-transverse ligament; 4, articulation of the head of the rib, laid open, and exhibiting the interarticular ligament separating two synovial cavities. Portion of the occipital bone, with the atlas and axis, front view. 1, origin of the anterior ver- tebral ligament from the basilar process; 2, ante- rior occipito-atloid ligament on each side of the former; 3, widening of the anterior vertebral lig- ament from the axis; 4, anterior atlo-axoid liga- ment; 5, 6, 7, capsular ligaments of the articular processes. This ligament, besides forming a strong bond of union to the verte- brae, also affords an origin to the crura of the diaphragm, and gives attachment to the pharynx and oesophagus, the aorta, thoracic duct, azygos vein, and inferior cava. The Posterior vert'ebral lig'ament1 is a strong fibrous band, with fes- Fig. 86. Fig. 87. Portion of the cranium and of the atlas and axis, viewed from behind; the posterior portions of the occipital and two last bones removed. 1, declivity of the sphenoid bone; 2, occipital bone; 3, atlas; 4, axis; 5, origin of the posterior verte- bral ligament from the basilar process; 6,7, capsu- lar ligaments of the articular processes. Bodies of three dorsal vertebra, connected by the intervertebral ligaments, viewed from behind; the vertebral arches having been removed. 1, intervertebral ligaments; 2, pedicles of the verte- bral arches; 3, portion of the posterior vertebral lig- ament, exhibiting its lateral festooned borders, 4. THE SKELETON. Ill tooned margins, situated within the spinal canal, and extending from the inner surface of the basilar process of the occipital bone to the end of the coccyx. In its course it widens opposite the intervertebral disks, to which and the contiguous margins of the vertebral bodies it tightly adheres ; and it narrows toward the middle of the latter, from which it is separated by the transverse veins of the spinal sinuses. The articular processes of the vertebrae are invested with cartilage; and each joint possesses a synovial membrane and a thin capsular liga- ment.2 The extent of motion in the joints formed by the vertebral artic- ular processes generally is very feeble, consisting only of a slight gliding in the bending of the vertebral column. The Su'pra-spi'nous lig'ament3 is a thin fibrous band connecting the summits of the spinous processes from the last cervical vertebra to the end of the coccyx. It is strongest in the lumbar region, and is continu- ous at its upper extremity with the nuchal ligament. Its lower extremity, by expanding, closes, in this position, the spinal canal. The Interspi'nous lig'aments4 are thin fibrous membranes connecting the contiguous spinous processes of the vertebrae, and extending from the former ligament. The Nu'chal lig'ament5 is a partition of loose fibrous tissue, separat- ing the muscles of the two sides of the neck, and extending from the cervical spinous processes along the median line of the occipital bone to the occipital protuberance. In man this ligament is a mere rudiment of the powerful elastic nuchal ligament which sustains the pendant head in quadrupeds. ARTICULATIONS OF THE OCCIPITAL BONE, THE ATLAS, AND THE AXIS. The Anterior and posterior occip'ito-at'loid lig'aments6 are thin, broad fibrous membranes extended between the contiguous borders of the occipital foramen and atlas, before and behind the position of the con- dyles and articular processes. 1 Posterior common ligament; 1. longi- tudinale posterius; 1 corporibus verte- brarum posterius; fascia longitudinalis postica. The upper extremity, usually described as distinct, with the names apparatus ligamentosus, membrana liga- mentosa, and occipito-axoidean ligament. 2 Ligamenta processuum obliquorum. 8 Ligamentum apicum ; its lower end, the lig. sacro-coccygeum posticum. 4 Lig. interspinalia; membrana inter- spinalis 5 Lig. nuchae ; fascia nuchalis ; paxy- waxy ; paxwax ; packwax; faxwax; tax- wax ; lig. cervical; descending ligament of Diemerbroeck. 6 Membrana annuli anterioris et pos- terioris atlantis; m. obturatoria ante- rior et posterior. 112 THE SKELETON. The Anterior and posterior at'lo-ax'oid lig'aments are likewise thin fibrous membranes, the former connecting the anterior bridge of the atlas with the front of the body of the axis, and the latter connecting the contiguous borders of the arches of the atlas and axis. Fig. 88. Fig. 89. Portion of the occipital bone, with the atlas and axis, front view. 1, origin of the anterior vertebral ligament; 2, anterior occipito-atloid liga- ment on each side of the former; 3, widening por- tion of the anterior vertebral ligament; 4, anterior atlo-axoid ligament; 5, 6, 7, capsular ligaments of the articular processes. Portion of the occipital bone and the upper three cervical vertebra. 1, atlas; 2, axis; 3, posterior occipito-atloid ligament; 4, capsular lig- aments of the occipital condyles and articular processes of the atlas; 5, posterior atlo-axoid liga- ment; 6, capsular ligaments of the articular proc- esses between the atlas and axis; 7, first pair of yellow ligaments; 8, capsular ligaments of the ar- ticular processes between the second and third cer- vical vertebrae. The membranes constituting the above four ligaments are compara- tively loose and flexible, so as not to interfere with the peculiar move- ments of the skull and first pair of cervical vertebrae. The capsular ligaments of the articular processes of the occiput, atlas, and axis are likewise comparatively loose, so as to permit rotation, flexion, and extension of the head. Fig. 90. Portion of the skull, the atlas, and axis, viewed from behind; the posterior portions of the occipital and two latter bones removed. 1, up- per extremity of the posterior vertebral ligament; 2. transverse ligament, with its two appendices, 3 and 4; 5, odontoid ligaments; 6,7, capsular liga- ments. The Trans'verse lig'ament1 is a strong band extended between the tubercles on the inner side of the atlas, and serves the purpose of re- taining the odontoid process of the axis in its proper position. To render its functions more effective, it sends from its middle a process upward, to be attached to the ante- rior border of the occipital fora- men, and another one downward, to be attached at the root of the odontoid process, so that altogether it has a crucial form.2 1 L. transversum atlantis; 1. transversale. 2 L. crucialum. THE SKELETON. -Q3 The Odon'toid lig'aments1 are three bands which ascend from the sides and summit of the odontoid process of the axis, to be attached to the anterior border of the occipital foramen. The lateral bands are much stronger than the middle one. These ligaments serve to limit the rotary movement of the head. The contiguous surfaces of the odontoid process and atlas are invested with cartilage, and form a joint lined with a synovial membrane and en- circled with a capsular ligament.2 A similar joint is formed between the odontoid process and the transverse ligament. The movements of flexion and extension of the head, as before indi- cated, occur between the occipital bone and atlas, for which the pecu- liar construction of the condyles of the former and articular processes of the latter are well adapted; while they are limited in extent by the capsular, occipito-atloid, and nuchal ligaments. The rotary movement of the head occurs between the atlas and axis; the centre of motion being the odontoid process, and the circle of rotation the contiguous articular processes. It is limited by the capsular, atlo-axoid, and odon- toid ligaments. The general flexibility of the cervical portion of the vertebral column permits a slight increase in the movements indicated. THE VERTEBRAL COLUMN VIEWED ENTIRE. The Vertebral column averages about two and a quarter feet in length, and varies but little in this respect in comparison with the stature of persons, the difference depending more on the proportionate length of the lower extremities. The first vertebra forms a capital to the column sustaining the head. The other true vertebrae successively increase in bulk, forming a tapering column resting with its base upon the sacrum, which, like the key-stone of an arch, is inserted between the hip bones. The breadth of the vertebrae increases from the second to the seventh, then decreases to the fourth of the dorsal region, and afterwards grad- ually increases again to the sacrum, which rapidly diminishes to the end of the coccyx. The height of the cervical vertebrae is nearly uniform ; the others gradually increase in this respect to the last. The intervertebral ligaments gradually increase in thickness from the third dorsal vertebra to the sacrum. Above the former point they increase to the middle of the neck, and then again decrease. 1 Ligamenta alaria and 1. rectum medium ; 1. dentis suspensorium; moderator and middle straight ligaments. » Vaginal ligament. 8 114 THE SKELETON. The intervals between the vertebral arches arc occupied by the yellow ligaments. They are widest in the loins, and least so in the lower por- tion of the neck and back. The spi'nal canal'1 is largest and is triangular in the neck and loins, is narrower and cylindrical in the dorsal region, and is smallest and triangular in the sacrum. The intervertebral foramina increase in size from the first to the last; the sacral foramina successively decrease. The spaces between the spinous and transverse processes constitute the vertebral gutters, and are occupied by the extensor muscles of the back. Viewed in profile, the vertebral column presents a series of four curves, which, except in the case of the sacrum, depend on the difference in thickness between the fore and back parts of the vertebral bodies and the intervertebral disks. In the neck and loins the convexity of the curves is directed forward, in the dorsal region and pelvis backward. The strongest degree of convexity is that presented in the loins; its lower part being produced by the promontory of the sacrum. The curvatures commence to become particularly evident with the first efforts of the child to stand or walk ; prior to this period the vertebral column being nearly straight. More or less lateral curvature is quite frequently observable in the dorsal region, most usually with the convexity toward the right. This abnormal character appears to depend on the excess of muscular action upon the side to which the convexity is directed. The sacrum is the only portion of the vertebral column which is entirely immovable, and it is through this bone that the weight of the trunk is communicated to the lower extremities. The mobility in other portions of the vertebral column varies, being greatest in the cervical region, and least in the dorsal region. The motions of the vertebral column, though very restricted, occur in all directions; being those of flexion and extension, bending to either side, and rotation upon its axis. THE RIBS. The Ribs,2 of which there are twelve pairs, form a series of narrow arches on each side of the trunk, extending from the dorsal vertebrae toward the sternum. Anteriorly they are prolonged by the cos'tal car'- 1 Vertebral canal; rachidian canal; 2 Costae; pleurae ; pleurapophyses; canalis medullae spinalis; specus pro pleuromata. medulla spinali, or vertebralis; solen. THE SKELETON. 115 tilages.1 The upper seven pairs join the side of the sternum through the latter, and are called true or ster'nal ribs.2 Of the others, called false or aster'nal ribs,3 three successively join one another and the cartilage of the last true rib, by means of their cartilages. The remaining two have their cartilages unattached, and are thence called free or floating ribs.4 The ribs successively increase in length from the first to the eighth, and then decrease to the last one. In breadth and degree of curva- FlG- 91- ture they gradually diminish from first to last. In direction from the vertebral column, they are first di- rected from the bodies outward and backward to the transverse processes, from thence outward and slightly forward, and subsequently more abruptly forward and inward. In proceeding from the vertebrae they likewise incline downward, so that their anterior extremity is lower than the posterior. In the latter direction the ribs exhibit a slight twist, so that they will not lie with their whole length in con- tact with a level surface. The ribs have an outer and inner broad smooth surface ; an upper rounded border and a lower sharp one. Within the greater part of the length of the lower border there is a groove5 for the intercostal blood-vessels. The posterior extremity of a rib is the head,6 and this presents two articular facets, separated by a slight ridge, which articulate with the corresponding facets of a contiguous pair of vertebral bodies. The narrow part of the rib succeeding the head is its neck,7 and this is bounded externally by the tu'bercle,8 upon which is an articular facet for the transverse process of the lower of the two vertebrae joined by the Front view of the thorax. 1, 2, 3, the three pieces of the sternum; 4, 5, the dorsal vertebrae; 6, the first true rib; 7, its head; 8, neck; 9, tubercle; 10, the seventh true rib; 11, costal cartilages; 12, the floating ribs; 13, groove for the intercostal blood-vessels. Cartilagines costarum ; haemapophy- ses. 2 Costae verae; c. genuinae; c. sternales. 8 Costae spuriae; c. mendosoe ; c. aster- nales; nothaa costae. 4 Costae fluctuantes. 5 Sulcus costalis. 6 Capitulum costae. 7 Cervix; collum. 8 Tuberculum. 116 THE SKELETON. head of the rib. Externally to the tubercle is a rough mark called the angle,1 corresponding with the point at which the rib is rather abruptly directed forward. The distance of the angle from the tubercle succes- sively increases from the first to the last rib. The anterior extremity of the rib is the most compressed portion, is obtuse at both borders, and is continuous with its costal cartilage, which, after separation by maceration, leaves an elliptical pit at the end of the bone. The broad surfaces of the ribs are so arranged in succession that the outer ones present the periphery of an oval, and the inner ones in the same manner are related to the interior of an oval. Several of the ribs present exceptional characters to those given in the general account. The first rib has no twist, has its broad surfaces directed upward and downward, and its borders, which are narrow, inward and outward. The upper surface at its fore part is marked by two slight impressions produced by the subclavian blood-vessels. The head presents but a single articular facet. The eleventh and twelfth ribs are compara- tively feebly developed; have only one articular facet to the head, and have no tubercle. The Cos'tal car'tilages2 successively increase in length from the first to the seventh, and then decrease to the last. Their direction is one of convergence toward the sternum; the first one descends, that succeeding is horizontal, and the others gradually become more and more ascending. The outer extremity of the costal cartilages is absolutely continuous with the structure of the ribs. The inner extremity of those of the true ribs, except the first pair, forms a movable articulation with the side of the sternum. The inner end of the succeeding three pairs of cartilages is pointed and attached to the cartilage next above. The last two pairs of costal cartilages are pointed and free. Between the fifth to the eighth pair of costal cartilages, processes usually exist blending their contiguous borders together. The ribs commence ossification even before the vertebrae. They are formed from a principal piece, an epiphysis for the head, and another for the tubercle, except in the last two pairs, which have no epiphysis for the latter process. Usually after the prime of life, in the male, the costal cartilages become partially ossified, but in the female this is much less liable to occur, and then only in advanced age. 1 Angulus, or cubitus costae. 2 Cartilagines costarum; haemapophyses. THE SKELETON. 117 THE STERNUM. The Ster'num or breast bone1 is situated in the median line, in front of the thorax, sloping from above downward and forward. It is long, broad, and nearly flat, and bears a general resemblance to the ancient broad-sword, from which the older anatomists called its three pieces the handle, the blade, and the point. Its anterior surface is slightly convex; its posterior surface slightly concave. In structure it is light and spongy, and is invested with a thin layer of moderately compact substance. The handle or first piece2 is the broadest and thickest bone of the sternum. It is irregularly hexahedral; slightly convex in front, and slightly concave behind. Its upper border is thick, rounded, and trans- versely concave ;3 its lower border is straight, and joins the second bone of the sternum. The upper, short, lateral border slopes off and articu- lates with the clavicle.4 The lower, long, lateral border curves downward and inward; its upper end is continuous with the first costal cartilage; its lower end articulates with part of the second costal cartilage. The second piece or body5 is the longest portion of the sternum. It is oblong, quadrate in form, and usually widest at its lower part. Its anterior and posterior surfaces are nearly flat, and are commonly more or less marked by several transverse lines indicating the original separa- tion of the bone into parts. Its lateral borders present successively, first, at the upper end an articular surface forming part of the articulation for the second costal cartilage, then four notches for the third to the sixth costal cartilages inclusive, and finally, at the lower end a surface for part of the seventh costal cartilage. The distance between these articulations successively decreases from above downward. The third piece or point6 of the. sternum is usually the narrowest, thinnest, and shortest portion. It is quite variable in shape, being flat, long and pointed, or ensiform; tongue-shaped, or discoidal; or it is forked. It commences ossification several years after birth, and even in advanced age is rarely entirely ossified; hence its name of en'siform car'tilage.7 With the commencement of its lateral border, the seventh costal cartilage partially articulates. The upper two pieces of the sternum commence ossification about the fifth or sixth month of foetal life; and they do so from a variable number 1 Sternon; os pectoris ; o. xiphoides; o. gladioli; o. ensiforme; o. asser; scu- tum pectoris, or cordis; haemal spine. 2 Manubrium; episternum. 3 Incisura semilunaris; os jugularis. * Incisura clavicularis. 5 Corpus; blade; mesosternum. 6 Processus xiphoideus; p. mucrona- tus ; p. ensiformis ; hyposternum. 7 Cartilago ensiformis. 118 THE SKELETON. of points. At puberty the handle forms a single bone ; the body usually presents five segments, which successively co-ossify from below upward. Generally the three pieces or bones of the sternum remain separated, but frequently the upper two become united, and occasionally in old age all three are found co-ossified. The sternum is variable in its form in different individuals, principally in the proportion of length and breadth of the different pieces. Articulations of the Sternum.—The three pieces of the sternum are conjoined by fibro-cartilage, and are much strengthened in their union by a thick fibrous investment, partially derived from the costo-sternal ligaments. ARTICULATIONS OF THE RIBS WITH THE VERTEBRAE AND STERNUM. Costo-vertebral articulations.—The articulation between the head of the ribs and the bodies of the dorsal vertebrae is surrounded with a cap'- sular lig'ament, and, except in the case of that of the first and the last two ribs, is divided into two parts by an interartic'ular lig'ament,1 Fig. 92. Anterior view of three dorsal vertebrje a\d their articulation with the ribs. 1, portion of the anterior vertebral ligament; 2, radiating liga- ment ; 3, anterior costo-transverse ligament; 4, ar- ticulation of the head of the rib laid open, exhibit- ing the cavity divided into two by aninterarticular ligament. Posterior view of four dorsal vertebr* and their articulation with the ribs. 1, supraspi- nous ligament; 2, yellow ligament, seen just below the edge of the vertebral arches; 3, anterior costo- transverse ligaments; 4, posterior costo-transverse ligaments. which is a short band connecting the ridge on the head of the ribs with the contiguous intervertebral disk. In front the articulation is strength- ened by the ra'diating lig'ament,2 consisting of three bands diverging 1 L. interarticulare; 1. transversum. - L. capituli costae anterius ; 1. radiatum. THE SKELETON. 119 from the head of the rib to the sides of the contiguous pair of vertebral bodies and the intervertebral disk. The slightly movable articulation between the tubercle of the upper ten ribs and the neighboring transverse processes of the dorsal vertebrae is likewise surrounded with a cap'sular lig'ament. Besides this, each rib is connected with the transverse processes by three ligaments, as follows: The anterior cos'to-trans'verse lig'ament.1—This is a membranous band connecting the neck of the rib with the transverse process above. The posterior cos'to-trans'verse lig'ament.2—This is a short band connecting the tubercle of the ribs with the end of the contiguous trans- verse process. The middle cos'to-trans'verse lig'ament.3—This consists of short fibres intervening between the neck of the rib and the contiguous trans- verse process. Costo-sternal articulations.—The costal cartilages, except the first, form articulations with the side of the sternum surrounded by capsular ligaments and lined with synovial membranes. Behind, and especially in front, the articulations are strengthened by fibres radiating from the cos- tal cartilages upon the sternum, constituting the anterior and posterior cos'to-ster'nal lig'aments.* Those of the two sides blend together and with the aponeurotic origin of the pectoral muscles. A thin fibrous band connecting the seventh costal cartilage with the third piece of the sternum is called the cos'to-xi'phoid lig'ament.5 The contiguous margins of the costal cartilages from the sixth to the ninth, if not blended together, have opposed articular surfaces surrounded with cap'sular lig'aments. THE THORAX. The Tho'rax or chest6 is a conical or ovoidal case, with its narrower part uppermost. It is flattened before and behind, which is the reverse of the condition observable in the lower mammals generally, and hence it is that man can readily lie on his back, while the lower animals cannot. It is formed of the dorsal vertebrae, ribs, and sternum; and its sides are also called its walls. 1 L. costo-transversale anterius; 1. transversarium internum; int. costo- transverse ligament; 1. costo-transver- sarium inferius. 2 L. costo-transversale posterius; 1. transversarium externum; ext. costo- transverse ligament. 3 L. costo-trans. medius; 1. colli costae; 1. cervicuin costae. * L. costo-sternalia ant. et post.; 1. radiata. 5 L. costo-xiphoideum. 6 Pectus; stethus; cassa; venter me- dius; citharus; scutum pectoris; bir; chelys. 120 THE SKELETON. The front wall of the chest, or the breast, is flatter and shorter than any other portion, and is formed of the sternum and cartilages of the true ribs. It slopes forward and downward to such an extent that the lower end of the sternum is re- Fig. 94. moved twice the distance of the upper end from the vertebrae. The posterior wall is the back, in the most restricted use of the term. It is also flattened, is di- vided in the middle by the imbri- cating spinous processes of the dor- sal vertebrae, and is defined on each side by the angles of the ribs, which indicate the extent to which the dorsal extensor muscles reach outwardly. The lateral walls of the chest are the longest, most prominent, and convex. The cavity of the tho'rax1 is subdivided posteriorly by the intru- sion of the bodies of the dorsal vertebrae; and it is open above, below, and between the ribs. The superior opening of the tho'rax2 is formed by the first dor- sal vertebra, the first pair of ribs, and the first piece of the sternum. It is reniform, with its transverse diameter more than twice as great as the antero-posterior, and with its plane inclining a little downward and forward. The inferior opening,3 by far the largest, is formed by the last dorsal vertebra, the last pair of ribs, the cartilages of all the false ribs, and the last piece of the sternum. It is likewise reniform, with its transverse diameter about one-third greater than the antero-posterior, and with its plane inclining upward and forward. The intercos'tal spaces4 increase in width anteriorly, and are occupied by muscles of the same name. The greatest circumference of the thorax is just below the middle, and not at the bottom or base. The ribs incline downward and forward in such a manner that the anterior extremity of the first rib is on a level Front view of the thor*x. 1, 2, 3, the three pieces of the sternum; 4, 5, the dorsal vertebrae; 6, the first true rib; 7, its head; 8, neck; 9, tu- bercle ; 10, the seventh true rib; 11, costal cartil- ages; 12, the floating ribs; 13,groove for the inter- costal blood-vessels. 1 Cavum thoracis. 3 Apertura thoracis inferior. 2 Apertura thoracis superior. * Spatia intercostalia. THE SKELETON. 121 with the second dorsal vertebra, the anterior extremity of the seventh rib is on a level with the tenth dorsal vertebra, and the end of the last rib is on a level with the first lumbar vertebra. The movements of the thorax consist of a moderate degree of eleva- tion and depression of the ribs and sternum, as in inspiration and expiration. From the direction of the ribs, when their anterior part is raised they assume a more horizontal position, and the diameter of the chest is increased. The thorax is more ovoidal and less compressed antero-posteriorly in the female than the male. Tight-lacing makes it still more assume the form of an oval. THE HIP OR INNOMINATE BONES. The Hip or Innominate bones,1 though included in the account of the trunk, really belong to the lower extremities, holding the same relation to them that the shoulder bones do to the upper extremities. In the lower animals their presence is observed to be in a great measure dependent on the existence of hinder extremities.2 Together with the sacrum, they constitute the pelvis, which incloses a portion of the diges- tive and genito-urinary apparatus. For convenience of description they are viewed as consisting of three parts : the il'ium, is'chium, and pu'bis, corresponding with the original divisions of the bones as existing in infancy. The Il'ium3 is a broad, thick plate forming the upper part of the hip bone. Its inner side presents three surfaces: an anterior, broad, smooth concavity, called the il'iac fos'sa ;4 a posterior, uneven surface, partly devoted to articulation with the sacrum, and partly to ligamentous attachment; and an inferior, small, nearly plane surface, forming part of the true pelvis. The outer or dorsal surface of the ilium is convex at its fore part, and concave behind. It is marked by two feeble ridges, called the superior and inferior curved lines.5 The space between them gives origin to the small gluteal muscle; the space above them to the middle gluteal muscle, except a rough surface at the posterior superior part of the bone, which gives attachment to the great gluteal muscle. 1 Ossa innominata ; ossa anonyma; o. coxarum; o. lateralia pelvis; the haunch bones. 2 In some animals hip bones exist with- out the presence of limbs, but in such cases they are quite rudimentary; as in the dolphin, whale, and glass snake. 8 Os ilium ; os ilei; ileum; ileon ; haunch; haunch bone. 4 Fossa iliaca. 5 Lineae arcuatae; 1. semicircularis su- perior et inferior. 122 THE SKELETON. The upper border, or crest of the il'ium,1 is thick and rounded, and is convex and sigmoid in its course. It gives attachment to the broad Fig. 95. Fig. 90. Inner view of the left hip or innominate bone. The dotted line indicates its division into ,three parts: 1, the ilium, 2, the iinKiiirn, and 3, tne$iublj. (1, iliac fossa:) 4, crest of the ilium; 5, 6, anterior superior, and inferior spinous processes; 7, 8, pos- terior superior, and inferior spinous processes; 9, articular surface for the sacrum; 10, rough surface for the attachment of ligaments. (2, body of the pubis :) 11, symphyses; 12, horizontal, and 13, de- scending ramus; 14, upper border of the body; 15, spine of the pubis; 16, pectineal line. (3, plane of the ischium:) 17, ramus of the ischium; 18, tuber- osity; 19, spine of the ischium; 20, ilic-pubic eminence; 21, obturator foramen; 22, great sciatic notch; 23, lesser sciatic notch. Outer view of the left hip or innominate bone 1, ilium; 2, ischium; 3, pubis. (1, dorsal surface of the ilium :) 4, crest of the ilium; 5, 6, superior and inferior curved lines ; 7, surface of the great gluteal muscle; 8, 9, anterior superior, and inferior spinous processes; 10, 11, posterior superior, and inferior spinous processes. (2,body of the ischium:) 12, spine of the ischium; 13, great sciatic notch; 14, lesser sciatic notch; 15, tuberosity of the is- chium; 16, ramus of the ischium. (3, body of the pubis:) 17, horizontal ramus of the pubis; 18, de- scending ramus; 19, acetabulum; 20, obturator foramen. muscles of the abdomen, and terminates at each end in a prominence, called the anterior superior, and posterior superior spi'nous proc'ess.2 Below these processes is a notch, succeeded by the anterior inferior, and posterior inferior spi'nous proc'ess.3 Following these processes are other notches : one anteriorly, terminated below by the ilio-pubic eminence; the other posteriorly being the great sciat'ic notch.4 1 Crista ilei. 2 Processus spinosus ant. sup. et post. sup.; spina ant. sup. et post. sup. 3 P. s. ant. inf. et post, inf.; spina ant. inf. et post. inf. * Incisura ischiadica major; incisura iliaca; part of the sacro-sciatic notch. THE SKELETON. 123 The Is'chium1 forms the inferior part of the hip bone, and consists of a body and a ramus, united in the form of a hook. The body2 is the posterior thicker portion joining the ilium. It is trilateral, one side looking outward, another inward, and the third backward. Below, it forms a strong prominence, the tuberos'ity,3 upon which we sit, and which gives origin to the flexor muscles of the back of the thigh. Behind, the ischium possesses a strong process, the spine,4 which separates the greater sciat'ic notch5 above from the lesser sciat'ic notch6 below. The ra'mus7 of the ischium proceeds from the lower extremity of the body upward and forward to the pubis. It presents an inner and an outer surface, and an anterior thick border, which gives attachment to the cms of the penis. The Pu'bis8 is situated at the anterior part of the hip bone, and con- sists of a body and two ra'mi or branches. The body is the inner ex- panded part, flattened before and behind, and having at its inner border an uneven articular surface, forming part of the sym'physis, or junction of both pubes. The upper part of the body forms an obtuse ridge9 termin- ating externally in a small eminence, the spine,10 which gives attachment to the lower end of Poupart's ligament. The horizontal ra'mus of the pubis proceeds outward from the body, and at its junction with the ilium forms the il'io-pu'bic eminence.11 It is three sided, and presents three margins, of which one is inferior, another is obtuse and proceeds from the spine of the pubis outwardly to the acetabulum, and the third is sharp and is called the pecti'neal line.12 This proceeds from the spine of the pubis to the inner side of the ilio- pubic eminence, and at its commencement gives attachment to Gimber- nat's ligament. The descending ra'mus of the pubis proceeds outward and downward to join the ramus of the ischium. It is small and flattened from without inward. Having described the separate divisions of the hip bones, it remains to point out some anatomical characters formed by their conjunction. At the union of the three pieces of the hip bone, externally there is 1 Os ischii; os coxendicis; ischion; buckle bone ; seat bone. 2 Ramus descendens. 3 Tuberositas or tuber ischii; os seden- tarium. * Spina ischii: spinous process. 5 Incisura ischiadica major. 6 In. isch. minor; luna Albini. 7 Ramus ascendens. 8 Os pubis; os pectinis; pecten ; epis- chion. 9 Crest; crista pubis. 10 Tuberosity of the pubis; tuberculum pubicum; spina pubis. 11 Ilio-pectineal protuberance; tuber- culum ilio-pubicum; tub. ilio-pectineum. 12 Crista; pecten; linea pectinea; cris- ta ilio-pectinea. 124 THE SKELETON. situated a hemispherical or cup-shaped cavity, the acetab'ulum,1 for articulation with the head of the thigh bone. To it, the pubis contributes one-fifth, and the ilium and ischium contribute each about two-fifths. It is bounded by a prominent margin,2 except internally, where it is deeply notched.3 The greater part of the surface of the acetabulum is smooth and covered with cartilage, but at its bottom there is an irregular pit,4 communicating with the notch of its margin, which is occupied by a cushion of fat. In advance of the acetabulum, between the pubis and ischium, is a large hole, the obtura'tor fora'men,5 which is closed by a fibrous mem- brane. It is oval, with a tendency to assume a trilateral form, especially in the female. Above the position of the acetabulum is the il'io-pu'bic emi'nence,6 corresponding with the union of the horizontal ramus of the pubis with the ilium. To the inner side of this eminence there proceeds for- ward and backward the ilio-pectineal line, which separates the true and false pelvis. Internal to the position of the acetabulum, within the pelvis, there is a vertical surface formed by the ilium and ischium, and called by obstet- ricians the plane of the is'chium. Behind it, formed between the poste- rior inferior spinous process of the ilium and the spine of the ischium, is the great sciatic notch. The hip bone is composed of spongy substance with a moderately thick investment of compact substance, which is perforated in many places with large foramina for nutritious blood-vessels. Frequently the two plates of compact substance come into contact at the middle of the iliac fossa, and in this position are so thin as to be translucent. The hip bone is ossified from three principal pieces, corresponding with its divisions indicated, and four epiphyses. Ossification commences early in foetal life, and is not completed until after adult age. The epiphyses, which begin to appear subsequent to puberty, consist of one for the crest of the ilium, another for the tuberosity, and small ones for the anterior inferior spinous process and the pubic symphysis. 1 Cotyle; cotyloid cavity ; fossa coty- loidea; sinus coxae ; acetabulum pyxis. 2 Supercilium acetabuli. 3 Incisura acetabuli. 4 Fossa acetabuli. 5 F. obturatum or obturatorium; f. ovale; f. thyroideum; f. infra-pubianum; f. amplum pelvis. 6 Ilio-pectineal eminence. THE SKELETON. 125 ARTICULATIONS OF THE HIP BONES. The hip bones are immovably articulated together and with the sacrum by means of fibro-cartilaginous plates and strong ligaments. The Pu'bic sym'physis1 is formed by the conjunction of the pubes through a thick plate of fibro-cartilage, as in the union of the vertebral bodies. It is strengthened by fibrous bands passing from one bone to the other, constituting the pu'bic lig'aments, which are named, from their relative position to the symphysis, anterior, posterior, etc. The inferior or sub-pubic ligament2 is the strongest. Fig. 98. Fig. 97. Ligaments of the pelvis and hip joint. 1, lower part of the anterior vertebral ligament; 2, pubic symphysis; 3, ilio-lumbar ligament; 4, sacro-iliac symphysis, with the anterior sacro-iliac ligament; 5, obturator membrane; 6, edge of the tendon of the external oblique muscle of the abdomen, techni- cally named Poupart's ligament; 7, extension of the latter along the pectineal line named Gimbernat's ligament; s, capsular ligament of the hip joint; 9, ft strong accessory band of the latter ligament. The Obtura'tor mem'brane3 is a fibrous structure, closing the obturator foramen, except at its upper and outer part, where there is an orifice4 for the passage of the obturator vessels and nerve. The surfaces of the membrane give origin to the obturator muscles. The Sa'oro-il'iac sym'physis5 is formed by the union of the corre- 1 Symphysis pubis. 2 Lig. arcuatum. 3 Membrana obturatoria; ligamentum obturatorium ; sub-pubic membrane. * Canalis obturatorius. s Symphysis sacro-iliaca. Ligaments of the pelvis and hip joint. 1, pos- terior sacro-iliac ligament; 2, great sacro-sciatic ligament; 3, small sacro-sciatic ligament; 4, great sacro-sciatic foramen; 5, small sacro-sciatic fora- men; 6, cotyloid ligament surrounding the border of the acetabulum; 7, round ligament; 8, cut edge of the capsular ligament; 9, obturator membrane. 126 THE SKELETON. sponding articular surfaces of the ilium and sacrum through means of fibro-cartilage, which is separable by force into two plates adhering one to each bone. The joint is strengthened by the anterior and posterior sa'cro-il'iac lig'aments.1 The former consists of short bands uniting the contiguous bones in front of the symphysis. The latter is composed of strong bands passing transversely and obliquely from the posterior spi- nous processes and contiguous uneven surface of the ilium to the corre- sponding surface of the sacrum, behind the symphysis. The Il'io-lum'bar lig'ament2 is a fibrous band springing from the end of the transverse process of the last lumbar vertebra, and expanding outwardly to be attached to the posterior part of the crest of the ilium. The Great sa'cro-sciat'ic lig'ament3 is a strong triangular band attached by its base to the posterior inferior spinous process of the ilium and the margin below of the sacrum and coccyx, and by its apex to the inner margin of the tuberosity of the ischium, along which it presents a narrow expansion. The Small sa'cro-sciat'ic lig'ament,4 less strong than the preceding, springs in conjunction with it from the margin of the sacrum and coccyx, and converges to be attached to the spine of the ischium. By means of the sacro-sciatic ligaments, the sciatic notches are con- verted into the great and small sciat'ic fora'mina.5 The former is oval and transmits the pyramidal muscle, the sciatic nerve, and the gluteal, pudic, and ischiatic vessels and nerves. The latter foramen is more tri- lateral, and transmits the obturator muscle, and the internal pudic vessels and nerve. THE PELVIS. The Pel'vis6 is the basin-like portion of the trunk formed by the hip bones, the sacrum, and the coccyx. It is situated in an oblique position from the vertebral column, downward and backward, so that the end of the coccyx is nearly on a level with the middle of the pubic symphysis. By means of the il'io-pectine'al line,7 and the upper projecting part of the sacrum, called its promontory,8 the pelvis is divided into the superior or false, and the inferior or true pel'vis. 1 Lig. sacro-iliacum ant. et post.; the posterior consisting of the lig. sacro-ili- acum Ion gum et breve. 2 L. ilio-lumbale. 3 L. sacro-ischiaticum majus; 1. posti- cus ; 1. tuberoso-sacrum. 4 Lig. sacro-ischiaticum minus, or an- ticus, or internum; 1. spinoso-sacrum. 5 Foramina sciatica, or ischiatica, or ischiadicum majus et minus, or major et minor. 6Choana; pyclos ; lecane. 7 Linea arcuata interna; 1. innomina- ta; 1. terminalis. 8 Promontorium. THE SKELETON. 127 Fig. 99. The superior pel'vis1 is formed on each side by the ilium, and is com pleted by the lumbar verte- brae and the soft walls of the abdomen. The inferior pel'vis2 is composed of the pubes and ischia, the sacrum and coccyx. Its cavity is curved cylindrical, nar- rowing below and becom- ing deeper from before backward. Its inlet and outlet are also called the superior and inferior straits, the ideal planes of which converge anterior- The superior strait3 corresponds with the ilio- pectineal line and pro- montory of the sacrum, the projection of which gives it a cordiform out- line. The inferior strait4 is bounded by three prominences, separated by as many notches. Of the prominences, two are lateral and correspond with the tuberosities of the ischia, and the other is formed by the sacrum and coccyx. Of the notches, one is the pu'bic arch,5 bounded on each side by the rami of the ischium and pubis. It is triangular, and has for its apex the symphysis of the pubes. The other notches, called from their position sa'cro-sci- at'ic, by means of ligaments of the same name are converted into fora- mina likewise distinguished by the same designation. The axis of the inferior pelvis constitutes a curved line6 passing out at the centre of the straits. Front view of a female pelvis. 1, last lumbar vertebra; 2, intervertebral ligaments; 3, sacrum, the figure being placed on its promontory; 4, transverse lines indicating the original separation of the sacrum into five vertebral segments; 5, end of the coccyx; 6, iliac fossa; 7,8, anterior superior, and inferior spinous processes; 9, acetabulum; 10, its notch on the inner side; 11, body of the is- chium ; 12, tuberosity of the ischium; 13, spine of the ischium, seen through the obturator foramen; 14, body of the pubis; 15, symphysis of the pubis; 16, arch of the pubis; 17, upper part of the body of the pubis; 18, spine of the pubis; 19, pectineal line; 20, ilio-pubic eminence; 21, great sacro-sciatic notch. 1 The great, or greater pelvis; false pelvis; labrum pelvis. 2 The small, or lesser pelvis; pelvis minor; p. vera. 3 Brim of the pelvis; apertura pelvis superior; introitus ; angustia abdomi- nalis; upper opening. * Apertura pelvis inferior; lower open- ing ; exitus; angustia perinaealis. 5 Arcus ossium pubis; arch of the pubis. 6 The curve of Carus. 123 THE SKELETON. In the infant the capacity of the inferior pelvis is so small that the urinary bladder for the most part occupies the space of the superior pelvis. SEXUAL DIFFERENCES OF THE PELVIS. The sexual differences of the pelvis are greater than in any other por- tion of the skeleton. In the female the pelvis is more capacious in its breadth and less deep than in the made. In consequence of this most important difference, the birth of the infant is easier and quicker than it could be under the opposite conditions. The bones of the pelvis are thinner and less marked by muscular attachments. The sides of the superior pelvis, formed by the ilia, are more expanded. The promontory of the sacrum is less projecting, and in consequence of this difference the superior strait is less cordiform or is more oval. The cavity of the inferior pelvis is more uniformly cylindrical, from the ischia converging less below or from their being more parallel. The depth of the inferior pelvis is less, but its breadth is greater. The diminution in depth depends on the less extent of the ischia. The sub-pubic arch is lower, wider, more obtuse at the summit, and less everted at the sides. The sacrum and coccyx are shorter and wider; the ilio-pectineal line is longer; and the obturator foramen is more trilateral. The following table gives the comparative measurements of the inferior pelvis in the two sexes :— superior strait. male. female. Antero-posterior diameter1 .... Transverse diameter..... Oblique diameter...... Circumference....... Antero-posterior diameter Transverse diameter Depth at the pubic symphysis Depth posteriorly Depth at the sides Circumference . 4 inches. 4^ inches 4f " 54 <• 44- •' 4| •• 15 164 •• 4^ inches. 44 inches 4 44 « If •' H " H " 5 4 34 •< 134 " 151 » inferior strait. Antero-posterior diameter; from the mobility of the coccyx capable of being extended an additional inch.........3£ inches. 4| inches. Transverse diameter.......31 « 41 « At the approach of the end of pregnancy, the symphyses of the pelvis undergo a slight degree of relaxation, which facilitates child-birth. Conjugate diameter. THE SKELETON. 129 THE UPPER EXTREMITIES. The Upper extremities are suspended from the thorax at the sides of the skeleton, with which they articulate only by the inner end of the clav- icle, so that when this bone is absent, as in many quadrupeds, the fore legs have no ligamentous union with the other part of the skeleton. Each upper extremity consists of two bones to the shoulder, one to the arm, two to the forearm, and twenty-nine to the wrist and hand. BONES OF THE SHOULDER. The two bones of the shoulder are the clavicle and scapula. By means of the former it is connected with the sternum and first rib, and by means of the latter with the arm bone. THE CLAVICLE. The Clav'icle1 or collar bone is situated in front of the upper part of the thorax, extended transversely between the sternum and the acromion of the scapula. It is cylindroid, with a sigmoid curve; is more curved and robust in the male, and most so in vigorous persons. The ster'nal end2 is thickened, and presents an irregular triangular surface, partly for articu- lation with the sternum, and partly for the attach- ment of ligaments. The acro'mial end3 is com- pressed from above down- r Clavicle of the right side, upper view. 1, sternal end; 2, por- Ward, and has a Small ar- tion which joins the cartilage of the first rib; 3, anterior convexity ticular rSUrfaCe for Union and llne °f attachment of the Sreat pectoral muscle; 4, upper surface of the acromial end; 5, its articular surface; 6, anterior With the acromion. concavity, giving attachment to the deltoid muscle; J, posterior The UDDer Surface Of convexitv> giving attachment to the trapezius muscle; 8, position of origin of the sterno-mastoid muscle. the clavicle is covered only by the skin and subcutaneous fascia. The lower surface is directed toward the first rib and the coracoid process of the scapula, and is marked by the ligamentous attachments with these bones. In the curva- tures of the clavicle, the convexity of its acromial extremity is directed backward ; that of the sternal extremity forward. 1 Clavicula; clavis; furcula; ligula; 2 Extremitas sternalis. osjuguli; jugulum; cleidion. 3 Extremitas acromialis. 130 THE SKELETON. The clavicle is a most important agent in maintaining the position of the upper extremity; removing the shoulder joint a convcnioiit distance from the thorax, thus contributing to the greater range and freedom of movement of the limb. If it is removed or broken, the shoulder is de- pressed, and the head of the arm bone falls against the side of the tho- rax and is much restricted in its movements. In animals which use the fore legs only for support, the clavicle does not exist, as in the ruminants and the horse; its degree of development is intimately related with the freedom of movement of the fore extremi- ties of other animals. Thus it is well developed in squirrels, bats, and birds, and is feebly developed in dogs and cats. THE SCAPULA. The Scap'ula1 or shoulder blade is situated at the upper back part of the thorax, extending from the position of the second to the seventh rib. It is broad, flat, thin, and triangular, and presents two surfaces, three borders, three angles, and three processes. Of the surfaces, the anterior2 forms the shallow subscap'ular fos'sa,3 which is crossed by ridges,4 and gives attachment to the subscapular mus- cle. The posterior surface5 is divided by a projecting plate, the spine, into two unequal parts, of which the upper and smaller is called the su'pra-spi'nous fos'sa,6 and the lower the in'fra-spi'nous fossa;7 both being occupied by like-named muscles. Of the borders, the superior8 is the shortest and thinnest. At its outer part is the cor'acoid notch,9 which is converted by a transverse fibrous band, the cor'acoid lig-ament,10 into the cor'acoid fora'men." The posterior border12 or base is the longest, is irregularly convex in its course, and gives attachment to muscles. The inferior border13 inclines toward the axilla, and is thick and partially grooved. At its upper part is a rough impression produced by the attachment of the long head of the triceps extensor muscle. 1Scapulum; spatula; scaptula; pla- ta; omoplata; pterygium; chelonium; epinotion; os latum huireri; scutum tho- racis; latitudo humeri; blade bone; plate bone; spade bone; shield bone. 2 Venter. 3 Fossa subscapularis. i Costae scapulares. 5 Dorsum; dorsal surface; testudo scapulae. 6 Fossa supra-spinatus. 7 F. infra-spinatus. 8 Costa superior; cervical border. 9 Incisura coracoidea ; i. scapulae ; lu- nula ; supra-scapular notch. 10 Lig. coracoideum. 11 Foramen coracoideum. 12 Vertebral border. 13 Costa inferior; axillary border. THE SKELETON. 131 Of the angles, the superior is thin, and is formed at the conjunction of the upper border and base. The inferior angle is thick, and expanded Fig. 101. Fig. 102. The scapula of the left side, posterior view. 1, supra-spinous fossa; 2, infra-spinous fossa; 3, supe- rior border; 4, coracoid notch; 5, inferior border; 6, glenoid cavity; 7, inferior angle; 8, neck of the scapula; 9, posterior border or base; 10, spine; 11, its triangular commencement, upon which the ten- don of the trapezius muscle moves; 12, acromion; 13, one of the nutritious foramina; 14, coracoid Anterior view of the scapula. 1, ridges cross- ing the subscapular fossa; 2, upper boundary of the latter; 3, superior border; 4, superior angle; 5, co- racoid notch; 6, coracoid process; 7, acromion; 8, spine of the scapula; 9, articular surface for the clavicle; 10, glenoid cavity; 11, elevated bor- der of the same; 12, neck; 13, inferior border; 14, inferior angle; 15, base; 16, position at which the spine commences posteriorly. at its outer part, where it gives origin to the greater terete muscle. The external angle1 is massive, and supports a vertically ovate, shallow, con- cave surface, the gle'noid cavity,2 forming part of the shoulder joint. The cavity has an obtuse prominent border, and is supported by a nar- rowed portion of the bone, named the neck of the scap'ula.3 Of the processes, the spine* is the most conspicuous, consisting of a strong triangular plate springing backward and a little upward from the posterior surface of the scapula and separating the supra- and infra-spi- nous fossae. Its anterior border curves over the neck of the scapula, and is thick and rounded. Its posterior border commences in a triangular expansion at the base of the bone, is thick and strong, and has attached 1 Corpus scapulae. 2 Cavitas, or fossa glenoidea; acetabu- lum humeri; cavitas humeri glenoides; omocotyle; entyposis. 3 Cervix, or collum scapulae. 4 Spina scapulae. 132 THE SKELETON. the trapezius and latissimus muscles. The angle of conjunction of the anterior and posterior borders is prolonged outwardly and expanded into a broad process, the acro'mion,1 which forms the summit of the shoulder and overhangs the joint. From above the glenoid cavity the strong hook-like cor'acoid proc'ess2 curves outwardly toward the front of the shoulder joint. Its end and base are tuberous for the attachment of ligaments, and behind it is the coracoid notch. The scapula is almost completely enveloped in muscles, and it is only the posterior border of its spine and the acromion that can be readily felt beneath the skin, and which become conspicuous in emaciated persons. The processes and borders of the bone are for the most part thick and strong. In the position of the infra- and supra-spinous fossae the bone is usually thin and translucent, and sometimes is even imperfect. At the base of the spine there are usually from one to three large nutritious foramina. BONES OF THE ARM AND FOREARM. A single bone, the humerus, enters into the constitution of the arm.3 It joins the glenoid cavity of the scapula, from which it extends verti- cally, with a slight inclination inward, to join the bones of the forearm.4 These are the radius and ulna, which lie side by side, separated by an interspace, and extend downward to the wrist with a slight inclination outward and forward. THE HUMERUS. The Hu'merus5 or arm bone is long and cylindroid, and presents for special examination its shaft and extremities. The shaft or body is rounded at its upper, and trilateral at its lower part. The posterior surface is smooth, rounded above and flat- tened below, and is occupied its entire extent by the triceps extensor muscle. The anterior surface below inclines on each side to a ridge separating it from the posterior surface, and is occupied by the brachial muscle. Near the middle of the shaft internally, is a slight roughness 1 Acromium; acrocolium; os acromii; humerus, or armus summus ; caput scap- ulae ; mucro humeri; rostrum porcinum. 2 Processus coracoideus; p. uncinatus; p. cornicularis; p. anchoralis; p. rostri- formis; p. ancyroides. 3 Brachium. * Antibrachium. 5 Os brachii; os brachiale; os humeri; os adjutorium; brachium; lacertus; shoulder bone. THE SKELETON. 133 Fig. 103. 1 " A ridges bounding the latter and giv- groove. The greater tuberosity6 is external ing attachment to muscles; 9, posi- to the other, and at its upper part presents «on of insertion of the deltoid mus- cle; 10, principal nutritious fora- three impressions for the attachment Of the men; 11, articular eminence for the supra- and infra-spinous and lesser terete mus- radius; 12, trochlea for the uina; 13, .14, external and internal condyles; cles. The smaller tuberosity7 gives attachment 15,16, condyloid ridges ascending to the subscapular muscle. from the latter; 17' foS9a for the r< coronoid process of the ulna. burgical writers apply the term neck8 to that portion of the bone just below the tuberosities, which, though not anatomically correct, is convenient for practical purposes. The lower extremity of the humerus is expanded laterally, and pre- sents at the sides prominent tuberosities, the con'dyles, from which 1 Tuberositas. 2 Sulcus, or fossa bicipitalis ; sulcus intertubercularis. 3 Bicipital ridges; spina tuberculi ma- joris et minoris. * Caput. 5 Cervix humeri anatomicum. 6 Tuberculum majus. 7 Tuberculum minus. 8 Cervix humeri chirurgicum, 134 THE SKELETON. ascend the con'dyloid ridges. The internal con'dyle1 is more promi- nent than the other, gives attachment to the internal lateral ligament of the elbow joint, and gives origin to the short pronator and most of the flexor muscles on the inner part of the forearm. The external con'- dyle2 gives attachment to the external lateral ligament, and the ridge above it, more prominent than the opposite one, gives origin to the supinator and extensor muscles on the outer and back part of the forearm. Between the condyles is the articular surface for the bones of the fore- arm. The outer portion of this surface is a convex eminence3 adapted to the head of the radius. The inner portion, the trochlea, as expressed by the name, is pulley-like, and articulates with the ulna. Above the •front of the trochlea is a pit4 which accommodates the point of the coro- noid process of the ulna in the flexion of the forearm; and above it posteriorly is a more extensive fossa5, which receives the olecranon in extension of the forearm. The canal for the nutritious artery of the marrow descends at the lower third of the shaft internally. THE ULNA. The TTl'na6 occupies the inner side of the forearm, and is a little longer than the radius. It is prismoid in form, and diminishes toward its lower extremity. Its shaft presents three surfaces separated by prominent borders. The anterior surface is slightly depressed, and gives origin to the deep flexor of the fingers The inner surface above is expanded for the origin of the latter muscle, and below is rounded and subcutaneous. The posterior surface above presents an elongated, shallow depression, which accom- modates the anconeus muscle, and below this a flattened surface for the extensor muscles of the thumb. Of the three borders, the inner two are obtuse, and the outer one is acute and gives attachment to the inter- osseous membrane. The upper extremity, which is the thickest portion of the ulna, term- inates in two robust processes inclosing the articular surface for the 1 Condylus internus; c. flexorius. 5 Fovea supra-trochlearis posterior; 2 Condylus extensus; c. extensorius. greater sigmoid cavity. 3 Eminentia capitata; capitellum ; the 6 Cubitus; focile majus or inferius; little head; rotula. canna major brachii; os cubiti inferius; 4 Fovea supra-trochlearis anterior; cubit; os procubitale; arundo brachii lesser sigmoid cavity. major; olene. THE SKELETON. 135 Fig. 104. humerus. The posterior and larger process, the olec'ranon,1 is on a line with the shaft of the bone. Its upper part is truncated and receives the insertion of the triceps extensor muscle. Its back part presents a tri- lateral surface, which is subcutaneous. The cor'onoid process2 projects from the front of the bone, and is roughened3 at the fore part of its base for the insertion of the brachial muscle. Between the olecranon and coronoid processes is the greater sig'- moid cavity,4 which articulates with the trochlea of the humerus. Its outer side is continuous with the lesser sig'moid cavity,5 a transverse concave surface, which ar- ticulates with the head of the radius. The lower extremity of the ulna is narrow and cylin- droid. It terminates in a rounded head articulating with the radius, and a coni- cal sty'loid process,6 to which is attached the internal lat- eral ligament of the wrist. Between the styloid proc- ess and head is a depression, into which is inserted a fibro- cartilage separating the ra- dio-ulnar from the radio-car- pal articulation. Behind the styloid process is a groove which transmits the tendon of the ulno-carpal extensor. The two bones of tfie ms* fore- arm, viewed in front; the ulna to the right and the radius to the left of the. figure. 1, shaft of the ulna; 2, greater sigmoid cavity; 3, lesser sigmoid cavity articulating with the head of the radius; 4, olecra- non ; 5, coronoid process; 6, nutri- tious foramen; 7, sharp ridges of both bones of the forearm for the attachment of the interosseous membrane; 8, head of the ulna; 9, styloid process; 10, shaft of the radius; 11, head of the same; 12, neck ; 13, tuberosity; 14, rough- ened attachment of the terete pro- nator muscle; 15,carpal extremity of the bone; 16, its styloid process. THE RADIUS. The Ra'dius7 is placed at the outer side of the ulna, and extends a little lower in the forearm. Its shaft is trilateral, with an acute border internally for the attach- 1 Olecranon; o. mobile; olecranum; acrolcnion; ancon; processus anconaeus; p. uncinatus ulnae; glans ulno&; corona ulnae; corona posterior ulnae; addita- mentum necatum, or uncatumulnae; ver- tex cubiti; patella fixa ; rostrum exter- num, or posterius ; top of the cubit. 2 Processus coronoideus. 3 Tuberositas ulnae. 4 Cavitas sigmoidea major; c. lunata major; semilunar fossa: olecranoid cav- ity. 5 Cavitas sigmoidea minor; c. lunata minor. 6 Processus styloideus. 7 Manubrium manus ; focile minus, or superius; additamentum ulnae; canna minor; cercis ; os ad cubitale ; arundo brachii minor; parapechyon. 136 THE SKELETON. ment of the interosseous membrane. The external surface is rounded, and near its middle is impressed by the insertion of the terete pronator muscle. The anterior surface is flattened, expands below, and is slightly grooved at the middle for the origin of the long flexor of the thumb. The posterior surface is rounded above, and is flattened below, where it accommodates the extensor of the thumb. The upper extremity of the bone in front presents a rough eminence, the tuberos'ity,1 into which the biceps muscle is inserted. Above it is the neck,2 and this supports a discoidal head,3 the wide margin of which articulates with the ulna, and the upper concave surface with the humerus. The lower extremity of the radius is its thickest portion. In front, it is broad and depressed, and bounded below by a prominent ridge giving attachment to the capsular ligament of the wrist. Behind, it is irregu- larly convex, and exhibits a narrow groove separating two broad ones, all of which transmit extensor tendons. Its outer side presents another broad groove, which likewise transmits tendons. Below the latter groove is a pyramidal eminence, the styloid process,4 with which the external lateral ligament of the wrist is connected. On the inner side of the lower extremity is a transverse excavation, the semilunar cavity,5 for articulation with the head of the ulna. Below is a large concavity, the carpal articular surface,6 which is divided by a slight ridge into two parts, corresponding with the position of the scaphoid and lunar bones. The canal for the nutritious artery of the marrow, in both bones of the forearm, ascends from the front of their upper third. BONES OF THE HAND. The bones of the hand are situated in the same general plane with those of the forearm, and are subdivided into those of the carpus, of which there are eight; of the metacarpus, of which there are five ; and of the fingers, of which there are sixteen. BONES OF THE CARPUS. The Carpal bones,7 or those of the carpus or wrist,8 eight in number, are arranged in two rows, of which one joins the forearm, the other the metacarpus. Those of the first row, indicated from the outer side of 1 Tuberositas; bicipital tuberosity. 5 Incisura semilunaris. 2 Cervix; collum. 6 Fossa scaphoidea; f. navicularis. 3 Caput. 7 Ossa carpi. 4 Processus styloideus. 8Carpismus; brachiale; raseta. THE SKELETON. 137 Fig. 105. the wrist, are the scaphoid, lunar, cuneiform, and pisiform bones; and those of the second row, in the same direction, are the trapezial, trape- zoid, capitate, and unciform bones. The Scaphoid bone1 is the largest of the first row of the carpus, and is oblique in its position. It is oblong, concavo- convex, with a tubercle on the outer end for the attachment of the annular liga- ment. It articulates with the radius above, the lunar bone within, and the trapezial, trapezoid, and capitate bones below. The Lunar bone2 is the second in size of the first carpal row, and is square and concavo-convex. It articulates with the radius above, the scaphoid bone on.its outer, and the cuneiform bone on its inner side, and the capitate and unciform bones below. The Cu'neiform bone3 is irregularly pyramidal, and articulates with the lunar and unciform bones on its outer side, and the pisiform bone in front. The Pis'iform bone,4 irregularly round- ed, is the smallest of the first carpal row, and articulates alone with the cuneiform bone. The Trape'zial bone5 is the third in size of the second carpal row, and is irregular in form. In front it has a groove, which accommo- dates the tendon of the radio-carpal flexor, bounded by a ridge exter- nally, which gives attachment to the annular ligament. It articulates above with the scaphoid bone, below with the first metacarpal bone, and on the inner side with the trapezoid and second metacarpal bones. The Trap'ezoid bone6 is the smallest of the second carpal row, and is Bones of the carpus, and those with which they articulate; right hand, poste- rior view. Of the upper bones U is the lower end of the ulna, and R is the lower end of the radius; F indicates the posi- tion of a fibro-cartilage which separates the radio-carpal from the radio-ulnar ar- ticulation. Of the bones of the carpus, in the first row, S is the scaphoid, L the lu- nar; C the cuneiform, and P the pisiform bone; and in the second row, T T are the trapezial and trapezoid bones, 7 the capi- tate, and U the unciform bones. Below, are the bases of the metacarpal bones. 1 Os scaphoideum; os scaphoides; os naviculare; os cotyloides; os cymbi- forme; boat-like bone. 2 Os lunatum, or lunare; os semiluna- tum, or semilunare. 3 Os cuneiforme; os triquetrum ; os pyramidale; os cubitale; os triangu- lare. 4 Os pisiforme; os subrotundum ; os orbiculare; os lentiforme; os extra or- dinem carpi. 5 Trapezium; os trapezium, or trape- zoides; os multangulum majus; os rhom- boides. 6 Os trapezoides; os multangulum mi- nus; os trapezium; os pyramidale. 138 THE SKELETON. an irregular truncated pyramid, wedged, with its narrow end forward, be- tween the scaphoid bone above and the second metacarpal bone below, the trapezial bone on its outer side and the capitate bone on its inner side. The Cap'itate bone,1 the largest of the second carpal row, has a promi- nent convex head articulating with the scaphoid, lunar, and unciform bones, and an irregular cubical base joining the trapezoid and unciform bones at the sides, and the intermediate three metacarpal bones below. The Un'ciform bone,2 the second in size of the second carpal row, is irregularly quadrate, and has a broad hook-like process in front for the attachment of the annular ligament. It articulates above with the lunar and cuneiform bones, on its outer side with the capitate bone, and below with the last pair of metacarpal bones. All the carpal bones are composed of spongy substance, with a thin layer of compact substance. Associated, the bones of the garpus form a convexity on the dorsal surface, and a concavity toward the palmar surface. The concavity on the inner side is bounded by the pisiform bone and the hook-like process of the unciform bone; on the outer side by the tuberosity of the scaphoid bone and the ridge of the trapezial bone. Between the two sides a strong fibrous band, the anterior annular ligament, is extended, con- verting the carpal concavity into a canal, through which the flexor ten- dons reach the palm of the hand. The upper border of the carpus, as formed by the scaphoid, lunar, and cuneiform bones, is convex, and forms the lower part of the radio-carpal articulation, with which the pisiform bone has no connection. The lower border of the carpus forms an irregular transverse plane, with which the metacarpus articulates. The capitate and unciform bones together form a convex prominence received into a concavity formed by the scaphoid, lunar, and cuneiform bones, an arrangement of the two rows of carpal bones which contributes to the strength of their articu- lation. BONES OF THE METACARPUS. The Metacar'pal bones,3 or those which compose the metacar'pus,4 correspond in number with the fingers, which they join below. They belong to the class of long bones, and are slightly bent forward. Their shaft is trilateral, convex behind, and sloping off on each side 1 Os capitatum; os magnum. In some animals the smallest bone of the wrist. 2 Os unciforme, or uncinatum; os ha- matum; os cuneiforme. 3 Ossa metacarpi. 4 Metacarpion ; postcarpium; postbra- chiale; torsus manus. THE SKELETON. 139 Fig. 10G. anteriorly. Their upper extremity or base is quadrate, and varies in character with the difference of articulation with the carpus. Their lower extremity forms a spheroidal head,1 with a pit and pair of tuber- cles on each side for ligamentous attachment. The metacarpal bone of the thumb2 is the shortest and most robust. It is also disconnected and divergent from the others. The succeeding bones gradually dimin- ish in size to the last, and lie nearly parallel to one another. They are articulated at their contiguous ex- tremities, and form the least mov- able portion of the hand. The spaces between the meta- carpal bones are called inter- osseous, are numbered from with- out inward, and are occupied by muscles. The left hand, viewed in front, or on the palmar surface. 1, scaphoid bone; 2, semilunar; 3, cunei- form; 4, pisiform; 5, trapezial; 6, groove in the latter; 7, trapezoid; 8, capitate; 9, unciform; 10, the five metacarpal bones; 11, first row of pha- langes of the fingers; 12, second row; 13, last row; 14,15, phalanges of the thumb. Each has three bones, called pha- BONES OF THE FINGERS. The Fingers3 are named, in suc- cession, the thumb,4 the index or forefinger,5 the middle finger,6 the ring finger,7 and the little finger.8 lan'ges,9 or joints, except the thumb, which has two. The middle finger is the longest, the index and ring fingers are next in length and nearly equal. The three bones of the little finger are longer than the two of the thumb, but these are much more robust, and the last phal'- anx of the latter is larger than the corresponding bone of any of the other fingers. 1 Capitulum. 2 Os metacarpi pollicis. 3 Digiti, dactyli. 4 Pollex; alius pollex; digitus primus, or magnus: promanus ; anticheir; ma- nus parva majori adjutrix. 5 Digitus index, secundus, salutaris, or demonstratorius; indicator; demon- strator ; lichanos. 6 Digitus medius, tertius, famosus, in- famis, impudicus, obsccenus, or verpus ; long finger. 7 Digitus annularis, quartos, medicus, or cordis; paramesos ; iatricus. 8 Digitus parvus, minimus, quintus, auricularis, myops, or otites. 9 Phalangial bones; o^sa, nodi, inter- nodia, articuli, condyli, agmina, acies, scutulae, or scytalides digitorum manus. 140 THE SKELETON. The first row of phalan'ges1 are the largest. They have a demi- cylindrical shaft, convex behind and flattened in front, with a ridge on each side for the attachment of the vaginal ligaments. The upper extremity or base is the most expanded portion of these bones, aud supports a concave articular surface for the head of the metacarpal bones, and on each side a tubercle for the attachment of lateral liga- ments. The inferior extremity presents a pulley-like articular surface, or trochlea, for the second phalanges, and a slight fossa on each side for lateral ligaments. The second row of phalan'ges" are constructed like those of the first row, except that their upper extremity supports a double concavity, to correspond with the trochlea of the former. The third row of phalan'ges3 are the shortest. Their base is con- structed like that of the second row, their shaft is compressed conical, and they end in a rough tuberosity for the attachment of the soft tips of the fingers. In front of the head of the metacarpal bone of the thumb are placed, side by side, the two ses'amoid bones.4 They are oval, with a palmar convex surface enveloped in the tendon of the short flexor of the thumb, and with an articular facet moving upon the head of the metacarpal bone. THE HAND. The Hand at rest occupies the same plane as the forearm, but by means of the mobility of the radio-carpal articulation or wrist joint it may be brought nearly to a right angle before and behind, and also may be moved at an obtuse angle outward and inward. The dorsal surface or back of the hand is convex. When the hand is closed as in forming the fist, the heads of the metacarpal bones and extremities of the phalanges become prominent, as the knuckles. The inner or palmar surface is concave, and is rendered more so by the flexion of the fingers. The concavity of the metacarpus is the basis of the palm5 or hollow of the hand. The fingers may all be flexed or bent inward at a right angle to the metacarpus, but cannot be extended or bent backward beyond the line of the latter. They are all capable of convergence and divergence, or of adduction and abduction. The phalanges may be flexed at right 1 Metacarpal phalanges ; procondyli. 4 Ossa sesamoidea. 2 Middle phalanges; mesocondyli. 5 Palma; vola; platea; thenar; pocu- 3 Phalanges unguium; metacondyli. lum; patera; supellex Diogenis. THE SKELETON. \^\ angles with one another, and extended back to their former straight line, but have no other movement. From the mobility of the first metacarpal on the trapezial bone, the thumb is opposable to the other fingers, and enjoys a greater range of movement. The different length of the fingers makes their tips cor- respond with the hollow of the hand when this is closed, and perhaps adapts them better for seizing objects of varied forms; and thus when a spherical body is clasped it will be found that the tips of the fingers are brought to the same plane. DEVELOPMENT OF THE BONES OF THE UPPER EXTREMITIES. The clavicle commences to ossify earlier than any other bone. It is developed from a principal piece, and an epiphysis which appears at the sternal end on the approach of adult age. The scapula commences ossification about the same time as the vert- ebrae. It is formed from a principal piece, and several epiphyses added subsequent to birth. The acromion and coracoid process are each formed from two epiphyses, another is developed at the lower angle, and one along the base of the scapula. The humerus commences to ossify after the clavicle, and before the vertebrae. At birth the shaft is ossified, but the extremities are car- tilaginous. The head and tuberosities are formed from two ossific centres; the condyles and lower articular extremity from four centres. The radius and ulna begin to ossify shortly after the humerus. Their extremities are cartilaginous at birth, and an epiphysis is formed for each. The carpus is cartilaginous at birth, and ossification commences with the capitate bone during the first year. Each bone is developed from a single ossific centre. At birth the shaft of the metacarpal bones and phalanges is ossified. Subsequently the head of the inner four metacarpal bones is formed as an epiphysis ; but in the first metacarpal bone and the phalanges, it is the base which appears as an epiphysis. ARTICULATIONS AND MOVEMENTS OF THE UPPER EXTREMITY. THE STERNO-CLAVICULAR ARTICULATION. The joint formed between the upper angle of the sternum and the end of the clavicle is surrounded by a cap'sular lig'ament, the stronger por- T42 THE SKELETON. tions of which constitute the anterior and posterior ster'no-clavic'- ular lig'aments. The joint is divided into two parts by a biconcave inter-artic'ular fi'bro-car'tilage, Fig. 107. which is attached by its margin to the capsular ligament, the first cos- tal cartilage, and the upper border of the clavicle. The sterno-clavicular articulation is further strengthened by two ac- cessory ligaments: the inter-clav- ic'ular lig'ament,1 a narrow band connecting both clavicles across the upper part of the sternum; and the cos'to-clavic'ular ligament,2 a strong band connecting the first costal cartilage with the under part of the clavicle. Notwithstanding the strong ligamentous union of this joint, which is the only one between the trunk and the upper extremity, it possesses a considerable degree of mobility in every direction. In this motion the entire limb participates, while the sternum is passive. Sterno-clavicular, costo-clavicular, and cos- to-sternal articulations. 1, capsular ligament of the sterno-clavicular articulation; 2, inter-clav- icular ligament; 3, costo-clavicular ligament; 4, inter-articular fibro-cartilage; 5, anterior costo- sternal ligaments. THE SCAPULO-OLAVICULAR ARTICULATION. The joint formed between the acromion and clavicle is surrounded by a cap'sular lig'ament, the stronger portions of which are the superior and inferior aero'mio-clavic'ular lig'aments. It possesses but little mobility, and is further restricted by the cor'aco-clavic'ular ligament,3 which consists of two strong fibrous bands passing between the base of the coracoid process and the under surface of the clavicle. In the movements of the bones*of the shoulder the centre of motion is the sterno-clavicular articulation. The clavicle and scapula from this point move upward and downward, forward and backward. In the movements of the scapula, it glides upward and downward, or forward and outward; or it rotates on its axis, as in the shrugging of the shoul- ders. 1 L. interclavicular. 2 L. costo-claviculare; 1. rhomboides. 3 L. coraco-claviculare ; 1. conoides et trapezoides; 1. scapulae commune con- oides et trapezoides. THE SKELETON. \4g THE SHOULDER JOINT. The Scapulo-humeral articulation or shoulder joint is surrounded by a thin, loose cap'sular lig'ament,1 which is attached above to the margin of the glenoid cavity, and below to the neck of the humerus. Its upper part is much strengthened by a broad band, the cor'aco-hu'- meral lig'ament,2 which extends between the coracoid process and the greater tuberosity of the humerus. The shoulder joint is the most movable one of the body; possessing a wide range of motion in every di- rection. From this circumstance Fl°- 108' it is very liable to dislocation, not- withstanding its many means of protection. The head of the humerus has more than three times as much sur- face as the glenoid cavity upon which it moves. To deepen the cavity, a prismoid, fibro-cartil- aginous band, the gle'noid lig'- ament,3 is attached around its mar- gin. The upper part of this lig- ament gives origin to the tendon of the long head of the biceps flexor muscle, which passes through the shoulder joint to the bicipital groove of the humerus, and acts functionally the part of a ligament. As it passes through the joint it is separated from the cavity by a reflection of the synovial membrane. A strong, triangular, fibrous band, the cor'aco-acromial lig'ament,4 is attached by its apex to the acromion, and by its base to the coracoid process. The two processes thus associated form a wide arch above the shoulder joint, which prevents the dislocation of the humerus in this direc- tion, unless the arch is broken. The deltoid muscle also contributes greatly to the strength and protection of the upper part of the shoulder joint. In front and behind, the latter is closely enveloped by the tendons of the subscapular, supra- and infra-spinous, and lesser terete muscles, as Scapuloclavicular and scapulo-humeral ar- ticulations. 1, acromio-clavicular articulation, surrounded with its capsular ligament; 2, coraco- clavicular ligament; 3, coraco-acromial ligament; 4, coracoid ligament; 5, capsular ligament of the shoulder joint; b, coraco-humeral ligament; 7, ten- don of the biceps flexor muscle. 1 L. capsulare magnum. 2 L. ascititium ; accessory ligament. 8 L. glenoides. i L. coraco-acromiale; 1. triangulare; 1. scapulae proprium anterius. 144 THE SKELETON. they proceed to be inserted into the tuberosities of the humerus. Infe- riorly the joint is in relation with the long head of the triceps extensor muscle. If the muscles surrounding the shoulder joint are detached, on account of the looseness of the capsular ligament, the head of the humerus falls nearly an inch below its usual point of contact with the glenoid cavity. The movements of the shoulder joint are forward, backward, outward, upward, and downward, and those of circumduction and rotation. THE ELBOW JOINT. The Elbow joint is formed between the humerus and both bones of the forearm, is lined with a single synovial membrane, and is inclosed by a capsular ligament strengthened with lateral ligaments. Fig. 110. The elbow joint, Sgbt side, viewed antero-inter- TnE -fctitE elbow joint, viewed externally. 1, nally. 1, the capsular ligament in front; 2, inter- posterior surface of the humerus; 2, ulna; 3, ra- nal lateral ligament; 3, annular ligament; 4,round dius; 4, external lateral ligament; 5, 6, annular ligament; 5, interosseous membrane; (Maternal ligament; 7, 8, capsular ligament; 9, interosseous condyle. 1*^ membrane. The cap'sular lig'ament,1 thin and loose, is attached above the articu- lar surface of the humerus, including the pits for the accommodation of the olecranon and coronoid process; and is attached below to the margin of the sigmoid cavities of the ulna and to the annular ligament. Its back portion is much weaker than its fore part. Fig. 109. 1 Membrana capsularis cubiti. THE SKELETON. 145 The internal lateral ligament1 is a strong band radiating from the internal condyle of the humerus to the inner margin of the greater sig- moid cavity of the ulna, between the olecranon and coronoid process. The external lateral ligament2 is a narrow band extended between the external condyle and the annular ligament surrounding the head of the radius. The ordinary movements of the bones of the forearm upon the humerus are those of flexion and extension. The motions of the ulna are restricted to these alone, but the radius has in addition a rotary movement occur- ring upon the ulna and humerus together. THE SUPERIOR RADIO-ULNAR ARTICULATION. The superior radio-ulnar articulation forms part of the elbow joint, one synovial membrane and capsular ligament being common to both. The head of the radius and the lesser sigmoid cavity of the ulna form this articulation, the former being surrounded by a strong fibrous band, the an'nular ligament,3 the extremities of which are attached to the ulna before and behind the latter cavity. THE MIDDLE RADIO-ULNAR ARTICULATION. The lower four-fifths of the interval of the radius and ulna are occu- pied by the interos'seous membrane,4 which is thin but strong, and is composed of oblique fibres descending from the sharp edge of the radius to the opposed edge of the ulna. It is perforated by blood-vessels, and serves to give origin to some of the muscles of the forearm, as well as to connect the bones. At the upper part of the interosseous space an oblique band, the round ligament,5 descends from the coronoid process of the ulna to the radius below its tuberosity. THE INFERIOR RADIO-ULNAR ARTICULATION. The inferior radio-ulnar articulation is separated from the wrist joint by a triangular, interarticular fibro-cartilage, the base of which is attached to the lower margin of the semilunar cavity of the radius, and the apex to the pit between the styloid process and head of the ulna. This ar- ticulation is surrounded by a loose capsular ligament6 connected with the articular margins of the radius, ulna, and fibro-cartilage. 1 L. laterale internum; 1. brachio-cu- * L. interosseum;membranainterossea. bitale ; 1. radiatum ; 1. triangulare. 5L. teres; 1. obliquum ; chorda trans- 2 L. laterale externum ; 1. brachio-ra- versalis. diale. 6 Membrana capsularis sacciformis. 3 L. annulare; 1. orbiculare. 10 14'3 THE SKELETON The radius rotates inwardly upon the ulna and becomes obliquely crossed in front of it. The hand follows the motion of the radius, in the pendant condition of the upper extremity the palm becoming directed backward; and this constitutes the movement of pronation. The reverse motion, by which the radius assumes a position parallel to the outer side of the ulna, and the palm of the hand is directed forward, is called that of supination. In these movements of the radius, its head rotates upon the humerus and the lesser sigmoid cavity of the ulna within the annular ligament, and its lower extremity rotates upon the head of the ulna. THE WRIST JOINT, OR RADIO-CARPAL ARTICULATION. Fig. 111. The Wrist joint is formed above by the radius and triangular fibro- cartilage connecting it Ligaments of the wrist and . hand, anterior view. i, lower wltn the ulna; and below part of the interosseous mem- by the Scaphoid, lunar, brane; 2, lower radio-ulnar ar- - .„ . ticuiation inclosed by a capsu- and cuneiform bones. It lar ligament; 3, fore part of the iS inclosed by a loose radio-carpal joint inclosed by » , ,. » ., a capsular ligament; 4, exter- Cap'sular lig'ament1 COn- nal lateral ligament of the nected with the COntigU- wrist; 5, internal lateral liga- . n ,, ' ' , .. , ous margins of the ar- ment; 6, palmar portion of ° the capsular ligament of the ticular Surfaces. It is carpus; 7, pisiform bone with , , i -, •■ .. , .. ^ „ , strengthened by a strong, its capsular ligament; 8, pal- ° » °' mar portion of the capsular rounded, internal lateral ligament connecting the car- ligamellt,2 Connecting the pus with the base of the meta- a ° carpus; 9, capsular ligament Styloid process of the ulna with the cuneiform bone and a strong ex- ternal lateral ligament,3 of the trapezial and metacar- pal bone of the thumb; 10, pal- mar or anterior ligament of the metacarpo-phalangial ar- ticulation of the thumb; 11, f external lateral ligament of extended between the sty- L Wi£ the same joint; 12, palmar or l0i(J procesg 0ft]ie ra(Jius ^^ Vfl anterior ligament of the cor- . . , . responding joint of the index anC* the SCaphOld DOne. finger,represented as removed A Single Synovial mem- in the other fingers; 13,lateral ligaments of the same articulation; i ,. ,, vnMn nor 14, transverse ligaments connecting the heads of the contiguous ulclue llue» lIle Iciuiu-Ldi- metacarpal bones; 15,16, palmar or anterior ligaments and lateral pal articulation, and nei- ligaments of the phalangial articulations. ther communicates with the radio-ulnar articulation nor extends between that of the carpal bones. 1 Anterior and posterior radio-carpal ligaments; 1. accessorium rectum et ob- liquum et rhomboideum ; membrana ar- ticuli cubiti et carpi capsularis. 2 L. laterale internum; 1. laterale ul- nare; funiculus ligamentosus. 3 L. laterale externum; 1. laterale ra- diale. THE SKELETON. 147 The movements of the Wrist joint are flexion and extension, abduc- tion and adduction, and circumduction. The turning of the hand de- pends on the rotation of the radius. THE INTERCARPAL AND CARPO-METACARPAL ARTICU- LATIONS. The pisiform bone forms a distinct joint with the cuneiform bone, sur- rounded by a strong capsular ligament lined with synovial membrane. The scaphoid, lunar, and cuneiform bones of the first row of the carpus are connected at their upper part by intervening interosseous liga- ments. In the same manner the trapezoid, capitate, and unciform bones of the second row are connected at their middle, and this is likewise the case with the bases of the inner four metacarpal bones. All the carpal bones except the pisiform bone, and the bases of all the metacarpals, except that of the thumb, are connected with one another by short fibrous bands constituting the pal'mar and dor'sal ligaments. The association of these ligaments forms^ a sort of capsular ligament investing the carpus and base of the metacarpus. A single synovial membrane lines the intercarpal and carpo-metacarpal articulations. These joints possess but little mobility, except the one between the two rows of carpal bones, which has a hinge-like motion. The metacarpal bone of the thumb forms, with the trapezial bone, a freely movable joint surrounded with a capsular ligament. Each articu- lating surface is convex in one direction and concave in the other, and the two surfaces are applied in a crossing manner, allowing the meta- carpal bone to be moved backward or forward, inward or outward, thus rendering the thumb opposable to the other fingers. The heads of the inner four metacarpal bones are associated in front by thin and rather loose transverse ligaments. THE METACARPO-PHALANGIAL, AND PHALANGIAL ARTICU- LATIONS. The metacarpo-phalangial, and phalangial articulations, are con- nected by strong lateral ligaments, which descend from the sides of the bones above, obliquely forward to the sides of the bones below. The fore part of these articulations is protected by a thick, fibro-cartilaginous palmar ligament,1 extended between the position of the lateral liga- ments. It is firmly attached to the margin of the bone below the joint, and but slightly to that above; and it is grooved on its palmar aspect Anterior ligament. 148 THE SKELETON. for the passage of the flexor tendons. The back part of these articula- tions is covered by the expanded extensor tendons, which act in this po- sition as ligaments. The spheroidal head of the metacarpal bones, and the single concavity of the bases of the first row of phalanges, permit the movements of flexion and extension, abduction and adduction. The phalangial articulations or finger joints possess only the move- ments of flexion and extension. THE LOWER EXTREMITY. The lower extremity extends from below the pelvis, with which it articulates by means of the head of the thigh bone. Each consists of a single bone to the thigh, one to the knee, two to the leg, and twenty- eight to the foot. THE FEMUR. The Fe'mur, or thigh bone,1 is the largest and longest bone of the skeleton, and extends from the hip bone downward, with an inward inclination, to the tibia. The shaft is cylindrical, with a prominent crest behind, called the as'per- ous ridge, (linea aspera.) Its front and sides are smooth, and occupied by the quadriceps extensor muscle. The asperous ridge, for the attachment of muscles, is acute at the middle, and is rough only at its upper part, which diverges in two divisions to the trochanters. Its lower part is less well developed, and diverges in two divisions to the condyles, in- closing a triangular surface forming the basis of the popliteal space. The upper extremity of the shaft terminates in two processes, called trochanters.2 The greater trochan'ter is situated at the highest part of the shaft externally. It is convex and rugged on its outer surface, and presents an oblique ridge for the attachment of the middle gluteal muscle. Its inner surface, less extensive, exhibits a pit, the trochanter'ic fos'sa,3 into which the small rotary muscles of the thigh are inserted. The smaller trochan'ter4 is a rounded eminence situated at the posterior and inner side of the bone, and gives attachment to the tendon of the psoas and iliac muscles. In front and behind, the trochanters are conjoined by the intertro- chanter'ic ridges, of which the posterior is much the most prominent, 1 Os femoris ; merium. s Fossa trochanterica. 2 Trochanteres; rotatores. * Line* trochantericae. THE SKELETON. 149 The anterior Fig. 112. and gives attachment to the quadrate femoral muscle ridge is feebly developed, but is longer than the other. From the trochanters and their associating ridges the neck of the femur1 projects upward and inward at an obtuse angle from the shaft. It is cylindrical, compressed from before back- ward, and joins the latter by a strong, expanded base. It supports a spherical head,2 which is covered with cartilage, and articulates with the acetabulum. On the inner side of the head is a pit for the attachment of the round ligament of the hip joint. The lower extremity of the femur is the most expanded and massive portion of the bone. It terminates in two large eminences, the con'dyles, which are separated behind by a deep notch, the intercon'dyloid fos'sa.3 The articular surfaces of the condyles are continu- ous in front by a pulley-like surface, the trochlea, upon which the knee-cap moves. The internal con'dyle is the larger, but the external con'dyle projects most anteriorly. On the remote sides of the condyles is a tuberos'- ity4 for the attachment of the lateral ligaments of the knee joint. Below the external tuberos- ity is a crescentic fossa, which gives origin to the tendon of the popliteal muscle. When the femur is placed vertically, the in- ternal condyle appears much longer than the external, and the summit of the greater tro- chanter rises nearly as high as the head of the bone. The natural position of the latter is oblique, so that the lower extremities of both thigh bones are brought nearly into contact, and the upper extremities are the most remote from each other. In this position the articulating surfaces of the condyles are on a level, and the summit of the greater trochanter is on the same line with the centre of the head. In the female the neck of the femur is longer and more rectangular Femur op the right side, front view. 1, the shaft; 2, head; 3, neck; 4, great trochanter; 5, ante- rior inter-trochanteric ridge; 6, less- er trochanter; 7, external, and 8, internal condyles; 9, tuberosity for the external lateral ligament; 10, groove for the popliteal tendon; 11, tuberosity for the internal lat- eral ligament. 1 Cervix, or collum femoris. s Fossa intercondyloidea ; f. poplitea. 2 Caput femoris. i Tuberositas condyli. 150 THE SKELETON. Fig. 113. in its relation with the shaft than in the male, so that the thigh bones in the former sex are more oblique or more divergent above. One or two canals, for the principal medullary nutritious vessels, ascend at the inner side of the asperous ridge, in the vicinity of its middle. THE PATELLA. The Patel'la, or knee-cap,1 viewed by some anatomists as the repre- sentative of the olecranon, by others as a sesa- moid bone of the tendon of the quadriceps ex- tensor muscle, is situated in front of the knee joint. It is a chestnut-shaped bone, with its apex downward and attached by a strong lig- ament to the tibia. Its base is thick, and has inserted into it the tendon of the quadriceps extensor. Its fore part is convex and rough; and its back part presents a transversely oval articular surface, elevated from each side into a median ridge so as to correspond with the trochlea of the femur, upon which it moves. The patella is composed of a mass of spongy substance enveloped in a thin layer of compact substance. Patella of the right side, pos- terior view. 1, 2, articular faces for the trochlea of the femur; 3, apex of the bone roughened for the attachment of its ligament. THE BONES OF THE LEG. The bones of the leg consist of the tibia and fibula, placed side by side. The tibia joins the femur above, and, together with the fibula, joins the astragalus below. The former alone receives the pressure of the upper part of the body, and transmits it to the foot; while the latter appears mainly of importance in extending the surface of the leg for muscular attachment. THE TIBIA. The Tib'ia, or shin bone,2 situated at the fore and inner part of the leg> extends in a straight line from the thigh bone to the tarsus, and is the second largest and longest bone of the skeleton. Its shaft is a trilateral prismatic column, with sharp borders, and is most expanded toward the upper extremity. The inner surface, smooth and slightly rounded, is iRotula; epigonis; caucaloides; su- pergenualis; acromyle: mylacris; myle; mola; gamba; concha; oculus; orbis, orscutumgenu; osscutiforme,disciforme, thyroides, or sesamoideum magnum; olecranon mobile. 2 Cneme ; procnemium ; focile majus; arundo, or canna major; canna domes- tica cruris. THE SKELETON. 151 subcutaneous. The outer surface, occupied by muscles, is slightly grooved above, and is rounded below, where it inclines forward. The posterior surface is flat and covered with muscles, and at the upper part is marked by a feeble, oblique ridge, indicating the lower border of attachment of the popliteal muscle. The anterior border, called the crest or shin,1 is waving in its course, and acute at the middle. The outer border gives attachment to the interosseous membrane; the pos- terior border, less sharp than the others, gives attachment to muscles. The superior extremity expands into the head, which is the most massive portion of the bone, and appears as if it were pressed backward, so that its front is Fl<>. 114. flattened and it overhangs the posterior sur- face of the shaft. Its prominent lateral por- tions constitute the con'dyles,2 which have thick porous borders, and support a pair of smooth, oval surfaces,3 invested with cartilage, for articulation with the condyles of the femur. The inner articular surface is the longer antero- posteriorly, and is slightly concave in this direction ; while the other is slightly convex. Both are elevated at the middle of their ap- proximate border upon a small pyramidal emi- nence, the spi'nous proc'ess,4 the base of which is the centre of attachment for the semilunar cartilages and crucial ligaments. The articular surfaces are separated by a rough, depressed tract, which crosses the spinous process and expands on the fore and back part of the head. Below the back part of the external condyle is a small, smooth surface, covered with cartilage, for articulation with the head of the fibula. Below the head, in front, at the commence- ment of the crest, is a conspicuous eminence, the tuberos'ity,5 into which the ligament of the patella is inserted. The lower extremity of the tibia is ex- panded, and at its termination is quadrate. In front it is smooth and convex, and bounded below by a prominent mar- TlBIA AND FIBULA OF THE LEFT leg. 1, shaft of the tibia; 2, 3, con- dyles ; 4, spinous process; 5, tuber- osity ; 6, crest or shin; 7, lower ex- tremity of the bone; 8, internal malleolus; 9, shaft of the fibula; 10, its head; 11, external malleo- lus. 1 Crista; spina. 2 Condyli; tuberosities. 3 Condyli. 4 Acclivitas, or eminentia condyloidea. or intercondyloidea; spine. 5 Tuberositas tibiae; tuberculum; tu- bercle. 152 THE SKELETON. gin for the attachment of the capsular ligament of the ankle joint. Behind, it slopes to an obtuse border, for the same purpose as the latter, and its outer side is excavated and roughened for ligamentous attach- ment with the fibula. Its inner part is prolonged into a strong promi- nence, the internal malle'olus or ankle.1 The inner surface of this process is convex and subcutaneous; and behind, is marked with a groove for the tendon of the posterior tibial muscle. At the bottom of the tibia is the tar'sal articular surface, a quadri- lateral concavity, which at its inner side is prolonged downward on the malleolus. It is covered with cartilage, and joins the upper and inner side of the astragalus. The canal of the medullary nutritious vessels is situated at the upper third of the posterior surface of the shaft, and is directed downward. Fig. THE FIBULA. The Fib'ula2 is a long, slender bone, situated at the outer side of the tibia. Its upper extremity articulates beneath the back part of the head of the latter; but, in descending, the bone gradually advances in position, so that its lower extremity is nearly as far forward as the internal mal- leolus, and extends rather lower than this. The shaft presents three irregular surfaces separated by prominent borders. The inner surface is divided by an oblique ridge, to which the interosseous membrane is attached. The outer surface is grooved above the middle; at its upper part inclines forward, and at its lower part inclines backward. The posterior surface is con- vex ; its upper part inclining outward, its lower part in- ward. The upper extremity ex- pands into the head,3 which is prominent at the sides for the attachment of ligaments and the tendon of the biceps flexor; and supports at its inner part a small smooth surface for articulation with the external condyle of the tibia. Tibia and fibula of the right leg, posterior view. 1, 2, articu- lar surfaces for the condyles of the femur separated by the spinous pro- cess; 3, the inner condyle of the tibia; 4, surface occupied by the popliteal muscle defined by the ob- lique line 5; 6, nutritious foramen; 7, surface covered by the flexors of the toes; 8, internal malleolus; 9, grooves for tendons; 10, shaft of the fibula; 11, its head; 12, subcuta- neous surface at the lower part of the bone; 13, external malleolus; 14. groove for tendons, 1 Inner ankle bone. 2 Os perone; peroneum; canna, or arundo minor; sura; fistula cruris; cru- ris radius; focile minus; tibia minima; spell, or splinter bone. 3 Capitulum. THE SKELETON. 153 The lower extremity, rather larger than the other, is prolonged, below its junction with the tibia, into the external malle'olus or ankle.1 This is longer and more prominent than the internal one, and supports a smooth, triangular, articular facet, which joins the outer side of the astragalus and forms part of the ankle joint. Behind the articular sur- face is a fossa for the attachment of the external lateral ligament of the ankle joint, and above it is a convexity, which is conjoined with the tibia by means of a ligament. The fore part of the malleolus is convex and subcutaneous; and its back part is marked by a groove for the tendons of the peroneal muscles. The canal for the medullary nutritious vessels is situated near the middle of the posterior surface of the shaft, and, like that of the tibia, is directed downward. BONES OF THE FOOT. The bones of the foot are situated at a right angle with those of the leg, and are subdivided into those of the tarsus, of which there are seven; those of the metatarsus, of which there are five; and those of the toes, of which there are sixteen. BONES OF THE TARSUS. The Tarsal bones,2 or those composing the tarsus, seven in number, consist of the astragalus and calcaneum, the scaphoid, cuboid, and three cuneiform bones. The Astragalus,3 or ankle bone, is the only one of the tarsus which articulates with those of the leg; and is the highest and second in size of the former. Its posterior part, or body, is quadrate, and is received between the two malleoli. Its upper articular surface, for the tibia, is antero-posteriorly convex, transversely slightly concave, and is continu- ous at the sides with vertical articular surfaces for the malleoli. Be- neath the body, at its back and outer part, is a concave articular sur- face, which rests on the calcaneum. In advance of the body is the neck terminating in the head, which supports an anterior, convex, articular surface for the scaphoid bone, and an inferior articular surface for the calcaneum. The latter surface and that beneath the body are separated by a deep groove, corresponding with a similar one of the calcaneum, for an interosseous ligament. 1 Outer ankle bone. 2 Ossa tarsi; planta prima; rasceta pe- dis; pedium; caviculae pedis nodus. 3 Talus ; quatrio ; diabebos; cavicula ; cavilla ; tetroros ; astrion ; os balistse ; os tesserae ; sling bone; huckle bone. 154 THE SKELETON. Fig. 116. The Calcan'eum, or heel bone,1 is the largest one of the tarsus. It is placed beneath the astragalus, extends nearly as far forward, and posteriorly extends far beyond, where it forms the basis of the heel. It is irregularly oblong quadrate. At its upper part in front is a large, irregular fossa, containing two articular surfaces, for the as- tragalus, separated by a rough tract.2 The larger articular surface is convex, and situated at the back of the fossa; the other is narrow and concave, and rests on a lateral process3 internally. In advance of the fossa is a ver- tical articular surface for junction with the cuboid bone. Posteriorly, the calcaneum terminates in a large, convex tuberosity,4 the lower part of which gives attachment to the "tendon of Achilles." The upper surface of the tuberosity is saddle like, and cor- responds with the depression above each side of the heel. The bottom of the tuberosity dorsal surface of the right foot. .g subdivided into two tubercles,5 which give 1, body of the astragalus; 2, its / ° head; 3, calcaneum; 4, scaphoid attachment to the plantar fascia and mus- bone; 5, 6, 7, internal, middle, and c]eg jn a(Jvance 0f the tubercles, the Under external cuneiform bones; 8, cuboid bone; 9, metatarsal bones; io, n, surface of the bone forms an obtuse ridge. phalanges of the great toe; 12,13, rj^g outer surface of the calcaneum is vertical 14, phalanges of the other toes. and rough. Its inner surface forms, with the lateral process, a concavity,6 which transmits the tendons of the flexor muscles and the plantar vessels and nerves. The Scaph'oid bone,7 situated at the inner side of the tarsus, is ovoid in outline, with a posterior concave articular surface for the head of the astragalus, and an anterior convex surface, divided into three facets, for junction with the cuneiform bones. Its upper and lower borders are rough; and its inner part forms a tuberosity for the insertion of the posterior tibial muscle. The Cu'boid bone8 is situated at the anterior outer part of the tarsus, 1 Os calcis; calcaneus ; calcar pedis; calcia; ichnis; pternium. 2 Sulcus calcanei. 3 Processus lateralis; sustentaculum tali; small apophysis. 4 Tuberositas calcanei; talus ; calx ; heel. 5 Greater and lesser tuberosity. 6 Sinuosity. 7 Os scaphoides ; os scaphoideum ; os naviculare; os cymbiforme; boat-like bone. 8 Os cuboides; os cubiforme; os cu- boideum ; os cyboides ; os cyrtoides; os grandinosum ; os tesserae; os varium. THE SKELETON. 155 and is the third in size of the tarsal bones. Its upper surface inclines outwardly, and is rough. Its under surface, also rough, presents a tu- berosity for the attachment of the calcaned-cuboid lig'ament. and, in advance of this, a groove for the transmission of the tendon of the long peroneal muscle. Posteriorly it has a vertical articular facet for the calcaneum; and anteriorly, another, which is subdivided to join the outer two metatarsal bones. Its inner surface is rough, and near the middle has a small articular facet for the raternal cuneiform bone. The three Cu'neiform bones1 are situated in a row in front of the sca- phoid bone, with which they articulate. As expressed by the name, they are wedge shaped. The internal cuneiform bone2 is the largest, and has its base downward; the middle cuneiform bone3 is the smallest, and it, with the external cuneiform bone,4 have their base upward. The three bones together contribute to the dorsal convexity of the tarsus, and to its plantar concavity. Anteriorly they articulate with the inner three metatarsal bones, and the external one also articu- lates with the cuboid bone. All the tarsal bones are composed of masses of spongy substance with a com- paratively thin investment of compact substance, which presents many perfora- tions for the transmission of vessels. The tarsus forms one-half of the length of the foot, and is connected near its middle with the leg. Behind the bones of the latter, a small portion of the astragalus and about one-half the length of the calcaneum project, and in front of them project the head of the astragalus, a small portion of the calca- neum, and the five smaller tarsal bones. The portion of the tarsus in front of the ankle joint, or the instep,5 is convex on its dorsal surface and concave on its plantar surface. On the Sole of the left foot. 1, concavity of the calcaneum; 2, outer face of the same; 3, groove for the tendon of the long flexor of the toes; 4, head of the astragalus; 5, scaphoid bone; 6, its tuberosity; 7,8,9, internal, middle, and external cuneiform bones; 10, cuboid bone; 11, its groove for the tendon of the long peroneal muscle; 12, metatarsal bones; 13, first row of pha- langes; 14, second row; 15, last row; 16, last phalanx of the great toe. 1 Ossa cuneiformia; ossa, or ossicula chalcoidea. 2 Os cuneiforme internum, primum, or magnum. 3 Os cuneiforme medium, secundum, or minus. i Os cuneiforme externum, or tertium. 5 Collum pedis; neck of the foot. 156 THE SKELETON. outer part of the tarsus, between the astragiilus and calcaneum, is a large space or sinus,1 which narrows into a canal, proceeding obliquely inward and backward to the inner side of the tarsus. Both sinus and canal are occupied by interosseous ligaments connecting the astragalus and cal- caneum. Back of the astragalus a groove is observable, leading toward another beneath the lateral process of the calcaneum, both of which accommodate the tendon of the long flexor of the great toe. The articulation of the astragalus and calcaneum with the other bones of the tarsus is so nearly in a direct line, that it affords a convenient position for disarticulation, when necessary, from injuries of the foot. BONES OF THE METATARSUS. The Metatarsal bones,2 or those composing the metatar'sus,3 corre- spond in number with the toes, which they join in front. They are enumerated from within outward, have the same general construction as the metacarpal bones, and are slightly bent in their length so as to con- tribute to the concavity of the sole of the foot. The shaft is trilateral; one surface presenting downward, another out- ward, and the third inward and upward. The shaft of the outer four bones gradually narrows to its head; that of the great toe is more uni- form in diameter. The posterior extremity, or base, is the most expanded part, is quad- rate, and varies in form with the different bones. The base of the first, at its lower part, has a tubercle for the insertion of the long peroneal tendon; the bases of the succeeding three are wedge shaped, and by their lateral adaptation contribute to the convexity of the back and the concavity of the sole of the foot. The base of the last metatarsal is prolonged outward and backward into a tuberosity for the insertion of the short peroneal tendon. The bases of the outer four metatarsals ar- ticulate with one another by opposed smooth surfaces: those of the inner three metatarsals articulate with the cuneiform bones; and those of the outer two with the cuboid bone. The anterior extremity, or head, is constructed like the correspond- ing part of the metacarpal bones, but is smaller, in proportion with the length of the bones, except in the case of that of the great toe. The first metatarsal bone is the shortest, but is twice as robust as the others ; the second and fifth metatarsals are the longest, and are nearly equal; the third and fourth are next in length, and are also nearly equal. All the metatarsals lie parallel to one another, and they contribute in 1 Sinustarsi. 2 Ossa metatarsi. 3 Metatarsium; metapedium; praecordium, solum, or vestigium pedis. THE SKELETON. I57 their union to the convexity of the back and the concavity of the sole of the foot. The interosseous spaces are enumerated from within out- ward. BONES OF THE TOES. The Toes1 are enumerated from within outward, as the first or great toe,2 the second, third, fourth, and fifth or little toe. They diminish in length from first to last, and possess the same number of bones as the fingers. The phalan'ges,3 or joints, of the toes have the same general form as those of the fingers, but are smaller, except those of the great toe, which are as long and of more robust proportions than those of the thumb. In the first row of phalanges, except in the great toe, the shaft resem- bles that of the corresponding bones of the fingers, but compressed later- ally so as to assume a more cylindroid form. In the second and third rows of phalanges of the outer two or three toes, the characteristic extremities are so nearly approached that the shaft is more or less obsolete. The second and third phalanges of the little toe are frequently co-ossified. The two ses'amoid bones of the great toe are like those of the thumb, and occupy a corresponding position in the sole of the foot. THE FOOT. The Foot is placed at a right angle with the leg, and rests upon the ground with the tuberosity of the calcaneum, the heads of the metatarsal bones, and the under parts of the phalanges. The heel pro- jects behind the leg at the outer part of the foot, of which it is the nar- rowest portion. From the fore part of the tarsus, or the instep, the foot in advance gradually expands in breadth and becomes thinner. The upper or dorsal surface, or back of the foot, is convex in its length and breadth ; and the under or plantar surface, or sole, in the same direction is concave. The arch formed by the foot is higher and more open on the inner side. When covered with soft parts, the heel, outer border of the foot, and the under part of the toes touch the ground ; the inner archway constituting the hollow of the foot. The feet of the two sides diverge from each other in front, in consequence of the rotary muscles of the thigh directing the limbs outwardly. The hinge-like joint of the ankle 1 Digiti pedis. 2 Pollex pedis ; hallux, or hallus. 3 Ossa, articuli, or internodia digitorum pedis. 158 THE SKELETON. allows flexion and extension of the foot. In the former movement the foot is bent forward; in the latter the back of the foot approaches the same line as the front of the leg. The movement of the foot directing its sole inward and in a feebler degree outward, occurs between the astra- galus and the tarsal bones with which it articulates. The bones of the tarsus and metatarsus together exhibit but very little movement among themselves, with the exception just mentioned. The toes present a greater degree of extension upon the metatarsus than the fingers on the metacarpus, but their power of flexion is much more limited, and that of abduction and adduction are feeble. The phalanges of the toes have the same movements among themselves as those of the fingers, but are restricted from their comparatively feeble development. A continuance of extension of the toes flexes the foot; the reverse action of the toes extends the foot. When the toes are covered with their soft parts, the second appears a little longer than the first, a feature which has not escaped the attention of artists, but the great toe of the skeleton is actually the longer. DEVELOPMENT OF THE BONES OF THE LOADER EXTREMITY. The femur begins to ossify about the middle of the second month of embryonic life, being earlier than the vertebral column. At birth its shaft is formed, and an ossific centre has appeared in the lower extremity as an epiphysis. Subsequently the head, the greater and the smaller trochanter successively ossify as epiphyses. The patella is formed from a single centre of ossification, appearing several years after birth. The shaft of the tibia commences ossification about the same time as that of the femur, and the shaft of the fibula begins the process a little later. In both bones, after birth, the extremities ossify as epiphyses. The astragalus and calcaneum begin to ossify before birth; the other tarsal bones subsequently. An epiphysis is developed upon the tuber- osity of the calcaneum. The metatarsal and phalangial bones are ossi- fied in the same manner as the corresponding bones of the hand. ARTICULATIONS AND MOVEMENTS OF THE LOWER EXTREMITIES. The support of the trunk of the body requires that the articulations of the lower extremities should be more extensive, and stronger than those of the upper extremities, a condition which has been gained at the expense of comparative freedom in movement. The hip bones, THE SKELETON. 159 described as part of the trunk, but which correspond with the bones of the shoulder, are entirely immovable. THE HIP JOINT. The Hip joint,1 formed between the acetabulum and the head of the thigh bone, is the strongest articulation of the body, and the best instance of a ball-and-socket joint. Though admitting of movement in every direction, it is nevertheless much restricted in this respect in comparison with the shoulder joint. The acetabulum is deepened by a prismatic fibro-cartilaginous ring, the cot'yloid lig'ament,2 at- tached around its margin. FlG- 118- As the ligament passes over the cotyloid notch, this is converted into a foramen, which transmits articular ves- sels iDto the joint. From the pit on the head of the femur, a strong fibrous cord, the round lig'ament,3 diverges inwardly to be at- tached to the margins of the cotyloid notch. The cap'sular lig'ament4 of the hip joint is the strong- est one of the body. It is attached by its upper extrem- J x A Ligaments of the rap. 1, portion of the posterior sacro- ity around the border Of the iliac ligament; 2, the greater sacro-sciatic ligament; 3, the acetabulum iliclosina* tllP CO- 'e3sersacr°-sciat";l'6alnent; j*> the greater sacro-sciatic fora- . . _ men; 5, the lesser sacro-sciatic ligament; 6, the cotyloid liga- tyloid ligament; and by its ment surrounding the acetabulum; 7, the round ligament; 8, lower extremitv is attached attacnment; of the capsular ligament of the hip joint to the neck of the femur; 9, obturator membrane. to the anterior mter-trochan- teric ridge of the femur, and less strongly to the neck of the latter just above the posterior inter-trochanteric ridge. In front of the joint it is strengthened by a broad fibrous band, the ac'cessory lig'ament,5 which is extended between the anterior inferior spinous process of the ilium and the anterior inter-trochanteric ridge. The capsular ligament is surrounded 1 Coxo- or ilio-femoral articulation. 2 Labrum cartilagineum. 8 Lig. teres; interarticular ligament. 4 Membrana capsularis femoris. 5 Superior ligament; ilio-femoral liga- ment. 160 THE SKELETON. with large muscles, which contribute to the strength of the joint. Intern- ally it is°lined with synovial membrane, which also invests the neck of the femur, and is reflected upon the round ligament. Even when all the muscles, together with the capsular ligament sur- rounding the hip joint, are cut away, it requires considerable force to remove the head of the femur from its socket, in consequence of the pressure of the atmosphere retaining it in position. THE KNEE JOINT. Fig. 119. The Knee joint is the largest and most complex of the articulations. It is hinge like and slightly rotary in its movements. It allows the leg to be almost doubled in flexion on the back of the thigh, but permits its exten- sion only to a straight line with the latter. When the leg is flexed the articulation of the knee permits it to rotate moderately on its axis from side to side, but not when in the extended condition. The condyles of the femur and tibia, with a pair of interposed fibro-cartilages, and the patella, form the basis of the joint; the contiguous surfaces of the bones being invested with cartilage. It is enveloped in a thin capsular ligament lined with an extensive synovial mem- brane, and is strengthened by strong cord- like ligaments and the contiguous ten- dons of muscles. Upon the condyles of the tibia rest the semilu'nar fi'bro-cartilages,1 a pair of prismoid, C-like plates, with their ex- tremities attached in front and back of the spinous process.2 Their exterior border is thick, and they slope off to a thin interior edge, by which arrangement they deepen the shallow ar- ticular surfaces of the tibia into suitable concavities for the play of the The right knee joint, laid open from the front. 1, articular surface of the fe- mur; 2, 3, crucial ligaments; 4, inser- tion of one of these ligaments into the tibia; 5, attachment of the alar folds of the synovial membrane to the femur; 6, 7, internal and external semilunar fibro- cartilages; 8, ligament of the patella turned down, so as to exhibit the syno- vial bursa (9) beneath; 10, superior ti- bio-fibular articulation; 11, interosseous membrane. 1 Fibro-cartilagines, or cartilagines semilunares, interarticulares, falcatae, lunatse, meniscoideae, or sigmoideae. 2 The attachments of these fibro-carti- lages constitute the ligamenta cartilagi- num semilunatarum. A connection of the two in front, the lig. transversum. THE SKELETON. 161 condyles of the femur. The inner fibro-cartilage is adherent by its cir- cumference to the capsular and lateral ligaments; the outer one is not so much adherent, and therefore glides more freely to and fro with the move- ments of the femur. Besides adapting the condyles of the tibia to those of the femur, the semilunar fibro-cartilages protect the condyles from attrition, act as elastic cushions to reduce the force of concussions, and prevent the atmosphere from pressing the capsular ligament between the bones. From the sides of the intercondyloid fossa of the femur a pair of strong, fibrous cords, the cru'cial lig'a- ments,1 cross each other and descend to be attached in front and behind the spinous process of the tibia. These ligaments re- strict the flexion and extension of the leg, and give firmness to the joint, especially when the limb is flexed. The cap'sular lig'ament2 is a thin, capa- cious envelope, attached to the rough borders of the condyles of the femur and tibia, and the sides of the patella, and associated with the tendons of the various muscles attached in the vicinity of the articulation. It is so thin as to appear to be a mere continuation of the periosteum of the contiguous bones strengthened at particular points with pro- cesses from neighboring tendons. A pro- cess3 of this kind, at the back of the joint, is derived from the tendon of the semi-mem- branous muscle, and is extended between the external condyle of the femur and the internal condyle of the tibia. Above the patella, the tendon of the quadriceps extensor occupies position and function of a strong ligament to the knee joint; below is the lig'ament of the patella,4 a broad, thick, fibrous band, which is an extension of the tendon of the muscle just mentioned descending from the apex and front of the patella to the tuberosity of the tibia. Just above its insertion the ligament is separated from the head of the tibia by a synovial bursa, not communicating with the knee joint. 1 L. cruciata. 3 Lig. posticum Winslowii; 1. popli- 2 Membrane capsularis genu. teum; posterior ligament. 4 Lig. patella?. 11 Fig. 120. Front view of the right knee joint. 1, tendon of the quadriceps extensor muscle; 2, patella; 3, liga- ment of the patella, or tendinous in- sertion of the muscle just mentioned; 4, capsular ligament; 5, 6, internal and external lateral ligaments; 7, superior tibio-fibular articulation. 162 THE SKELETON. Fig. 121. The internal lateral ligament1 of the knee joint is a long, broad, and strong band, extended between the tuberosity of the internal condyle of the femur and the upper part of the inner border of the tibia. The external lateral ligament2 is a rounded cord, extended between the tuberosity of the external con- dyle of the femur and the head of the fibula. These ligaments sus- tain the firmness of the articulation, more especially in the extended con- dition of the leg. The synovial membrane of the knee joint lines the capsular liga- ment, and is reflected upon the semilunar fibro-cartilages and cru- cial ligaments. It is also reflected upon a mass of fat intervening be- tween the ligament of the patella and the front of the head of the tibia, and is extended along the sides of the joint as two crescentic appendages named the a'lar folds.3 These unite and are prolonged in a conical, cord-like process,4 ascending obliquely backward, to be attached to the front margin of the intercondyloid fossa of the femur. Above the patella and its trochlea the synovial membrane is reflected as a pouch for several inches upward, between the tendon of the quadriceps extensor and the femur. In the flexion of the leg this pouch is drawn down to the edge of the trochlea of the femur; and in extension is again drawn up by fleshy slips5 of the quadriceps muscle. Behind the joint, the synovial membrane extends upward between the condyles of the femur and the tendinous heads of the origin of the gastrocnemius muscle. Longitudinal section of the left knee joint. 1, femur; 2. tendon of the quadriceps extensor muscle; 3, patella; 4, ligament of the patella; 5, tibia; (i, synovial bursa; 7, cushion of fat occupy- ing the angular interval between the patella and head of the tibia; ****** reflections of the synovial membrane; 8, pouch of this mem- brane extending upward between the tendon of the quadriceps extensor and the front of the femur; 9, the outer alar fold of the synovial membrane; 10, connection of the alar folds with the femur; 11, crucial ligament; 12, back of the capsular liga- ment. 1 L. laterale internum. 2 L. laterale externum. 3 Ligamenta alaria; 1. alare majus in- ternum et minus externum. 4 Mucus ligament; ligamentum mu- cosum. 5 Musculi subcrurales; m. articulares genu. THE SKELETON. 163 THE TIBIO-FIBULAR ARTICULATIONS. Fig. 122. The fibula articulates immovably with the tibia. The superior tib'io-fib'ular articulation,1 between the head of the former and the outer condyle of the lat- ter, has the opposed surfaces covered with cartilage. It is inclosed in a capsular liga- ment, the stronger portions of which consti- tute the anterior and posterior ligaments. The wide interval between the two bones of the leg is occupied by an interosseous membrane,2 composed of parallel fibres de- scending obliquely from the outer border of the tibia to the opposed border of the fibula. The membrane is perforated above for the passage of the anterior tibial vessels. It gradually narrows below, and between the inferior extremities of the bones consists of short, strong fibres3 firmly connecting them together. The inferior tib'io-fib'ular articulation is strengthened by the anterior ligament,4 which is an oblique band extending from the front of the tibia downward to the ex- ternal malleolus; and the posterior ligament,5 which consists of two bands pursuing the same course behind the bones. Posterior view of the inferior tibio-fibular and ankle joints. 1. interosseous membrane; 2, 3, two fasciculi of the posterior tibio-nbular ligament; 4, internal lateral liga- ment of the ankle joint; 5, 6, poste- rior and outer fasciculi of the exter- nal lateral ligament; 7, capsular ligament of the ankle joint; 8, cal- caneum. THE ANKLE JOINT. The Ankle joint6 is formed by the transverse arch between the malleoli and the body of the astragalus. It is a simple hinge-like articulation, permitting flexion and extension. The joint is surrounded by a thin cap'sular lig'ament, connecting the contiguous borders of the articular surfaces of the bones, strengthened by lateral ligaments. 1 Pereneo-tibial articulation. 2 Membrana interossea; septum longi- tudinale interosseum. 3 Inferior interosseous ligament. 4 L. tibio-fibulare anticum superius et inferius; 1. malleoli interni anticum. 5 L. tibio-fibulare posticum superius et inferius; the posterior and transverse ligaments; 1. malleoli interni anticum. 6 Articulatio pedis ; articulatio talo- cruralis. 164 THE SKELETON. The external lateral ligament1 consists of three strong fibrous bands diverging from the outer malleolus; one proceeding backward to the posterior border of the astragalus, a second descending to the outer part of the calcaneum, and the third passing forward to the anterior border of the astragalus. Fig. 123. Fig. 124. External view of the right ankle joint. 1, Internal view of the ankle joint. 1, internal tibia; 2, external malleolus of the fibula; 3, astra- malleolus of the tibia; 2, astragalus; 3, calca- galus; 4. calcaneum; 5, cuboid bone; 6, 7, 8, three neum; 4, scaphoid bone; 6, internal cuneiform fasciculi of the external lateral ligament; 9,front bone; 6, internal lateral ligament; 7, capsular lig- of the capsular ligament. ament; 8, Achilles'tendon. The internal lateral ligament2 is a strong band diverging from the lower border of the inner malleolus to the corresponding side of the astragalus and the lateral process of the calcaneum. THE INTERTARSAL AND TARSO-METATARSAL ARTICULA- TIONS. ARTICULATIONS OF THE ASTRAGALUS, CALCANEUM, AND SCAPHOID BONE. The astragalus and calcaneum are conjoined by a thick interos'seous lig'ament, occupying the sinus formed by the contiguous grooves of those bones. The ligament separates two joints, of which the poste- rior is surrounded by a short, thin cap'sular lig'ament, lined with a synovial membrane. The other joint is continuous inferiorly with that between the head of the astragalus and the scaphoid bone; both being enveloped in a common cap'sular lig'ament, and lined writh a continuous synovial membrane. This articulation is strength- ened above by a broad fibrous band, the astrag'alo-scaph'oid lig'a- 1 L. laterale externum; 1. fibulare tali et anticum ; 1. fibulae posticum, medium, posticum et anticum et 1. fibulare calca- et anticum. nei; 1. malleoli externi posticum, medium, 2 L. laterale internum ; 1. deltoides ; 1. tibio-tarsium. THE SKELETON. 165 ment j1 at its outer side by the external calcan'eo-scaph'oid lig'ament, - connecting the corresponding bones in the interval between the astraga- lus and cuboid bone. Below the articulation is the inferior calcan'eo- scaph'oid ligament,3 which is a strong, broad band proceeding from the lateral process of the calcaneum, beneath the head of the astragalus, to the scaphoid bone. ARTICULATION OF THE CALCANEUM AND CUBOID BONE. The intervening articulation of the calcaneum and cuboid bone is sur- rounded by a short cap'sular lig'ament, strengthened above and below by a broad band of fibres constituting the superior and inferior calcan'- eo-cu'boid lig'ament.4 Ligaments of the sole of the foot. 1, calcaneum; 2, astraga- lus; 3, scaphoid bone ; 4, long plantar ligament; 5, inferior cal- caneocuboid ligament; 6,inferior calcaneo-scaphoid ligament; 7, plantar ligaments between the cuneiform bones and base of the metatarsus; 8, tendon of the long peroneal muscle passing through a groove of the cuboid bone above the long plantar ligament to be inserted into the first meta- tarsal bone; 9, capsular ligament between the latter and the inter- nal cuneiform bone; 10, plantar ligaments, having the same rela- tionship with the metatarso-pha- langial and phalangial articula- tions that the palmar ligaments have with the corresponding joints of the fingers; 11, lateral ligaments; 12, transverse liga- ments; 13, lateral ligaments of the phalangial articulations. Fig. 125. ARTICULATION OF THE SCAPHOID, CUBOID, AND CUNEIFORM BONES TOGETHER AND WITH THE BASES OF THE META- TARSAL BONES. All the bones here mentioned, with the exception of the first metatar- sal, are joined with one an- other, on the back and sole of the foot, by fibrous bands associating those contiguous, and constituting the dor'sal and plan'tar lig'aments,5 which together form a sort of capsular ligament. Interos'seous lig'aments,6 consisting of short interven- ing fibres, conjoin the scaph- oid with the cuboid bone, the latter with the external cunei- form bone, the three cunei- form bones with one another, and the bases of the outer four metatarsal bones. The synovial membrane of the articulation of the scaphoid and cuneiform bones is prolonged to that 1 L. astragalo-scaphoideum. 2 L. calcaneo-scaphoideum externum, interosseum, or dorsale; 1. calcaneo- navicular interosseum. 3 L. calcaneo-scaphoideum inferius; 1. calcaneo-naviculare plantare. 4 L. calcaneo-cuboideum superius et inferius, or dorsale et plantare, or breve. 5 L. dorsalia et plantaria. ? L. interossea. 166 THE SKELETON. of the cuboid and external cuneiform bone, and also to the articulation between the outer two cuneiform and the second and third metatarsal bones. Another synovial membrane lines the joint of the cuboid and outer pair of metatarsal bones. The first metatarsal bone and internal cuneiform bone form a separate joint surrounded by a capsular ligament with a distinct synovial mem- brane. The Long Plan'tar lig'ament,1 the most conspicuous of the ligaments of the foot, commences on the under surface of the calcaneum, and proceeds forward, gradually expanding, to be attached to the tuberosity of the cuboid bone and the bases of the last two metatarsal bones. It converts the groove of the cuboid bone into a canal, through which passes the tendon of the long peroneal muscle. METATARSO-PHALANGIAL AND PHALANGIAL ARTICULA- TIONS. The metatar'so-phalan'gial and phalan'gial articulations are con- structed exactly like the corresponding joints of the hand. 1 L. longum-plantae; 1. calcaneo-cuboideum plantare; inferior or long calcaneo- cuboid ligament. CHAPTER III. THE FIBROUS, CARTILAGINOUS, FIBRO-CARTILAGINOUS, ELASTIC, AND ADIPOSE TISSUES. In describing the articulations of the skeleton, many structures were mentioned, which enter into their composition, in addition to the bones. As these structures likewise enter into the constitution of many other parts of the body, it has appeared to us convenient to defer an examination of their nature until the present moment. Those to which we espe- cially refer are the fibrous, cartilaginous, fibro-cartilaginous, and elastic tissues. To these we might add the serous, adipose, and muscular tissues, but an account of the former and latter will be deferred to other oppor- tunities ; while the adipose tissue, which appears to be unessential to the constitution of any organ, may be conveniently described in the present chapter. FIBROUS TISSUE. Fi'brous tis'sue1 is one of the most abundant and extensively diffused materials of structure of the body. It mainly composes the dermis or true skin; the superficial and deep fasciae; the periosteum and perichon- drium ; nearly all the ligaments ; the sheaths of blood-vessels and nerves; the tendons, aponeuroses, and sheaths of muscles; the dura mater, sclero- tica, and the outer layer of the pericardium; the capsules of the spleen, kidneys, testes and ovaries; the submucous, subserous, and subglandular tissues; and the general connective or areolar tissue of most organs of the body. Fibrous tissue is white, bluish white, or yellowish white, and more or less glistening. When dried it becomes hard, yellow, and transparent; but assumes its former appearance on the imbibition of water. It is the strongest and most tenacious of all animal tissues, is very inex- tensible, but highly flexible. From these physical properties it is admi- rably adapted to the various purposes for which it is employed in the White fibrous tissue. (16T) 168 THE TISSUES. body, viz., the protection, sustaining, and connection of other tissues ami organs. Fig. 127. Fig. 12ti. Example of fibrous tissue. Portion of one of the lateral ligaments of a phalangial articulation, exhibiting its composition of bundles of parallel filaments of fibrous tissue; highly magnified. Examples of fibrous tissue. 1, a small tendin- ous cord from the right ventricle of the heart. The upper extremity exhibits its division and expan- sion into the edge of the tricuspid valve. 2, a por- tion of the dura mater of the spinal cord. The great strength, tenacity, and durability of fibrous tissue have ren- dered it of important service in the arts. The so-called "cat-gut," fiddle strings, and the like, are the twisted fibrous structure of the small intes- tine of the sheep. All varieties of leather consist of the fibrous derm of the skins of animals, rendered less liable to the ordinary causes of decay by union with certain chemical substances, such as tannin. Parch- ment is likewise derived from the same source; and the savage finds it invaluable as a bow-string. By boiling fibrous tissue it is resolved into gelatin; and hence frag- ments of skin, tendons, and ligaments are the chief source of the glue of commerce. Fibrous tissue is mainly composed of exceedingly fine homogeneous filaments, measuring from the ,„,',„„ to the 1T)})T)Ji of an inch in diameter, collected into minute inextensible bundles, which may be associated into larger bundles, as in the formation of tendons and ligaments, or they may interlace with one another into more or less extensible membranes. The intervals of the bundles of filaments of fibrous tissue are occupied by a colorless homogeneous liquid resembling serum, but its exact nature lias not been positively determined. THE TISSUES. 169 1, Portion of connective tissue, from that which envelops the flexor tendons of the fingers as they pass beneath the annular ligament, treated with acetic acid. The pale, dotted portion is in- tended to represent the fibrous element fading away; the blacker tortuous lines and nets represent the mixture of elastic tissue. 2, 3, simple tortuous fibres, and a net of elastic tissue, isolated from the preceding specimen. All • structures of fibrous tissue contain more or less intermingled elastic tissue in the char- Fig. 128. acter of slender fusiform fibres, or as fine net- works. The elastic tis- sue is rendered evident, on treating portions of any of the fibrous struc- tures with acetic acid, beneath the microscope. By this process the fibrous tissue is ren- dered so transparent as to appear indistinct, while the fibres of the elastic tissue become sharply defined. In the formation of tendons, the primary bundles of fibrous tissue are closely associated parallel to one another, thus producing strong inexten- Fig 1^9 sible cords, admirably adapted to convey the muscular power to the bone or other part to be moved. Likewise in the construction of the band-like ligaments, intended to unite the bones in the strongest manner, the fibrous tissue is col- lected into parallel bundles, per- mitting free flexibility, but no stretching or extensibility. In the constitution of aponeu- roses, the deep fasciae, and the dura mater, bundles of fibrous tis- sue are arranged parallel to one another in layers, and crossed by bundles which closely associate the former together. In most other fibrous structures, the filaments and bundles of fibrous tissue interlace with one another in such a manner as to permit of more or less extensibility. Fibrous tissue. 1, portion of tendon exhibiting its composition of prismatic bundles of fibrous tis- sue, the filaments all parallel to one another; 2, a few bundles drawn from the others, exhibiting their union by delicate crossing filaments of con- nective tissue, (3) one of the varieties of fibrous tis- sue; 4. a single bundle, more highly magnified, with a portion (5) of the filaments fretted out. This property 170 THE TISSUES. is, however, entirely dependent on the arrangement alone of the fibrous tissue, as it is in all cases entirely inextensible in the direction of its fila- ments. The fact may be easily understood by referring to a familiar illustration: thus, while a handkerchief or other similar fabric is inexten- sible in the direction of its threads, it is quite extensible and contractile diagonally to the course of those threads, or in the bias direction, as it is usually termed. Simply by the arrangement then of the filaments of fibrous tissue, we find in the body structures composed of it exhibiting every degree of softness and extensibility, from the delicate, cottony connective tissue, to the unyielding tendon. Connect'ive or are'olar tis'sue,1 found almost everywhere in the body in the form of a moist, tough, white, downy substance, is composed of Fig. 130. Fig. 181. Crossing bands of fibrous tissue, from the ex- Portion of connective tissue, from the axilla, ternal, or fibrous coat of the facial artery. Inter- exhibiting its composition of bundles and filaments vals are left in the drawing to exhibit clearly that of fibrous tissue crossing in every direction. The there are two layers of fibrous tissue, of which the rounded bodies represent a single row and a por- filaments cross one another in their spiral course tion of a small group of fat cells. around the vessels. interlacing bundles of fibrous tissue, and of all materials is the best adapted, from its combined strength, softness, and yielding character, to connect, sustain, and strengthen organs, while it permits a certain degree of mobility among them. Thus it tenaciously holds together the vessels, 1 Cellular tissue; tela cellulosa, or cellularis; reticulated, filamentous, laminated, or porous tissue; cellular, or reticular substance; context us cellulosus; ethmyphe, tela Hippocratis cribrosa. THE TISSUES. 171 nerves, muscles, bones, and skin, fills up intervals and forms soft beds of support for them, and yet allows them moderate freedom of movement. In like manner it holds together the muscular fibres, the nerve fibres, and the constituents of other tissues, and gives them strength without incon- veniently impeding their movements. Comprising as it does the submu- cous and subserous layers of the hollow viscera, while these derive from it their main strength, it yet permits their expansion. In the sheath of blood-vessels and muscular fasciculi, the filaments of fibrous tissue cross one another diagonally to the course of the former in a most beautiful manner, and while they give strength they allow movement in all directions. While the band-like ligaments, com- posed of parallel bundles of fibrous tissue, firmly unite the bones and are simply flexible, the capsular ligaments, composed of interlacing bundles of the same material, are moderately extensible. The tendon, composed of closely parallel bundles of fibrous tissue, does not stretch, but follows the contraction of the muscle whose swelling form is observed through the more yielding fasciae and skin. The fibrous tissues are furnished with comparatively few and small blood-vessels; the large arteries and veins frequently observed in them, as for instance in the submucous tissues and the dura mater, being des- tined to supply the contiguous structures. The nerves are also few, and hence the sensibility of these tissues is of the feeblest character. The dermis would appear to be an exception in comparison with other fibrous structures, but the vessels and nerves in this case are rather intended for the functions of various accessory parts, as for example the papillae of touch and of the hairs, the glands, and the epidermis. Fibrous tissue, of all others, appears to be the most easily reproduced in cases where it has been destroyed. It forms the structural element of most cicatrices, false membranes, adhesions, etc. CARTILAGE AND FIBRO-CARTILAGE. Car'tilage or gristle1 is a dense substance, of less hardness than bone, of a bluish-white or yellow color, with an opalescent or pearly appear- ance. It is elastic, flexible but inextensible, and, though of firm consist- ence, is less tough than fibrous tissue. Easily cut or sliced with the knife, in thin pieces it is translucent; and to the naked eye appears homogeneous in structure. By drying it becomes very hard, yellow, and Cartilago; chondros. 172 THE TISSUES. transparent, but readily assumes its former condition through the imbibi- tion of water. From its physical properties cartilage is admirably adapted to con- tribute to the formation of the joints of the skeleton, and to give form and strength to other organs, with- out too great a degree of rigidity. It constitutes the articular carti- lages, the cartilages of the ribs, those of the larynx, except the epi- glottis, those of the trachea and its divisions, and those of the nose. In association with fibrous tissue it forms the fibro-cartilages, as the intervertebral disks, the fibro-car- tilages of the symphyses, the inter- articular fibro-cartilages, the epi- glottis, the cartilages of the ear and Eustachian tube, and those of the eyelids. The bones originate, for the most part, in the condition of cartilage, and to a much less degree in the form of fibrous tissue; and their subse- quent development and growth are step by step preceded by a produc- tion of the latter tissues. The cartilages which ossify and form part of the skeleton are commonly termed temporary car'tilages; although the others, named in contradistinction permanent car'tilages, in many cases at a later period of life become ossified, or show more or less disposition to do so. Thus the cartilages of the larynx may become completely ossified, and the costal cartilages are liable to partial ossification. The articular cartilages, the cartilages of the nose, and the fibro-cartilages exhibit no tendency to ossification, at least under ordinary circum- stances. In structure, cartilage consists of a solid matrix with imbedded nucleated cells. The matrix is colorless and translucent, or resembles in appearance ground glass, or it is faintly amber colored. It is amorphous, indis- tinctly granular, or obscurely filamentous, passing into a distinctly fib- rous condition. The nucleated cells may be single, but are usually in compressed, elongated oval groups, which seem as if they had origin- ated through the division of simple cells, as they are seen in the earliest condition of cartilage. In the deeper part of the articular cartilages, and the more interior part of the others, the groups of cells are ar- ranged vertically to the direction of the free surfaces ; but, approaching the latter, they become more numerous and parallel to them. The car- Fig. 132. Cartilage; section through the thickness of the oval cartilage of the nose. 1, toward the exterior; 2, toward the interior surface; highly magnified. It exhibits groups of cartilage cells imbedded in a homogeneous or faintly granular matrix. THE TISSUES. 173 tilage cells are observable from single ones up to groups of twenty or more. They have more or less thickened walls, with faintly granular contents, usually a nucleus, and frequently one or more oil globules. Fig. 134. i 'ft ' Xi x1 - 4 '" /% ~ .a ,\m\. - ■ Vertical section of articular cartilage, from the carpal surface of the radius. 1, 2, 3, articular cartilage; below this is a portion of the bone, 5, 6, 7. 1, exterior portion of the cartilage, exhibiting the groups of cells lying parallel to the slightly irregular free surface; 2, 3, the cells arranged ver- tically in the deeper part of the cartilage; 4. groups of cells obscured by osseous deposits; 5, structure of the bone, exhibiting the concentric laminae, and lacunae; 6, avascular canal; 7, a marrow areola of the spongy substance of the bone. The specimen is highly magnified, but the depth of the articular cartilage is proportionately reduced, so as to ex- hibit the relation of all the parts without making too large a figure. Section of costal cartilage. The upper part is toward the exterior surface,'where the groups of cells are arranged parallel to it; the lower part is toward the interior, where the groups are ar- ranged vertically to the free surfaces; highly mag- nified. Fi'bro-car'tilage consists of a more or less dense fibrous matrix, with imbedded cartilage cells. Be- tween pure fibrous tissue and pure cartilage we may distinguish very various degrees of intermixture of the two elements in the constitution of the fibro-cartilages. Thus the cartilages of the eyelids, and the semilunar and other interarticular carti- lages, are almost entirely composed of fibrous tissue. This is likewise the case with the exterior of the intervertebral disks, but the more pulp-like central portion contains numerous mingled cartilage cells. In the cartilages of the ear and the epiglottis a more equal admixture of the two elements is observable, groups of cells being contained in the meshes of an intricate intertexture of fibres. Even in the costal carti- lages, classed with the pure cartilages, portions of the interior not un- frequently present a decidedly fibrous matrix, including the cell groups. 174 THE TISSUES. Fibro-cartilages combine the elasticity of cartilage with the tenacity of fibrous tissue, and are well adapted for the firmest union of bones, accompanied with a moderate degree of flexibility. Fig. 135. Section of costal cartilage, crossing the free surfaces, but taken from near the centre. To the left, which was toward the exterior surface, the groups are imbedded in a homogeneous matrix; toward the right, the matrix has assumed a decidedly fibrous character. Specimen from an adult of about forty years of age. By long boiling cartilage is resolved into chondrin, a substance resem- bling gelatin, but, unlike it, is precipitable by^the mineral acids. The mine- ral salts of cartilage are like those of bone, and amount to about three and a half parts in the hundred. Fibro-cartilage f by boiling is re- solvable into gelatin. The articular cartilages consist of thin layers covering the artic- ular surfaces of bones in the con- struction of movable joints. They are entirely non-vascular, and de- void of nerves; but they derive nourishment from the blood-vessels in contact with their surface beneath or continuous with the bones. The other cartilages are invested with a fibrous membrane, named the peri- chondrium, which serves as a means of attachment with contiguous parts, and as a nidus to the blood-vessels nourishing the cartilages. The comparatively thick costal cartilages are pervaded with vascular canals, continuous with those of the ribs, and contain nutrient vessels com- municating with those of the latter and of the perichondrium. Fibro- cartilages receive more vessels than the true cartilages, but the num- ber of them is very small. Fig. 136. Section of fibro-cartilage from the auricle of the ear. The cells are seen imbedded in a fibrous matrix. 1, exterior surface, where the cells are parallel to it; 2, toward the middle. Highly magnified. THE TISSUES. 175 ELASTIC TISSUE. Fig. 137. The Elas'tic tissue,1 though widely distributed in the body, seldom forms masses of any important size. It composes the yellow ligaments of the ver- tebral arches; is the chief component of the thyro-hyoid ligament, the vocal membrane, and the structure conjoining the rings of the trachea and bronchia ; and it enters largely, in association with muscular tissue, in the formation of the middle coat of the blood-vessels. In small quan- tity it is found mingled with most of the fibrous structures, as the der- mis, the superficial fasciae, etc. In its most striking condition of development it is observed composing the nuchal ligament of quadrupeds, especially the more bulky ones, as the elephant, elk, and the ox, in which, through its elasticity, it sustains the weight of the head, and thus economizes muscular power. In the same animals it also constitutes a strong layer in the abdominal wall, where it sustains the pressure of the contained viscera. Elastic tissue in its ordinary condition is dull yellow, opaque, tough, and coarsely fibrous. Viewed by means of the microscope, it is found to be composed of re- ticulating fibres, the abruptly broken ends of which appear curled. The fibres vary exceed- ingly in diameter in different parts of the body. Those found in the subserous or sub- mucous tissues form nets of filaments almost as fine as those of fibrous tissue. Those of the yellow ligaments of the vertebrae measure about the --^jj of an inch in diameter. Fi- nally, in the middle coat of the blood-vessels the elastic tissue in part consists of wide reticu- lar bands, together having the appearance of a perforated membrane.2 In the formation of ligaments and mem- branes, the bundles Of elastic tissue Composing , Elastic tissue, highly magnified, from the yellow ligaments of the them are associated by areolar tissue, and the vertebra. The specimen is observed former also are invested with the same material to be composed of coarse anastomos- ing fibres. as the latter. Long boiling resolves elastic tissue into a brownish liquid, which smells like glue, but does not form a jelly on cooling. The structures composed of elastic tissue are furnished with few blood- vessels, the capillaries of which pursue the general course of the fibres Yellow elastic tissue. 2 Perforated, or fenestrated membrane; striated membrane. 176 THE TISSUES. of the former. The supply of nerves is small, and little is known in regard to them. Fig. 139. Elastic tissue, from the middle coat of the pul- Elastic tissue, from the middle coat of the ca- monary artery of the horse; highly magnified. rotid artery of the horse; highly magnified. ADIPOSE TISSUE. Ad'ipose or fat tis'sue is remarkable as a physical element of the body, from the fact that it does not appear to be essential to the constitution of any organ. Its quantity depends much upon the condition of health, habits of life, and other circumstances of the individual; in certain dis- eases, or from starvation, disappearing almost entirely; in healthy per- sons frequently adding greatly to the bulk of the body, and sometimes accumulating to such an extent as in the condition itself to be viewed as a disease. It exists generally wherever connective tissue is found, occu- pying the areolae of the latter, and filling the interspaces of organs, thus contributing to the symmetry of form of the body. Examined microscopically, adipose tissue is observed to consist of masses of delicate, transparent vesicles, distended with a liquid, yellow- ish fat. From mutual pressure the fat vesicles are polyhedral, but when isolated are spherical and of variable diameter, but average the 4^ of an inch. They consist of nucleated cells, the nuclei of which are attached to the walls of the latter, and are rendered invisible by the presence of the contained oil. In emaciated or dropsical subjects these cells may often be detected with the nucleus distinctly visible, and with the cell contents consisting of a serous liquid and one or more drops of yellow oil. Adipose tissue forms a considerable and continuous layer1 beneath the skin, lodged in the meshes of the dermis and in the adjacent connective tissue. In this position it is most abundant in the female, contributing 1 Panniculus adiposus. THE TISSUES. 177 It is especially Fig. 140. Adipose tissue, with connective mainly to her characteristic, rounded symmetry of form. thick beneath the skin of the breast, abdomen, and buttocks. In the palms of the hands and soles of the feet, it serves as an elastic cushion to relieve the influence of pressure, and is always present, even under the greatest ex- tent of emaciation. Mostly it is confined to the subcutaneous layer of the superficial fascia, and only when excessive does it pervade the deeper layer of the same fascia. The adipose tissue also occupies the inter- vals of muscles, the hollows of the temples and cheeks, and the interspaces of the important organs of the orbits. The disappearance of this material in disease gives rise to the sunken appearance of the eyes, the cheeks, and the temples. Adipose tissue also Collects along the COUrse ™s™> from the superficial fascia of . the abdomen; highly magnified. of the blood-vessels and nerves, especially those The groups of fat vesicles are ot- of the heart and intestines. It often accumu- 8erved contained ^ the meshes of lates in large quantity around the kidneys and the lower extremity of the rectum, and between the folds of the perito- neum ; according to its extent in these positions producing in a great measure the protuberant abdomen of fat persons. It likewise constitutes the marrow of the medullary cavities of bones, fills up intervals about the joints, and occupies the synovial folds ; but surrounding the articula- tions it is usually in less quantity than elsewhere subjacent to the skin. In the healthy condition, no adipose tissue exists in the subcutaneous connective tissue of the eyelids, and of the penis and scrotum. It also does not exist in the submucous connective tissue; nor is it found in the interior of the cranium, the dura mater of the spinal cord, the eyeball, or the lungs. The blood-vessels of the adipose tissue form a capillary net, with polyhedral meshes, including the fat vesicles. Nerves are transmitted to important structures through adipose tissue, but appear to give it no branches. 12 CHAPTER IV. THE MUSCULAR SYSTEM. The Mus'cles1 are the principal organs of motion in animals. They constitute the greater portion of the human body, and in an important degree contribute to the production of its outward form. They are numerous, of very different sizes, and of various shapes, dependent in some measure upon the position they occupy. They consist of a soft, red, fleshy part, named the belly,2 usually attached, by means of ten'dons, between two or more points of the skeleton. The substance of the mus- cular belly, named flesh or mus'cle, is the active agent of motion, while the tendons are entirely passive, simply communi- d c eating the power of the former to the part to be moved. Fig. 142. Fig. 141. Transverse section of the lower end of the ulno-carpal flexor, moderately magnified, a, section of tendon appearing as two crescents, composed of prismatic fasciculi of fibrous tissue; b. a secondary fasciculus of crescentic shape, consisting of primary bundles of muscular fibres; c, a flattened cylindrical secondary fasciculus, consisting of primary bundles of muscular fibres; d, secondary and primary bundles in outline; e, sheath of the mus- cle, composed of fibrous tissue. Transverse section of a muscular fasciculus, exhibiting its prismoid form, and its composition of pris- matic muscular fibres. From the biceps flexor of the arm. Highly mag- nified. The belly of a muscle is composed of an aggregation of peculiar, soft, red fibres, named mus'cular fi'bres.3 These are collected into primary bundles, or fascic'uli,4 which are associated into larger or secondary fascic'uli, and these again may unite in the formation of still coarser bundles, as those of the great gluteal muscle. The fibres and fasciculi 1 Musculi. Singular: musculus; lacer- tus ; torus ; mys. 2 Venter, or medium musculi. (178) s Flesliy fibres. Sing.: fibrum muscu- lare; fibrilla muscularis. 4 Lacerti musculorum. THE MUSCULAR SYSTEM. 179 are held together and enveloped with delicate connective tissue, the fila- ments of which cross one another diagonally to the direction of the former, as represented in figure 143, so as to interfere in the least degree with muscular movement. The prismatic form of the fibres and fasciculi enables them to give the most com- pact condition to the muscles, and thus economize space. In some muscles the fasciculi run parallel to one another through- out the length of the former, as in the sartorius and gracilis muscles. In others, they converge from one attachment to the other, producing a triangular or ra'diated mus'cle,1 as in the temporal and pectoral muscles. In some, the fasciculi converge toward both attachments, as in the biceps flexor of the arm. In others, the fasciculi converge from each side of a muscle to a median tendon, producing what is called a pen'niform mus'cle,2 from its resemblance in arrangement to a feather, as in the rectus muscle of the thigh, or the dorsal interosseous muscles of the hand. When the fasciculi of a muscle proceed ob- liquely from one attachment to a tendon on the other side, a semi-pen'niform mus'cle is produced,3 as in the case of the peroneal muscles of the leg. From their extent, muscles are often mentioned as long, short, and broad muscles; from their form, as triangular, quadrate, terete or rounded, fusiform, and ribbon-like muscles; and from the direction of their fasciculi, as straight, oblique, and transverse muscles. The point of attachment of a muscle from which it ordinarily acts is called its origin, and the corresponding extremity of the muscle is named its head. The point of attachment which is to be moved is called the in- sertion. Generally, the origin is the point of attachment nearest the vert- ebral column. Functionally, the origin and insertion, if these be viewed as the fixed and moving points, will vary according to the circumstances in M. radiatus. 2 M. penniformis; m. pennatus. 8 M. semi-penniformis. Fig. 143. Two portions of a muscular fasciculus, from the trapezius muscle; highly magnified. 1, two por- tions of a muscular fasciculus, composed of pris- matic striated fibres terminating below, in rounded extremities, among the fibrous tissue of the com- mencing tendon; 2, cut extremities of the fibres, showing their prismatic form; 3, delicate sheath composed of obliquely crossing filaments of fibrous tissue; -1, the fibres of the commencing tendons. Partly a diagram. 18() THE MUSCULAR SYSTEM. which the body is placed. Thus, the muscles emanating from the trunk and shoulders, which ordinarily raise the arms, by fixing the latter, may be made to raise the body, as instanced in the experiment of elevating the head to the level of a horizontal bar placed above it. The number of points of attachment of muscles varies, and thus the latter are said to arise by one, two or more heads, as the case may be. From the number of heads, the muscles are mentioned as single headed, biceps, triceps, and many headed. The number of insertions likewise vary, a muscle with a single head not unfrequently ending in a number of tendons of insertion, as in the common extensor of the fingers. The names of the muscles are derived from some prominent character, as the position, direction, form, attachments, number of heads, or physi- ological action. The ten'dons or sinews1 vary in character, some consisting of the shortest attachment of the muscular belly to the points of origin and insertion, while some are spread out in broad membranous expansions, named aponeuroses,2 and others form strong, flattened, cylindrical cords. They are bluish or yellowish white, longitudinally striated, and glisten- ing ; and are very flexible but entirely inextensible. In their connection with the muscular bellies they usually commence in the interior as a wide expansion, or upon the exterior as an aponeurotic facing. From the belly, the tendons may continue with the same width to their origin and insertion, but frequently become gradually narrowed into flattened, cylin- dricalcords. As relates to the more intimate structure of the muscles, an examina- tion of both the muscular and tendinous tissue is required. Fig. 144. Two muscular fibres, from the lower end of the ulno-carpal flexor; highly magnified. To the right of the figure, the muscular substance is observed to be gradually resolved among the fibrous tissue of the commencing tendon. The muscular fibres, viewed with the microscope, are found to be of variable diameter, though uniform in each case, and they average about the — of an inch. They appear moderately translucent, pale 1 Leaders; thews. Sing.: tendo; tenon; pronervatio. 2 Sing.: expansio nervosa; denervatio; pronervatio. THE MUSCULAR SYSTEM. 181 reddish, faintly striated longitudinally, and distinctly and regularly stri- ated transversely, whence the name applied to them of striated muscu- lar fibres,1 in contradistinction to those of the hollow viscera, which for the most part are unstriated. A further analysis of the muscular fibres proves each to consist of a bundle of numerous and exceedingly minute filaments, named muscular fi'brils, inclosed together in a delicate wall of structureless membrane called the myolem'ma.2 The muscular fibrils are composed of highly refractive particles3 of uniform size and arrangement, to which is due the regularly transverse striated appearance of the muscular fibres. Fig 145. Fig. 146. Fibrils from a muscular fibre of the axolotl, a batrachian reptile; highly magnified, a, Bundle of fibrils; b, an isolated fibril. A muscular fibrItof a salamander, a batrachian reptile, which had been long kept in weak alcohol. 1, muscular substance; 2, nuclei; 3, muscular sub- stance split into disks; 4, the myolemma. Occasionally the latter are broken in the direction of their transverse striae, when they appear as if composed of a series of superimposed disks, as represented in figure 146. The muscular fasciculi, in approaching their tendinous connections, be- come pointed, from one muscular fibre after another ceasing in the ten- dinous structure. In many instances the muscular fibres terminate in rounded or bluntly-pointed extremities, but in other instances the fibrils of the fibres appear gradually to resolve themselves among the tendinous structure. Striped muscular fibres. 2 Sarcolemma. 3 Myoline; sarcous element, matter, or substance. 182 THE MUSCULAR SYSTEM. When treated with acetic acid the muscular fibres are rendered more translucent, and a number of elongated nuclei, imbedded among the fibrils, are brought into view. These nuclei remain from the organic cells, from which the muscular fibres were originally developed. Muscular fibres possess the property named contractility, which is excited ordinarily during life through impressions received from the ner- vous system, though a variety of stimuli, as mechanical irritation, chem- ical agencies, change of temperature, and electricity, are capable of call- ing it into action. By this property the muscles shorten or contract, and thus by approaching the two extremities move the insertion. When the contraction ceases, the muscles again become elongated, and the con- tractile power is lost only with the death of the muscular tissue. With the contraction there is a corresponding increase of bulk in the breadth and thickness of the muscle. When muscular fibres are observed con- tracting beneath the microscope, the transverse striae are observed to approach more closely, while the fibres increase their diameter. When muscles are inserted into soft organs, they usually have no ten- dinous attachment, but their fibres resolve themselves into the contiguous parts, as in the insertion of the muscles around the mouth. The tendons are composed of dense bundles of fibrous tissue, the fila- ments of which are associated with one another in a perfectly parallel manner. In the thicker tendons the finer bundles are collected into coarser prismatic fasciculi, associated by a looser texture of the same material, forming their connective tissue. From the parallel arrange- ment of the fibrous structure of the tendons they are rendered inexten- sible, which quality, together with their great strength and small size, admirably adapts them to communicate the power of the comparatively bulky muscular belly not only to distant parts, but also to very limited points of insertion. The muscles are invested with fibrous sheaths, continuous with those of the muscular fasciculi and with one another. Portions of these sheaths between muscles in many instances present a tendinous or apo- neurotic character, constituting the so-called intermuscular partitions, from which the muscles in part frequently arise. The groups of muscles in different regions of the body are enveloped together in fibrous sheaths, named the fas'ciae, as the brachial fascia, the femoral fascia, etc. These fasciae are usually denser or more aponeurotic in their character than the sheaths of the individual muscles. In many instances the latter partly arise from the fasciae, or are partly and even wholly inserted into them. To preserve the position of tendons in their course they are frequently confined in grooves, or upon narrow surfaces of the bones, by means of THE MUSCULAR SYSTEM. 183 appropriate ligaments, as in the passage of the extensor tendons through grooves at the carpal extremity of the radius, and the passage of the flexor tendons of the fingers beneath the annular ligament of the wrist and the vaginal ligaments of the phalanges. When muscles or their tendons pass over prominences of the bones, thin walled, serous pouches, named syno'vial bur'sae,1 intervene, with the object of alleviating friction. Similar bursa? are reflected upon ten- dons as they pass through grooves or beneath annular and vaginal liga- ments. In some instances these bursae are much divided or folded, as in the reflection of the synovial bursa upon the flexor tendons of the fingers as they pass beneath the annular ligament of the wrist. When muscles are accidentally torn, they are not restored by the re- production of muscular tissue, but the parts are reunited by means of ordinary fibrous tissue. The muscles are highly vascular, in accordance with their great activity. Their capillary blood-vessels generally pursue a course parallel to and between the muscular fibres, and frequently anastomose across the latter. The tendons are but slightly vascular. The lymphatic ves- sels are few in the muscles, and have not been detected in the tendons. Though possessing only a moderate degree of sensibility, the muscles are abundantly supplied with nerves, their office, however, being mainly to convey motor impressions. The terminal branches of the nerves anas- tomose with one another and form intricate plexuses among the muscular fibres. The tendons are almost devoid of nerves, and, at least in a con- dition of health, are entirely insensible. GENERAL REMARKS ON THE HEAD. The Head2 is composed of the skull with its contents, covered with muscles and the skin. The cranial vault is covered with the occipito- frontal, temporal, and auricular muscles, and the scalp. The front of the cranium is the forehead, its back the occiput, and its sides the temples or tem'poral regions. The forehead3 terminates below with the eyebrows and the intervening space, named glabel'la; on each side is bounded by the temple, and above by the scalp. The occiput4 extends between the position of the ears posteriorly, and is covered at its lower part by the muscles of the neck. The temple,5 so called from the Latin tempus, time, because in this region white hairs first appear, is defined above by the course of the temporal ridge, below by the zygoma. 1 Bursae mucosae. 2 Caput; cephale ; poll. 3 Sinciput; front; frons : brow. 4 Occipitum ; regio occipitalis; mion. 5 Regio temporalis ; crotaphus. 184 THE MUSCULAR SYSTEM. The Face,1 formed by the forehead above, bounded by the base of the lower jaw below, and the ear on each side, presents to us in succession beneath the glabella: the root of the nose, which is its origin from the forehead; the bridge or back of the nose ;2 the column of the nose,3 which separates the nostrils or anterior nares; the labial groove4 of the upper lip; and the labio-mental groove,5 between the lower lip and the chin. From the bridge slope off the sides of the nose, connected below with the dilated wings, which bound the nostrils externally. The fissure of the mouth is terminated on each side by the conjunction of the lips, named the angles of the mouth or oral angles.6 The upper lip is defined on each side by the naso-labial furrow,7 which becomes more marked with the advance of age. Below the eyebrows are the eyelids, separated by the pal'pebral fissure, the extremities of which are the angles or canthi of the eye, or of the orbit. The cheeks are bounded by the zygoma, the ear, the angle and base of the lower jaw, the chin, lips, and nose. The space in the vicinity of the ear extending to the angle of the jaw and the sterno-mastoid prominence of the neck, is the parotid region. The scalp8 or skin of the vault of the cranium where covered with hair, is thick, dense, and inextensible; and its deeper part is filled with hair follicles, sweat glands, and sebaceous glands, associated with adipose tissue. On the forehead and temples it is thinnest and most extensible. The hairs of the scalp diverge in whorls from a central point at the top of the head, called the crown or vertex.9 The scalp tightly adheres by short connective tissue to the occipito-frontal muscles, and follows all their movements; but the skin alone of the forehead is thrown into transverse wrinkles by the contraction of their frontal bel- lies. The skin of the eyebrows is thick and dense, and is moved with that of the forehead. The skin of the eyelids is thin, and the con- nective tissue attaching it to the orbicular muscle beneath is devoid of fat. In injuries about the entrance of the orbit, blood readily pervades this connective tissue, giving rise to what is commonly called "black eye." The skin of the nose is thin and movable above, but is thicker, more dense, and intimately connected with the subjacent part below, in which position it is filled with large sebaceous glands. The skin 1 Facies; vultus ; prosopon. 5 Sulcus mento-labialis. 2 Dorsum nasi. 6 Commissures of the mouth. 3 Columna nasi. 7 Sulcus naso-labialis. 4 Philtrum ; amatorium; amabile; sul- 8 Capillitium. cus, or lacuna labii superioris. 9 Spondylus. THE MUSCULAR SYSTEM. 185 of the lips, where furnished with large hairs, is thick; but at the borders is very thin and closely adherent to the orbicular muscle. The skin of the chin is thick, filled with hair follicles, sebaceous and sweat glands, and is most intimately blended with the muscles beneath. The skin of the cheeks is thin, and closely associated with a thick subcutaneous adipose layer involving several of the muscles; and in the interval of the masseter and buccinator muscles, the cheek is occupied with a large mass of soft fat tissue. The skin at the back part of the cheek is like that of the chin, though less dense, and is not blended with the contiguous muscles. FASCIA OF THE HEAD. Fasciae readily separated from the contiguous parts as distinct layers, on the head are found only in the temporal region. In other positions they are represented by the thin and closely adherent investments of the muscles of the scalp and face, and by the subcutaneous adipose layer. The Superficial temporal fascia1 is a thin but distinct layer of loose fibrous tissue beneath the skin of the temple. It is attached above to the aponeurosis of the occipito-frontal muscle, and is continuous with the thin layers of connective tissue investing the fleshy bellies of the latter and the palpebral orbicular muscle. It incloses the auricular muscles and the superficial temporal blood-vessels. The Deep temporal fascia2 is a strong, bluish-white and shining fibrous membrane extended between the curved boundary of the tem- poral fossa and the zygoma. Its lower part is divided into two layers, between which is some loose areolar tissue and more or less fat. The inner surface of the fascia affords a point of origin to the temporal muscle. MUSCLES OF THE SCALP. The Occip'ito-front'al mus'cle3 extends from the occiput to the fore- head, and consists of two fleshy bellies connected by an intermediate aponeurosis. . The occipital belly,4 shorter and narrower than the other, arises from the superior semicircular ridge of the occipital bone, and ascends in an inward direction to its aponeurosis. 1 Fascia temporalis superficialis. 2 Fascia temporalis profunda; f. tem- poralis ; temporal aponeurosis. 3 M. occipito frontalis; m. epicranius ; m. digastricus cranii. * M. occipitalis. 186 THE MUSCULAR SYSTEM. Fig. 147 The frontal belly,1 paler than the former, arises from the internal angular process and superciliary ridge of the frontal bone, and ascends to its apo- neurosis. A prolongation from this belly, at the root of the nose to the nasal compressor mus- cle, is usually described as distinct, under the name of the nasal pyramidal muscle.2 The occipito-frontal aponeurosis3 is a thin sheet of tendinous fibres cover- ing the upper part of the head continuously from side to side. Between the occipital bellies of the two muscles it is attached to the occipital protuber- ance, and in the vicinity of the temporal ridge on each side is blended with the superficial temporal fascia. It is loosely at- tached to the periosteum beneath, but is closely ad- herent to the integument above, so that in the ac- tion of its muscular bellies the scalp is moved back- ward and forward on the cranium. Muscles of the head and neck. 1, 2, occipito-frontal muscle: 1, its frontal belly; 2, its occipital belly; 3, nasal pyramidal mus- cle; 4, superior, and 5, posterior auricular muscles; 7, labio-nasal elevator; 8, elevator of the upper lip; 9, nasal compressor; 10,11, zygomatic muscles; 12, masseter muscle; 13, buccinator; 14, de- pressor of the oral angle; 15, oral orbicular muscle; 16, elevator of the oral angle; 17,18, depressor of the lower lip; 19, sterno- mastoid muscle; 20, trapezius; 21, posterior belly of the digastric and the stylo-hyoid muscle; 22, anterior belly of the former; 23, loop of fibrous tissue attaching the tendon of the digastric mus- cle to the hyoid bone; 24, omo-hyoid muscle; 25, sterno-hyoid; 26, sterno-thyroid, seen to the outer side and behind the anterior belly of the omo-hyoid; 27, mylo-hyoid; 28, splenius; 29. elevator of the scapular angle; 30, 31, middle and anterior scalene mus- cles ; 32, clavicle. 1 M. frontalis. 2 M. pyramidalis nasi; m. nasum dila- tans; m. processus nasi; fronto-nasal muscle. 3 Epicranial aponeurosis ; membrana epicrania; galea capitis; galea aponeu- rotica capitis; g. tendinea Santorini. THE MUSCULAR SYSTEM. 187 MUSCLES OF THE EYELIDS AND EYEBROWS. The Pal'pebral Orbic'ular muscle1 forms a thin elliptical layer sur- rounding the entrance of the orbit, immediately beneath the skin. It arises from the internal angular process of the frontal bone, the nasal process of the superior maxillary bone, and the internal palpebral liga- ment. From this origin the muscle proceeds outwardly in the upper eye- lid and the eyebrow, and returns below the palpebral fissure to be inserted into the same points from which it started. The portion corresponding with the eyelids is thinner and paler than elsewhere, and has been described as distinct under the name of the cil'iary muscle.2 A fasci- culus or offset, springing from the back part of the lachrymal bone and passing upon the eyelids along the course of the lachrymal canals, was particularly described, by the late Professor Horner, under the name of the tar.'sal ten'sor.3 The palpebral orbicular muscle closes the eyelids and draws the skin in a radiating manner toward the inner angle. The ciliary portion is constantly engaged in the act of winking. The Pal'pebral Ele'vator muscle4 is contained within the orbit. It arises above the optic foramen, and passes forward beneath the roof of the orbit; expanding in its course, and terminating in a broad, thin ten- don, it is inserted into the edge of the superior palpebral cartilage. As indicated by the name, the muscle raises the upper eyelid. The Supercil'iary muscle5 arises from the inner extremity of the super- ciliary ridge, and proceeds outwardly and a little upward to become blended with the palpebral orbicular and occipito-frontal muscles, between which and the bone it is situated. The muscles of the two sides throw the skin at the middle of the fore- head into vertical wrinkles, as in frowning. 1 M. orbicularis palpebrarum; m. o. oculi; m. pal. ciliaris ; m. palpebrals ; m. naso-palpebralis; m. maxillo-palpe- bralis ; m. orbicularis latus; palpebra- rum duo musculi; sphincter, or constric- tor palpebrarum, or oculi. 2 M. ciliaris. 3 M. tensor tarsi; m. Horneri; m. sacci lachrymalis. 1 M. levator palpebral superioris; pal- pebrae superioris primus; apericus pal- pebrarum rectus; seclusor palpebrarum; apertor oculi; orbito-palpebral muscle. 5 M. superciliaris ; m. supercilii; m. corrugator supercilii; m. c. frontis; m. c. Coiterii; m. cutaneo- or fronto-super- ciliaris; m. frontalis verus. 188 THE MUSCULAR SYSTEM. MUSCLES OF THE EYEBALL. See the Account of the Eye. MUSCLES OF THE EAR. See the Account of the Ear. MUSCLES OF THE NOSE. The Na'sal Compress'or1 is a thin, triangular muscle arising from the fore part of the superior maxillary bone and diverging upon the side of the nose. On the back of the latter it terminates in a thin aponeurosis, which conjoins that of the opposite side, is attached to the tip of the nose, and is connected with a pair of fleshy slips2 from the occipito-frontal muscles. The Na'sal Dila'tor3 consists of short, indistinct muscular fibres, situ- ated between the cartilages of the wing of the nose and the skin, with which they are intimately blended. MUSCLES OF THE LIPS AND CHEEK. The O'ral Orbic'ular muscle4 is an elliptical fasciculus of fibres sur- rounding the mouth, and blended with all the muscles which converge to it. At the angles of the mouth its fibres, except the most superficial ones, decussate with those of the buccinators, and with the elevators and depressors of the oral angles. This muscle is a sphincter, and antagonizes all the other muscles of the mouth. When closely contracted, it projects the lips as in the acts of kissing and sucking. The Lab'io-na'sal el'evator5 arises from the nasal process of the supe- 1 M. compressor naris; m. transver- salis nasi ; m. triangularis nasi; m. na- salis ; m. rinalus ; m. myrtiformis; m. constrictor naris; m. dilatator alae nasi. 2 Nasal pyramidal muscles. 3 M. levator proprius alae nasi anterior et posterior; m. dilatator naris ant. et post.; m. pinnae dilatator. * M. orbicularis oris; m. constrictor oris; m. sphincter labiorum ; m. oscula- torius; m. basiator; m. labialis; m. semi- or demi-orbicularis; m. supra-semi-or- bicularis. 5 M. levator labii superioris alaeque nasi; elevator of the upper lip and wing of the nose; m. incisiyus lateralis et pyramidalis. THE MUSCULAR SYSTEM. 189 rior maxillary bone, and as it descends separates into two fasciculi, of which one is inserted into the wing of the nose, while the other is pro- longed to the upper lip, where it is blended with the contiguous muscles. The La'bio-na'sal depress'or1 is a small muscular slip situated just exterior to the mucous membrane of the upper lip at the side of the fraenum. It arises from the point of the incisive alveoli of the superior maxillary bone, and ascends to be inserted into the wing and column of the nose and become blended with the upper margin of the oral orbicular muscle. The El'evator of the Upper Lip2 arises from the malar and superior maxillary bones just above the infra-orbital foramen, and descends to become blended with the contiguous muscles of the upper lip. The El'evator of the O'ral Angle3 is partially concealed by the pre- ceding muscle. It arises from the superior maxillary bone below the infra-orbital foramen, and descends in a convergent manner to the angle of the mouth. Between it and the elevator of the upper lip are the infra-orbital nerve and artery. The Zygomat'ic muscles are two narrow fasciculi extending obliquely from the most prominent part of the cheek to the angle of the mouth. The Larger Zygomat'ic muscle,4 external to the smaller one, arises from the zygomatic process of the malar bone, and, after reaching the angle of the mouth, becomes blended with the contiguous muscles. The Smaller Zygomat'ic muscle5 is inconstant in size and exact position, and occasionally is absent. It arises from the malar bone, and terminates near the angle of the mouth by blending with the elevator of the upper lip. The zygomatic muscles elevate the angles of the mouth outwardly, as in smiling. The Depress'or of the Lower Lip,6 a square muscle situated at the 1 M. depressor labii superioris alaeque nasi; depressor of the upper lip and of the wing of the nose; m. depressor alae nasi; m. myrtiformis. 2 M. levator labii superioris; m. in- cisivus. 3 M. levator anguli oris; elevator of the angle of the mouth; m. caninus; m. abducens labiorum; m. elevator labio- rum communis. 4 M. zygomaticus major; m. distortor oris; zygomato-labial muscle. 5 M. zygomaticus minor; small zygo- mato-labial muscle. 6 M. depressor labii inferioris; m.quad- ratis menti; m. mento-labialis. 190 THE MUSCULAR SYSTEM. side of the chin, arises from the base of the lower jaw and ascends in- wardly to be inserted into the lower lip. The El'evator of the Lower Lip1 is a small square muscle situated just exterior to the mucous membrane of the lower lip at the side of the fraenum. It arises from the front of the outer incisive and canine alveoli of the lower jaw, and descends inwardly to be inserted into the lower lip. The Depress'or of the O'ral Angle2 is a triangular muscle, which arises from the base of the lower jaw at the side of the chin, and is inserted by its apex into the angle of the mouth, where it blends with the contiguous muscles. The Buccina'tor muscle3 contributes to the formation of the cheek. It arises from the pterygo-maxillary ligament and from the alveolar border of both jaws as far forward as the first molar tooth. From these points the fibres proceed forward and converge to the angle of the mouth, where they cross one another and become confluent with the oral orbicu- lar muscle. Internally it is in contact with the mucous membrane of the mouth, and externally is closely invested with a thin fascia. Its back part is sepa- rated from the ramus of the lower jaw by means of a mass of fat, re- markable for its softness and slight attachment to the contiguous struct- ures. The disappearance of this fat in emaciation gives rise to the hollow cheek. Opposite the second molar tooth of the upper jaw the buccinator is perforated by the termination of the parotid duct. When the buccinators alone contract, they widen the mouth; but if they contract in conjunction with the oral orbicular muscle, they press the cheeks close to the jaws; or if the mouth is filled with air, this is com- pressed, as in the acts of blowing and whistling. The Pter'ygo-max'illary lig'ament is a fibrous band, extended be- tween the external pterygoid process of the sphenoid bone and the pos- terior end of the molar ridge of the lower jaw, serving as a common origin to the buccinator muscle and the superior constrictor of the pharynx. 1 M. levator labii inferioris; m. levator menti; m. incisivus inferior; m. penicil- latus ; mento-labial muscle. 2 M. depressor anguli oris; depressor of the angle of the mouth ; m. triangu- laris oris; m. maxillo-labialis; m. de- pressor labiorum communis. 3 M. retractor anguli oris; m. bucco- alveolo-maxillaris ; m. alveolo-labialis; m. mansorius. THE MUSCULAR SYSTEM. 191 THE MUSCLES OF THE LOWER JAW, OR OF MASTICATION. The Mass'eter muscle,1 thick and oblong square, is situated at the back of the cheek, and extended between the zygoma and angle of the lower jaw. It has a number of tendinous bands interspersed with its structure, and is separable into two portions, the fibres of which pursue a different course. The superficial and larger portion of the muscle arises tendinously from the upper maxillary bone and the lower margin of the malar bone, and descends backward to be in- serted into the lower half of the ramus and angle of the lower jaw. The deeper portion arises from the zygomatic process of the temporal bone, and descends a little forward to be inserted into the upper half of the ramus of the lower jaw. The External Ptery'goid muscle2 is short, thick, and triangular, and occupies the upper part of the spheno-maxillary fossa. It arises from the under surface of the great wing and the outer surface of the external pterygoid process of the sphenoid bone, and converges to be inserted, by means of a short, thick tendon, into the depressed sur- face of the front of the neck of the lower jaw. Externally this muscle is crossed by the internal maxillary artery and the tendon of the temporal muscle; and internally it is in contact with the internal pterygoid muscle and the inferior maxillary nerve. The Internal Pter'ygoid muscle3 is square and thick, and is situated within the position of the ramus of the jaw. It arises from the ptery- 1 M. mandibularis; m. zygomato-max- 3 M. pterygoideus internus, or major; illaris. m. masseter internus; m. latens in ore; 2 M. pterygoideus externus, or minor; m. pterygo-anguli-maxillaris; m. ptery- m. pterygo-colli-maxillaris; m. pterygo- go-maxillaris majus; m. alaris, or ali- maxillaris minus; m. alaris, or aliformis formis major, minor. Fig. 148. View or the interior part op the left side of the pace. 1, condyle of the lower jaw; 2, angle of the jaw; 3, base; 4, symphysis; 5, sub-maxillary fossa; 6, attachment of the mylo-hyoid muscle to the corresponding ridge; 7, origin of the genio- hyoid muscles; 8, origin of the genio-glossal muscles; 9, masseter muscle; 10, internal ptery- goid muscle; 11, external pterygoid muscle. 192 THE MUSCULAR SYSTEM. goid fossa, and descends outward and backward to be inserted into the inner surface of the ramus and angle of the lower jaw. The Tem'poral muscle1 occupies the temporal fossa, and is covered by the temporal fascia. It arises from the entire surface of the former and from the upper part of the latter, and converges to an interior tendinous layer, which becomes a thick, flattened fasciculus, descending to be in- serted into the inner surface and anterior border of the coronoid process of the lower jaw. The temporal, masseter, and pterygoid muscles are the active agents in mastication. The movements produced are those of elevation of the lower jaw, together with a lateral, forward and backward motion. The elevation of the lower jaw, productive of firm pressure of the lower against the upper teeth, is the result of the contraction of the tem- poral muscles and the internal portions of the masseters. Depression of the lower jaw occurs by its weight alone, though aided by the digas- tric and other muscles extended between it and the hyoid bone, when this is fixed in its position. The grinding movement of the lower jaw is performed by the pterygoid, masseter, and temporal muscles. The external Fig. 149. View of the temporal muscle. The temporal fascia and zygoma removed. pterygoid muscles and the external portions of the masseter muscles draw the jaw forward; the temporal muscles and internal portions of the masseters draw it back again; and the internal pterygoid muscles, contracting alternately, draw the jaw to either side. 1 M. temporalis; m. crotaphites; m. arcadi-temporo-maxillaris; m. temporo max- illaris. THE MUSCULAR SYSTEM. 193 THE NECK. The Neck,1 which forms the short cylindrical column connecting the head with the thorax, varies in length and thickness in different individ- uals of the same age and sex. Its bony axis is situated more posteriorly than anteriorly, in consequence of which the head is disposed to fall for- ward. The front of the neck, or the throat,2 presents a prominence in the adult male, commonly called "Adam's apple."3 This is produced by the larynx, which, from its less degree of development before puberty, and at all periods of life in the female, is not evident externally. The elevation on each side of the neck, descending from behind the position of the ear to the sternum, is produced by the sterno-mastoid muscles. The concavity between the latter just above the breast is the ju'gular fossa;4 and the shallower depression outside of the muscle above the clavicle is the supra-clavic'ular fossa.5 The skin of the neck is thin and movable, and is readily elevated into folds. The two conspicuous folds, observed in old people, descending from the sides of the chin toward the lower part of the neck, are pro- duced upon the anterior borders of the subcutaneous cervical muscles, which become extended through elevation of the lower jaw consequent on the loss of the teeth and their alveoli in both jaws. Beneath the muscles just mentioned is the cervical fascia, which incloses the sterno- mastoid muscles. The middle of the neck in front of the vertebras is occupied by the pharynx and oesophagus, the root of the tongue, the hyoid bone, the larynx and trachea, and the thyroid body. At the sides of these parts the principal cervical blood-vessels and nerves are situated, enveloped in the deep cervical fascia. MUSCLES AND FAS CLE OF THE NECK. THE SUBCUTANEOUS CERVICAL MUSCLE. The Subcuta'neous Cer'vical muscle6 is a broad, thin, and pale lam- ina arising in the connective tissue covering the upper part of the del- toid and pectoral muscles. Passing over the clavicle, it ascends the 1 Collum ; cervix; trachelos; anchen. 5 Fovea supra-clavicularis. 2Guttur; jugulum. fi M. s. cervicis, or colli; m. platysma 8 Pomum Adami; eminentia thyroidea; myoides ; m. cutaneus ; m. latissimus nodus gutturis. colli; m. peaucier. 4 Fossa jugularis. 13 194 THE MUSCULAR SYSTEM. neck inwardly to the lower jaw, where its most anterior fibres join those of the opposite muscle, while others are inserted into the side of the chin, and become blended with the depressors of the lower lip and oral angle, and the most posterior ones terminate in the fascia investing the masseter muscle and parotid gland. A small offset1 crosses the check transversely from over the masseter muscle to the vicinity of the angle of the mouth. This muscle will aid the depression of the lower jaw; but its main purpose appears to be to extend the skin of the neck between the cla- vicle and lower jaw, thus elevating it from the influence of exterior pres- sure upon the air-passages and blood-vessels. THE CERVICAL FASCIA. Upon removing the subcutaneous cervical muscle, the Cer'vical fas'cia2 is exposed to view. Its upper part forms a sheath for the parotid and submaxillary glands, which are separated from each other by a well- marked process of the fascia, called the sty'lo-max'illary lig'ament,3 which extends from the styloid process of the temporal bone to the angle of the lower jaw. and inwardly to FlG- 150- the sheath of the principal cervical blood-vessels. In advance of the parotid gland, the fascia invests the masseter muscle and adheres along the base of the lower jaw. At the lower part of the neck the fascia adheres along the upper bor- der of the sternum and clavicle, and is continuous in front of these bones Inner part of the ramus of TnE lower jaw, right . . _ . . , side. 1, temporal bone; 2, lower jaw; 3, capsular With the tllOraClC laSCia. liellincl ligament of the articulation of the latter; 4. spheno- ^he neck, it is COntinUOUS with the maxillary ligament; 5, entrance of the inferior . dental canal; 6, stylo-maxillary ligament. %er inclosing the trapezius mUS- cle; and in proceeding forward it incloses the sterno-mastoid muscle, and the elevators and depressors of the hyoid bone and larynx. Processes of the fascia, continued inwardly, inclose the trachea and larynx, the oesophagus and pharynx; form the sheath of the large cervical blood-vessels, and become continuous with the fibrous investment of the muscles in front of the cervical vertebne. 1 M. risorius Santorini. 2 Fascia cervicalis; fascia colli; fascia superficialis et profunda cervicis; super- ficial and deep or proper cervical fascia. 3 Ligamentum stylo-maxillare. THE MUSCULAR SYSTEM. 195 Another process, separating the pterygoid muscles, and extended from the spinous process of the sphenoid bone to the lower jaw at the inner border of the dental foramen, constitutes the sphe'no-max'illary lig'a- ment.1 THE STERNO-MASTOID MUSCLE. The Ster'no-mas'toid muscle2 is the largest and most conspicuous of the muscles of the neck. It arises by a flat tendon from the upper fore part of the sternum, and ten- dinous and fleshy from the inner third of the clavicle. The two portions are sep- arated at their origin by an angular interval, but as the clavicular portion ascends nearly vertically, while the sternal portion inclines backward in its ascent, the two conjoin about the middle of the neck and form a single thick rounded belly, which proceeds to be inserted into the mastoid process and the superior semicircular line of the occipital bone. When the muscles of the two sides act together, the head is drawn downward; but when one alone contracts, the face is directed toward the opposite side. DEPRESSORS OF THE HYOID BONE AND LARYNX. The Ster'no-hy'oid muscle3 is a flat band arising from the inner sur- face of the upper part of the sternum and the contiguous portion of the 1 Erroneously described under the name cleido-mastoideus; m. cleido-mastoideus; of internal lateral ligament of the articu- m. mastoideus ; m. metator capitis. lation of the lower jaw. 3 M. sterno-hyoideus ; m. sterno-clei- 2 M. sterno-mastoideus; m. sterno- do-hyoideus; m. hyoides primus. Fig. 151. Front view of thb muscles of the neck. 1, posterior, and 2, anterior belly of the digastric; 3, its intermediate tendon at- tached to the hyoid bone and passing through the insertion of the stylc-hyoid muscle, 4; 5, mylo-hyoid; 6, genio-hyoid; 7, genio- glossal muscle of the tongue; 8, hyo-glossal; 9, stylo-glossal; 10, stylo-pharyngeal muscle; 11, sterno-mastoid muscle; 12, its ster- nal origin; 13, its clavicular origin; 14, sterno-hyoid; 15, sterno- thyroid ; 16, thyro-hyoid; 17, 18, omo-hyoid muscle; 19, trape- zius ; 20, anterior scalene muscle; 21, middle scalene muscle. 196 THE MUSCULAR SYSTEM. clavicle. Ascending the neck inwardly, it is inserted into the lower bor- der of the body of the hyoid bone. The Ster'no-thy'roid muscle,1 broader than the preceding, arises from the inner surface of the upper part of the sternum, and ascends the neck between the former muscle and the trachea, to be inserted into the oblique line at the side of the thyroid cartilage. The Thy'ro-hy'oid muscle,2 apparently a continuation of the muscle just described, arises from the oblique line of the thyroid cartilage, and ascends to be inserted into the lower border of the hyoid bone. The O'mo-hy'oid muscle3 consists of two fleshy bellies united by an intermediate tendon. It arises from the upper border of the scapula, in the vicinity of the coracoid foramen, crosses the neck in an oblique man- ner beneath the sterno-mastoid muscle, and is inserted into the lower margin of the body of the hyoid bone. The two bellies of the muscle in their course form an obtuse angle with each other, and this position is maintained by a connection of their tendon with the cervical fascia. Besides depressing the hyoid bone and larynx, the omo-hyoid muscles fix the median position of these parts in the neck. ELEVATORS OF THE HYOID BONE AND LARYNX. The Digas'tric muscle,4 as indicated by the name, consists of two fleshy bellies which are united by an intermediate rounded tendon. The posterior belly arises from the digastric fossa of the temporal bone, and the anterior belly from the inner surface of the lower jaw near its sym- physis. Both descend to the side of the hyoid bone, where their inter- vening tendon passes through the insertion of the stylo-hyoid muscle, and is attached to the former by means of a fibrous band. A thin aponeu- rosis, continuous with the latter, is extended between the anterior bellies of the two muscles. The Sty'lo-hy'oid muscle5 lies in contact with the posterior belly uf the preceding muscle. It arises from the middle of the styloid process of 1 M. sterno-thyroideus; m. bronchius. 2 M. thyro-hyoideus; m. hyo-thyroi- deus. 3 M. omo-hyoideus: m. coraco-hyoi- deus; m. scapula-hyoideus; m. hyoidus quartus. 1 M. digastricus; m. biventer; m. b. maxillae ; m. deprimens maxillae biven- ter ; m. bigaster. 5 M. stylo hyoideus; m. stylo-hyoides major: m. stylo-ceratoides; m. stylo- cerato-hyoideus. THE MUSCULAR SYSTEM. 197 the temporal bone, and descends to be inserted into the side of the body of the hyoid bone, where it is perforated by the tendon of the digastric muscle. The My'lo-hy'oid muscle1 is a triangular layer, forming with its fellow of the opposite side the muscular floor of the mouth. It arises from the molar ridge of the lower jaw, from whence its fibres proceed obliquely inward to conjoin with those of the opposite muscle, in the median line, extending from the chin to the hyoid bone. The Geni'o-hy'oid muscle2 is a slender band arising from the posterior mental tubercle, and descending in contact with the corresponding mus- cle of the other side, to be inserted into the body of the hyoid bone. It is situated between the inner part of the mylo-hyoid and the genio- glossal muscle. ^ . MUSCLES OF THE TONGUE, PALATE, AND PHARYNX. See the account of these different organs. MUSCLES OF THE LARYNX. See the account of this organ. DEEP MUSCLES OF THE FRONT OF THE NECK. The Anterior Scalene' muscle3 is deeply situated at the lower part of the side of the neck. It arises from the transverse processes of the third to the sixth cervical vertebrae inclusively, and descends to be in- serted into the anterior part of the first rib. In front of the insertion of this muscle the subclavian vein passes over the first rib. The Middle Scalene' muscle4 arises from all the cervical transverse processes, usually excepting the first, and descends behind the preceding muscle to be inserted into the posterior half of the first rib. Between the anterior and middle scalene muscles the axillary plexus of nerves and the subclavian artery take their course. 1 M. mylo-hyoideus ; m. mylo-pharyn- geus. 2 M. genio-hyoideus ; m. mento-bicor- nens. 3 M. scalenus anticus; m. s. prior; m. costo-trachelius. i M. scalenus medius; m. s. secundus. 198 THE MUSCULAR SYSTEM. The Posterior Scalene' muscle,1 small and thin, arises from the two or three lower cervical transverse processes, and descends to be inserted into the back part of the second Fia. 152. rib. The scalene muscles act- ing from above elevate the ribs ; but acting from be- low they flex the neck. The Larger Straight muscle2 arises by as many distinct tendinous heads, from the third to the sixth cervical transverse proc- esses inclusively, and as- cends inwardly to be in- serted into the basilar process of the occipital bone. The Smaller Straight muscle3 arises from the side of the atlas, and as- cends inwardly to be in- serted into the basilar process, beneath the last muscle. The two straight mus- cles are flexors of the head. Oeep muscles of the front of the neck. 1, basilar process of the occipital bone; 2, mastoid process; 3, larger straight mus- cle; 4, smaller straight muscle; 5, lateral straight muscle; r, 7, long cervical muscles; 8, posterior scalene muscle; 9, anterior scalene muscle ; 10,middle scalene muscle; 11,12, first and second ribs; 13, position at which the subclavian artery and axillary plexus of nerves emerge over the first rib, between the anterior and middle scalene muscles; 14, third dorsal vertebra; 15, atlas; 16,17, intertransverse muscles. The Long Cer'vical muscle4 extends along the side of the neck, and is quite complex in its arrangement. It consists of two portions, of which one arises from the side of the bodies of the three upper dor- sal and the three lower cervical vertebrae, and ascends to be inserted by distinct tendons into the fourth and fifth cervical transverse processes, and partially tendinous and fleshy into the bodies of the second, third, and fourth cervical vertebrae. The remaining portion arises by distinct ten- 1 M. scalenus posticus; m. s. tertius. 2 M. rectus capitis anticus major; m. r. c. internus major; m. r. c. anterior longus ; m. trachelo-basilaris ; larger an- terior straight muscle. 3 M. rectus capitis anticus minor; m. r. c. internus minor; m. r. c. anterior brevis ; m. trachleo-basilaris minus; m. rennuens; m. annuens; smaller anterior straight muscle. 4 M. longus colli; m. pre-dorso-cervi- calis; m. pre-dorso-atloideus. THE MUSCULAR SYSTEM. 199 dons from the third, fourth, and fifth cervical transverse processes, and ascends to conjoin with the preceding portion and to be inserted in front of the atlas. This muscle bends the neck forward. TOPOGRAPHICAL SKETCH OF THE ANATOMY OF THE NECK. Upon removing the skin of the neck and the subcutaneous cervical muscle, the cervical fascia is exposed, with the external jugular vein de- scending from behind the angle of the jaw to about the middle of the clavicle, where it dips inward to join the subclavian vein. Upon removing the superficial layer of the cervical fascia, the sterno-mastoid muscle is seen pursuing its course from the sternum to the mastoid process, and beneath it, crossing the neck in an opposite direction, is the omo-hyoid muscle. If the line of the latter be continued to the chin, the side of the neck will be divided by the two muscles into four triangles. The posterior cer'vical triangle is occupied with muscles, to be described in the account of the back. The anterior cer'vical triangle contains the root of the tongue, the hyoid bone, larynx and trachea, and, behind these, the pharynx and oeso- phagus. The larynx and trachea are covered by the depressor muscles of those organs; and beneath them, on the trachea, is the thyroid gland. The lower part of this triangle corresponds with the depression above the sternum, called the ju'gular fossa. The inferior cer'vical triangle corresponds with the supra-clavic'ular fossa. The deeper layer of the cervical fascia being removed from it, a quantity of loose areolar tissue, containing the supra-clavicular lymphatic glands, is exposed. Upon removing the latter, the triangle will be found to extend into a deep fossa between the clavicle and first rib, and con- tinuous outwardly with the axilla. The extent of the fossa varies with the position of the shoulder. If this is elevated and thrown back, the fossa is deepened and narrowed; if depressed and thrown forward, the fossa is rendered shallower and broader, and its parts become more dis- tinctly visible. Crossing the lower part of the triangle are the supra- scapular and transverse cervical blood-vessels. At the outer part of the triangle the scalene muscles are seen descending from the cervical verte- brae to the first rib. In front of the insertion of the anterior scalene muscle the subclavian vein passes over the first rib. Between the anterior and middle scalene muscles the subclavian- artery and axillary plexus of nerves emerge in their course to the axilla. The superior cer'vical triangle corresponds with the submax'illary fossa. Its upper part contains the submaxillary gland, lodged in an oval 200 THE MUSCULAR SYSTEM. depression of the deeper layer of the cervical fascia, the outer portion of which is a partition separating it from the parotid gland, and corre- sponding with the sty'lo-max'illary ligament. If the deeper layer of the cervical fascia is removed, above the submaxillary gland, the muscu- lar floor of the mouth is seen, formed by the mylo-hyoid muscle; and below the gland are the stylo-hyoid and digastric muscles. At the outer border of the triangle is the external carotid artery, from which diverge forward, in succession from below, the superior thyroid, lingual, and facial arteries. Curving across the triangle below the digastric muscle is seen the hypo-glossal nerve, giving off a descending branch to the depressor muscles of the hyoid bone. Upon detaching the sterno-mastoid muscle, the great cervical vessels are observed inclosed within a sheath and ascending the neck from the position of the sterno-clavicular junction toward the angle of the jaw. The sheath being opened, is seen to contain the primitive carotid artery at the inner side, the internal jugular vein to the outer side, and the pneumogastric nerve between them. The primitive carotid artery divides opposite the upper border of the larynx into the external and internal carotids, the former of which ascends to penetrate the parotid gland; the latter takes a deeper course to reach the carotid canal of the temporal bone. Behind the great cervical vessels lies the sympathetic nerve, and to their outer side a chain of lymphatic glands. FRONT OF THE THORAX. The front of the Thorax or chest, usually called the breast or bosom, on each side extends to the shoulder, the armpit, and the back. Be- low the clavicle it is slightly depressed, forming there the infra-clavicu- lar fossa. In lean persons it exhibits the outlines of the sternum and ribs, in vigorously muscular men the outlines of the superficial muscles, and in fat persons hemispherical elevations corresponding with the mammae. At the lower part of the sternum, over the position of the ensiform cartilage, is a depression, "the pit of the stomach."1 From this the lower border of the thorax slopes off on each side downward and outward. The skin of the breast is thin, readily raised into folds on each side, but adheres more closely over the sternum. Beneath it, is a layer of fascia containing more or less fat, excepting over the position of the sternum. Beneath the fatty layer2 is a thin layer of fascia invest- ing the muscles. Scrobiculus cordis ; procardium; anticardium. 2 Panniculus adiposus. THE MUSCULAR SYSTEM. 201 MUSCLES OF THE FRONT AND SIDES OF THE THORAX. The Great Pec'toral muscle1 occupies the front of the upper part of the chest and axilla. It arises from the sternal two-thirds of the clavicle, the front of the sternum and the upper six costal cartilages, and Fig. 153. Muscles of the front of the thorax and abdomen. 1, great pectoral muscle; 2, deltoid muscle; 3, latissimus muscle; 4, great serrated muscle; 5, subclavian muscle; 6, small pectoral muscle; 7, coraco- brachial muscle; 8, biceps flexor; 9, coracoid process of the scapula; 10, origin of the great serrated muscle; 11, intercostal muscles; 12, external oblique muscle of the abdomen; 13, its aponeurosis; 14, lower border of the latter, named Poupart's ligament; 15, external abdominal ring, the lower extremity of the inguinal canal; 16, straight muscle of the abdomen; 17, pyramidal muscle; 18, internal oblique muscle; 19, conjoined tendon of the internal oblique and transverse muscles; 20, position of the inguinal canal below the arching edges of the preceding two muscles. from the aponeurosis of the external oblique muscle of the abdomen. Proceeding outwardly, its fleshy fasciculi converge to a broad tendon, 1 Greater pectoral muscle; m. pectoralis major; m. adductor brachii; m. sterno' humeralis; m. sterno-costo-clavi-humeralis; m. sterno-cleido-brachialis. 202 THE MUSCULAR SYSTEM. which is inserted into the anterior margin of the bicipital groove of the humerus. The clavicular portion of the muscle is separated from the other by an interval filled with connective tissue. The outer portion of the muscle, with its tendon, is doubled on itself so as to produce the thick anterior fold of the axilla, and the lower fleshy fasciculi by this arrange- ment become inserted into the humerus higher than the upper ones. The Small Pec'toral muscle1 lies beneath the preceding muscle, and arises by serrations from the third, fourth, and fifth ribs. Proceeding upward and outward, its fibres converge to a short tendon, which is inserted into the coracoid process of the scapula. The great pectoral muscle draws the arm downward and forward, in which movement it is aided by the small pectoral muscle drawing the shoulder in the same direction. If the bones of the shoulder and arm are fixed, the pectorals aid in respiration by elevating the ribs. The Sub-clav'ian muscle2 arises by a short tendon from the first costal cartilage, and is inserted along the under surface of the clavicle. Exter- nally it is invested with a strong fascia, the cos'to-cor'acoid membrane,3 which starts from the end of the coracoid process, and diverges upward and inward to be attached along the under margin of the clavicle and the anterior end of the first rib. The Great Ser'rated muscle4 is a broad quadrate fleshy layer situated at the side of the thorax. It arises by angular serrations from the upper eight or nine ribs in advance of their middle, and proceeds backward to be inserted into the inner aspect of the base of the scapula. The five lower serrations alternate with as many points of origin of the external oblique muscle of the abdomen. Internally it is in contact with the ribs and intercostal muscles, externally it is subcutaneous, reach- ing upward into the axilla between the pectoral and latissimus muscles. It draws the scapula, and with it the whole shoulder, forward, or, if the latter is fixed, it may contribute to respiration by aiding the pectoral muscles in elevating the ribs, and thus increasing the capacity of the thorax. 1 Smaller pectoral muscle; m. pecto- vicular fascia; bifid ligament; liga- ralis minor; m. serratus anticus minor ; mentum bicorne. m. costo-coracoideus. 4 Anterior great serrated muscle; m. 3 M. subclavius, subclavicularis, or serratus magnus anticus; m. s. major; subclavianus; m. costo-clavicularis. m. costo-scapularis ; m. costo-basi-scap- 3 Ligamentum costo-coracoideum; cla- ularis. THE MUSCULAR SYSTEM. 203 THE BACK. The Back,1 as the term is commonly used, applies to the posterior part of the trunk, but, in its most restricted sense, refers to the posterior part of the thorax.2 A groove descends along the median line of the back, which is deepened in fat persons from the deposit of adipose tissue occurring on each side, while the skin tightly adheres to the summits of the spinous processes. On each side of the thorax, the scapula and its muscles produce a prominence, which is convex in stout individuals, but exhibits the outline of the scapula, with its projecting spine, in thin persons. The skin of the back is thicker and denser than in any other position of the body. It is attached to the parts beneath by long, extensible con- nective tissue, which allows it readily to be moved or raised into folds. The muscles of the back are invested with a thin layer of fascia, inde- pendently of the extensible areolar tissue just mentioned. They are divided into superficial and deep muscles; the former being broad, and for the most part intended to move the upper extremities. The latter are comparatively long and narrow, occupy the gutters along the verte- bral column, and are intended to maintain the erect position of this and the head. SUPERFICIAL MUSCLES OF THE BACK. The Trape'zius muscle3 arises from the superior curved line and pro- tuberance of the occipital bone, the nuchal ligament, and the summits of the spinous processes of the dorsal vertebrae. From this extensive ori- gin it converges, to be inserted into the outer third of the clavicle and into the upper margin of the acromion and spine of the scapula. Between the spinous processes, the muscles of the two sides conjoin by means of intervening tendinous fibres. The lower fibres of the muscle, in their ascent, as they approach the scapula, become tendinous, and glide upon the triangular surface at the commencement of its spine. The muscles of the two sides together have the outline of a trape- zium, whence their name. They fix the position of the shoulders, in the respiratory action of the pectoral and great serrated muscles. They also draw them upward, directly backward, or downward, according as their upper, middle, or lower fasciculi contract separately. If the 1 Dorsum; tergum ; notos; noton ; metaphrenon. 2 Dorsum ; dorsal region. 3 M. trapezius; m. cucullaris; m. mensalis; m. dorso-supra-acromialis; m. occipito-dorsi-acromialis. 204 THE MUSCULAR SYSTEM. shoulders are fixed, they may draw the head backward; or, if one alone acts, it may draw the latter to one side. Fig. 154. Mvsci.es of the back. 1, 2, trapezius; 3, acromion; 4, latissimus; 5, deltoid; 6, infra-spinous, and to its outer side the terete muscles; 7, external oblique muscle of the abdomen ; 8, middle gluteal; 9, external gluteal muscle; 10, elevator of the scapular angle; 11,12, rhomboid muscles; 13,14, splenius; 15, aponeu- rosis extending from the superior to the inferior serrated muscle, 16; 17, supra-spinous; 18, infra-spinous muscle; 19, lesser terete, and 20, greater terete muscle; 21, triceps extensor; 22, great serrated muscle; 23, internal obUque muscle of the abdomen. The Latis'simus muscle1 occupies the lower part of the back, extend- ing upwardly along the side of the thorax to the back of the humerus. It arises by a thin aponeurosis from the spinous processes of the lower six dorsal vertebrae, and all of those of the lumbar vertebra? and sacrum; from the posterior third of the crest of the ilium, and from the lumbar fascia. Its broad, fleshy belly ascends outwardly, in its course receiving 1 M. latissimus dorsi; m. dorsi-lumbo-sacro-humeralis; m. lumbo-humeralis; m. scalptor ani; m. tersor ani; m. brachium movens quartus. THE MUSCULAR SYSTEM. 205 fasciculi from the lower three ribs. It glides over the inferior angle of the scapula, from which it also usually receives a slip, and converges to a broad, tendinous band inserted into the posterior border of the bicip- ital groove of the humerus. Folding around the greater terete muscle, it forms the posterior boundary of the axilla; and, like the great pec- toral muscle, it has its lowest fasciculi inserted highest into the'humerus. A synovial bursa is interposed between the muscle and the inferior angle of the scapula, and another between its tendon and that of the greater terete muscle. The latissimus muscle draws the humerus downward and backward. In conjunction with the pectoral muscles, it is the chief agent in climb- ing and in walking with crutches. The Rhom'boid muscle1 is situated beneath the trapezius muscle. It arises from the lower extremity of the nuchal ligament and the spinous processes of the upper four dorsal vertebrae, and proceeds obliquely downward and outwrard to be inserted into the base of the scapula from its spine to its inferior angle. The muscle draws the scapula backward and upward. The fasciculus derived from the nuchal ligament is frequently more or less separated by a narrow interval from the lower portion of the muscle, leading to the usual division of the latter into the lesser and greater rhomboid muscles.2 The Elevator of the Scap'ular angle3 is situated at the side of the neck, and consists of a thick, fleshy bundle arising tendinously from the transverse processes of the upper four cervical vertebras, and descending to be inserted into the upper angle of the scapula. The Superior Ser'rated muscle4 is situated beneath the rhomboid muscle. It arises by a thin aponeurosis from the lower part of the nu- chal ligament and the upper three dorsal spinous processes, and descends obliquely outward to be inserted, by angular serrations, into the upper border of the second, third, fourth, and fifth ribs, beyond their angle. A thin aponeurosis extends between this and the succeeding muscle, covering the extensors beneath. 1 M. rhomboideus ; ni. cervici-dorso- scapularis. 2 M. rhomboideus minor and major, or superius and inferius. 3 M. levator scapulae; m. 1. anguli scapulae; m. 1. proprius scapulae; m. an- gularis ; m. patientiae ; m. trachelo-scap- ularis; elevator muscle of the angle of the scapula. * M. serratus posticus superior; m. dorso-costalis ; m. cervici-dorso-costalis. 206 THE MUSCULAR SYSTEM. The Inferior Ser'rated muscle1 is situated at the lower part of the back, beneath the latissimus muscle. It arises by a thin aponeurosis from the lower two dorsal and the upper three lumbar spinous processes, and ascends obliquely outward to be inserted by serrations into the lower border of the four inferior ribs. The two serrated muscles are antagonistic in their action. The supe- rior one aids in elevating the ribs, the inferior in depressing them, and thus both assist in respiration. DEEP MUSCLES OF THE BACK, OR EXTENSORS OF THE HEAD AND TRUNK. The extensor muscles, which maintain the erect position of the head and trunk, are situated at the back of the latter, and occupy the sides of the neck, the intervals between the angles of the ribs and spinous proc- esses of the vertebrae, and the sides of the loins, extending into the angular intervals of the sacrum and hip bones. They lie beneath the trapezius, latissimus, rhomboid, and serrated muscles, and consist of numerous fleshy and tendinous fasciculi, which are more or less intimately connected, so that they may be described as com- paratively few or many distinct muscles. The Dor'sal Exten'sor2 is a large muscle occupying the groove of the back at the side of the vertebral column. It is exceedingly complex in its arrangement, consisting of intermingled fleshy fasciculi and tendinous bands, and having many points of attachment to the vertebral column and ribs. Its lower portion is superficially composed of a strong apo- neurosis, from which many fleshy fasciculi have their origin. The muscle commences in a pointed manner upon the sacrum, is thickest in the loins, and gradually thins away on the thorax, from which, by accessory fasciculi, it is continued to the neck. It arises from the posterior surface of the sacrum, the posterior third of the crest of the ilium, and the spinous processes of the lumbar and lower two or three dorsal vertebrae, and in the vicinity of the last rib divides into two portions, named the longissimus and sacro-lumbar muscles. The Longis'simus muscle3 is the internal and larger portion of the dorsal extensor. It is inserted into the transverse processes of the 1 M. serratus posticus inferior; m. lumbo-costalis; m. dorso-lumbo-costalis. 2 M. extensor dorsi, or trunci commu- nis; m. erector spinae; m. sacro-spinalis; m. lumbo-costalis; m. opistothenar. 3 M. longissimus dorsi; m. semi-spi- natus; m. lumbo-dorso-trachelius; m. extensor dorsi internus. THE MUSCULAR SYSTEM. 207 lumbar- andj dorsal vertebrae, into the ends of the upper dorsal spinous processes,1 into the ribs within the position of their angles; and by accessory slips, derived from the upper dorsal transverse processes, is Extensor muscles of the back. 1, 2, 3, 4, 5, 6, the dor- sal extensor muscle. 1, origin prolonged to the lower from the ilium, sacrum, lum- four or five cervical bar> and lower dorsal verte- transverse processes.2 The Sa'cro-lum'bar muscle,3 in its ascent, receives accessory slips4 from the upper border of the ribs, and is in- serted by a series of tendons into the angles of the ribs and into the four or five lower cer- vical transverse proc- esses.5 brae; 2, insertion into the ribs, named the sacro-lumbar mus- cle; 3, insertion, named the longissimus muscle; 4, offset, named the dorsal spinal mus- cle ; 5, 6, prolongations to the neck, named the ascending and transverse cervical muscles; 7, trachelo-mastoid muscle; 8, complex muscle; 9, prolonga- tion of the longissimus, named the transverse cervical muscle; 10,11, semispinal muscle; 12, 13, smaller and larger straight muscles of the head; 14.15, su- perior and inferior oblique muscles; 16, multifid-spinal muscle; 17, elevators of the ribs; 18, inter-transverse mus- cles; 19, quadrate lumbar muscle. The Sple'nius mus- cle6 is situated at the back of the neck, beneath the trapezius muscle. It arises from the upper six dorsal spinous processes and the lower half of the nuchal ligament. Proceeding upward and outward, it divides into two portions, of which one7 is inserted into the upper four cervical transverse processes, and the other8 is inserted into the mastoid portion of the temporal bone and the con- tiguous part of the surface between the curved lines of the occipital bone.( 1 M. spinalis dorsi. Usually described as distinct, ascending from the upper two lumbar and the three lower dorsal spinous processes, to the upper eight or nine dorsal spinous processes. 2 M. transversalis cervicis, or colli; m. t. major colli, are names given to the portion prolonged to the neck. 3 M. sacro-lumbalis; m. sacro-costalis; m. ilio-costalis; m. lumbo-costo-trache- lius ; m. extensor dorsi externus. * M. accessorii, or additamentum ad sacro-lumbalcm. 5 M. cervicalis ascendens, or descend- ens Diemerbroeckii; m. accessorius ad sacro-lumbalem; m. transversalis colla- teralis colli, are names given to the por- tion prolonged into the neck. 6 Posterior mastoid muscle ; m. cervi- co-dorso-mastoideus. 7 M. splenius colli; m. dorso-trachc- lius. 8 M. splenius capitis ; m. cervico-mas- toideus. \ 208 THE MUSCULAR SYSTEM. The Com'plex muscle,1 partly concealed by the last, arises from the transverse processes of the upper four to six dorsal vertebras and the transverse and articular processes of the lower four cervical vertebra), and ascends to be inserted into the inner part of the surface between the curved lines of the occipital bone. Its upper portion is partially inter- sected by a transverse tendinous structure ; and a large fasciculus of the muscle is divided into two bellies by an intermediate tendon.2 The splenius and complex muscles of the two sides of the neck are important agents in maintaining the erect position of the head. The Trache'lo-mas'toid muscle,3 situated between the upper end of the dorsal extensor and the complex muscle, is intimately connected with the former, and may with propriety be considered its prolongation to the head. It arises by narrow tendons from the roots of the transverse processes of the lower four cervical vertebrae, and ascends outwardly to be inserted into the mastoid process of the temporal bone beneath the sterno-mastoid and splenius muscles. The Semispi'nal muscle1 consists of fleshy and tendinous fasciculi, obliquely extended between transverse and spinous processes in the back and neck, beneath the dorsal extensor and complex muscles. It arises from the dorsal transverse processes, except the one or two lower ones, and is inserted into the upper five dorsal spinous processes and the lower five of those of the neck. The upper and lower portions are sometimes separated by an interval, and these are usually described as distinct, with the names of semispinal muscle of the neck5 and of the back.6 The Mul'tifid spi'nal muscle,7 partially concealed beneath the last, consists of numerous short, oblique fasciculi, extended from the trans- verse and articular processes to the contiguous spinous processes, from the sacrum to the axis. The fasciculi vary in length, some extending 1 M. complexus; m. c. major; m. tra- chelo-occipitalis; m. dorso-trachelo-oc- cipitalis. 2 This double-bellied fasciculus consti- tutes the m. biventer cervicis. 3 M. trachelo-mastoideus; m. complex- us minor. 4 M. semispinalis dorsi et colli. 5 M. semispinalis colli, or cervicis; m. spinalis, or transversalis colli, or cervi- cis; m. transverso- or articulo-spinalis colli; m. semispinatus colli. 6 M. semispinalis dorsi, or externus; m. transverso-spinalis dorsi; m. semispi- natus dorsi. 7 M. multifidus spinae; m. transveralis dorsi; m. transverso-spinalis; m. t. s. lurubarum dorsi et colli; m. spinales et transversales lumbarurn; m. sacer; m. semispinalis internus et transverso-spi- nalis colli pars interna ; m. lumbo-dorsi- spinalis; lumbo-cervical portion of the spinal muscle; in part, the musculi ro- tatores spinae. THE MUSCULAR SYSTEM. 209 between two vertebrae, others between three, and a few between four, or even five. This and the preceding muscles are extensors of the vertebral column. The Inter-spi'nal muscles1 consist of short, fleshy bundles, situated in pairs between the contiguous spinous processes of the vertebrae. They are best developed in the neck, and usually are obsolete in the dorsal region. The Inter-trans'verse muscles2 consist of short, fleshy bundles, occu- pying the intervals of the contiguous transverse processes. They are best developed in the neck, where they are double, are rudimental in the dorsal region, and are well marked in the loins. These and the preceding small muscles aid in the extension of the ver- tebral column. The Larger Straight muscle3 arises tendinously from the spinous process of the axis, and ascends to be inserted into the inferior curved line of the occipital bone. The Smaller Straight muscle4 arises from the rudimental spinous process of the atlas, and is inserted into the occipital bone below its inferior curved line. The Lateral Straight muscle5 arises from the transverse process of the atlas, and is inserted into a ridge of the corresponding process of the occipital bone. The Superior Oblique muscle6 arises from the extremity of the trans- verse process of the atlas, and ascends obliquely inward to be inserted into the outer part of the surface between the curved lines of the occip- ital bone. The Inferior Oblique muscle7 arises from the spinous process of the 1 M. interspinals; m. i. colli, dorsi et 5 M. rectus lateralis; m. rectus capi- lumbarum. tis lateralis; m. lateralis Fallopii; m. 2 M. intertransversarii. transversalis anticus primus; m. trache- al, rectus major; m. rectus capitis lo-atloido-basilaris; m. atloido-subocci- posticus major; m. axoido-occipitalis; pitalis. m. spini-axoido-occipitalis; larger pos- 6 M. obliquus capitis superior, or mi- terior straight muscle. nor; m. atlo-, post-, or submastoideus; 4 M. rectus minor; m. r. c. p. minor; m. trachelo-atloido-occipitalis. m. atlo-occipitalis ; m. tuber-atloido-oc- 7 M. o. c. inferior, or major; m. axo- cipitalis; smaller posterior straight mus- atloideus ; m. spini-axoido-tracheli-atloi- cle. deus. 14 oiQ THE MUSCULAR SYSTEM. axis, and passes obliquely outward and upward to be inserted into the extremity of the transverse process of the atlas. The straight and oblique muscles contribute to maintain the erect con- dition of the head. The inferior oblique and larger straight muscles rotate the latter, together with the atlas upon the axis. MUSCLES OF THE RIBS. The Intercos'tal muscles, of which there are eleven pairs on each side of the thorax, occupy the intervals of the ribs. They consist of two planes of short, fleshy and tendinous fibres, extended between the contiguous borders of the ribs and costal cartilages. The External Intercos'tal muscles1 commence at the tubercles of the ribs, and, with their fibres directed obliquely downward and forward, advance to the costal cartilages, between which they terminate in a thin aponeurosis. The Internal Intercos'tal muscles2 commence at the sternal ends of the costal cartilages, and, with their fibres directed obliquely downward and backward, crossing the course of those of the preceding muscles, proceed to the angles of the ribs, where they terminate in a thin aponeu- rosis, extending to the vertebrae. On the inner surface of the ribs, more or less frequently, a variable number of fasciculi of fibres of the internal intercostals extend over two or even three intercostal spaces.3 Between the intercostal muscles the intercostal blood-vessels and nerves pursue their course. The internal intercostal muscles are in con- tact with the pleura; the external ones with the pectoral and great ser- rated muscles. The Ster'no-cos'tal muscle,4 variable in its extent and attachments, is situated within the front of the thorax. It arises by a thin aponeurosis from the inner surface of the lower two divisions of the sternum and the contiguous ends of the costal cartilages, whence its fibres diverge upward and outward, to be inserted by digitations into the costal cartilages from the fifth to the second inclusively. The Cos'tal El'evators5 are twelve in number, on each side of the thorax, and lie beneath the extensor muscles of the back. They con- 1 M. intercostales externi. - M. intercostales interni; m. inter- pleuro-costales. 3 M. infracostales; m. subcostales. 4 M. sterno-costalis; m. triangularis sterni; m. pectoralis internus. 5 Elevator muscles of the ribs; m. lr- vatores cos1 arum breviores et longiorcs; m supra-costales. THE MUSCULAR SYSTEM. 211 sist of narrow bundles arising tendinously from the ends of the trans- verse processes of the last cervical and all the dorsal vertebrae, except the last one. Descending obliquely outward, their fibres diverge to be inserted into the contiguous ribs, between their tubercles and angles. The lower muscles of the series send an additional fasciculus to the second ribs below their origin. The intercostal muscles act together, and either raise or depress the ribs according as the first or last of the series of the latter becomes the more fixed point of action. Thus, if the scalene muscles draw up the first and second ribs, this will determine the intercostals to raise all the ribs. If, on the other hand, the quadrate lumbar muscles draw down the last ribs, then all the others will be depressed by the intercostals. The costal elevators, as expressed by their name, and the superior serrated muscles, raise the ribs. The sterno-costal and inferior serrated muscles depress the ribs. From the above, it will have been perceived that all the muscles men- tioned concur in promoting the function of respiration. THE ABDOMEN. The Abdo'men or belly1 is that part of the'trunk which is included between the thorax and pelvis. The large vacuity observed in the skeleton between the inferior mar- gin of the thorax and the superior border of the pelvis, is closed by the soft, extensible abdom'inal pari'etes or walls, composed of skin, the superficial fascia, six pairs of muscles, the transverse fascia, and the peritoneum. The abdominal parietes are longest anteriorly, and become gradually shortened as they approach the back part, named the loins or lumbar regions,2 situated on each side of the vertebral column. In the upright position the abdominal walls are convex and protuberant, vary- ing in these respects according to the fatness of the individual. In the recumbent position they sink inwardly, and in very lean persons even the vertebral column may be felt through them. Inspiration increases their protuberance, and expiration their depression. In vigorous men, the outlines of the muscular bellies of the abdominal parietes are visible through the skin. In fat persons, usually including healthy women, these are obscured by the subcutaneous fat. Over the position of the end of the sternum is a depression called the pit of the 'Venter; gaster; abdomen; alvus; venter imus, or infimus; epischion; hypo- gastrion; hypoccelium; hypoutrion; hypochoilion; etron; nedys; neira; physce. 1 Luiuhi; lendis; psoae; reins. 212 THE MUSCULAR SYSTEM. stomach,1 which becomes more evident with an increase of fat. Xear the centre of the abdomen, in front, is the umbili'cus or navel,- which is a cicatrix remaining from the connection of the umbilical cord of the foetus. From the close adhesion of the skin to the umbilicus, its depth increases with the accumulation of fat around. The lower part of the abdominal walls is defined on each side by the prominence corresponding with the crest of the ilium and named the hip; and in advance of this by the groin and prominence of the pubes. The groin or in'guinal region3 corresponds with the crease descend- ing from the hip to the pubis and separating the abdomen from the front of the thigh. The skin of the abdomen is rather thin and moderately extensible; in lean persons is readily elevated into folds, but not in fat persons. Its extensibility is not so great as might be supposed from the frequent occurrence of distention of the abdominal walls from the accumulation of fat, pregnancy, dropsy, or other causes. In such cases partial rup- tures of the dermis take place; and even after the distention is removed, the position of these ruptures is indicated by their cicatrix-like marks on the skin. SUPERFICIAL FASCIA OF THE ABDOMEX. The Superficial Fascia4 is well developed, especially toward the lower part of the abdomen, where it is observed to consist of two distinct layers. It is continuous above with the superficial fascia of the thorax, and behind with that of the back. Its two layers, blended together, adhere along the median line of the abdomen, along the crest of the ilium, and Poupart's ligament, and become continuous with the super- ficial fascia of the thigh, that of the spermatic cord, and the penis. Where the two layers are separable, the subcutaneous one is found to be composed of loose areolar tissue containing more or less fat, which increases in descending toward the pubis. At the umbilicus it never contains fat, so that the fatter the individual the more depressed the umbilicus will appear. The deeper layer is thinner and more membran- ous in its character than the other, and is not disposed to the develop- ment of fat in its interstices. Between the two layers are contained the subcutaneous blood-vessels, among which, the superficial epigastric artery and vein are conspicuously observed ascending obliquely from the groin. 1 Scrobiculus cordis. 3Inguen; plica inguinalis; bubo. 2Umbilic; umbo; omphalos; mesom- 4 Fascia superftlcialis abdominis. phalium; radix, or medium ventris. THE MUSCULAR SYSTEM. 213 MUSCLES OF THE ABDOMEN. The front and lateral walls of the abdomen are composed of six pairs of muscles, of which three are broad muscles, and the others are long ones. The External Oblique muscle,1 the stoutest of the three broad ab- dominal muscles, consists of a fleshy portion occupying the side of the abdomen, and a strong aponeurotic portion extending over the front of the latter. It arises by angular digitations from the outer surface of the lower eight ribs ; the digitations being received between similar processes of the origin of the great serrated and latissimus muscles. The fleshy fas- ciculi incline downward and inward, the lowest ones being inserted into the crest of the ilium, while the others terminate in an aponeurosis, which extends to the median line of the abdomen, from the sternum to the pubis, and conjoins with that of the opposite side. The upper three-fourths of the aponeurosis present the appearance of a broad band at the side of the median line of the abdomen; and its lower fourth widens outward to the anterior superior spinous process of the ilium. Though mainly composed of fibres continuing in the direc- tion of the fleshy fasciculi, it nevertheless contains many crossing ones, apparently derived from the aponeurosis of the opposite muscle. In several positions the fibres by their separation leave small square inter- vals, through which blood-vessels reach the superficial fascia and integu- ment. The upper part of the aponeurosis is connected with the origin of the great pectoral muscle, and is attached to the third piece of the sternum. As the aponeurosis approaches the pubis its fibres diverge, leaving between them a triangular interval, the external abdom'inal ring,2 which gives passage to the spermatic cord of the male, and the round ligament of the uterus of the female. The direction of the ring is obliquely downward and inward ; its base being formed by the body3 of the pubis, and its sides or columns4 by the diverging fibres of the aponeurosis. The inner or upper column is attached in front of the pubic symphysis, and interlaces with the corresponding insertion of the opposite muscle. The outer or lower column is formed by the inferior and somewhat thick- 1 M. obliquus abdominis externus, de- scendens, or major; m. costo-abdomi- nalis; m. ilio-pubo-costo-abdominalis. 2 Abdominal ring; annulus abdomi- nis, or inguinalis; inguinal ring. 3 Crest of the pubis. i Pillars; crura. 214 THE MUSCULAR SYSTEM. ened fibres of the aponeurosis, extended between the anterior superior spinous process of the ilium and the spine of the pubis, constituting the so-called Poupart's ligament1 or femoral arch,2 important in its relations with inguinal and femoral herniae Mcscles OF the frost of the trlxk; on the left side are seen the superficial muscles, on the right the deeper ones. 1, great pectoral; 2, deltoid; 3, latissimus; 4, great serrated; 5, subclavian; 6, small pec- toral; 7, coraco-brachial; 8, biceps flexor muscle; 9, coracoid process; 10, great serrated muscle; 11, inter- costals; 12, external oblique; 13, its aponeurosis; 14, Poupart's ligament; 15, external abdominal ring; the figure rests upon the falciform process of the fascia of the thigh bounding the saphenous opening exter- nally; 16, straight muscle of the right side, exposed by removing the front of its sheath, which remains on the left side; 17, pyramidal muscle; 18, internal oblique; 19, conjoined tendon of the internal oMiqne and transverse muscles; 20, position of the inguinal canal below the arching edges of the muscles just named. Above the position of the external abdominal ring, transversely cross- ing fibres proceed from the line of Poupart's ligament toward the median line of the abdomen, apparently with the object of preventing a greater separation of the columns of the ring. From the edges of the latter, a 1 Ligament of Fallnpius. - Crural, or inguinal arch. THE MUSCULAR SYSTEM. 215 thin layer of connective tissue1 is prolonged upon the spermatic cord, or round ligament. Poupart's ligament in its course makes a curve with the convexity downward, and is somewhat inflected or directed inwardly. Below, it is continuous with the femoral fascia. At its insertion, a process of the same structure extends a short distance along the pectineal line of the pubis, and terminates in a crescentic margin, constituting the so-called Gimbernat's ligament,2 important in its relations with femoral hernia. The Internal Oblique muscle3 is placed beneath the last, and, like it, is fleshy at the side of the abdomen, and aponeurotic in front. It arises from the outer half of Poupart's ligament, the crest of the ilium, and the lumbar fascia. From this origin the fleshy fasciculi radiate forward, the more posterior ascending obliquely and becoming attached to the margin of the lower four costal cartilages contiguous to their internal intercostal muscles, while the others terminate in an apo- neurosis extending from the sternum to the pubis. At its upper extrem- ity the aponeurosis is attached to the end of the sternum and the seventh and eighth costal cartilages. For three-fourths of its extent it splits at the semilunar line into two laminae, of which one proceeds in front of the straight muscle and identifies itself with the aponeurosis of the external oblique muscle, while the other proceeds behind the straight muscle, and in like manner identifies itself with the aponeurosis of the transverse muscle. The lower fourth of the aponeurosis passes without division in front of the straight muscle. The inferior fibres of the internal oblique muscle arch forward and downward over the course of the spermatic cord, or round ligament of the uterus, and, in conjunction with corresponding fibres of the trans- verse muscle, form the conjoined tendon,4 which is inserted into the body and pectineal line of the pubis, within the position of the external ab- dominal ring, thus affording a protection against the escape of any por- tion of the bowels through this aperture. The Transverse muscle5 lies beneath the preceding muscles, and like them presents the same relation of fleshy and aponeurotic portions. It arises from the outer half of Poupart's ligament, the crest of the ilium, the lumbar fascia, and the inner surface of the lower six costal 1 Intercolumnar fascia; fascia sperma- tica. 2 Hey's ligament.^Xo < *v *^*^ -il' 1 M. obliquus abdominus internus, as- cenduns, or minor; m. ilio-abdominalis ; m. ilio-lumbo-costo-abdominalis; m. ac- clivis. * Superficies intercruralis. 5 M. transversalis abdominis; m. lum- bo-abdominalis. 216 THE MUSCULAR SYSTEM. Fig. 157. cartilages, where it indigitates with the origin of the diaphragm. The fleshy fasciculi, as indicated by the name of the muscle, proceed trans- versely forward and terminate in an aponeurosis, of which the upper three-fourths join the posterior lam- ina of the aponeurosis of the in- ternal oblique muscle, and with it proceed to the median line of the abdomen, while the lower fourth passesin front of the straight muscle, and, in conjunction with the corres- ponding portion of the aponeuroses of the other broad muscles, likewise proceeds to the median line of the abdomen. The inferior fibres of the trans- verse muscle, like those of the in- ternal oblique, arch forward and downward to the conjoined tendon. Internally this muscle is invested with a thin, fibrous membrane, the transverse fascia,1 which attaches it to the peritoneum. The Straight muscle2 is a broad, fleshy band, situated at the side of the median line of the abdomen, and extending from the pubis to the front of the thorax. It arises by a flat tendon from the symphysis and body of the pubis, expands gradually to the breadth of three or four inches, and ascends to be inserted in front of the fifth, sixth, and seventh costal cartilages. In its course it presents three or four short tendinous intersections,3 which ex- tend through the breadth and thickness of the muscle, and adhere tightly to the aponeurosis covering the latter. These tendinous intersections appear to represent the abdominal ribs of lizards. The straight muscle is inclosed in a sheath,4 formed by the aponeu- VlEW OF THE LEFT SIDE OF THE ABDOMEN. 1, por- tion of the latissimus muscle; 2, origin of the great serrated muscle; 3, origin of the external oblique; 4, external intercostals; 5, internal intercostals; 6, transverse muscle; 7, its aponeurotic origin; S, its aponeurotic insertion; 9, lower part of the internal oblique muscle; 10, straight muscle of the right side; 11, position of the inguinal canal between the arched border of the internal oblique and trans- verse muscles and Pouparfs ligament; the figure rests on the transverse fascia; 12, the gluteal mus- cles. 1 Fascia transversalis. 2 M. rectus abdominis; m. pubio-sternalis. 3 Inscriptiones tendineas. * Vagina musculi recti. THE MUSCULAR SYSTEM. 217 roses of the broad muscles, which is incomplete, however, at its lower fourth posteriorly, where the muscle is in contact with the transverse fascia. The deficiency in the sheath is more or less defined by a thin, lunated edge,1 which is confluent with the transverse fascia extending toward the pubis. In consequence of the deficiency in the aponeurotic sheath of the straight muscle a space is left, recently described2 as the preperitone'al cavity,3 which accommodates the urinary bladder in a distended con- dition. The Pyram'idal muscle4 is situated beneath the aponeuroses of the broad muscles upon the lower extremity of the straight muscle. It arises from the symphysis and body of the pubis, and ascends one-third the distance toward the umbilicus, to be inserted into the median line of the abdomen. This muscle sometimes exists only on one side, and not unfrequently it is altogether absent. At the median line of the abdomen, the aponeuroses of the three pairs of broad muscles are intimately associated with one another, the tendin- ous fibres of one side crossing and intersecting those of the opposite side. From its white appearance, rendered more conspicuous by the dark color of the straight muscle being seen through the aponeurosis on each side, it is named the linea alba.5 This is wide above but narrow below, and separates the straight muscles. Near its middle the umbilicus ap- pears as a fibrous cicatrix. The aponeuroses of the broad muscles commence nearly in the same position, corresponding with the outer border of the straight muscles. This position also appears as a white line, in contrast with the fleshy bellies on each side, and is named, from its curving inwardly as it ap- proaches the pubis, the semilunar line.6 Crossing from the semilunar to the median line, the tendinous intersec- tions of the straight muscle are seen through the aponeurosis investing the latter, and are named, from their course, the transverse lines.7 One of these exists nearly opposite the lower end of the sternum, a second about half the distance from this to the umbilicus, a third nearly on a level with the latter, and usually an imperfect one half way between the umbilicus and pubis. They intimately adhere to the aponeurosis in front 1 Linea semicircularis; linea Dou- i M. pyramidalis abdominis; m. pu- glasii; plica semilunaris Douglasii. bio-umbilicalis; m. Fallopii; m. succen- 2 Sitzungsberichte der K. Akad. der turiatus; m. auxiliarius. Wissenschaften. Wien, 1858, page 259. 5 l. centralis ; 1. candidula. 5 Cavum praeperitoneale ; c. p. Retzii; 6 l# semilunaris. porta vesicae ; p. v. Retzii. 7 L. transversa?. 218 THE MUsrULAlt SYSTEM. of the straight muscle, and, in powerfully muscular men, together with the median and semilunar lines, indicate the position of the intervening fleshy bellies, even through the tegumentary covering of the abdomen. The Quad'rate Lum'bar muscle1 is situated at the side of the lumbar vertebrae, and is inclosed in a sheath formed by the lumbar fascfa. It arises tendinously from the crest of the ilium back of its middle, and ascends to be inserted into the last rib and the transverse processes of the lumbar vertebrae, except the last one. The muscles of the abdomen support and compress the viscera of its cavity. By depressing the ribs and elevating the abdominal viscera, they antagonize the action of the diaphragm, and thus become the prin- cipal muscles in expiration. They act also in the expulsion of the con- tents of the bowels and urinary bladder, in the birth of the child, in vomiting, etc. THE LUMBAR FASCIA. The Lum'bar fas'cia2 consists of two fibrous layers inclosing the qnadrate lumbar muscle, and forming part of the origin of the internal oblique, transverse, and latissimus muscles. The anterior layer is at- tached to the front of the roots of the transverse processes of the lumbar vertebrae, the crest of the ilium, and the last rib; in which latter position its thickened margin constitutes the external arc'uate ligament.3 The posterior layer, thicker and more aponeurotic than the other, is attached to the ends of the transverse processes of the lumbar vertebrae, the crest of the ilium, and the last rib. It separates the quadrate lumbar muscle from the dorsal extensor, and is joined at the outer border of the former by the anterior layer, in which position it gives origin to the muscles above mentioned. THE TRANSVERSE FASCIA OF THE ABDOMEN. The Transverse fascia4 of the abdomen is a thin, fibrous membrane investing the inner surface of the transverse muscles, and attaching them to the peritoneum. It is strongest in the inguinal region, and in this position is important in its relations with hernia. It invests the straight muscle where its sheath is incomplete, and closely adheres to the lunated margin of the latter, as it does also to the body and pectineal line of the pubis, behind the tendon of the straight muscle and the conjoined tendon 1 M. quadratus lumborum, or dorsi; m. lumbaris externus; m flectans par lumborum; m. ilio-costalis; m. ilio- lumbo-costalis. 2 F. lumborum. 3 L. arcuatum externum. * F. transversa; f. transversalis ; f. Cooperi; f. endogastrica. THE MUSCULAR SYSTEM. 219 of the internal oblique and transverse muscles. Traced upward, it becomes thinner, and is continuous with the fibrous attachment of the peritoneum to the diaphragm. Traced toward the loins, it becomes thinner and looser in texture. It tightly adheres to the crest of the ilium and Poupart's ligament, and from these positions is continuous with the iliac fascia. Half way between the anterior superior spinous process of the ilium and the symphysis of the pubis, just above Poupart's ligament, the trans- verse fascia is prolonged downward and inward as a sheath1 to the sper- matic cord. The entrance of this prolongation, viewed as an orifice, is named the internal abdom'inal ring, the commencement of the inguinal canal. THE INGUINAL CANAL. The In'guinal canal2 is the space in the lower part of the abdominal walls which gives passage to the spermatic cord of the male, and the round ligament of the uterus in the female. It is narrower in the latter, in accordance with the smaller size of the round ligament than the spermatic cord. Fig. 158. View of the inguinal canal. 1, por- tion of the fleshy belly of the external ob- lique muscle; 2, its aponeurosis; 3, por- tion of the latter raised up, exposing the inguinal canal; 4, linea alba; 5, insertion of the aponeurosis of the external oblique into the body of the pubis; 6, its insertion into the spine of the pubis, named Pou- part's ligament; 7, division of the fibres of the aponeurosis crossed "by transverse fibres; 8,external abdominal ring, the ter- mination of the inguinal canal; 9, anterior superior spinous process, the origin of Poupart's ligament; 10, arching lower bor- der of the internal oblique and transverse muscles; 11, conjoined tendon of the latter muscles; 12, fibres of the cremaster muscle descending on the spermatic cord from the edges of the muscles just named; 13, rests on the transverse fascia; to its right are the epigastric vessels crossing the course of the inguinal canal; 14, iliac portion of the femoral fascia; 15, pubic portion; 16, falciform process; 17, saphenous opening; 18, saphenous vein joining the femoral vein through the saphenous opening; 19, the femoral artery and vein exposed by raising the portion of fascia which forms the falciform process; 20, suspensory ligament of the penis. The canal is about an inch and a half long; its upper extremity being the internal abdom'inal ring,3 and its lower extremity the external 1 Infundibuliform fascia; fascia sper- 2 Canalis inguinalis; spermatic canal. matica interna, or propria. 3 Apertura interna; a. abdominalis. 220 THE MUSCULAR SYSTEM. abdom'inal ring.1 Iu front it is bounded by the aponeurosis of the external oblique muscle, behind by the transverse fascia and conjoined tendon of the internal oblique and transverse muscles, above by the arching borders of the latter muscles, and below by Poupart's ligament. The middle of the inguinal canal is crossed behind by the epigastric blood-vessels, which pursue their course, involved in the structure of the transverse fascia, from the external iliac blood vessels, upward and in- ward toward the umbilicus. The interior surface of the abdominal wall, in the inguinal region, presents a slight fold of peritoneum pursuing the same course as the epi- gastric blood-vessels, and hence called the epigas'tric fold.2 The fold / divides the inguinal region into two shallow depressions named the : internal and external in'guinal fossae.3 The deeper part of the internal in'guinal fossa4 corresponds with the position of the external abdominal ring, and is the point at which direct inguinal hernia occurs. The deeper part of the external in'guinal fossa corresponds with the position of the internal abdominal ring, into which the peritoneum is sometimes prolonged, especially in the female, as a small funnel-like pit;5 and at this point oblique inguinal hernia has its commencement. REMARKS ON INGUINAL HERNIA. The protrusion of any portion of the contents of the abdomen through an opening in its parietes is called a her'nia; the varieties of which are named from the particular positions of their occurrence, and thus we have umbilical hernia, inguinal hernia, femoral hernia, and others. The pro- truding part pushes before it the membranous structures it meets in its passage, and these furnish coverings to the hernia. The peritoneum, which is the membrane first protruded, forms the so-called her'nial sac. An inguinal hernia may occur either from the internal or the external inguinal fossa. Most frequent from the latter position, it follows the course of the inguinal canal, and emerges at the external abdominal ring, and receives the name of oblique in'guinal her'nia. In this variety the hernial sac has for its coverings, in the order of their protrusion: first, a membrane, more or less distinct, formed by the association of the trans- . verse and intercolumnar fasciae, including the fibres of the crcmaster muscle; second, the superficial fascia; and third, the skin. * Triangle of Hesselbach. 5 Canal of Nuck. 1 Annulus inguinalis; apertura externa. - Plica epigastrica. 3 Fovese inguinales. THE MUSCULAR SYSTEM. 221 The protrusion of a hernia directly through the external abdominal ring occurs from the internal inguinal fossa, and receives the name of direct in'guinal hernia.1 The coverings of the hernial sac in this variety, in the order of protrusion, are: first, a membranous investment, derived from the transverse fascia and the intercolumnar fascia, including some loose fibres of the conjoined tendon; second, the superficial fascia; and, third, the skin. If the protrusion occurs through a separation or interval of the fibres of the conjoined tendon, this structure would not contribute to form the first covering of the hernial sac. In consequence of the comparative narrowness of the inguinal canal and smallness of the abdominal rings, inguinal hernia is of rare occur- rence in the female. In oblique inguinal hernia, the excretory duct of the testicle and ves- sels of the spermatic cord and the epigastric blood-vessels lie at the inner side of the neck of the hernia; but in direct inguinal hernia, the sper- matic cord and epigastric vessels are at the outer side. THE DIAPHRAGM. The Di'aphragm2 is a muscular partition separating the thorax and abdomen. Its under or abdominal surface is deeply vaulted, and is invested by the peritoneum ; its upper surface is convex, and is covered by the two pleurae and the pericardium. Its centre rises to a level with the fifth costal cartilages ; and on the right side, apparently to accom- modate the liver, it rises higher than upon the left. The origin of the diaphragm is from the inferior margin of the thorax as constituted by the end of the sternum and the lower six ribs, from the arcuate ligaments, and from the bodies of the upper four lumbar verte- bras. From this extensive circle the fleshy fasciculi ascend and converge to a central tendon. The origin from the ribs is by fleshy serrations included between similar processes of the transverse muscles of the abdomen. The arc'uate ligaments3 are thin and narrow fibrous arches, of which the inner one extends over the upper extremity of the psoas muscle from the body of the first lumbar vertebra to its transverse process; the outer one forms the upper edge of the anterior layer of the lumbar fascia, 1 Internal inguinal hernia; ventro-in- guinal hernia. 2 Diaphragma; musculus phrenicus ; midriff; diaphraxis ; disseptum ; discre- torium: hypozoma; perizoma; diazomo; phrenes; prsecordia; praecinctus; suc- centura; muse, succinct us; septum transversum; respiratorium ventris. 3 Ligamenta arcuata. 0">0 THE MUSCULAK SYSTEM. Fig. 1 .">«.). extended from the transverse process of the first lumbar vertebra to the end of the last rib. The portions of the diaphragm proceeding from the lumbar vertebra' are named its crura.1 The right crus is the larger, and arises tendinously from the bodies and in- tervening fibro-cartilages of the upper four lumbar vertebras; the left crus arises in the same manner from the upper three. The central tendon2 of the diaphragm is a broad aponeurosis, composed of converging and inter- woven fibrous bands, and is entirely surrounded by the fleshy part of the muscle. It is usually de- scribed as somewhat heart shaped, with the notch di- rected backward, or more correctly as trilobed, one lobe being directed forward, and one backward on each side. Three important orifices exist in the diaphragm for the passage of the aorta, oesophagus, and inferior cava, The aort'ic orifice3 is formed between the crura of the diaphragm in front of the first lumbar vertebra. The tendons of origin of the crura meet behind the aorta, and conjoin in a narrow arch in front of it, so that the vessel is inclosed by fibrous structure and is not liable to constriction from the action of the fleshy portion of the muscle. Besides the aorta, the thoracic duct passes through the aortic orifice of the diaphragm. The cesophage'al orifice4 is an elliptical opening, situated above and a little to the left of the aortic orifice, in the muscular structure of the diaphragm. In the ascent of the crura of the latter, their fleshy fasci- culi cross in front of the aortic orifice, and then, proceeding upward to Inferior view of the diaphragm. 1, 2. 3, the three lobes of the central tendon, surrounded by the fleshy fasciculi derived from the inferior margin of the thorax, the crura, 4, 5, and the arcuate ligaments, 6, 7 ; 8, aortic orifice; 9, oesophageal orifice; 10, quad- rate foramen; 11, psoas muscle; 12, quadrate lumbar muscle. 1 Pillars; columns; pars lumbalis. 2 Centrum tendineum, phrenicum, or nerveum; pars tendinea; tendo dia- phragmatis; speculum Helmontii; cordi- iorm tendon; phrenic centre. 3 Hiatus aorticus; semicirculus ex- culptus. * Oesophageal aperture or foramen; for. oesophageum. THE MUSCULAR SYSTEM. 223 reach the central tendon, leave between them the oesophageal orifice. The fleshy constitution of the borders of this aperture adapts it to act the part of a sphincter muscle to the oesophagus. The remaining orifice, which transmits the ascending cava, is situated in the central tendon, to the right of its middle. Formed between the crossing fibrous bands of the tendon, it is somewhat square, with rounded angles, and hence is named the quad'rate foramen.1 Besides the orifices described, the crura of the diaphragm are pierced by the great sympathetic nerves and azygos veins. The diaphragm is the most important of the respiratory muscles. In contracting it descends, and thus increases the capacity of the chest, and produces inspiration. The abdominal muscles are the chief antagonists to its action. It performs an important part in coughing, laughing, sneezing, yawning, sighing, crying, sobbing, hiccoughing, singing, vomit- ing, the voiding of the excrement, and the expulsion of the foetus. MUSCLES OF THE PERINEUM. See the article Perineum, after the account of the generative appa- ratus. THE UPPER EXTREMITY. The Upper Extremity commences with the prominence of the shoulder, beneath which is the axil'la2 or armpit, bounded in front and behind by thick borders, the ax'illary folds. The arm3 is cylindrical, and terminates in the bend of the arm or elbow, which is bounded on each side by the prominences of the condyles, and behind by the prominence of the ole- cranon, the elbow. The forearm4 is club shaped, and compressed from within outwardly. Its prominent inner portion above is produced by the flexor and pronator muscles; its corresponding outer portion, by the extensor and supinator muscles. The back or dorsal surface of the hand is broad and convex, and presents no indication of the separation existing between the carpus and metacarpus. The palm or palmar sur- face exhibits the hollow of the hand, bounded above by the prominence of the carpus or wrist, and at the sides by the ball of the thumb5 and little finger.5 The wrist joint, or radio-carpal articulation, is indicated in front by transverse furrows of the skin. The metacarpo-phalangial articulations are indicated by the knuckles behind, and transverse furrows at the ante- 1 F. quadratum; f. venosum. ■ Assella; fovea axillaris; cordis emunctorium; hypomia: male; mas- clialis. 3 Brachium. 4 Antibrachium; pars inferior brachii; cubitus. 5 Thenar and liypothenar eminences. 224 THE MUSCULAR SYSTEM. rior third of the palm. The phalangial articulations are likewise indi- cated by knuckles, and by transverse furrows of the skin before and behind. The fingers, as previously mentioned, are named in succession, the thumb,1 the index or fore finger,2 the middle,3 the ring,* and the little fingers.5 The skin of the upper extremity is moderately thick and dense exter- nally or posteriorly; thin and extensible internally or anteriorly. It is readily movable to and fro on the parts beneath, except in the palm of the hand. FASCLE OF THE UPPER EXTREMITY. The Superficial fascia of the upper extremity is a rather loose layer of areolar tissue connecting the skin with the deep fascia and with the various subcutaneous prominences and ridges of the bones. Its super- ficial portion contains more or less fat, the superficial venous trunks, and the cutaneous nerves in their course to the skin. Accumulation of fat involves the veins just mentioned, and, occupying the angular intervals of the different groups of muscles, gives the characteristic rounded form to the limbs of young children, well-developed women, and fat men. The deeper portion of the fascia is more membranous in character, and defines the fatty layer from the parts beneath. Upon the acromion and olecranon the superficial fascia is always devoid of fat; and in the latter position it contains an irregular synovial bursa, devoid of an epithelium. Approaching the wrist and hand, the fatty layer of the superficial fascia decreases, but is never absent from the palm of the hand, where it is intimately blended with the under surface of the skin. The Deep fascia6 of the upper extremity is a continuation of the thin membrane investing the pectoral, trapezius, latissimus, and great serrated muscles. Adhering to the clavicle, acromion, and spine of the scapula, it gives the deltoid muscle a thin covering, and extends downward upon the arm. A portion invests the subscapular and terete muscles; but stronger portions cover the supra- and infra-spinous muscles, adhering intimately to the borders of the fossae whence the muscles arise. It incloses the axilla by crossing from the pectoral to the latissimus muscle, and it is intimately associated with the sheath of the axillary and brachial vessels and nerves. It is thin upon the inner part of the arm, is thicker on the back part, and increases in strength as it approaches the elbow, 1 Pollex. * D. annularis. 2 Digitus indicis. 5 D. minimus. 3 D. medius. 6 Brachial and antebrachial fascia. THE MUSCULAR SYSTEM. 225 where it adheres to the olecranon, the condyles, and the condyloid ridges,—the attachments to the latter constituting- intermuscular parti- tions. It receives offsets from the tendons of insertion of the pectoral, latissimus, and triceps muscles, and also gives origin to some of the fleshy fasciculi of the latter. In the forearm the deep fascia has an aponeurotic appearance; is bluish white, and shining, and is composed of transverse fibres conjoined by others running longitudinally. From the tendon of the biceps it receives a conspicuous offset, which expands upon the muscles arising from the internal condyle, and separates the median basilic vein from the brachial vessels and median nerve. Extensions of the fascia inwardly between the muscles constitute intermuscular partitions, which, together with the inner surface of the fascia afford origin to many of the fleshy fasciculi of the muscles. At the wrist, by strong accessions of transverse fibres, the deep fascia forms the annular ligaments, which serve to maintain the position of the flexor tendons in their course to the hand. The Anterior an'nular ligament1 is a strong, thick, and wide band extended from the inner to the outer side of the front of the carpus, being attached by one extremity to the pisiform and unciform bones, by the other to the trapezial and scaphoid bones. With the concavity of the carpus it forms a canal for the passage of the flexor tendons and median nerve to the palm of the hand. The Posterior an'nular ligament,2 less distinct and strong than the preceding, is a wide band of oblique fibres extended from the outer border of the lower end of the radius to the inner side of the ulna and the pisiform bone. As it crosses the radius and ulna, it tightly adheres to the parallel ridges at their lower ends, thus converting the intermediate grooves into canals, through which the extensor tendons pass to the back of the hand. The deep fascia on the back of the hand extends as a thin layer from the ligament just described to the fingers, and is intimately connected with the extensor tendons beneath. The palmar fascia3 extends from the annular ligament, as a thin investment to the ball of the thumb and little finger. The middle portion is a strong, triangular aponeurosis, composed of fibres diverging from the annular ligament and connected by transverse fibres. Its apex partly receives the insertion of the tendon of the long palmar muscle; its base divides into four processes, each of which subdivides upon the flexor tendons as these diverge to the fingers, 1 L. annulare, or transversum anterius; 1. commune, or carpi volare. 2 L. annulare, or transversum posterius; 1. commune, or carpi dorsale. 8 Aponeurosis palmaris. 15 226 THE MUSCULAR SYSTEM. and the subdivisions are attached to the vaginal ligaments and those of the metacarpo-phalangial articulations. The Vag'inal ligaments1 are fibrous sheaths, inclosing the flexor ten- dons, in front of the phalanges, with the lateral edges of which they arc firmly attached. They are composed of transverse and obliquely cross- ing bands, thick and strong in front of the phalanges, but thin upon the articulations, so as not to impede the movement of the latter. The tendons of the flexor and extensor muscles, as they pass through the canals formed by the annular and vaginal ligaments, are invested with synovial sheaths.2 MUSCLES OF THE SHOULDER. The Supra-spi'nous muscle3 arises from the corresponding fossa of the F 16Q scapula and from an in- vesting aponeurosis. Its fleshy fasciculi converge to a tendon which pro- ceeds beneath the acro- mion, adheres to the cap- sular ligament of the shoulder joint, and is in- serted into the upper part of the greater tuberosity of the humerus. The Infra-spi'nous Muscles ox the back of the scapula. 1, supra-spinous muscle; mus°le arises from the 2, infra-spinous muscle; 3, lesser terete muscle ; 4, greater terete Corresponding foSSa Of the mu3Cle' scapula and converges to a tendon, which, proceeding over the capsular ligament of the shoulder joint, is inserted into the middle part of the greater tuberosity of the humerus. The Lesser Te'rete muscle5 arises from the upper part of the outer border of the scapula, and, in contact with the preceding muscle, fre- quently more or less conjoined with it, ascends to be inserted into the lower part of the greater tuberosity of the humerus. The Subscap'ular muscle6 arises by broad fasciculi from the corre- 1 L. vaginalia; vaginal and crucial ligaments. 2 Vaginae synoviales. 3 M. supra-spinatus ; m. supra-scapu- laris; m. superscapularis superior. 4 M. infra-spinatus; laris inferior. 5 M. teres minor. 8 M. subscapularis. m. superscapu- THE MUSCULAR SYSTEM. 227 Fig. 161. sponding fossa of the scapula, and converges to a strong tendon, which passes in front of the shoulder joint, and is inserted into the lesser tu- berosity of the humerus. It lies upon the great ser- rated muscle, from which it is separated by a thin fascia1 and some loose are- olar tissue extending from the axilla. Between its tendon and the neck of the scapula a synovial bursa is interposed. Muscles on the front of the scapula. 1, subscapular muscle; 2, greater terete muscle; 3, upper part of the triceps extensor; -1. supra-spinous muscle. Fig. 1G2. The subscapular muscle rotates the arm inwardly, and the supra-spinous, infra-spinous, and lesser terete muscles rotate it outwardly. The tendons of these four muscles, as they approach their insertion, partially surround the shoulder joint, form an intimate connection with its capsular liga- ment, and contribute very greatly to its strength. MUSCLES OF THE ARM. The Greater Te'rete muscle2 forms part of the posterior fold of the axilla. It arises from the lower part of the inferior border and angle of the scapula, ascends beneath the latissimus muscle, and terminates in a broad tendon, which is inserted into the posterior bicipital ridge of the humerus, in contact with the ten- don of the latissimus. The longhead of the triceps separates the greater from the lesser terete muscle. The greater terete muscle assists the latissimus in its action The deltoid muscle. 1, its insertion; 2, its ori- gin from the clavicle; 3, origin from the spine and acromion of the scapula. The Del'toid muscle3 forms the convex prominence of the shoulder. 1 Fascia subscapularis. 3 M. deltoideus; m. deltiformis; m. - M. teres major; m. scapulo-humer- supra-acromio-humeralis; m. attollens ahs. humeri. 228 THE MUSCULAR SYSTEM. It arises, partially tendinous and fleshy, from the outer third of the clavicle, the acromion, and the lower margin of the spine of the scapula, and converges to be inserted, partially tendinous and fleshy, into the roughness near the middle of the outer part of the humerus. The muscle lias coarse, fleshy fasciculi, intermingled with tendinous fibres. The deltoid muscle is the elevator of the arm, and may raise the limb to a vertical position. It is also an efficient aid in drawing the arm backward or forward, and greatly contributes to the strength of the shoulder joint. Fig. 163. The Cor'aco-bra'chial muscle,1 situated along the upper and inner part of the arm, arises tendinously, in common with the short head of the biceps muscle, from the coracoid process of the scapula, and pro- ceeds downward to be inserted about the middle of the inner side of the humerus. It is usually perforated by the external cutaneous nerve in its course to the outer part of the arm. The Bi'ceps Flex'or2 is situated in front of the arm, extending from the scapula to the forearm. As the name indicates, it arises by two heads, of which the internal or short one is derived, in common with the preceding mus- cle, from the coracoid process of the scapula. The long head arises from the summit of the glenoid cavity, by a narrow tendon which passes through the upper part of the shoulder joint, insheathed by the synovial membrane, and de- scends along the bicipital groove of the humerus. The two heads conjoin and form a thick, fleshy belly, terminating in a strong tendon, which penetrates between the supinator and flexor muscles of the forearm, to be inserted into the back part of the tuberosity of the radius. Between the tendon of insertion and the fore part of the latter tuberosity, a synovial bursa is interposed; and from the commence- ment of the same tendon an aponeurotic process of the forearm just below the internal condyle. Muscles of the fore part of the arm. 1, coracoid process of the scapula; 2, coraco-clavicular liga- ment; 3,coraco-acromial ligament; 4, subscapular muscle; 5, greater terete muscle; 6, coraco-brachial muscle; 7, biceps flexor; 8, its in- sertion into the tuberosity of the radius; 9, brachial muscle; 10, tri- ceps extensor. is given off to the fascia 1 M. coraco-brachialis, or humeralis; m. perforatus, or m. p. Casserii. 2 M. biceps flexor cubiti; m. biceps brachialis; m. biceps internus; m. coraco- radialis; m. scapulo-radialis; the biceps. THE MUSCULAR SYSTEM. 229 Fig. 164. The Bra'chial muscle1 lies beneath the biceps muscle at the lower part of the arm, and covers the front of the elbow joint. It arises from the humerus each side of the insertion of the deltoid muscle and from the surface of the bone below, and converges to be inserted tendinously into the fore part of the aornocid process of the ulna. Ctti t.r > d The coraco-brachial muscle draws the arm inwardly. If the hand is prone, the biceps supinates it by rotating the radius outwardly, and if the action of the muscle continues, the forearm is flexed. The brachial muscle is also a flexor of the forearm, and from its position greatly contributes to the strength of the elbow joint. The Tri'ceps Extensor2 forms the whole of the fleshy mass on the posterior part of the arm, and, as the name implies, arises by three heads. The external head3 arises from the humerus, below the greater tuberosity ; the short head4 arises from the humerus, below the greater te- rete muscle; and the long head5 arises from the border of the scapula, below the glenoid cavity. The three heads conjoin in one fleshy belly, which in its descent receives a constant accession of fasciculi from the surface of the humerus, and terminates in a strong aponeur- otic band facing the muscle posteriorly and in- serted into the olecranon process of the ulna. Between the tendinous insertion and the top of the process, a synovial bursa is introduced. This muscle is the extensor of the forearm. ^*i' '• ■ i The Ancone'us muscle^appears to be a con- tinuation of the triceps below the outer part of the elbow. View of the triceps extensor, on the back of the right arm. 1, external head; 2, long head; 3, short head; 4, insertion of the mus- cle into the olecranon of the ulna; 5, radius; 6, capsular ligament of the shoulder joint. It arises 1 M. brachialis anticus ; m. b. inter- nus ; m. b. humero-cubitalis; m. bra- chiaeus ; anterior brachial muscle. 2 M triceps extensor cubiti, or brachii; m. triceps brachialis. 8 Caput externum; anconaeus exter- nus; vastus externus; short head of the biceps externus. * C. internum; internal head; anc. in- ternus ; v. int.; brachialis externus. 5 C. longum ; c. medius ; middle head; first head; long head of the biceps ex- ternus ; anconaeus longus, or major. 6 M. anconaeus; m. a. quartus, or mi- nor ; m. brevis cubiti; m. cubitalis Rio- lani. 230 THE MUSCULAR SYSTEM. from the external condyle of the humerus, and is inserted into the trian- gular space at the upper and outer part of the ulna. It acts with the triceps, and was formerly described as a fourth head to this muscle. MUSCLES OF THE FRONT OF THE FOREARM. The Long Pal'mar muscle1 lies between the radio- and ulno-carpal flexors. It arises from the internal condyle and intermuscular partitions, and forms a small belly terminating in a long tendon, which descends to be inserted into the annular ligament of the wrist and the palmar fascia. The Te'rete Pro'nator2 is a small muscle extended obliquely across the upper part of the front of the forearm. It arises from the internal condyle of the humerus, and passes outward and downward to be inserted into a rough surface on the outer side of the radius. The Quad'rate Pro'nator3 is a square muscle crossing the lower part of the forearm, beneath the flexor muscles. It arises from the front of the lower part of the ulna, and passes over the interosseous membrane to be inserted into the front of the radius. Superficially it is invested with a thin aponeurosis. The two pronator muscles, by rotating the radius inwardly upon the ulna, pronate the hand; or, in other words, turn it with the palm down- ward. The Radio-carpal Flexor4 lies in front of the forearm, extending obliquely from the inner condyle to the outer side of the metacarpus. It arises from the internal condyle and intermuscular partitions, and con- verges to a long, flat tendon, which, after passing through a fibrous canal at the outer part of the carpus, is inserted into the base of the second metacarpal bone. The Ulno-carpal Flexor5 lies superficially on the ulnar side of the forearm. It arises from the internal condyle and the olecranon and by a strong aponeurosis from the upper part of the inner border of the ulna. Its belly terminates in a tendon, which is inserted into the pisiform bone and base of the last metacarpal bone. 1 M. palmaris longus; m. ulnaris gra- cilis ; latescentis chordae ; m. epitrochlo- carpi-palmaris. 2 M. pronator radii teres; m. pronator rotundus ; m. p. obliquus; m. epitrochlo- radialis. 3 M. pronator radii quadratus; m. pronator transversus; m. quadratus ra- dii ; m. cubito-radialis. * M. flexor carpi-radialis; m. radialia internus ; m. palmaris magnus. 5 M. flexor carpi-ulnaris; m. ulnaris internus ; m. cubitalis internus, or ante- rior. THE MUSCULAR SYSTEM. 231 Between the origin of this muscle from the humerus and the ulna, the ulnar nerve takes its course. Fig. 165. Fig. 166. Superficial muscles of the front of the fore- arm. 1, lower part of the biceps flexor; 2, brachial muscle; 3, lower part of the triceps extensor; 4, terete pronator; 5, radio-carpal flexor; 6, long palmar muscle; 7, superficial flexor of the fingers; 8, ulno-carpal flexor; 9, palmar fascia; 10, short palmar muscle; 11, abductor of the thumb; 12, short flexor of the thumb; 13, long supinator; 14, extensors of the thumb. The crossing and trans- verse bands on the fingers are the vaginal liga- ments inclosing the flexor tendons. Deep muscles of the front of the forearm. 1, internal lateral ligament of the elbow joint; 2, capsular ligament of the same; 3, annular liga- ment inclosing the head of the radius; 4, deep flexor of the fingers; 5, long flexor of the thumb; 6, quadrate pronator; 7, adductor of the thumb; 8, 9, interosseous muscles. The Superficial Flexor of the Fingers1 is situated in front of the forearm, between the preceding muscles. It arises from the internal con- dyle, the internal lateral ligament, the coronoid process of the ulna, and the radius below its tuberosity. The fleshy belly at the lower third of the forearm divides into four tendons, which proceed together beneath the annular ligament of the wrist, and diverge to be inserted into the base 1 M. flexor sublimus perforatus; m. f. digitorum sublimus, or perforatus. 232 THE MUSCULAR SYSTEM. of the second phalanges of the fingers. In front of the first phalanges the tendons are split, to give passage to the tendons of the deep flexor. Between the ulnar and radial origin of this muscle the median nerve pursues its course. Fig. 167. Metacarpal and phalangial bones of the fingers, with their tendons and ligaments. In the upper figure the flexor tendons are retained in position by the vaginal ligaments composed of transverse and obliquely crossing bands; in the lower figure the flexor tendons are freed from the vaginal ligaments. 1, metacarpal bone; 2, tendon of the superficial flexor; 3, tendon of the deep flexor, passing through a perforation (*) of the former; 4, tendon of the common extensor; 5, a lumbrical muscle, arising from the deep flexor tendon and inserted into the extensor tendon; 6, an interosseous muscle, also inserted into the latter tendon. The Deep Flexor of the Fingers1 is stronger than the preceding muscle, and is beneath it. It arises from the upper two-thirds of the front surface of the ulna and from the contiguous portion of the interosseous membrane, and likewise divides into four tendons. These, after passing through the annular ligament of the wrist, take their course through the perforations of the tendons of the superficial flexor, and are inserted into the base of the last phalanges. The Lum'brical muscles,2 as implied by the name, are worm-like, fleshy fasciculi, four in number, situated in the palm of the hand. They arise from the radial side of the tendons of the deep flexor, and proceed to be inserted into the corresponding side of the tendinous expansions on the back of the fingers. The Long Flexor of the Thumb,3 situated at the outer side of the deep flexor of the fingers, arises from the front of the radius and the contiguous portion of the interosseous membrane. The fleshy belly terminates in a tendon, which passes beneath the annular ligament of the 1 M. flexor profundus perforans ; m. f. 2 M. lumbricales ; m. fidicinales. digitorum profundus, or perforans; m. f. s M. flexor longus pollicis ; m. f. tertii tertii internodii digitorum; m. perforans internodii, or longissimus pollicis. manus. THE MUSCULAR SYSTEM. 233 wrist, turns outwardly, and proceeds between the two portions of the short flexor to be inserted into the base of the last phalanx of the thumb. The tendons of the flexor muscles proceeding to the fingers are retained in their position by the vaginal ligaments.1 In their passage beneath the latter they are attached to the front of the phalanges by narrow, accessory bands,2 apparently serving to conduct nutritious vessels to the tendons. Synovial bursae3 lining the vaginal ligaments and fronts of the phalanges are thence reflected upon the flexor tendons and their accessory bands. MUSCLES OF THE BACK OF THE FOREARM. The Common Extensor of the Fingers4 arises from the external con- dyle, contiguous intermuscular partitions, and the fascia of the forearm. Below the middle of the latter its fleshy belly separates into four ten- dons, which pass beneath the posterior annular ligament, and diverge to the fingers, upon the backs of which they expand. As they pass over the first phalanges they receive an addition of fibres at the sides from the lumbrical and interosseous muscles, and their middle portion is in- serted into the base of the second phalanges, while the lateral portions proceed onward and converge to be inserted together into the base of the last phalanges. On the back of the hand the inner three of the ten- dons are connected together by short, intervening bands, which associate their action much more than with the remaining tendon. The Long Supina'tor5 lies on the radial side of the forearm, and ex- tends from near the middle of the humerus to the wrist. It arises from the external condyloid ridge below the insertion of the deltoid muscle, and converges to a long, flat tendon, which is inserted into the base of the styloid process of the radius. The Longer Radio-carpal Extensor6 is partially covered by the pre- ceding muscle, and arises just below it from the same ridge. Its belly converges to a long, flat tendon, which descends along the radius, and is inserted into the base of the second metacarpal bone. The Shorter Radio-carpal Extensor,7 partially concealed by the last Ligament a vaginalia. 2 Vincula vasculosa; v. accessoria ten- dinum; tenacula. 3 Vaginae synoviales. 4 M. extensor digitorum communis; m- digitorum tensor. 5 M. supinator longus; m. s. radii lon- gus ; m. s. major; m. brachio-radialis. 6 M. extensor carpi-radialis longior; m. radialis externus longior, or primus. 1 M. extensor carpi-radialis brevior; m. radialis externus brevior, or secundus. 234 THE MUSCULAR SYSTEM. muscle, arises from the external condyle of the humerus, and is inserted by a flat tendon into the base of the third metacarpal bone. Fig. 168. Fig. 169. Muscles of the back of the forearm. 1, biceps flexor; 2, brachial muscle; 3, triceps extensor; 4, long supinator; 5, longer radio-carpal extensor; 6, shorter radio-carpal extensor; 7, insertion of the tendons of the last two muscles; 8, common exten- sor of the fingers; 9, extensor of the little finger; 10, ulno-carpal extensor; 11, short supinator; 12, ulno-carpal flexor; 13, metacarpal and first phal- angial extensors of the thumb; 14, second phalan- gial extensor of the thumb; 15, posterior annular ligament. Ueep muscles on the back of the forearm. 1, humerus; 2, olecranon; 3, ulna; 4, anconeus muscle; 5, short supinator; 6, metacarpal extensor of the thumb; 7, first phalangial extensor; 8, second phalangial extensor of the thumb; 9, extensor of the index finger; 10, the dorsal interosseous muscles between the metacarpal bones. The Ulno-carpal Extensor1 lies at the ulnar side of the forearm, and arises from the external con- dyle, the upper part of the inner border of the ulna, and the fascia of the forearm. Its belly converges to a long, flat tendon, which descends to be inserted into the base of the last metacarpal bone. 1 M. extensor carpi-ulnaris; m. ulnaris externus; m. cubitalis externus, or pos- terior. THE MUSCULAR SYSTEM. 235 The Extensor of the Little Finger1 lies at the ulnar side of the com- mon extensor, with which it has its origin ; and its tendon, after passing through a separate canal of the annular ligament, conjoins the fourth tendon of the common extensor. The Short Supina'tor2 is concealed by the long supinator and the radial extensors. It arises from the external condyle of the humerus, the external lateral ligament of the elbow joint, and the ulna, and winds obliquely outward and downward upon the radius, into the upper third of which it is inserted. The Metacarpal Extensor of the Thumb3 crosses the forearm obliquely below the preceding muscle, and arises from the ulna, the interosseous membrane, and the radius. Its belly terminates in a tendon, which crosses those of the radio-carpal extensors, and, after passing through a groove in front of the styloid process of the radius, is inserted into the base of the metacarpal bone of the thumb. The First Phalan'gial Extensor of the Thumb4 is a small muscle situ- ated below the preceding to its ulnar side, and has the same points of origin. Its fleshy belly terminates in a narrow tendon, which accompa- nies that of the preceding muscle, and is inserted into the base of the first phalanx of the thumb. The Second Phalan'gial Extensor of the Thumb5 arises below the preceding muscle from the ulna and interosseous membrane. Its belly terminates in a tendon, which passes through a distinct canal of the an- nular ligament from that occupied by the tendons of the first phalangial and metacarpal extensors, and proceeds to be inserted into the base of the last phalanx of the thumb. The Extensor of the Index Finger6 lies at the ulnar side of the pre- ceding muscle, and has the same points of origin. Its tendon of inser- tion passes through a groove of the radius, and conjoins the tendon of the common extensor to the index finger. 1 M. extensor minimi digiti, or m. e. proprius m. d ; m. auricularis. 2 M. supinator radii brevis, or minor ; m. epicondylo-radialis. s M. extensor ossis metacarpi pollicis ; m. abductor longus pollicis; m. e. primi internodii ossis pollicis. 4 M. extensor primi internodii pollicis; m. extensor brevis, or minor pollicis; m. e. pollicis primus; m. e. secundi internodii ossis pollicis. 5 M. extensor secundi internodii polli- cis ; m. extensor longus, or major polli- cis; m. e. pollicis secundus; m. e. tertii internodii ossis pollicis. 6 M. extensor indicis; indicator; m. ext. proprius indicis ; m. e. p. primi di- giti. 236 THE MUSCULAR SYSTEM. MUSCLES OF THE HAND. 1 M. palmaris brevis; caro quadrato; m. carpaeus. 2 M. abductor pollicis; m. a. brevis pol- licis; m. a. brevis alter p.; m. scapho- carpo-superphalangeus pollicis. s M. flexor ossis metacarpi pollicis; m. The Short Pal'mar muscle1 is a thin layer of fleshy fibres situated beneath the skin at the inner side of the palm of the hand. It arises from the annular ligament and pal- mar fascia, and proceeds inwardly to be attached to the integument. MlSCLES OF the palmar surface of the hand. 1, anterior annular ligament; 2, origin and inser- tion of the abductor of the thumb; its belly re- moved so as to expose 3, the metacarpal flexor; 4,5, two bellies of the short flexor; 6, adductor of the thumb; 7, lumbrical muscles; 8, tendons of the deep flexor of the fingers passing through the slits of the superficial tendons; 9, tendon of the long flexor of the thumb, passing from between the bellies of the short flexor; 10, abductor of the little finger; 11, short flexor of the little finger, with the edge of the adductor seen beneath; 12, pisiform bone; 13, first interosseous muscle. ato; opponens pollicis; m. f. primi internodii pollicis; m. antithenar. pol- * M. flexor brevis pollicis; m. f. secundi pho- internodii p.; m. f. primi et secundi i. p.; m. thenar. ; m. 5 M. adductor pollicis; m. metacarpo- phalangeus pollicis. MUSCLES OF THE BALL OF THE THUMB. The Abductor2 is the most superficial and external of the muscles of the ball of the thumb. It arises from the annular ligament of the wrist, and is inserted into the base of the first phalanx of the thumb. The Metacarpal Flexor,3 beneath the preceding, arises from the same source, and is inserted into the length of the metacarpal bone of the thumb. The Short Flexor4 consists of two portions, between which lies the tendon of the long flexor of the thumb. It arises from the annular liga- ment and the second row of carpal bones, and is inserted tendinously into the base of the first phalanx of the thumb. Within its tendinous insertion the sesamoid bones are imbedded The Adductor5 is a triangular muscle, arising from the length of the THE MUSCULAR SYSTEM. 237 middle metacarpal bone, and converging to be inserted into the base of the first phalanx of the thumb. MUSCLES OF THE LITTLE FINGER. The Abductor1 lies on the margin of the palm. It arises from the pisiform bone, and is inserted into the base of the first phalanx and ex- tensor tendon of the little finger. The Short Flexor2 arises from the annular ligament of the wrist and the unciform bone, and is inserted into the base of the first phalanx of the little finger. It is not unfrequently inseparable from the preceding muscle. The Adductor3 arises from the same points as the preceding muscle, and is inserted into the length of the metacarpal bone of the little finger. THE INTEROSSEOUS MUSCLES. The Interos'seous muscles4 are seven in number, and, as implied by their name, are situated in the intervals of the metacarpal bones—four on the back, and three on the palm of the hand. The Dorsal Interos'seous muscles,5 four in number, arise from the contiguous sides of the metacarpal bones, and each forms a penniform belly, terminating in a tendon, which partially conjoins the extensor ten- dons on the back of the finger, and is partially inserted into the base of the first phalanx. The first of this series is inserted into the radial side of the index ringer, and is an abductor; the succeeding two are inserted into the opposed sides of the middle finger, and act as an abductor and adductor; and the last one is inserted into the ulnar side of the ring finger, and is an adductor. The Palmar Interos'seous muscles,6 three in number, arise from a single side of the metacarpal bones of the index, ring, and little fingers, and terminate in the same manner as the dorsal series. The first is on the ulnar side, and is an adductor, and the other two are on the radial side, and are abductors. 1 M. abductor minimi digiti; m. exten- sor tertii internodii m. d.; m. carpo-pha- langeus m. d.; m. hypothenar minor metacarpeus. 2 M. flexor brevis, or parvus minimi digiti. 3 M. adductor minimi digiti; m. a. metacarpi m. d.; m. carpo-metacar- peus m. d. * M. interossei. 5 M. i. externi; m. i. bicipites. 6 M. i. interni. 238 THE MUSCULAR SYSTEM. THE LOWER EXTREMITIES. The Lower Extremities, which support and carry the other portions of the body, are accordingly larger and stronger, and provided with more powerful muscles than the upper extremities. At the back part of the hips are the buttocks or nates,1 separated by the fissure of the anus, and from the thighs below by the sub-ischiatic grooves. The thigh2 is separated from the abdomen by the groin or inguinal region, and gradu- ally becomes narrowed to the knee.3 Behind the latter is the space called the poplite'al region, or hollow of the knee,4 bounded on each side by the "ham-strings." The condyles of the femur and tibia pro- duce the lateral prominences of the knee, the knee-cap producing the eminence in front. The calf5 or thick mass of the leg6 narrows down- ward to the "tendon of Achilles," which terminates at the heel.7 The ankles correspond with the malleoli of the tibia and fibula. The skin of the buttock is thick, but becomes thin in the fissure of the anus. Upon the outer part of the thigh and leg it is thick, dense, and comparatively dull in sensibility; becomes thinner, more extensible, and sensitive toward the inner part, and is everywhere quite movable. Upon the back of the foot the skin is thin and extensible; but upon the sole, is thick, inextensible, and quite immovable. FASCLE OF THE LOWER EXTREMITY. The Superficial fascia of the lower extremity, as in other divisions of the body, is in most parts separable into two layers, of which the inner one is thin and membranous, the outer one loose in texture, and more or less filled with fat. Upon the buttock the superficial fascia is ordinarily occupied with a large quantity of fat. Upon the thigh and leg it also usually contains much fat, except over the great trochanter and the patella, in which positions synovial bursse are substituted. In the sole of the foot it is always occupied with fat, and is most intimately blended with the struc- ture of the skin. At the heel, and bend of the first and last metatarsal bones, it contains synovial bursas. Between the fatty and membranous layers of the superficial fascia, the superficial veins and cutaneous nerves have their course. 1 Glutia; sedilia; clunes; podex ; pos- teriors ; bottom. 2 Femur; crus; merus. 5 Genu. * Popliteal fossa; the hock; the hough; the ham. 5 Sura; gastrocnemium. 6 Crus; scelos; cneme. 7 Calx; talus. THE MUSCULAR SYSTEM. 239 The fatty layer at the groin and hip is continuous with the correspond- ing layer of the superficial fascia of the abdomen. The deeper or mem- branous layer adheres to Poupart's ligament and the crest of the ilium. At the saphenous opening it is pierced by the cutaneous vessels of the contiguous regions, from which circumstance this perforated portion of the superficial fascia is called the crib'riform fascia.1 The Deep fascia of the lower extremity, like that of the upper ex- tremity, forms a complete envelope to the limb, sends partitions between the muscles, and gives sheaths to the great blood-vessels. It is called, from its relative positions, the femoral fascia, the crural fascia, and the fascia of the foot. The Fem'oral fas'cia or fas'cia la'ta,2 is attached along the crest of the ilium, the back of the sacrum and coccyx, the border of the ischium and pubis and Poupart's ligament, with which it is continuous. Upon the great gluteal muscle it forms a thin investment; but in ad- vance of this, and extending in the same line the entire length of the outer part of the thigh, it is so thick and strong as to appear like an aponeurosis. This portion of the fascia is composed of longitudinal fibres strengthened by transverse ones; gives partial origin to the middle gluteal muscle; receives, over the position of the great trochanter, part of the insertion of the great gluteal muscle; and after insheathing its own peculiar tensor muscle, receives the insertion of this altogether. In passing from the outer to the inner part of the thigh, the femoral fascia becomes gradually thinner, and is mainly composed of transverse fibres. Between all the muscles it sends partitions, among the most important of which are the so-called external and internal intermuscular par- titions.3 The former of these is a strong process separating the quadriceps extensor and the biceps flexor, and attaching itself to the asperous ridge from the insertion of the great gluteal muscle to the outer condyle of the femur. The other is a thinner partition separating the quadriceps extensor from the adductor muscles, and connecting itself with the aspe- rous ridge leading to the inner condyle. At the knee the fascia receives offsets from the extensor and flexor tendons, forms a general envelope4 to the joint, and becomes continuous with the crural fascia, Below the groin, the femoral fascia is so important in its relations with the femoral blood-vessels and the subject of femoral hernia, that it re- quires special attention. The inner and outer portions of the fascia, 1 Fascia cribrosa. s Ligamentum intermusculare exter- 2 Fascia femoris; f. lata aponeurosis ; num et internum. f. aponeurotica femoris: vagina femoris; * Involucrum generale. crural, or femoral aponeurosis. 240 THE MUSCULAR SYSTEM. from the muscles they immediately invest, are conveniently named the pectineal and sartorial fascia. Fm. 171. View of the inguinal canal. 1, por- tion of the fleshy belly of the external ob- lique muscle; 2, its aponeurosis; 3, por- tion of the latter raised up, exposing the inguinal canal; 4. linea alba; 5, insertion of the aponeurosis of the external oblique into the body of the pubis; 6, its insertion into the spine of the pubis, named Pou- part's ligament; 7, division of the fibres of the aponeurosis crossed by transverse fibres; 8,external abdominal ring,the ter- mination of the inguinal canal; 9, anterior superior spinous process, the origin of Poupart's ligament; 10, arching lower bor- der of the internal oblique and transverse muscles; 11, conjoined tendon of the latter muscles; 12, fibres of the cremaster muscle descending on the spermatic cord from the edges of the muscles just named; 13, rests on the transverse fascia; to its right arc the epigastric vessels crossing the course of the inguinal canal; 14, iliac portion of the femoral fascia; 15, pubic portion; 16, falciform process; 17, saphenous opening; is. saphenous vein joining the femoral vein through the saphenous opening; 19, the femoral artery and vein exposed by raising the portion of fascia which forms the falciform process; 20, suspensory ligament of the penis. The pectine'al fas'cia1 invests the corresponding muscle behind the femoral blood-vessels. It is attached along the body and pectineal line of the pubis, and at its outer border becomes continuous with the iliac fascia investing the psoas and iliac muscles, and with the posterior layer of the sartorial fascia. The sarto'rial fas'cia,2 after including the corresponding muscle, in the groin is attached along Poupart's ligament and extends in front of the femoral blood-vessels. A couple of inches below the pubis, it be- comes continuous with the pectineal fascia, and between these two points includes an oval space named the saphe'nous opening,3 from the long saphenous vein entering at this position to join the femoral vein. The outer part of the saphenous opening is defined by a lunated edge of the sartorial fascia, named the fal'ciform process,4 the upper extremity5 of 1 Pubic portion of the femoral fascia, or fascia lata; fascia ischio-pubica. 2 Iliac portion of the femoral fascia, or fascia lata; fascia ilio-pectinea. 3 Fossa ovalis; inferior orifice of the crural canal. * Plica falciformis; falciform expan- sion, or semilunate edge of the fascia lata. 5 Cornu superius; upper horn; Hey's ligament; femoral ligament. THE MUSCULAR SYSTEM. 241 which is continuous with Gimbernat's ligament; the lower extremity,1 with the pectineal fascia. The inner part and bottom of the opening are formed by the latter fascia as it dips from within, outwardly, behind the femoral blood-vessels. The saphenous opening is occupied with a portion of the superficial fascia, called crib'riform fascia,2 from its being perforated by many small superficial vessels passing between the contiguous parts and the femoral vessels. The cribriform fascia is continuous with the falciform process, and careful manipulation is required to distinguish the lunated edge of the latter. When the fascia is removed, the falciform process is observed to overlie the femoral vessels; its upper and lower extremities are usually well marked, while the middle portion is less defined. The Cru'ral fascia3 or deep fascia of the leg, for the most part well marked and strong, adheres to the heads of the tibia and fibula, to the anterior and internal borders of the former bone, and to both malleoli. It receives offsets from the tendons of insertions of the sartorius, gra- cilis, semitendinous, and biceps muscles, and is mainly composed of transverse fibres. It is strongest in the outer part of the leg, where it gives partial origin to the heads of the muscles, and is continuous with their intermuscular partitions. It is thinnest on the back of the leg,4 where it consists of a layer investing the muscles of the calf, and another5 separating the latter from the deeper muscles. In the vicinity of the ankle joint, the crural fascia receives an acces- sion of fibres, much increasing its strength, and constituting the annular ligaments, which bind down the tendons of the muscles as they turn for- ward from the leg to the foot. The anterior an'nular ligament6 is a strong band extending obliquely in front of the ankle joint, from the inner malleolus to the anterior and outer part of the calcaneum. It consists of two layers, which inclose the tendons in several compartments as they cross the ankle joint. Thus the tendons of the long extensor of the toes occupy a compartment next to the fibula, that of the anterior tibial muscle occupies another next to the tibia, and the tendon of the extensor of the great toe an intermediate compartment. The anterior tibial blood-vessels and nerve are behind the ligament. A band of fibres,7 above the ankle joint, extended be- tween the front of the tibia and the fibula, is sometimes described as a portion of the anterior annular ligament; and another band crosses 1 Cornu inferius ; lower horn. 5 Deep fascia of the leg; deep crural 2 F. cribriformis. fascia. 3 Fascia cruralis. 6 Lig. annulare anterius; annular liga- 4 In this position called sural fascia; ment of the tarsus. f. suralis. ' Lig. transversum. 16 040 THE MUSCULAR SYSTEM. the annular ligament from the external malleolus to the inner side of the tarsus.1 The internal an'nular ligament2 is a band of loose fibres extending from the internal malleolus to the back of the astragalus and the inner side of the calcaneum. It converts the groove at the back of the inter- nal malleolus into a canal for the passage of the tendons of the posterior tibial and long flexor muscles; and the grooves at the back of the astra- galus and beneath the calcaneum into a canal for the passage of the tendon of the long flexor of the great toe. Between these two canals the ligament transmits the posterior tibial vessels and nerves. A thin offset from the ligament extends superficially to the tendon of Achilles and the tuberosity of the calcaneum. The external an'nular ligament3 is less marked than the preceding, and consists of a band of loose fibres starting from the external malleo- lus to be attached to the outer part of the calcaneum, and binding down the tendons of the peroneal muscles. As the tendons of the muscles pass in their course from the leg to the foot, beneath the annular ligaments, they are invested with synovial bursae. The fascia on the back of the foot is a thin extension from the ante- rior annular ligament. The plantar fascia4 consists of three portions, as in the case of the palmar fascia. The inner and outer portion is thin, and invests the small muscles of the toes. The middle portion is strongest, and resembles the corresponding portion of the palmar fascia. It is composed of longitudinal, diverging fibres, strengthened with transverse ones, and forms a triangular investment to the short flexor of the toes, to which it gives partial origin. Its apex is attached to the tuberosity of the calcaneum, and its base divides into five processes, each of which subdivides to be inserted into the metacarpo-phalangial and contiguous vaginal ligaments. At the sides it js continuous with the lateral portions of the fascia, and with intermuscular partitions dipping into the sole. The vag'inal ligaments which inclose the flexor tendons of the toes have the same arrangement as those of the fingers. SKETCH OF THE ANATOMY CONCERNED IN FEMORAL HERNIA. The position of the groin is defined by Poupart's ligament,5 which is the line of continuity of the aponeurosis of the external oblique muscle 1 Forming with the annular ligament, the lig. cruciatum. 2 Lig. annulare internum; 1. lacinia- tum internum. s Lig. annulare externum; 1. lacinia- tum externum; retinaculum tendinum pereneorum. 4 Aponeurosis plantaris. 5 Lig. Pouparti; 1. Fallopii; crural arch. THE MUSCULAR SYSTEM. 243 of the abdomen with the femoral fascia, extending from the anterior superior spinous process of the ilium to the spine of the pubis. Poupart's ligament constitutes the femoral arch,1 the bottom of which is formed by the anterior border of the ilium and the horizontal ramus of the pubis. The inner part of the arch is formed by Gimbernat's liga- ment,2 which is a triangular process from Poupart's ligament, extending a short distance outwardly along the pectineal line of the pubis. The femoral arch is occupied externally by the iliac and psoas muscles, with the anterior crural nerve situated in the angular interval of their conjunction. Internally it is occupied by the femoral artery, vein, and lymphatics, inclosed together within a sheath, and resting on the pec- tine'al fascia,3 which invests the corresponding muscle. Below the inner part of Poupart's ligament is the oval space, named the saphe'nous opening, from its admitting the saphenous vein to join the femoral vein. The opening is defined externally by the lunated edge of the fal'ciform process4 of the sarto'rial fascia.5 The upper end6 of this process is continuous with both Gimbernat's and Poupart's liga- ment, and its lower end is continuous with the pectineal fascia. The saphenous opening is occupied by the crib'riform fascia,' a portion of the superficial fascia, so named from its perforated condition, aris- ing from the transmission of the superficial vessels of the neighboring parts. Behind the falciform process, from without inwardly, lie in succession the femoral artery, vein, and lymphatics, which together are inclosed in a sheath8 closely connected with the contiguous fasciae. The femoral vessels included within their sheath may be viewed as occupying the tube of a membranous funnel whose expanded portion is formed by the trans- verse, iliac, and pelvic fascia of the abdomen and pelvis. Between the femoral vein and Gimbernat's ligament, within the sheath of the femoral vessels, is a small space named the fem'oral ring.9 This is occupied with lymphatic vessels, and a gland enveloped in some loose connective tissue,10 and is the position at which femoral hernia occurs. When the femoral ring is cleared of its contents, the end of the little finger may be introduced into it from the abdomen to the upper part of 1 Crural arch. 2 Lig. Gimbernati; Hey^Siliga^nertf' 3 Pubic portion of the fascia lata. 4 Plica falciformis; lunated edge of the fascia lata. 5 Iliac portion of the fascia lata. 8 Hey's ligament. ' F. cribrosa. 8 Femoral sheath; vagina vasorum cruralium. 9 Crural ring; annulus cruralis. 10 Septum crurale; septum transver- sum ; crural septum. 244 THE MUSCULAR SYSTEM. the saphenous opening, a depth of about half an inch.1 Its internal and anterior boundary2 is the edge of Gimbernat's ligament continuous with the edge of the falciform process; its outer boundary the femoral vein, and its posterior boundary the pubis and pectineal fascia. When the lower limb is extended and rotated with the toes directed outwardly, the falciform process and Gimbernat's ligament become tense, and the femoral ring is narrowed; and when the limb is flexed and ro- tated with the toes directed inwardly, the same points become relaxed, and the ring is widened.3 As the seat of constriction or strangulation of femoral hernia occurs within the circle of the femoral ring, the facts just mentioned afford important indications as to the mode of treatment. Besides the femoral vein, other blood-vessels in relation with the femo- ral ring are the epigastric artery and veins situated above it externally. When, as occasionally happens, the obturator artery is derived from the external iliac, as this is about to emerge from the femoral arch, it descends at the outer or sometimes at the inner side of the femoral ring. In femoral hernia, the hernial sac, consisting of a pouch of perito- neum containing a portion of the bowels, descends through the femoral ring within the sheath of the femoral blood-vessels. Arriving at the saphenous opening, and finding least resistance in front, it protrudes for- ward, and subsequently, as it increases, extends outwardly in the course of the groin. Such a hernia has for its coverings from without inwardly, the skin, the subjacent fatty layer of the superficial fascia, and lastly, a fibrous layer,4 more or less distinct, and derived from the cribriform fascia and the sheath of the femoral blood-vessels. MUSCLES OF THE BUTTOCK. The Great Glu'teal muscle5 is a thick, lozenge-shaped mass, composed of coarse fleshy fasciculi, and extending from the back of the pelvis to the upper and outer part of the thigh. It arises from the posterior fourth of the crest of the ilium, the posterior surface of the sacrum and 1 The depth of space has been named the femoral canal, its upper orifice being the femoral ring, its lower orifice the saphenous opening. 2 Usually stated to be Poupart's liga- ment, but as the falciform process is con- tinuous with both Gimbernat's and Pou- part's ligament, the anterior boundary may be considered as stated in the text. 3 The falciform process forms, with Gimbernat's ligament, a semispiral edge, which becomes more enrolled, and con- sequently includes a narrower space, when the limb is rotated outwardly, ami becomes partially unwound when the limb is rotated inwardly. 4 Fascia propria of femoral hernia. 5 M. glutaeus magnus, major, maximus, or extimus; m. sacro-femoralis ; m. ilio- sacro-femoralis. THE MUSCULAR SYSTEM. 245 but tbemiddle and small gluteal muscles may rotate them either inwardly i|r]o4t^fi^ly, acc^rding^rfliheir pqster^or o&antprior fibres ,artn$roijght cp«cyx, and from th<*greater sacro-rcchiatic ligament:' Prom this origin its fleshy fasciculi proceed outward and downward, and terminate in a thick aponeurosis, which is inserted into the femoral fascia over the greater trochanter of the femur, and into the rough surface extending from the latter process to the asperous ridge. — JV<- ,/'< . i ? Q The lower border of this muscle forms the fold of the buttock, and in the erect position of the body covers the tuberosity of the ischium, but glides from it in the sitting position. Between its tendon and the greater trochanter of the femur a large synovial bursa is interposed, and Fie. 172. another is situated between the muscle and the tuberosity of the ischium. The Middle Glu'teal muscle,1 covered at its fore part by a thick portion of the femoral fascia, and at its back part by the preceding muscle, arises from the dorsal sur- face of the ilium, between the crest of the latter and the superior curved line, and from the investing femoral fascia. Descending, its fasciculi converge to a short, thick tendon, which is inserted into the outer sur- face of the greater trochanter. Be- tween the upper part of the latter and the tendon, a synovial bursa is interposed. The Small Glu'teal muscle,2 con- cealed by the preceding, arises from the dorsal surface of the ilium be- tween the superior and inferior curved lines, and converges to a tendon, which is inserted into the inner part of the summit of the greater trochanter. Between the latter and the tendon a synovial bursa is inter- posed. Muscles of the buttock. 1, ilium; 2, sacrum; 3, posterior sacro-iliac ligament; 4, tuberosity of the ischium; 5,great sacro-ischiatic ligament; 6, small sacro-ischiatic ligament; 7, greater trochanter; 8, small gluteal muscle; 9, pyriform muscle; 10,12, geminous muscle, including between its two fasci- culi the termination, 11, of the internal obturator muscle; 13, quadrate femoral muscle; 14, upper part of the great adductor of the thigh; 15, exter- nal vastus muscle; 16, biceps flexor; 17, gracilis; 18, semi-tendinous muscle. 1 M. glutseus medius, or secundus; m. ilio-trochanterius. 2 M. glutseus minimus, minor, tertius, or intimus; m. ilio-ischio-trochantcrius. 046 THE MUSCULAR SYSTEM. The External Obtu'rator muscle1 is situated exterior to the cavity of the pelvis, and arises from the borders of the obturator foramen and from the obturator membrane. Converging to a tendon, it passes behind the neck of the femur to be inserted into the trochanteric fossa. The Pyr'iform muscle2 arises within the pelvis from the front surface of the second, third, and fourth divisions of the sacrum, and from the lower part of the sacro-iliac symphysis. Passing from the pelvis through the greater sacro-ischiatic foramen, it converges, to be inserted, by a round tendon, into the greater trochanter, beneath the small gluteal muscle. The Internal Obtura'tor muscle3 arises within the cavity of the pelvis from the border of the obturator foramen and from the obturator mem- brane. Converging to a tendon, it passes through the lesser sacro-ischi- atic foramen to be inserted into the trochanteric fossa.: ' The lesser ischiatic notch, upon which the tendon plays in the action of the muscle, is faced with fibro-cartilage, and furnished with a synovial bursa to facilitate movement. The Gem'inous muscle4 envelops the tendon of the preceding muscle, and consists of a pair of accessory fleshy fasciculi to it, usually described as two distinct muscles.5 It arises from the spine and back part of the tuberosity of the ischium, and after including the tendon of the internal obturator muscle, is inserted in company with it into the trochanteric fossa. The Quadrate Fem'oral muscle6 arises from the outer border of the tuberosity of the ischium, and proceeds outwardly to be inserted into the rough line descending from the greater trochanter. The gluteal muscles, accordingly as thev act from their origin or inser- tion, are abductors of the thighs, or they w the pelvis, and with it the trunk upon the lower extremities. They also rotate the thighs outwardly, 1 M. obturator, or obturatorius exter- nus ; m. sub-pubio-trochantereus exter- nus ; m. extra-pelvio-pubio-trochante- reus. 2 M. pyriformis; m. pyramidalis; m. p. femoris: m. iliacus externus; m. sacro-trochantereus; m. primus et supe- rior quadrigeminus. 8 M. obturator, or obturatorius inter- nus ; m. sub-pubio-trochantereus inter- nus ; m. marsupialis; m. bursalis; m. intro-pelvio-trochantereus. i M. geminus, or gemellus; m. gemini, or gemelli; marsupium carneum; m. marsupialis; m. ischio-spini-trochante- reus; m. canaliculatatus; m. accessorius obturatoris interni. 5 M. geminus, or gemellus superior and inferior; m. secundus et tertius quadrigeminus. 6 M. quadratus femoris; m. tuber-is- chio - trochantereus; m. ischio-subtro- chantereus; m. quartus quadrigeminus quadratus. './,,,-/.,,. , -THE MUSCULAR SY'STEM., • ,„.,. 247 yo(^,, <:.' - .- .-. *£<•■/<"<:/ -.-,. ■■■:..■.-. ■'■ ■■■■"■..- ' into action. t The obturator, pyriform, geminous, and quadrate femoral muscles rotate the thighs outwardly. THE ILIAC FASCIA. The Il'iac fas'cia1 invests the iliac and psoas muscles, and is a con- tinuation of the same fibrous membrane, constituting in other positions the transverse and pelvic fasciae. It adheres to the lumbar fascia, the arcuate ligaments, the vertebral column, the crest of the ilium, Poupart's ligament, and the pubis. Together with the transverse and pelvic fascia it converges to become the sheath of the femoral blood-vessels. MUSCLES OF THE ILIAC REGION AND LOIN. The Il'iac muscle2 arises from the corresponding fossa of the ilium, and converges to the femoral arch, under which it passes to be inserted, in con- junction with the psoas muscle, into the smaller trochanter of the femur. The Fso'as muscle3 arises from the sides of the bodies and transverse processes of the last dorsal and the lumbar vertebrae, and the interme- diate intervertebral disks. Descending from the loins along the brim of the pelvis, it passes under the femoral arch and terminates in a tendon, which, being joined by the preceding muscle, is inserted into the back part of the smaller trochanter. The upper extremity of the muscle has the internal arcuate ligament of the diaphragm extended across it. At the origin from the sides of the vertebrae, tendinous arches separate it from the lumbar arteries and veins and the anastomotic filaments of the sympathetic nerve. Between the tendon of insertion and "the smaller trochanter, a synovial bursa is interposed. Occasionally, a Small Pso'as muscle4 is situated in front of the for- mer. It arises from the sides of the bodies of the upper two lumbar ver- tebra?, and terminates in a thin tendon, which expands at the brim of the pelvis into the iliac fascia, and is connected with the ilio-pubic eminence. The iliac and psoas muscles, according to the fixation of their origin or insertion, bend either the trunk or the lower extremities forward. They also rotate the thighs outwardly, by drawing the smaller trochanter forward. In conjunction with the gluteal muscles they maintain the erect condition of the body. 1 Fascia iliaca. 2 M. iliacus; internal iliac muscle; m. iliacus internus; m. ilio-trochantereus; part of the m. flexor femoris; m. femur moventium Septimus. 3 Greater psoas muscle; m. psoas ma- jor; m. lumbalis; m. praelumbo-trochan- tercus ; part of the m. flexor femoris; m. femur moventium sextus. 4 M. psoas parous; m. prse-lumbo- pubius. 248 THE MUSCULAR SYSTEM. MUSCLES OX THE FRONT OF THE THIGH. Fio. 173. The Ten'sor of the Fem'oral Fas'cia1 is a short, flat muscle, situated at the upper and outer part of the thigh, and inclosed in a sheath of the femoral fascia. It arises from the anterior superior spinous process of the ilium, between the sartorius and gluteal muscles, and descends in front of the greater trochanter, to terminate in the femoral fascia, a short distance below the latter. The Sarto'rius muscle2 arises tendinously from the anterior superior spinous process of the ilium, and in the form of a long fleshy band descends obliquely across the thigh to the inner side of the knee, where it terminates in a tendon, which expands to be inserted on the inner side of the tibia, just below its tuberosity. The tendon of insertion gives off a process to the crural fascia, and between it and the tendon of the succeeding muscle a synovial bursa is interposed. The sartorius flexes the leg upon the thigh, and if it continues its action the leg is drawn across the opposite thigh. The Grac'ilis muscle3 arises by a thin apo- neurosis from the margin of the symphysis and descending ramus of the pubis. In the form of a long fleshy band it passes down on the in- ner part of the thigh, and terminates at the knee in a narrow tendon, which expands to be inserted beneath the sartorius tendon. Between its tendon and the tibia a synovial bursa is placed. The gracilis adducts the thigh, and assists the action of the preceding muscle. Muscles of the iliac region and FRONT OF THE THIGH. 1, Crest Of the ilium; 2, anterior superior spinous process: 3, middle gluteal muscle; 4, tensor of the femoral fascia; 5, sartorius; 6, rectus; 7, external vastus; 8, internal vastus; 9, inser- tion of the quadriceps extensor into the patella; 10, iliac muscle; 11, psoas muscle; 12, pectineal muscle; 13, long adductor; 14, great adduc- tor; 15, gracilis muscle. 1 M. tensor vaginae femoris ; m. t. fas- ciae latae ; m. fasciae latae ; m. membra nosus; m. fascialis; m. aponeurosis; ilio-aponeurosi femoralis. m. 2 M. sartorius; m. fascialis; m. f. longus; m. longissimus femoris; m. cristo-tibialis; m. ilio-prae-tibialis. 3 M. gracilis, or rectus internus, interior; m. pubio-prae tibialis. or THE MUSCULAR SYSTEM. 249 The Quad'riceps Exten'sor1 occupies the whole front and sides of the thigh, and, as implied by its name, has four heads of origin, called the rectus, the external and internal vastus, and the cruralis. The Rec'tus2 arises, by two short thick tendons, from the anterior infe- rior spinous process of the ilium and the summit of the acetabulum. Descending in front of the thigh, its fleshy fasciculi form a penniform belly ending in a stout, flat tendon, which is joined by the tendons of the other heads of the quadriceps, just above the knee. The remaining three heads, more intimately associated with one another than with the rectus, are sometimes described as a distinct muscle.3 The External Vas'tus,4 the largest portion of the quadriceps, arises by an aponeurosis from the base of the greater trochanter and from the outer border of the asperous ridge. The Internal Vas'tus5 arises from the inner border of the asperous ridge; and the Crura'lis6 arises from the front of the femur, between the two preceding heads of the quad- riceps. The fleshy fasciculi of the internal and external vastus pro- ceed downward and forward, those of the cruralis proceed directly down- ward, and all together terminate in a broad tendon, which conjoins with that of the rectus to be inserted into the base, sides, and front of the patella. Viewing the ligament of the patella as a continuation of the tendon of the quadriceps, this is then inserted into the tuberosity of the tibia. The quadriceps extends the leg upon the thigh. Some detached fas- ciculi7 of the muscle descend from the lower part of the femur to the synovial capsule of the knee joint, and serve to retain this capsule in its proper position. The Pectine'al muscle8 arises from the horizontal ramus of the pubis, between its spine and the ilio-pectineal eminence, and descends on the inner side of the femur to be inserted into the line leading from the smaller trochanter to the asperous ridge. The Long Adduc'tor,9 situated on the same plane as the former muscle, arises tendinously from the front of the pubis, and descends 1 M. quadriceps extensor cruris. 2 M. rectus femoris; m. rectus, or gra- cilus anterior, or cruris; m. ilio-rotuleus; anterior straight muscle. 1 M. triceps extensor cruris ; m. femo- ralis, or cruralis; m. trifemoro-rotuleus, or tibio-rotuleus. 4 M. vastus, or venter externus. 5 M. vastus, or venter internus. 6 M. vastus medius; m. venter poste- rior ; m. cruraeus. 7 M. subcrureus, or subcruralis; m. articulares genu. 8 M. pectineus, or pectinalis; m. pu- bio-femoralis; m. lividus. 9 M. adductor longus; m. a. femoris primus ; caput longum m. ad. tricipitis; m. ad. primus ; m. pubio-femoralis. 250 THE MUSCULAR SYSTEM. obliquely to be inserted into the middle third of the asperous ridge of the femur. The Short Adduc'tor,1 concealed by the preceding two muscles, arises from the body and descending ramus of the pubis, and descends ob- liquely to be inserted into the upper third of the asperous ridge of the femur. The Great Adduc'tor2 is a large, triangular muscle, forming a parti- tion between the front and back part of the thigh. It arises from the descending ramus of the pubis and the ramus and tuberosity of the ischium, and radiates outward and downward to be inserted tendinously into the whole length of the asperous ridge of the femur, extending also by a tendinous cord to the internal condyle. The lower third of the insertion of the great adductor is perforated -J for the passage of the femoral blood-vessels; besides which there are several smaller openings in the tendinous insertion of this muscle for the transmission of the perforating arteries and their companion veins. The pectineal and adductor muscles bend the thigh on the pelvis, rotate it outwardly, and act as powerful adductors. MUSCLES ON THE BACK OF THE THIGH. The Bi'ceps Flex'or,3 as expressed by the name, arises by two heads. The long head arises by a tendon, common to it and the semitendinous muscle, from the back part of the tuberosity of the ischium; the short head arises from the lower two-thirds externally of the asperous ridge of the femur. The fleshy fasciculi terminate in an aponeurosis narrowing into a stout tendon, which is inserted into the head of the fibula. From the tendon of insertion proceed two processes, of which one is inserted into the head of the tibia, and the other is continuous with the crural fascia. The Semiten'dinous muscle4 arises, in common with the tendon of the long head of the biceps flexor, from the tuberosity of the ischium, and descends upon the inner back part of the thigh. Just below the middle of the latter its fleshy belly ends in a long tendon, which proceeds to be 1 M. adductor brevis; m. a. femoris culi adductoris tricipitis; m. ischio-femo- secundus; caput breve m. ad. tricipitis; ralis. m. ad. secundus; m. subpubio-femoralis. 3 M. biceps femoris, or flexor cruris; 2 M. adductor magnus; m. a. femoris m. ischio-femoro-peronealis. tertius et quartus; caput magnum mus- 4 M. semitendinosus; m. ischio-prce- tibialis; m. seminervosus. THE MUSCULAR SYSTEM. 251 inserted into the inner side of the ti the insertion of the gracilis tendon The semitendinous, gracilis, and and nearly equidistant points of the hip bone, and converge to be inserted into the same point of the tibia. Acting together, they cross the leg upon the opposite thigh. The Semimem'branous muscle,1 situated on the inner side of the preceding muscle, arises from the back part of the tuberosity of the ischium by a broad tendon, which expands into an aponeurosis. From this a fleshy belly, composed of short fasciculi, proceeds to another aponeurosis narrowing into a cord- like tendon, which is inserted into the inner side of the head of the tibia. The tendon of insertion gives off processes to the back part of the capsular ligament of the knee joint and the fascia investing the popliteal muscle. The biceps flexor, semitendinous, and semimembranous muscles are all flexors of the leg upon the thigh. The tendon of insertion of the biceps is named the outer ham string; the corresponding tendons of the semitendinous and semi- membranous muscles, the inner ham strings. The space included by the ham strings is the poplite'al 1 M. semimembranosus; m. ischio-pop] 2 Popliteal fossa; fossa genu; hock; the knee. bia below its tuberosity and beneath sartorius muscles arise from remote Fig. 174. Muscles of the back of the RionT buttock and thigh. 1, middle gluteal muscle; 2, great gluteal muscle; 3, external vastus, covered hy the femoral fascia; 4, long head of the biceps flexor; 5, its short head; 6, semitendinous, and 7, semimembran- ous muscles; 8, gracilis muscle; 9, inner border of the great adductor; 10, lower extremity of the sar- torius muscle; 11, popliteal space; 12, gastrocne- mius muscle. region2 or the ham. [ito-tibialis. hoff; garetum; ignys; suffrago; hollow of OAO THE MUSCULAR SYSTEM. MUSCLES OF THE FRONT AND OUTER PART OF THE LEG, AND UPPER PART OF THE FOOT. The Anterior Tib'ial muscle1 arises from the upper two-thirds of the FlG j-.- outer part of the tibia, from the in- terosseous membrane and the crural fascia. Its fleshy belly descends the leg and ends in a flat tendon, which passes beneath the annular ligament of the ankle to the inner side of the foot, where it is inserted into the ^internal cuneiform bone and the base of the metatarsal bone of the great toe. This muscle flexes the foot. The Long Exten'sor of the Toes2 arises from the head of the tibia, the upper three-fourths of the length of the fibula, and from the interosseous membrane and crural fascia. Its fleshy fasciculi termin- ate in a tendon, which descends beneath the annular ligament of the ankle and divides into four tendons diverging to the four lesser toes, over the backs of which they expand in the manner of the ex- tensor tendons of the fingers. Muscles of the front of the leg and back of the foot. 1, tendon of the rectus muscle of the thigh; 2, subcutaneous inner surface of the tibia; 3, anterior tibial muscle; 4, long extensor of the toes; 5, long extensor of the great toe; 6, anterior peroneal muscle; V, long peroneal muscle; 8, short peroneal muscle; 9, borders of the soleus; 10, bor- der of the inner belly of the gastrocnemius; 11, short ■vqt of the toes, beneath the tendons of the long C^K Wisv< This muscle aids the anterior tibial The Anterior Perone'al muscle3 arises from the fibula, below the preceding, and ends in a tendon, which descends beneath the annu- lar ligament to be inserted into the base of the last metatarsal bone. in flexing the foot. 1 M. tibialis anticus; m. flexor tarsi- tibialis; m. tibio-supertarseus; m. tibio- ^upra-metatarseus; m. hippicus; m. ca- tenae. 2 M. extensor longus, or communis di- gitorum pedis; m. cnemodactylaeus. 3 M. peroneus anticus, or tertius; m. tarsi-fibularis; m. pereneo-supra-meta- tarseus brevis: m. nonus Yesalii. THE MUSCULAR SYSTEM. 253 The Exten'sor of the Great Toe1 lies between the anterior tibial and long extensor muscles. It arises from the lower two-thirds of the fibula and the interosseous membrane, and ends in a flat tendon, which descends beneath the annular ligament of the ankle and expands on the back of the great toe, being finally inserted into its last phalanx. The Short Exten'sor of the Toes2 is situated on the back of the foot. It arises from the outer side of the calcaneum- and the annular ligament of the ankle, and forms four fleshy bellies, each of which ends in a ten- don proceeding to join the extensor tendons of the great toe and the succeeding three toes. The Long Perone'al muscle,3 situated at the outer part of the leg, arises from the upper two-thirds of the fibula, from the contiguous inter- muscular partitions and the crural fascia. Its fleshy belly ends in a long tendon, which descends through a groove at the back of the external ankle, then proceeds along another groove on the outer surface of the calcaneum, and turns beneath the sole of the foot. Entering the groove of the cuboid bone, it passes obliquely forward and inward to be inserted into the base of the first metatarsal bone. In the course of the tendon, it twice changes its direction; once at the lower end of the fibula, and again at the cuboid bone. In these positions it acquires a thickened fibro-cartilaginous character, and at the turn of the cuboid bone not unfrequently has a sesamoid bone devel- oped in it. The grooves behind the external ankle and the outer face of the calcaneum, through which the tendons pass, are converted by fibrous bands into canals lined with synovial bursas. The groove of the cuboid bone is converted into a canal by the long plantar ligament, and is likewise provided with a synovial bursa. The Short Perone'al muscle4 arises from the lower half of the outer surface of the fibula, and the contiguous intermuscular partitions. Its fleshy belly terminates in a tendon, which descends, in company with that of the preceding muscle, behind the external ankle, and passes along the outer surface of the calcaneum to be inserted into^the base of the last metatarsal bone. The long and short peroneal muscles extend the foot, and are the antagonists of the anterior peroneal and tibial muscles.) •> M. extensor proprius pollicis, or hal- lucis ; m. e. longus hallucis. ■ M. extensor brevis digitorum pedis; ni. pedicus. 3 M. peroneus longus, primus, posticus, or maximus ; m. pereneo-sub-tarseus ; m. extensor tarsi-fibularis longior. * M. peroneus brevis, secundus, or medius; m. semifibulaeus; m. extensor tarsi-fibularis brevior. 254 THE MUSCULAR SYSTEM. MUSCLES ON THE BACK OF THE LEG. Fig. 176. The Tri'ceps Su'ral muscle,1 as expressed in the name, has three heads, the-fleshy bellies of which form the calf of the leg.2 Two of the bellies are superficial, and constitute the gastrocne- mius muscle, while the third is under cover of the former, and is named the soleus muscle. The Gastrocne'mius muscle3 arises tendin- ously just above the condyles of the femur; and its two fleshy bellies descend in contact with each other to terminate in a strong apo- neurosis. The Sole'us muscle4 arises from the head and half the length of the fibula, from the oblique line of the tibia just below the popliteal mus- cle, and from the inner border of the tibia for several inches below the latter. From this origin the fleshy fasciculi descend obliquely, and terminate in an aponeurosis facing the muscle posteriorly. The aponeuroses of the gastrocnemius and soleus muscles conjoin in the formation of the strongest cord-like ten- don of the body, named the tendon of Achilles,5 which descends to be inserted into the lower part of the tuberosity of the calcaneum. Between the upper part of the tuberosity and the tendon a synovial bursa is interposed. The triceps sural muscle by drawing on the calcaneum elevates the body upon the toes, as in walking. Dancing, jumping, or other active movements of the kind tend greatly to increase its size. Superficial muscles on the back of the right leg. 1, bi- ceps flexor; 2, tendons of the semitendinous, semimembra- nous, gracilis, and sartorius muscles; 3, popliteal space; 4, gastrocnemius; 5, soleus; 6, tendon of Achilles; 7, calca- neum; 8, tendons of the long and short peroneal muscles passing behind the outer an- kle ; 9, tendons of the posterior tibial muscle and long flexor of the toes passing behind the inner ankle. 1 M. extensor pedis ; m. triceps surae ; m. suras, or suralis; m. extensor tarsi magnus. 2 Sura; gastrocnemium. 3 M. gastrocnemius externus; m. ge- mellus suraB; m. gemellus externus and internus; m. bi-fcmoro-calcaneus. * M. gastrocnemius internus; m. tibio- calcaneus; m. tibio-pereneo-calcaneus. 5 Tendo Achilles; Achilles' tendon; chorda, or funis Hippocratis; corda magna; nervus latus. THE MUSCULAR SYSTEM. 255 The Plantar muscle1 arises from the femur just above the outer con- dyle, and from the contiguous portion of the capsular ligament of the knee joint. Its short, fleshy belly ends in a long, delicate tendon, which, after passing between the gastrocnemius and soleus muscles, descends at the inner margin of the tendon of Achilles to be inserted, in company with it, into the calcaneum. This muscle corresponds to the long palmar muscle of the forearm, but it is only in some of the lower animals that its tendon joins the plan- tar aponeurosis. Fig. 177. The Poplite'al muscle2 is situated immediately below the knee joint posteriorly, and is invested with a thin aponeurosis connected with the tendon of the semimembranous muscle. It arises by a tendon from the groove on the outer side of the external condyle of the femur, beneath the contiguous lateral ligament of the knee joint, and expands upon the triangular surface at the upper part of the tibia, into which it is inserted. The tendon of origin is attached to the external semilunar fibro-cartilage, and is invested by the synovial membrane of the knee joint. The popliteal muscle flexes the leg and rotates it inwardly. nEEP MUSCLES OF THE BACK OF THE leg. 1, femur; 2, posterior portion of the capsular ligament; 3, tendon of the semimembranous muscle in- serted into the head of the tibia, and giving an offset to the capsular ligament; 4, 5, internal and exter- nal lateral ligaments; 6, popliteal muscle; 7, long flexor of the toes; 8, posterior tibial muscle; 9, long flexor of the great toe; 10,11, long and short peroneal muscles; 12, tendon of Achilles; 13, tendons of the long flexor of the toes, and the posterior tibial muscle, just before passing beneath the internal annu- lar ligament. The Long Flexor of the Toes,3 situated under cover of the muscles of the calf, and below the popliteal muscle, arises from the tibia to within a short distance of its lower extremity. The fleshy fasciculi proceed obliquely to a tendon, which descends behind the inner ankle and turns beneath the concavity of the calcaneum into the sole of the foot. Receiving a process from the tendon of the long flexor of the '«& XX £ X 1M. plantaris; m. p. gracilis; m. exten- Bor tarsi minor; m. gracilis surae; m. tibi- alis gracilis; m. femoro-calcaneus brevis. 1 M. poplitaeus ; m. sub-poplitaeus; m. femoro-popliti-tibialis. 3 M. flexor longus digitorum; m. f. 1. d. pedis profundus perforans; m. flexor tertii internodii digitorum pedis; m. pe- ronodactylius. 256 THE MUSCULAR SYSTEM. great toe, it then divides into four tendons, which proceed forward and pass through perforations in the tendons of the short flexor of the toes, finally to be inserted into the bases of the last phalanges of the four lesser toes. The Long Flexor of the Great Toe,1 situated at the outer side of the preceding muscle, arises from the lower two-thirds of the fibula, and ends in a tendon which descends behind the inner ankle to the concavity of the calcaneum. Turning forward in the sole of the foot, after giving off a process to the tendon of the long flexor of the toes, it proceeds to be inserted into the base of the last phalanx of the great toe. The Posterior Tib'ial muscle,2 situated between the preceding pair of muscles, arises from the surface of the interosseous membrane and the contiguous borders of the tibia and fibula. Its fleshy fasciculi end in a tendon which descends through a groove behind the inner ankle, then proceeds beneath the calcaneum to be inserted into the scaphoid bone and the base of the first metatarsal bone. " This muscle is an extensor of the foot, MUSCLES OF THE SOLE OF THE FOOT. The Short Flexor of the Toes3 is covered by the middle portion of the plantar fascia, from which and the inner tubercle of the calcaneum it has its origin. Proceeding forward, it terminates in four tendons, which, after being perforated for the passage of the tendons of the long flexor of the toes, are inserted into the bases of the second phalanges of the latter. The Accessory Flexor4 arises from the concavity and under part of the calcaneum, and is inserted into the tendon of the long flexor of the nuiuat toes, to which, as the name indicates, it is an accessory head. The Lumbrical muscles5 are four fleshy fasciculi like those of the hand. They arise from the tendons of the long flexor of the toes, and 1 M. flexor longus pollicis pedis; m. f. 1. hallucis pedis. 2 M. tibialis posticus; m. nauticus; m. extensor tarsi-tibialis; m. tibio-sub-tar- seus. 3 M. flexor brevis digitorum pedis; m. f. b.d. p. perforatus; m. f. sublimus d. p. perforatus; m. flexor secundi internodii digitorum pedis. 4 M. flexor accessorius; m. accessorius flexoris longi digitorum pedis; massa car- nea Jacobi Sylvii; caro quadrata Sylvii; caro accessoria; m. plantarus verus. 5 M. lumbricales pedis. THE MUSCULAR SYSTEM. 257 proceed to be inserted into the corresponding extensor tendons and the bases of the first phalanges of the toes. The Abduc'tor of the Great Toe,1 the most superficial of the muscles on the inner side of the sole of the foot, arises from the calcaneum, the scaphoid and internal cuneiform bones, and the plantar fascia, and pro- ceeds forward to be inserted by a tendon into the base of the first phalanx of the great toe. Fig. 178. Fig. 179. Muscles of the sole of the foot. 1, calcaneum; 2, posterior extremity of the plantar fascia; 3, ab- ductor of the great toe; 4, abductor of the little toe; 5, short flexor of the toes; 6, tendon of the long flexor of the great toe; 7, insertion of the lumbrical muscles, which are seen to the right of the tendons of the short flexor of the toes. Oeep muscles of the sole. 1, attachment of the plantar fascia and short flexor of the toes; 2, ac- cessory flexor; 3, tendon of the long flexor of the toes; 4, tendon of the long flexor of the great toe; 5, two heads of the short flexor of the same; 6, ad- ductor of the great toe; 7, flexor of the little toe; 8, transverse muscle; 9, interosseous muscles; 10, course of the tendon of the long peroneal muscle, seen through the long plantar ligament. The Short Flexor of the Great Toe2 arises, as a pair of fleshy bellies, from the cuboid and outer two cuneiform bones, and proceeds forward to be inserted tendinously into the base of the first phalanx of the great toe. Between the two bellies of this muscle lies the tendon of the long flexor. The Adduc'tor of the Great Toe3 arises from the cuboid bone and the 1 M. abductor pollicis pedis; m. calco- sub-phalangeus pollicis. 2 M. flexor brevis pollicis, or hallucis pedis. 3 M. adductor pollicis, or hallucis pe- dis ; m. antithenar; m. metatarso-sub- phalangeus pollicis. It 258 THE MUSCULAR SYSTEM. bases of the third and fourth metatarsal bones, and is inserted tendinously into the base of the first phalanx of the great toe. The Transverse muscle1 consists of several fasciculi arising from the heads of the second, third, and fourth metatarsal bones, and inserted tendinously into the base of the first phalanx of the great toe. The sesamoid bones are inclosed within the insertion of the muscles into the base of the first phalanx of the great toe, and move upon the head of the metatarsal bone during the action of those muscles. The Abduc'tor of the Little Toe2 arises from the outer tubercle of the calcaneum, the plantar fascia, and the base of the last metatarsal bone, and proceeds forward to be inserted into the base of the first phalanx of the little toe. The Flexor of the Little Toes arises from the long plantar ligament and the base of the last metatarsal bone, and proceeds to be inserted into the base of the first phalanx of the little toe. THE INTEEOSSEOUS MUSCLES OF THE FOOT. The Dorsal Interos'seous muscles occupy the metatarsal intervals, with which they correspond in number. They arise from the adjacent sides of the metatarsal bones, and are inserted tendinously into the extensor tendons and bases of the first phalanges of the middle three toes. The first dorsal interosseous muscle is inserted on the inner side of the second toe, and acts as an adductor; while the others are inserted into the outer side of the second, third, and fourth toes, and act as abductors. The Plantar Interos'seous muscles, three in number, lie on the outer three metatarsal bones and arise from their inner side, from whence they proceed forward to be inserted into the extensor tendons and bases of the first phalanges of the corresponding toes, to which they act as adduc- tors. 1 M. transversalis, or transversus pe- - M. abductor minimi digiti pedis. dis; m. scandularius; m. metatarso-sub- 3 M. flexor minimi digiti pedis. phalangeus. CHAPTER V. ANATOMICAL ELEMENTS OF SEROUS AND MUCOUS MEMBRANES, THE GLANDS, THE LUNGS, AND THE SKIN. Serous and mucous membranes, glands, the lungs, and the skin pos- sess common anatomical elements, which hold the same relative position with one another. These elements are as follows: a cellular layer, a basement membrane, a fibrous layer, and blood-vessels, lymphatics, and nerves. The Cel'lular layer1 occupies the free surface of the structures above mentioned, and is named epithe'lium,2 except on the skin, where it is called epider'mis. It consists of from one to many layers of cells, of different forms in the various struc- tures indicated. The epi- thelium of the uriniferous tubules of the kidneys presents an example of a single layer of cells; the serous membranes, from one to four layers; the mucous membrane of the stomach, several layers in different stages of development; the mucous membrane of the mouth, many layers; and the epidermis, above all similar structures, presents the greatest number of layers of cells. From difference in form, and other peculiarities, the epithelium is 1 Implying its composition of organic cells, and not to be confounded with areolar or connective tissue, which, until within a comparatively short period, was called cellular tissue. 2 Epitelium: endepidermis. (259j) Fig. 180. Diagram exhibiting tue relative position of the cummon ana tomical elements of serous and mucous membranes, the glands THE lungs, AND THE skin. 1, epithelium, secreting cells, or epi- dermis, as the case may be, composed of nucleated cells, and occu- pying the free surface of the structure mentioned; 2, basement layer, in this and other diagrams purposely represented much thicker than natural, in comparison with the other layers; 3. fibrous layer, iu which the arteries and veins (4) terminate in a capillary net-work. 260 EPITHELIUM. divided into the following varieties: squamous epithelium; pavement epithelium; spheroidal, polyhedral, and irregular epithelium ; columnar epithelium ; and ciliated epithelium. The Squa'mous epithe'lium1 consists of many layers of broad, thin scales, which are flattened cells, containing a nucleus and a few scattered coarse granules. This variety forms the epithelium of the mucous membrane of the mouth, lower part of the pharynx, oesophagus, vagina, vulva, entrance of the urethra, conjunctiva, and entrance of the nose. Fig. 181. Fig. 182. PauiMom epithelium, consisting of nucleated Pavement epithelium, from a serous membrane, cells transformed into broad scales. From the mu- highly magnified, and seen to consist of flat, s.s- cons membrane of the mouth, highly magnified. sided nucleated cells. The Pavement epithe'lium2 consists of from one to four layers of flat nucleated cells, usually six-sided, and regularly arranged like the blocks of a pavement, whence the name. Such an epithelium forms the free surface of the serous membranes, including the synovial membranes and the lining membrane of the vascular system; it likewise constitutes the epithelium of the uriniferous tubules, sweat glands, and air-cells of the lungs. The Spheroidal, polyhedral, and irregular epithe'lium are modifica- tions of the same form. The spheroidal epithelium constitutes the secreting cells of the salivary glands and pancreas, but they are more or less modified into the polyhedral form by mutual pressure. The secret- ing cells of the liver are polyhedral, but more or less irregular. The epithelium of the excretory duct of the kidney and of the bladder exhibits singularly irregular forms of cells. The Columnar epithe'lium3 consists of a single layer of six-sided col- umnar cells, with a conical prolongation. The broad end of the cells is free, the sides are in contact, and the narrow end is imbedded in a pro- geny of developing cells. The columnar cells are more delicate than most other kinds, are provided with granular contents, and possess a large oval nucleus. Such an epithelium is found on the mucous mem- 1 Scaly, lamellar, tabular, flattened, pavement, or tesselated epithelium. 2 Tesselated epithelium. 3 Cylinder, prismatic, conical, or tu- bular epithelium; simple columnar epi- thelium. EPITHELIUM. 261 brane of the stomach, small and large intestines; in many glands, as the tubular glands of the intestines; in the ducts of most glands ; in the gall-bladder; and in the urethra. Fig. 183. Polyhedral epithelium, exemplified by secret- ing cells of the liver. The arrangement is ideal. 1, space occupied by a blood-vessel; 2, isolated cells. The Cil'iated epithe'lium1 dif- fers from the preceding, in the cells possessing at their free extremity a number of exceedingly fine filament- ous appendages, named, from their resemblance to the eyelashes, cil'ia.2 These are processes of the cell wall of uniform size, and during life are endowed with the power of rapidly and incessantly moving backward and forward. This vibratory movement is always uniform and wave-like in a long series of cells, so that when seen over a surface of some extent, it reminds one of the movement of a field of grain under the influence of a gentle breeze. The vibration of the cilia produces currents in the liquids in contact with them, and thus conveys the liquids from one posi- tion to another. The cil'iary motion even continues for some time after the cells have been scraped from the membrane of which they form a part; and the resistance of the liquid to the vibrating cilia of the de- tached cells causes these to move freely about, as if endowed with volun- tary power. A ciliated epithelium exists on the mucous membrane of the upper part of the nose and pharynx, the tympanum and Eustachian tube, the larynx, trachea, bronchi and their ramifications, and the cavity of the uterus and Fallopian tubes. The epidermis will be particularly described in the account of the skin. 1 Vibratile epithelium. 2 Vibratile cilia; vibrillse. a J'. Fig. 184. niAGRAM OF A VERTICAL SECTION OF MUCOUS MEM- BRANE OF THE small intestines, highly magnified. 1, fibrous layer, in which the blood-vessels are dis- tributed ; 2, basement membrane ; 3, young nucle- ated cells; 4, layer of columnar cells; 5, 6, cells in the act of being shed or thrown off; 7, free ends of the columnar cells, exhibiting their six-sided form; 8, a single columnar cell, exhibiting its actual form at all parts 262 BASEMENT MEMBRANE. Fig. 185. Diagram of a vertical section of the bronchial mucous mem- BRANE, highly magnified. 1, col- umnar ciliated epithelial cells; 2, cilia; 3, nuclei; 4, young cells; 5, basement membrane; 6, fibrous layer. works of elastic tissue. Basement membrane1 is a thin, homogeneous layer, or one devoid of visible structure, supporting the cellular layer of the serous and mucous membranes, the skin, and other organs above mentioned; and resolving itself beneath into the fibrous layer. In some instances it is very distinct and readily observed, as in the urin- iferous tubules; in others it certainly exists, but is not so easily demonstrable as in the mucous membranes and skin; and in some cases it is so difficult to detect, that in such positions by many its existence is denied, as in the liver. The fibrous layer,2 situated beneath and supporting the basement membrane and epi- thelial layer, is composed of an intertexture of bundles of fibrous tissue mingled with fine net- This layer, for the most part, is absent in the liver, exists in very small quantity in the kidneys, is well developed in other glands, and in the serous and mucous membranes, and reaches its greatest extent in the formation of the dermis. The fibrous layer gives strength and stability to the other structures, and in it, or in a correspond- ing position if it is absent, the blood-vessels, lymphatics, and nerves are distributed, and never penetrate the basement membrane or epithelial layer. The blood-vessels form capillary nets, which have the closest meshes in the glands, mucous membranes, lungs, and skin. The lym- phatics are more numerous in these than any other structures. The nerv- ous supply is also abundant. Most or perhaps all the structures, whose elements have been described above, lose the superficial portion of their cellular layer from time to time, which is as constantly renewed. The process is not very evident in the cellular layer of glands, nor is it much more clear in the pave- ment epithelium of serous membranes and allied structures. The colum- nar epithelium, including its ciliated variety, exhibits strong evidences of the process, but it is most strikingly obvious in the squamous epithelium and the epidermis. In a vertical section of the mucous membrane of the mouth, the cells of the epithelium in contact with the basement membrane are observed to be comparatively soft, polyhedral from mutual pressure, and of uniform 1 Structureless, or amorphous membrane; homogeneous layer; membrana inter- media, or limitans; primary or limitary membrane. 2 Membrana propria. SEROUS MEMBRANES. 263 diameters; the layers of cells in succession increase in breadth at the ex- pense of their depth; and the superficial cells form the broad thin scales char- acteristic of the squamous epithelium, of which shreds or flakes are con- stantly being cast off while they are renewed from be- neath. In a vertical section of the mucous membrane of the small intestine, sev- eral layers of cells are observable, in the deeper part of the epithelium, in various stages of development, from the simple spheroidal form to the columnar cells, which always exist in a single layer at the free surface of the epithelium. How, or whether these columnar epithelial cells are shed, has not been positively determined. On several occasions, the author, in some examinations of the structure of the small intestine in the lower animals, has observed isolated columnar cells ap- parently crowded from their position by pressure laterally and beneath, as represented in figure 184. Perhaps from these instances we may not be wrong in suspecting that the older or effete cells are thus pushed one after another from their place by the more vigorous cells around and the developing ones beneath. SEROUS MEMBRANES. The Serous membranes,1 named from the character of the liquid bathing their free surface, line cavities of the body having no exterior communication, and are therefore closed sacs. They serve to lubricate organs which move upon one another, and in many instances form folds, which retain the organs in their position, and from this circumstance, in some cases are named ligaments, as in the case of the suspensory liga- ment of the liver. The serous membranes are as follows:— 1. The two pleurae lining the sides of the thorax and investing the lungs. 2. The pericardium surrounding the heart. 3. The peritoneum lining the cavity of the abdomen and reflected upon its viscera. Fig. 186. Diagram of a section of the mucous membrane of the mouth, highly magnified. 1, fibrous layer, in which the blood-vessels are distributed; 2, basement layer; 3, young cells of the epithelium; 4, older cells transformed into scales; 5, shred of epithelium cast off; 6, a single scale, seen on its broad surface; 7, a similar scale, Been in its thickness. Membranse serosa. 264 SEROUS MEMBRANES. Fig. 187. 4. The vaginal tunic of each testicle. 5. The arachnoid membrane of the brain and spinal cord. 6. The lining membrane of the ventricles of the brain. 7. The synovial membranes of the joints. 8. The synovial bursae. 9. The lining membrane of the vascular system. 10. The lining membrane of the labyrinth. In the relation of the serous membranes to the contiguous parts, one portion is applied upon the interior surface of the cavity it lines, and another portion is reflected upon the organ or organs contained within the cavity. The former is named its pari'etal or lining portion; the latter, its reflected or vis'ceral portion. From this arrangement, the organs are not contained within the cavity of the serous sacs, but are excluded by the membrane being reflected over them. The outer surface of the serous membrane is attached to the neighbor- ing parts by connective tissue, named from its position sub-serous tissue; the inner surface is free, smooth, shining, and moistened with a serous liquid elaborated by the membrane itself. The free surfaces of the parietal and reflected portions of the serous membrane come into contact, so that the organs easily and smoothly move upon one another, and against the walls of the cavity containing them; the movement being facilitated by the liquid lubri- cating the surfaces. The liquid of the serous cavities resembles the serum of the blood in appearance and composition, but in some instances is more viscid, as in the case of that of the synovial membranes. The sub-serous connective tissue usually at- taches the serous membranes closely to the adjacent parts. In the case of the arachnoid membrane attached to the pia mater, it consists of scattered bands, the sub-arach'noid tissue, with the intervals occupied by a liquid like that contained within the cavity of the arachnoid membrane. When serous membranes invest the interior surface of fibrous mem- branes, as in the case of the arachnoid and dura mater, and the serous and fibrous pericardium, the two together are often named fibro-serous membranes. The serous membranes are thin, transparent, and colorless, moderately Diagram exhibiting the rela- tion OF A SEROUS MEMBRANE, THE PLEURA, TO THE ORGAN IT INVESTS AND THE CAVITY IT LINES. 1, lung ; 2, root of the lung, which is the only attached portion of the organ, all others being free; 3, side of the thorax; 4, diaphragm; 5, parietal pleura; 6, pulmonary or reflected pleura; 7, cavity of the pleura. SEROUS MEMBRANES. 265 strong, extensible and elastic. In structure they consist of one or more layers of pavement epithelium composed of six-sided cells; a thin base- ment membrane, and a layer of fibrous tissue with mingled elastic fibres. The blood-vessels are comparatively few, and form capillary nets, with wide meshes, in the fibrous layer. Numerous lymphatics and fine plexuses of nerves also pervade the latter, though the serous membranes are quite devoid of sensibility in a condition of health. The liquid of serous membranes consists of water, with from one to six percentage of albumen, chloride of sodium, and phosphate of soda and lime. Syno'vial membranes1 line the interior of the joints, but do not cover the articular cartilages. Their lubricating liquid, named syno'via,2 is more viscid than the liquid of other serous membranes. At the margin of the articulations the membrane frequently forms one or more folds containing fat, and named synovial fringes.3 These are yellow or red- dish yellow, more vascular than other portions of the synovial membrane, and apparently more active in the production of synovia. Syno'vial bur'sae4 occur where muscles or tendons move upon bones, fibro-cartilages, or ligaments, or frequently upon one another. In many positions they appear as simple, flattened spheroidal sacs, tightly adhe- rent by one side to the moving organ, and by the other side to the part against which the organ moves. Instances of this kind are seen in the bursa beneath the deltoid muscle, and that between the insertion of the biceps flexor tendon and the tuberosity of the radius. When tendons move through grooves of bones, or beneath annular or vaginal ligaments, the synovial bursa5 lines the groove or canal and is thence reflected upon the tendons. In the vicinity of joints the bursae often communicate with their cavity. In positions in which a number of tendons move upon one another, as in the case of the flexor tendons in the vicinity of the wrist, a highly extensible, fibro-elastic membrane6 is folded around and among them, which appears to have the same function as the synovial bursas, but presents no trace of an epithelium. Beneath the skin also in certain positions, as between that of the elbow and the olecranon, or that of the knee and the patella, pouches7 exist, apparently of the nature of 1 Capsulae synoviales. 2 Mucilago; humor, unguentum, smeg- ma, axungia, gluten, or humidum nativum articulorum; hydrarthrus; arthrohydrine. 3 Synovial glands of Havers; Haver- sian glands; glandulae articulares; syno- vial fimbriae; plicae synoviales, adiposae, or vasculosae ; ligamenta mucosa. 4 Bursa? mucosae ; b. m. vesiculares; b. or capsulae synoviales; sacci mucosi; synovial crypts or follicles; blennocys- tides; vesicae unguinosae tendinum. 5 Vaginae synoviales or mucilaginosae. 6 Bursae mucosae tendinosae. 7 B. m. subcutaneae. 266 MUCOUS MEMBRANES. synovial bursae. These have a ragged-looking internal surface devoid of an epithelium. MUCOUS MEMBRANES. Mucous membranes, though possessing common physical or anatomical elements, like the serous membranes, differ in most other respects. They line internal cavities and passages communicating with the exterior, together with various receptacles and glandular ducts opening on the surfaces of the former. They never form completely closed sacs, as the serous membranes, and are all continuous with one another and the skin. Habitually exposed to the contact of materials foreign to their structure, such as food, air, dust, the secretions and excretions of glands, their free surface is bathed with a viscous liquid named mucus, which is usually more consistent than the liquid of serous membranes. Mucous membrane lines the cavity of the nose and its communicating sinuses, the front of the eye and the lachrymo-nasal duct, the tympanum, mastoid sinuses and Eustachian tube, the mouth, pharynx, oesophagus, stomach, and intestines, the larynx, trachea, bronchi and their ramifica- tions, the salivary, pancreatic, and bile ducts, and the gall-bladder, the pelvis of the kidneys, ureters, urinary bladder and urethra, the semi- nal ducts and vesicles, the vagina, uterus, and Fallopian tubes, and the ducts of the mammary glands. From their isolation, all these mu- cous membranes together are divided into three groups, generally desig- nated as the gastro-pulmonary, genito-urinary, and mammary mucous membranes. At the edges of the eyelids, nostrils, mouth, anus, vulva, urethra, and orifices of the milk ducts, the mucous membranes become continuous structures with the skin. All the mucous membranes possess a free surface formed of an epithe- lium resting on a basement membrane, beneath which is a fibrous layer adhering to the contiguous parts by connective tissue, named from its position the submucous tissue.1 In the hollow viscera the latter forms an abundant and distensible layer, permitting considerable enlargement of the visceral cavities, as in the case of the stomach and urinary blad- der. In contraction of organs lined with mucous membrane this be- comes rugose, or thrown into folds, which are effaced on distention. These folds, however, should not be confounded with others of a perma- nent character existing in some of the mucous membranes, as for instance, the val'vulae conniven'tes of the small intestine. The mucous membranes are less transparent in general than the serous 1 Textus cellularis submucosus; tunica cellularis; fibrous coat; cellular coat. THE GLANDULAR SYSTEM. 267 membranes; are more vascular, and are also well supplied with lym- phatics and nerves. They vary from a white, grayish white and pale pink, to dark red, the shade or depth of redness depending mainly on the amount of blood supplied. Excitation heightens their color, and contact with the air favors their permanent redness. Nearly all mucous membranes are abundantly supplied with minute glands imbedded in their fibrous layer or the contiguous submucous tissue, and opening on their free surface. The epithelium of mucous membranes presents most of the varieties of cells which have been described. Those provided with a columnar epithelium are usually softer and more moist than the others. The base- ment membrane and fibrous layers of structure are sufficiently evident in all mucous membranes. Mucus, the material elaborated by the mucous membranes, and appa- rently by many of their glands, is a clear, colorless, transparent, viscid liquid, frequently rendered more or less turbid by cast-off epithelial cells, and isolated nuclear bodies, commonly called mucous corpuscles. It is composed of water, the peculiar organic principle mucosin, and alkaline salts. THE GLANDULAR SYSTEM. The name of Gland has been indiscriminately applied to almost every rounded, massive organ, if it was only supposed to elaborate certain liquid materials from the blood. Thus the liver, which produces the bile, the thyroid body whose office is unknown, the rounded masses situ- ated in the course of the lymphatics, and the pituitary body, a portion of the brain, have all been and yet continue to be called glands. In this confusion of parts with one general name, it is our object at present only to describe those which are commonly distinguished as the true glands. These may be defined to be organs which elaborate from the blood liquid matters poured forth by one or more ducts or orifices open- ing on the surface of the mucous membranes or skin. The material elaborated by a gland is called a secretion, and the same name is given to the act of elaboration. If the secretion is to be rejected from the body as useless, it is also called an excretion. The term secretion is likewise applied to mucus and serum, and to the elaboration of these by their appropriate membranes. In general, the glands may be described as consisting of a tube or series of tubes of basement membrane lined with nucleated cells, and in- vested externally with a fibrous layer in which are distributed the blood- vessels from which the glands elaborate their secretions. The difference 268 THE GLANDULAR SYSTEM. in the complexity and extent of glands depends mainly on the difference in number, length, and arrangement of the tubes. Fig. 188. Fig. 189. Simple gland dilated into a pouch. References as in the preceding figure. Diagram of two simple tubular glands. The dotted line 1 indicates the glandular epithelium or secreting cells; the thicker continuous line 2, is the basement membrane, and the shaded portion of the figure 3 represents the fibrous tissue in which the blood-vessels are distributed which sup- ply the glands. The simplest form of a gland consists of a short, straight tube, closed at one end, and opening at the other upon the surface of a mucous membrane, as instanced in the tubular glands of the small intestines. The complexity is slightly increased if the tube is dilated into a purse-like pouch, as in the simple sebaceous glands of the skin. If the simple tube or pouch is divided at bottom into two or more similar parts, the complexity is increased according to the number of the latter, as seen in the gastric glands, and compound sebaceous glands of the skin. The glandular tube may be rendered complex by becoming more or less elongated and convoluted, as in the case of the sweat glands. If Fig. 190. Fig. 191. Fig. 192. Fig. 190. Glands rendered slightly complex by division at bottom. References as in figure 188. Fig. 191. Increase of complexity of glands by the addition of similar parts. References as before. Fig. 192. A tubular gland rendered complex by becoming elongated and convoluted. Same references. the tube divide and subdivide, and the ultimate branches become elon- gated and convoluted, the gland is rendered complex according to the extent of branching and convolution, as exemplified by the kidneys and testicles. If the glandular tube divide and subdivide, and the terminal branches THE GLANDULAR SYSTEM. 269 dilate into vesicles, a complex arrangement is produced resembling in appearance a bunch of grapes, as represented in the construction of the salivary glands. If, on the other hand, the branching tubes form a net- work, a complex arrangement results such as is seen in the construction of the liver. Fig. 193. Fig. 194. Fig. 195. Fig. 193. Gland of complex form; the tubes branching and the terminal ones convoluted and dilated at the extremities. 1, main tube or duct; 2, branches; 3, convoluted portions dilated at the extremities. Fig. 194. Gland of complex form, whose arrangement resembles that of a bunch of grapes. 1, duct; 2, branches ending in vesicles; 3, branch of another lobule. Fig. 195. Gland of complex character in which the tubes anastomose, and thus form a net-work 1, duct; 2, net-work of tubes. The glands may be classified according to their structural arrangement, though it should be fairly understood that the different forms are not separated by trenchant characters, but pass by gradations into one another. The principal forms are as follows: the tubular, racemose, convoluted, and reticular glands. The Tubular glands consist of simple, straight or slightly tortuous tubes closed at one end, and opening at the other on the surface of a mucous membrane. They are usually short, of uniform diameter through- out, or slightly dilated toward the closed extremity; or in the latter po- sition they may divide into several tubular offsets or prolongations. They are imbedded in the fibrous layer of mucous membranes, and in most instances are provided with a columnar epithelium, besides the basement membrane and fibrous coat. Such are the tubular glands of the large and small intestine, the gastric glands, and the tubular glands of the nose and uterus. The Follic'ular glands, intermediate to the former and the succeeding variety, and passing insensibly from one into the other, are composed of one or more purse-like pouches lined with a spheroidal epithelium. When the pouches are numerous, they are usually collected into small groups or lobules opening into a common canal or duct, which conveys 270 THE GLANDULAR SYSTEM. the secretion to the surface of the skin or mucous membrane. To this variety belong the sebaceous glands of the skin, the follicular glands of the root of the tongue, soft palate and pharynx, and the tonsils. The Rac'emose glands are named from their structure resembling in arrangement the appearance of a raceme or cluster of grapes. In the construction of such glands, a tube divides and subdivides, and the smallest branches communicate with vesicular dilatations lined with spheroidal secreting cells, rendered polyhedral from mutual pressure. Groups of vesicles and their associating tubes, which may be compared with the small clusters of a bunch of grapes, are named lobules. In the construction of a large racemose gland, the latter are associated in still larger portions, a number of which together may form the largest divi- sions or lobes of the gland. The simplest racemose glands present a striking resemblance to a bunch of grapes, but the more compound Fig. 196. glands, or those consisting of a number of lobules and lobes, are modified in form from mutual pressure. The commencing vesicles are polyhedral, the lobules and lobes are pyramidal, and the whole are associated, by in- tervening connective tissue, into a more or less solid mass. The tubes or ducts, which collect the secretion from the commencing vesicles, finally emerge from the lobules and collect into A racemose gland. 1, duct; 2, J ° lobules composed of the terminal a principal duct, or sometimes several, issuing divisions of the ducts, ending in from the g]md ftnd opening on some muC0US membrane. The duct or ducts of the racemose glands have fibrous walls lined with mucous membrane, usually provided with a columnar epithelium. A few of the principal ducts in addition are furnished with unstriated muscular fibres. To the racemose glands belong the pancreas, the salivary glands, the lachrymal gland, the labial, buccal, palatine, lingual, pharyngeal, oeso- phageal, and duodenal glands, the tracheal and bronchial glands, the vaginal, prostatic, and urethral glands. The Convoluted glands are composed of simple or branching tubes, which, at their commencement, are enrolled upon themselves or convoluted into masses. The simplest forms are the sweat glands; the compound forms are the kidneys and testicles. The only gland exhibiting a reticular arrangement in its intimate structure is the liver. This organ is divided on the surface into several lobes, and these are composed of an aggregation of small and closely UNSTRIATED MUSCULAR TISSUE. 271 adherent polyhedral lobules or acini. Independently of the blood-ves- sels, the acini consist of a net-work of polyhedral glandular cells; but whether they occupy the interior of tubes of basement membrane, as in other glands, is still a point which remains undetermined to the satisfac- tion of most anatomists. Ducts proceeding from the acini, as in other secretory organs, converge to trunks composed of fibrous walls, with a lining of mucous membrane. The glands are most richly furnished with blood-vessels, which form capillary nets around or among the glandular tubes. They likewise pos- sess numerous lymphatics, and are also supplied with nerves. UNSTRIATED MUSCULAR TISSUE. Most of the hollow viscera, including the vascular system and a few other parts, are provided with muscular layers of a different structure Fig. 197. Unstriated muscular fibre. 1, from the small intestine; 2, from the middle coat of an artery; 3, from a vein. from that already described, and named, in contradistinction, the unstri- ated muscular tissue.1 The unstriated muscular fibres of the latter consist of fusiform, rounded, or slightly prismoid columns or bands, varying considerably in the proportions of length and breadth in the different organs. They range from the ^ to the T\ of a line in length, are faintly yellowish or colorless, homogeneous, or indistinctly granu- lar, and present no trace of transverse striation. They consist of single, elongated cells, pointed at the extremities, and always provided with a central, oblong oval nucleus. The unstriated muscular fibres are usually associated into fasciculi, and these are arranged into layers or membranes, having a yellowish- brown appearance. These muscular layers are abundantly supplied with blood-vessels and nerves, which have the same general arrangement as in the striated muscles. The unstriated muscular tissue is excited to contraction usually through reflex impressions, but may also be excited by the direct impression of most of the stimuli operating on the striated muscles, except the will. 1 Unstriped, or non-striated muscular tissue or fibres; smooth muscles, or mus- cular fibres; organic muscular tissue or fibres; muscular tissue of organic life. 272 UNSTRIATED MUSCULAR TISSUE. Unstriated muscular tissue constitutes the muscular coat of the stomach, small and large intestine, and the muscular fibres noticed in the mucous membrane of these organs. A thin layer is also found on the gall-bladder and in certain glandular ducts. It forms the muscular coat of the urinary bladder, the walls of the uterus, and a layer to the Fal- lopian tubes, vagina, and urethra. In association with elastic tissue, it composes the middle coat of the blood-vessels and lymphatics, and fur- ther constitutes the muscular structure of the trachea, bronchi and their ramifications. Finally, it forms the dartos layer of the scrotum, and is found in other parts of the skin, especially in the walls of the odoriferous glands of the axillae. CHAPTER YI. THE ALIMENTARY APPARATUS. The Aliment'ary apparatus consists of the aliment'ary canal,1 to- gether with a number of accessory organs. The former comprises two divisions, of which one is constituted by the mouth and the organs of degluti'tion, consisting of the pharynx and oesophagus; the other, by the diges'tive organs,2 contained within the abdomen, and composed of the stomach and the small and large intestines. The accessory organs are those of mastica'tion, consisting of the teeth, jaws, and appropriate muscles, and the tongue, salivary glands, pancreas, and the liver. THE MOUTH. The Mouth3 is the space included between the lips in front, the pharynx behind, and the cheeks at the sides. Above, it is bounded by the roof or palate, inclosed by the upper teeth and alveolar arch; below, is its floor, upon which rests the tongue, included within the lower teeth and alveolar arch. The closed jaws and teeth divide the mouth into two portions: the narrow interval4 between the lips, cheeks, and the jaws, and the larger cavity within the latter, containing the tongue. The cavity of the mouth,5 except on the teeth, is everywhere invested with a highly vascular mucous membrane, provided with a squamous epi- thelium. It is also furnished with conical papillae, for the most part minute and concealed beneath the epithelium, except at the margins of the gums, and more especially on the upper surface of the tongue, where they become conspicuous as the chief organs of taste. The Gums6 consist of reflections of the oral mucous membrane upon the alveolar arches. They closely adhere to the periosteum beneath, and form circular doublings or collars around the necks of the teeth, with which they are intimately connected. Canalis, tubus, or ductus alimenta- 3Os; stoma; cavum oris. rius, ciliarius, digestivus, or intestino- * Vestibulum oris. rum; digestive canal; intestinal canal; & Cavum, or spatium oris. primae viae. 6 Gingivae ; carnicula; ula. 2 Organon digestionis. 18 (273) 274 THE ALIMENTARY APPARATUS. The Lips1 are separated by the oral fissure,2 the extremities of which constitute the oral angles or commissures.3 Besides the exterior skin, with its subjacent connective tissue and fat, the lips are composed of vari- ous muscles converging to and surrounding the oral fissure, together with Fig. 198. Vertical section of the face and neck, through the median line antero-posteriorly, exposing to view the nose, mouth, pharynx, and larynx. 1, oval cartilage of the left nostril; 2, triangular cartilage; 3, line of separation between the two; 4. prolongation of the oval cartilage along the column of the nose; 5, superior meatus of the nose; 6, middle meatus; 7, inferior meatus; 8, sphenoidal sinus; 9, posterior part of the left nasal cavity, communicating with the pharynx; 10, orifice of the Eustachian tube; 11, upper extremity of the pharynx; 12, soft palate, ending below in the uvula; 13, interval of the mouth between the lips and jaws; 14, roof of the mouth, or hard palate; 15, communication of the cavity of the mouth with the interval between the jaws and cheek; 16, tongue; 17, fibrous partition in the median line of the latter; 18, genio-glossal muscle; 19, genio-hyoid muscle; 20, mylo-hyoid muscle; 21, anterior half arch of the palate; 22, posterior half arch of the palate; 23, tonsil; 24, 2o, floor of the fauces; 26, 27, pharynx; 28 cavity of the larynx; 29, ventricle of the larynx; 30, epiglottis; 31, hyoid bone; 32,33, thyroid cartilage; 34, thyro-hyoid membrane; 35, 36, cricoid cartilage; 37, vocal membrane. 1 Sing.: labium; pi.: labia; labrum, 3 Angles, or commissures of the mouth cheilos; upper and under lip; anocbei- or of the lips; commissura labiorium: ]<>s and catacheilos. prostomia. 2 Rima, apertura, orificium, or hiatus oris; os; peristomium. THE ALIMENTARY APPARATUS. 275 the lining mucous membrane and a number of glands. The orbicular muscle borders the oral fissure or orifice of the mouth, and is covered by thin skin, gradually passing into mucous membrane. Between the lips and jaws, in the median line, the mucous membrane forms doublings, named the superior and the inferior labial frse'num.1 The Cheeks2 have a composition similar to the lips, and their princi- pal muscle is the buccinator. At their back part they include the ramus of the lower jaw and its muscles, and also, usually between these and the buccinator muscle, a mass of soft adipose tissue. Beneath the mucous membrane of the lips and cheeks there are numer- ous small, rounded, pinkish racemose glands, opening by their ducts into the mouth, and named from their position the labial3 and buccal glands.4 Though they are supposed to secrete mucus, their office has not been satisfactorily determined. The Palate, or roof of the mouth,5 comprises two parts, called the hard and soft palate. The Hard palate6 is deeply vaulted, and is lined with a smooth mu- cous membrane, except at its fore part, where it is roughened by trans- verse ridges. It is divided by a faintly-marked median line,7 ending in a small prominence, corresponding with the position of the incisive fora- men. Its osseous basis is formed by the palate plates of the superior maxillary and palate bones, to which the mucous membrane adheres by a dense layer of fibrous tissue, containing numerous small racemose glands, named from their position the palatine glands.8 The Soft palate9 is composed of a doubling of mucous membrane, in- closing a fibro-muscular layer, together with many small racemose and follicular glands. It projects as a freely movable partition obliquely downward and backward from the hard palate, between the mouth and posterior nasal orifices. The IT'vula10 is the small, tongue-like appendage projecting from the 1 Frasnum, or fraenulum labii superi- oris et inferioris. 2 Genae; mala?. 3 Glandulae labiales. 4 Glandulae buccales. 5 Palatum; fossa palatina; uraniscos; hyperoa. 8 Palatum durum, or stabile. 7 Raphe. 8 Glandulae palatinae. 9 Palatum molle, mobile, or pendulum; velum palatinum, pendulum, or staphyli- num ; velum palati, or pendulum palati; pendulum, or claustrum palati; pendu- lous veil of the palate. 10Uva; uvigena; uvigera; staphyle; columella, or columna oris; sublingua; tintinnabulum ; gargarlon; gurgulis; in- terseptum; processus, or cartilago uvi- fer; pinnaculum fornicis gutturalis; la- mas ; plestrum; pap of the throat; the palate. 276 THE ALIMENTARY APPARATUS. middle of the soft palate, and consists of a pair of muscles inclosed in a pouch of mucous membrane. The Half arches of the Palate are two crescentic folds of mucous membrane, inclosing muscular fasciculi, and diverging from the base of the uvula, on each side of the palate, outward and downward, one to the side of the tongue, the other to the side of the pharynx. The anterior pair inclose the palato-glossal muscles, and together constitute the anterior palatine arch ;x the posterior pair inclose the palato-pharyngeal muscles, and constitute together the posterior palatine arch.2 The Fau'ces3 are the straits or passage leading from the mouth to the pharynx, and correspond with the space included between the palatine arches. The Ton'sils4 are two glandular organs, about the size and shape of an almond kernel, situated one on each side of the fauces, inclosed in the triangular recess between the half arches of the palate. They are in contact externally with the superior constrictor muscles of the pha- rynx, and move with the contraction of these muscles. Their surface toward the fauces presents a coarsely reticular appearance, due to a number of large orifices communicating with pouches, in the bottom of which the orifices of smaller pouches are visible. They are large com- pound follicular glands of peculiar constitution. Simple follic'ular glands of the same character as the tonsils occupy the floor of the fauces or the root of the tongue, the palate, and'the pha- rynx. These are distinguished as rounded prominences of the mucous membrane, with an orifice communicating with the mouth or pharynx. They consist of a purse or bottle-like inflection of the mucous mem- brane, and contain in their thick walls of submucous tissue a number of spheroidal capsules or vesicles resembling in composition the solitary glands of the intestines. The tonsils differ from the simple follicular glands only in their compound form, or, in other words, they consist of an aggregation of such bodies as constitute the glands just named. The recesses of the tonsils and simple follicular glands ordinarily appear to elaborate mucus, which lubricates the fauces in the passage of food. Under the influence of cold, these glandular organs are very sns- 1 Arcus palatinus anticus; a. palato- * Sing.: tonsilla; amygdala; paristh- glossus. mia; tola; spongos ; antias; amphibran- 2 Arcus palatinus posticus; a. palato- chium; glandula colli; almond of the pharyngeus. throat or of the ear. 8 Isthmus of the fauces; i. faucium; claustrum gutturis. THE ALIMENTARY APPARATUS. 277 ceptible to inflammation condition their recesses tallow-like matter, which of small, rounded balls. These, when crushed, ex- hale a heavy, disagreeable odor, indicating a source of foul breath, independ- ent of the more ordinary one. The material exam- ined beneath the micro- scope exhibits nothing but squamous epithelial cells, together with some oil globules, and minute, par- asitic, filamentous plants. and chronic enlargement. In the unhealthy frequently become filled with a dirty-white is from time to time expectorated in the form Fig. 199. f, u ■I Section of a follicular gland from the root of the tongue. a, epithelium; 6, papillse imbedded in the latter; c, outer part of the thick wall of the gland composed of connective tissue; d, mouth of the gland; e, its cavity; /, epithelium lining the lat- ter ; g, vesicular bodies resembling the solitary glands of the intestines. Highly magnified. MUSCLES OF THE PALATE AND FAUCES. The Eleva'tor of the Palate1 is a thin, flat muscle, which arises from the end of the petrous portion of the temporal bone and the contiguous Fig 200. Posterior view of the muscles of the palate and fauces. 1, elevator of the palate, on the left side its origin only remaining; 2, tensor of the palate, winding around the hook of the internal pterygoid process and ending in the soft palate; 3, uvular muscles; 4, Eustachian tube; 5, origin of the palato- pharyngeal and palato-glossal muscles; 6, part of the origin of the superior constrictor of the pharynx; 7, external pterygoid muscle. 1 M levator palati mollis; m. salpingo-staphylinus; m. s.-s. internus; m. petro- salpingo-staphylinus; m. pterygo-staphylinus externus; m. spheno-staphylinus; m. spheno-palatinus; m. peristaphylinus internus superior; m. petro-staphylinus. 278 THE ALIMENTARY APPARATUS. portion of the Eustachian tube, and descends at the side of the posterior nasal orifice to expand in the structure of the soft palate. The Ten'sor of the Palate1 is a narrow muscle arising from the^fossa, at the root of the internal pterygoid process, and from the contiguous portion of the Eustachian tube. Descending at the inner side of the pterygoid fossa, it terminates in a tendon which winds around the hook of the internal pterygoid process, and expands into a thin aponeurosis within the soft palate. The U'vular muscle2 is a fleshy fasciculus arising from the palate spine of the palate bone, and descending in company with its fellow into the uvula. The Pal'ato-glos'sal muscle3 is situated within the anterior half arch of the palate, extending from the side of the soft palate to the tongue. The Floor of the mouth, included within the lower jaw, is formed by the skin, the mylo- and genio-hyoid muscles, and the mucous membrane reflected from the gum to the under part of the tongue. THE SALIVARY GLANDS. Opening into the cavity of the mouth there are three pairs of salivary glands, named the parotid, submaxillary and sublingual glands. The Parot'id gland,4 the largest of the salivary glands, occupies a po- sition in front of the external ear, reaching a short distance over the masseter muscle. It extends as high as the zygoma, as far down as the angle of the lower jaw, and dips inwardly between the ramus of the latter and the mastoid process to the position of the styloid process and muscles. Passing through its length, we find the external carotid artery and accompanying vein, and, diverging through it in an opposite direc- tion, the facial nerve. The parotid is a large compound racemose gland, consisting of numer- ous polyhedral lobes, closely moulded upon the surfaces with which the gland comes into contact. The lobes are subdivided into lobules, the 1 M. tensor palati mollis; m. circum- flexus palati; m. salpingo-staphylinus; m. petro-salpingo-staphylinus; m. ptery- go-staphylinus; m. spheno-salpingo- staphylinus; m. peristaphylinus exter- nus or inferior; m staphylinus externus; m. palato-salpingeus; m. spheno-pterygo- palatinus ; m. tubae novae. 2 Azygos muscle of the uvula; m. azygos uvulae; m. palato-staphylinus; m. staphylinus; m. epistaphylinus; m. staphylinus medius. 3 M. palato-glossus: m. constrictor isthmii faucium; m. glosso-staphylinus; m. glosso-palatinus. * Glandula parotidea; g. adaures; pa- rotis; animellae; lacticinia. THE ALIMENTARY APPARATUS. 9~9 whole being connected together by dense areolar tissue, continuous ex- ternally with that enveloping the gland and adhering to the contiguous parts. The Parot'id duct,1 about the diameter of a crow-quill, and two inches in length, passes forward from the gland across the masseter muscle, a short distance below the zygoma, and opens into the mouth by perforat- ing the buccinator. Its orifice, somewhat contracted, is indicated by a small prominence opposite the position of the second upper large molar tooth. Usually a detached portion of the gland, named the accessory parotid,2 rests on the masseter muscle, and communicates by its duct with the main one. The Submax'iUary gland,3 about a third the size of the preceding^ ^ and separated from it by a strong process of the deep cervical fascials v?**** situated just within and below the base of the lower jaw. It is beneath the mylo-hyoid muscle ; is included below in the curve of the digastric muscle, and externally is covered by the subcutaneous cervical muscle and skin. Its structure is like that of the parotid gland, but its lobes are coarser, its connective tissue much less in quantity, and its attach- ment to the contiguous parts comparatively feeble. The Submax'iUary duct,4 about two inches in length, passes backward, turns over the posterior edge of the mylo-hyoid muscle, and is then di- rected forward between this and the hyo-glossal muscle to the side of the lingual frasnum, where it terminates at the summit of a small promi- nence.5 An accessory portion of the gland follows the duct a short distance and communicates with it. The Sublin'gual gland,6 the smallest of the salivary glands, is narrow oblong in shape, and rests on the floor of the mouth, projecting into its cavity as a conspicuous ridge beneath the side of the tongue. It ex- tends from the position of the lingual fraenum to the submaxillary gland. and is in contact with the duct of the latter. The sublingual gland has the same structure as the other salivary glands; but its lobules are less closely associated. It communicates with the cavity of the mouth by about half a dozen small ducts,7 which 1 Duct of Steno; ductus Stenonianus: * Duct of Wharton; ductus Whartoni- d. salivalis superior. anus; d. salivalis inferior. -' (ilandula socia parotidis ; accessory 5 Caruncula sublingualis. gland of the parotid: g. parotic acces- 6 Glandula sublingualis; in part, the soiia. glands of Rivinus. 3 Glandula submaxillaris; g. angula- 7 Ductus Rivini; d. Waltheriani. ris: g. maxillaris; hypognathaden; hy- posialaden. 280 THE ALIMENTARY APPARATUS. open upon the ridge indicating its position. Frequently several of the ducts unite into a single one,1 terminating near to, or in conjunction with, the submaxillary duct. The secretion of the salivary glands, the sali'va,2 is a colorless liquid of slightly alkaline reaction. It is rendered more or less viscid by the mixture of mucus, and contains a few epithelial scales and so-called mucous corpuscles or free nuclei. The parotid gland is supplied with arteries from the external carotid, the submaxillary gland from the facial, and the sublingual gland from the sublingual artery. The veins terminate in those accompanying the corresponding arteries. The nerves are derived from the contiguous vascular plexuses of the sympathetic, in conjunction with filaments of the trifacial nerve. THE TONGUE. The Tongue3 is a muscular organ invested with mucous membrane,4 and ordinarily, when at rest, occupies a position within the arch of the lower jaw. From its freedom of movement it aids in the process of mastication and deglutition, and contributes to articulation in speech; from the papilla? of its surface it constitutes the organ of taste. The posterior part of the tongue attached to the hyoid bone is named its root or base,5 and that which is attached along the middle to the floor of the mouth is the body. The tip,6 sides,7 and upper surface8 are free, and invested with mucous membrane, which, from beneath the tongue, is reflected to the lower gum. Between the root of the tongue and the epiglottis, the mucous mem- brane forms three folds, named the glos'so-epiglot'tic frse'na ;a and be- neath the tip of the tongue a median fold passes to the gum, and is called the lin'gual frae'num.10 The mucous membrane of the under part of the tongue is thin and translucent, and permits the blood-vessels, especially the ranine veins, and a number of small racemose glands, distinctly to be seen through it. Beneath the tip it forms a slightly elevated median line or raphe' which is continuous with the lingual fraenum. 1 Ductus Barthobni. 2 Sputum; sputamentum; ptyalon; sialon; spit; spittle. 3 Lingua; glossa; glotta. 4 Periglottis; membrana, or tunica vaginalis; involucrum; cutis; epider- mic: crusta villosae. 5 Radix ; hyoid extremity. 6 Dental extremity ; point. 7 Margins. 8 Dorsum. 9 Glosso-epiglottic ligaments; frama, or fraenula epiglotidis ; ligamenta mem- branacea; velamenta linguae. 10 Fraenum, fraenulum, or vinculum linguae ; glossodesmus; filetum. THE ALIMENTARY APPARATUS. 281 The upper surface or back of the tongue1 is marked along the middle by a slight furrow,2 which corresponds in position with a thin fibrous par- tition,3 dividing the organ into symmetrical halves. View of the upper surface of the tongue. 1, 2, V-like row of the circumvallate papillae; 3, capitate papilla?; 4, 5, conical papillae; 6, G, floor of the fauces, with numerous simple follicular glands; 7, tonsils; S, summit of the epiglottis; 9, the middle glosso-epiglottic fraenum, with depressions on each side bounded externally by the lateral fraena. Upon the anterior two-thirds of the upper surface of the tongue, the mucous membrane adheres most intimately to the muscular structure beneath, and is especially remarkable from its being densely beset with 1 Dorsum. - Linea mediana; raphe. 3 Septum lingua?; cartilago linguae ; c. mediana; lingual fibro-cartilage. 282 THE ALIMENTARY APPARATUS. small processes, named, from their function, the papiUae of taste.1 The principal of these are of a composite character, and present three varie- ties, called the circumvallate, capitate, and conical papillae. The Circumval'late papil'lae,2 the largest of the varieties, and about a dozen in number, form a Y-like row, defining the papillary layer at the posterior third of the tongue. They have the form of an inverted cone, surrounded by an annular, wall-like elevation, whence their name. The Cap'itate papil'lae,3 the second in size, and more numerous than the preceding, are conspicuous as small, red eminences, scattered over the surface of the tongue, but are especially numerous at and near the tip. They are rounded at the free extremity, and narrower at the basis of attachment. The Conical papil'lae,4 smaller and much more numerous than the others, are crowded in the intervals between them, but are arranged in rows diverging from the median line of the tongue. All the papillae of taste, as described above, and the intervals between them, are covered with numerous minute, simple papil'lae5 of a conical form. From those surmounting the conical papillae, the squamous epi- thelium rises in hair-like appendages, which give to these papillae a pencil- or brush-like arrangement, admirably adapted to the imbibition of liquids to be tasted. To these hair-like processes is due the velvety character of the surface of the tongue ; and it is upon them also that the so-called furred condition of the latter depends. The papillae of taste are processes of the mucous membrane of the tongue, richly supplied Fig. 202. with blood-vessels. The modes of termination of the nerves within these organs has not yet been satisfactorily determined, but the prevalent opinion is that they end in loops in the simple papillae. The capillary blood-ves- sels distinctly appear within the latter in the form of loops communicat- ing with the vascular trunks at their base. Oiagram of the papill.e of the tosgue, moderately magnified. 1, capitate papillae; 2, conical papillae; 3, epithelium; 4, the same structure forming bunches of hair-like processes; 5, connective tissue. 1 Papillae gustatoriae. 2 P. circumvallatae: p. vallatae; p. max- ims ; p. truncatae : p. calyciformes; p. mucosa?: p. lenticulares. 8 P. capitatae; p. fungiformes; p. cla- vatae ; p. mediae; p. semilenticulares. 4 P conicae; p. minimae; p pyrami- dales : p. villosa?; p. conicae et filiformes. 5 P. filiformes; filla; villi linguae. THE ALIMENTARY APPARATUS. 283 Back of the position of the circumvallate papillae, corresponding with the floor of the fauces, the tongue is provided with numerous glands, named the lingual glands.1 These are of two kinds : racemose glands^ probably secreting mucus; and follicular glands, which have the peculiar Fig. 203. Papilla of the tongue, highly magnified. 1, conical papillae; 2, capitate papilla; 3, simple papilla;, occupying the intervals of the compound papillae; 4, epithelium ascending from the conical papillse in hair-like processes; 5, isolated epithelial scales from the latter. constitution of the tonsils, the follicular glands of the palate and pha- rynx. A group of the lingual glands usually opens into a small pouch2 just behind the middle circumvallate papilla. As previously indicated, a number of racemose glands also exist beneath the tongue; and others likewise are found imbedded in the muscular structure of its sides. MUSCLES OF THE TONGUE. The muscles of the tongue form the great bulk of the organ. For the most part they are inserted into the fibrous layer of its investing mucous membrane, and, as they approach the latter, their fasciculi form an intricate intertexture, associated with many bundles of transverse,3 longitudinal,4 and vertical muscular fibres.5 Mingled with these fibres there is a quantity of adipose tissue, which in some measure appears to take the ordinary position of connective tissue. 1 Glandulae linguales. 4 M. longitudinalis superior; m. chon- 2 Foramen ccecum ; f. Morgagni. droglossus; m. superficialis linguaB ; mus- 3 Musculus transversus linguae; mus- culi longitudinales. culi transversales. » Musculi verticales. 284 THE ALIMENTARY APPARATUS. Fig. 204. The Hyo-glos'sal muscle1 is a quadrilateral plane of fibres arising from the great horn and body of the hyoid bone, and ascending to expand in the side of the tongue, between the stylo-glossal and lingual muscles. The Geni'o-glos'sal muscle2 is a thick, fan- shaped layer of fibres, arising tendinously from the posterior mental tu- bercle, and radiating back- ward and upward to be inserted into the tongue from its tip to its attach- ment to the hyoid bone. It is separated from the muscle of the opposite side by a thin partition of fibrous tissue. Side view of the muscles of the tongue. 1, 2, stylo-glossal muscle; 3, lingual muscle; 4, upper part of the tongue; 5,6, hyo- glossal muscle; 7, genio-glossal muscle; 8, stylo-pharyngeal muscle; 9, genio-hyoid muscle; 10,11, median line of the mylo- hyoid muscles. The Lin'gual muscle3 is a narrow fasciculus of fibres, situated between the insertion of the hyo-glossal and genio-glossal muscles, and extending from the hyoid bone to the tip of the tongue. The Sty'lo-glos'sal muscle4 arises from the extremity of the styloid process of the temporal bone and from the stylo-maxillary ligament, and descends to expand in the side of the tongue externally to the hyo-glossal muscle. The genio-glossal muscles, when the mouth is open, will protrude the tongue, and the hyo-glossal and lingual muscles will retract it again. The anterior portion of the genio-glossal muscles when alone contract- ing will draw down the tip of the tongue. The stylo-glossal muscles draw the sides of the tongue upward and backward. The arteries of the tongue are derived from the lingual branches of 1 M. hyo-glossus; m. basio-glossus, ce- rato-glossus, et chondro-glossus; m. hy- oideo-glossus; m. hyo-chondro-glossus; m. hypsilo-glossus. 2 M. genio-glossus; m. genio-hyo-glos- sus: m. meso-glossus ; m. nonus linguae. 3 M. lingualis; m. basio-glossus; m. glossianus; m. longitudinalis inferior. * M. stylo»glossus. THE ALIMENTARY APPARATUS. 285 the external carotids. The principal veins are the ranine, which usually join the facial vein on each side of the head. The nerves are the lingual branch of the inferior maxillary, the lingual branches of the glosso-pharyn- geal, and the hypoglossal nerve. The former two supply the mucous membrane and papilla? of taste; the latter supplies the muscular struc- ture. THE TEETH. Teeth1 have so close a relationship with the nature of the food and the habits of animals, that they present to the zoologist most important distinctive characters in classification. Three different substances gen- erally enter into their constitution: cement, a material resembling bone; dentine, a harder material forming the ivory of the tooth; and enamel, not only the hardest material of teeth, but the hardest of all organic substances. In the grinding teeth of herbivorous animals, as the horse, ox, and elephant, the three substances alternate with one another in such a manner that, as the teeth are worn, an uneven triturating surface is always preserved. In carnivorous and omnivorous animals, as the cat, dog, and hog, the body of the teeth is composed of dentine, while the crown or exposed part is capped with enamel, and the roots are covered with a thin film of cement. The teeth are properly appendages of the mucous membrane of the alimentary canal, and are developed from it. They are inserted into a portion of the skeleton so as to give them a firmly-fixed position. In birds and turtles we find their place on the jaws occupied by a corneous bill, which, like nails and hairs, is an appendage of the skin. In grami- nivorous birds, as the common fowl, pebbles swallowed with the food are a substitute for teeth. The gizzard, which is a powerfully muscular stomach with a thick epidermis-like lining, triturates the hard food through the aid of the pebbles. Man and almost all other mammals, in the course of life, are provided with two sets of teeth, of which the first are the temporary or milk teeth; the second, the permanent teeth. Reptiles and fishes are pro- vided with numerous sets, which succeed one another through life. The teeth are divided into four kinds, named inci'sors, canines', pre- molars or bicus'pids, and mo'lars. The protruding portion of the teeth is named the crown or body;2 the portion inserted into the alveoli or sockets of the jaws, is the fang Sing.: dens; odous; pi.: denies; odontes; mordices. 2 Corona. 286 THE ALIMENTARY APPARATUS. or root;1 and the slightly constricts! portion clasped by the gums, is the neck.2 The crown varies in form in the different kinds of teeth. The fang gradually tapers to its extremity, and is firmly attached to the sides of the alveolus, in which it is inserted, by fibrous tissue continuous with the periosteum of the jaws and the submucous tissue of the gums. At the neck of the tooth a slight accumulation of this tissue constitutes the dental ligament. The teeth have in their interior a small hollow called the pulp cavity,3 which has the general form of the teeth, and contains a soft, highly sen- sitive, and vascular structure named the pulp.4 This receives its blood- vessels and nerves through a narrow canal5 opening at the extremity of the fangs. The teeth in each jaw form an unbroken arch, which is rarely the case in any of the inferior animals. The upper arch is larger than the lower one, and projects slightly beyond it. This difference is mainly due to the obliquity forward of the upper front teeth, while the corresponding ones below are vertical, and those behind slightly inclined inward. When the jaws are shut, the upper incisors inclose those below, while the suc- ceeding upper teeth alternate with those below; the triturating surfaces of the molars being in contact. CHARACTERS OF THE PERMANENT TEETH. The Permanent teeth6 are thirty-two in number, sixteen in each jaw, or eight on each side of each jaw, as follows : two incisors, one canine, two premolars, and three molars. Occasionally there is a diminution or an increase in the number. When there are supernumerary teeth, they are usually small, and provided with a single fang. The Inci'sors,7 eight in number, are the four front teeth of each jaw, and are so named from their being adapted to cutting or bating the food. Their crown is wedge-shaped or chisel-like, being convex in front, beveled behind, and triangular at the sides. The cutting edge at first is narrow, and provided with three small tubercles, but these are soon obliterated from use, and the edge gradually widens. The fang is long, conical, and compressed at the sides. 1 Radix. 2 Cervix; collum. 3 Cavitas pulpae ; cavum dentis ; an- trum dentale. 4 Pulpa; blastema dentis. 5 Caaalis radicis, or dentalis. 6 Second teeth; last teeth; dentes per- manentes; d. serotini. 7 Incisive teeth; dentes incisivi, or incisores; d. primores; d. tomici, raso- sores, gelasini, ctenes, or dichasteres. THE ALIMENTARY APPARATUS. 287 The upper incisors are larger than the lower ones, and of the former the central incisors1 are the larger, while the lateral ones are the larger in the case of the lower incisors. The upper incisors are directed down- ward and forward, while the lower ones occupy a vertical position. Upper and lower permanent teeth, exterior j lateral view of the same teeth, as in the pre- view. 1,first incisors; 2, canines; 3, first premo- ' cedin°-fio-ure. lars; 4, middle molars. The Canine' teeth,2 four in number, are larger than the incisors, and succeed them in position, one on each side above and below. Their crown is blunt, conical, beveled behind, and becomes more blunt from attrition. Their fang is conical, compressed at the sides, and longer than in any of the other teeth. It is also marked laterally by a slight furrow, as if indicating a disposition to divide into two. The upper canines, commonly called eye teeth, are larger and longer than the lower ones, which are commonly known as the stomach teeth. In carnivorous animals the canine teeth are remarkable for their length and strength, and are admirably adapted to seizing, retaining, and tearing living prey. From their conspicuous character in the canine or dog tribe they have received their name. The Premo'lars, or bicus'pid teeth,3 eight in number, succeed the ca- 1 Eutter teeth. 2 Cuspid teeth; dentes cuspidati; ca- nini; angulares, orlaniarii; d. columel- lares; oculares, or mordentes; cynodon- tes; pug teeth. 3 Small molars; dentes bicuspidati; d. buccales. 288 THE ALIMENTARY APPARATUS. nines in position, two on each side above and below. Their crown is cubical with rounded borders, prominently convex externally and in- ternally, and less so or flattened at the sides. The triturating surface has a prominent border elevated before and behind into a pair of tuber- cles, of which the outer one is the larger and higher. The fang is coni- cal, much flattened, and deeply grooved at the sides, indicating a dispo- sition to divide. The upper premolars are larger than the lower ones, and their fang is usually more or less divided into two, especially that of the second upper premolar. The Mo'lars,1 twelve in number, are next in succession to the premo- lars, three on each side above and below. They are commonly known as grinders or jaw teeth; and have a large, cuboidal crown, with low, rounded sides and borders, but are generally least convex laterally, or are even flattened in this position. In the upper molars the grinding surface is rhomboidal, with a prominent border, elevated at the four angles into as many tubercles. In the lower molars, the grinding surface is nearly oblong square, with a prominent border elevated into five tubercles. The lower molars have a pair of conical fangs placed side by side, and much compressed and deeply grooved laterally. The upper molars have three conical fangs, two external and one internal; the latter being the larger and grooved, as if disposed to divide. The molars slightly decrease in size from first to last, and the lower ones are larger than the upper ones. The last of the series, from its comparatively late appearance in life, is named the wisdom tooth.2 It is liable to considerable variation in size and form, more especially in the case of the upper one. Its fangs are usually more or less confluent into a single cone. CHARACTERS OF THE TEMPORARY TEETH. The Temporary or milk teeth3 are twenty in number, ten in each jaw, or five on each side of each jaw, as follows: two incisors, one canine, and two molars. The incisors and canines correspond in number with those of the per- manent set, which they also resemble in form ; but they are smaller, and the crowns are broader in proportion to their length. 1 Dentes molares; large molars; true molars; dentes multicuspidati; d. maxil- lares, clavales, or gomphii; molae; my- lodontes; mylacri; momisci; cheek teeth; axle teeth; wall teeth; log teeth; grinding teeth. 2 Dens sapientiae ; d. serotinus; d. so- phroreticus ; d. sophronista ; wit tooth; last tooth. 3 Dentes lactei; d. caduci; d. tempo- rarii; deciduous teeth; primary, or shedding teeth. THE ALIMENTARY APPARATUS. 289 No premolars belong to the temporary set of teeth. The molars are eight in number, succeeding the canines in position, two on each side above and below. Fig. 207. 12 3 4 5 Fig. 208. Temporary teeth of one side. 1, 2, upper and lower incisors; 3, upper and lower canine; 4, 5, upper and lower molars; 6, 7, triturating surface of the lower molars; 8, 9, triturating surface of the upper molars. STRUCTURE OF THE TEETH. On splitting a tooth longitudinally, the exposed surface exhibits, besides the pulp cavity, three different sub- stances. The greater portion of the tooth appears to be composed of a yellowish-white substance, which is called dent'ine; the crown is capped with a harder and whiter layer, named the enam'el; and a thin, translucent investment to the fang is the cement'. The Dent'ine, or ivory,1 forms the principal bulk of the tooth, giving to it the general shape, and containing the pulp cavity. It is yellowish-white, and has the appearance of dense bone, which it further resembles in chemical composition. It consists of about twenty-eight parts of bone cartilage and seventy-two parts of earthy matters; mostly phosphate of lime, with a little carbonate of lime. In thin section, beneath the microscope, the Vertical section of a molar tooth. moderately magnified. 1, enamel, the lines of which indicate the arrange- ment of its columns; 2, dentine, the lines indicating the course of its tu- bules ; 3, thin lamina of the dentine forming the wall of the pulp cavity, the dots indicating the orifices of the dentinal tubules; 4, cement. 1 Ebur; substantia ossea, or eburnea; tooth bone; proper tooth substance; osseous substance. 19 290 THE ALIMENTARY APPARATUS. dentine is found to be composed of a translucent, amorphous substance, pervaded with a multitude of fine canals, possessing distinct walls from the intervening material. The canals, named dent'inal tu'bules,1 commence with open orifices at the surface of the pulp cavity, and radiate from thence to the periphery of the tooth. They have a general parallel and gently waving or undulating course. As they proceed outwardly, they divide into several principal branches, pursuing the same general parallel course Fig. 209. Fig. 209. Vertical section of the fang of a canine tooth, exhibiting the structure of the dentine and cement. 1, inner extremities of the dentinal tubules ; 2, outer extremities of the tubules, terminating in interspaces at the boundary of the dentine; 3, cement; 4 lacunae like those of bone. Highly magnified. Fig. 210. Section of dentine, cutting across the direction of its tubules, very much magnified. The tubules are seen to have thick walls, distinct from the intervening material. to one another. They also gradually become narrower, and give off in- numerable, fine, divergent branches, which anastomose with one another. The walls of the tubules are nearly as thick as their calibre, which, in the fresh tooth, is filled with a colorless liquid, replaced by air in dried specimens. In consequence of the latter condition, the dried microscopic sections of teeth, when viewed by transmitted light, appear pervaded by black lines; while by reflected light, the same lines appear silvery white. Fig. 211. Fig. 212. Three enamel columns, highly magnified; ex- Section of enamel, highly magnified, at right hibiting the six-sided prismatic and waving charac- angles to the course < if its columns; exhibiting the ter. six-sided character of the latter. The Enam'el2 is the glistening-white or bluish-white substance invest- ing the crowns of the teeth. It is thickest on the triturating surface, and gradually diminishes toward the neck, where it terminates by a 1 Canaliculi dentium. s. filamentosa; cortex; c. striata; crusta 2 Substantia vitrea; s. adamantina; adamantine; nitor dentium. THE ALIMENTARY APPARATUS. 291 sharply defined edge. As previously mentioned, enamel is not only the hardest of all the dental structures, but it is the hardest of all organized substances. In chemical composition it consists of only five parts of bone cartilage, with ninety-five parts of earthy matters, mostly phosphate of lime. Viewed with the microscope, enamel is found to consist of solid, hexa- hedral columns, resting with one extremity on the dentine of the crown, and with the other extremity free. The columns are not straight, but undulating in their course; and at the sides they present a faint, trans- versely striated appearance. The arrangement of the enamel columns is the most favorable that could have been adopted to prevent their detachment and rapid abrasion; though this arrangement, together with the great deficiency of bone car- tilage, renders the enamel brittle, and, under extremes of temperature, to which it is often subjected in the use of hot and cold food, it is liable to crack. The exterior surface of the unworn enamel, when treated with hydro- chloric acid, so as to remove its calcareous salts, separates in the form of a thin, homogeneous membrane,1 which, though it is intimately blended with the exterior ends of the enamel columns, appears to be an inde- pendent structure. The Cement'2 is a very thin layer of osseous substance investing the fangs of the teeth, commencing at the neck, and gradually becoming thicker to the extremities of the fangs. In the latter position, in the teeth of old persons, it frequently becomes much increased in thickness, and sometimes forms a nodular mass. Like true bone, the cement con- tains branching lacunae, but vascular canals pervade it only when it becomes much thickened. The teeth, like the epithelium of a mucous membrane, are entirely non-vascular, and their fluids are obtained by imbibition from the dental pulp and the periosteum of the fangs. The Dent'al pulp3 is a soft, translucent, reddish-white substance, filling the pulp cavity of the teeth. It is composed of an exterior layer of nu- cleated cells, with an interior mass of indistinctly defined areolar tissue, mingled with many nuclei, and containing an abundant colorless liquid. Highly sentient and vascular, its nerves and blood-vessels, entering the fine aperture at the ends of the fangs, are derived from the dental nerves of the trifacial, and the dental arteries of the internal maxillary artery. 1 Nasmyth's membrane; cuticle of the enamel; skin of the teeth. 2Cementum; crusta ostoides radicis; crusta petrosa; cortical substance ; sub- stantia ostoidea. 3 Pulpa dentis. 292 THE ALIMENTARY APPARATUS. DEVELOPMENT OF THE TEETH. The temporary teeth commence their development from the sixth to the tenth month of embryonic life, originating in a corresponding num- ber of papillae from the bottom of the dental groove,1 which is a semi- circular inflection of the mucous membrane at the margin of the gums. Processes2 from the dental groove gradually inclose the papillae in sepa- rate compartments, which contract in the course of the fourth month, and include the papillae in distinct cavities, named the dental sacs. The Fig. 213. Diagram of TnE mode of development of the teeth, a, section across the dental groove; b, papilla developed in the latter; c, the groove deepened and processes forming which ultimately close it; d, the groove becoming closed; e, dental sac containing a dental pulp, which is the rudiment of the crown of a temporary incisor; the cavity above is reserved for a permanent incisor; /, the crown of the temporary incisor fully formed, and the reserved cavity for the permanent tooth moving backward; g, fang of the temporary incisor produced, and origin of the dental papilla of the future permanent tooth; h, erup- tion of the temporary incisor, and the alveoli produced for both teeth; i, the temporary incisor occupy- ing its functional position, and the crown of the permanent incisor developed. papillae, now called dental pulps, gradually assume the form and size of the crowns of the future teeth, and are defined by a delicate basement membrane.3 The enlarging dental sacs, closely applied to the included pulps, also undergo a change in structure; and they are supplied with blood-vessels from the dental arteries as well as from those of the gums. From the fifth to the eighth month of foetal life the dental pulps com- mence transformation into dentine by the deposit of calcareous salts. This transformation begins at the summit of the pulps and proceeds toward their base, and from without inwardly. Primitive dental groove. 2 Opercula. 8 Membrana praeformativa. THE ALIMENTARY APPARATUS. 293 While this process is going on, the thick internal layer of the dental sacs, named the enamel organ,1 undergoes transformation into enamel, from within outwardly. The crown of the tooth being produced, the dental pulp now grows in length, and as it gradually develops the shape of the future fang, it is transformed into dentine, from without inwardly, and from the base toward the end of the fang. The lengthening of the fang occasions the eruption or so-called cut- ting of the teeth,2 in which process the latter burst their sacs and pro- trude from the gums. The eruption of the temporary teeth3 occurs after birth, during the period between six months and two and a half years; usually in'the(_ following order, the lower teeth generally taking precedence of the upper\ ones :— X The central incisors from the sixth to the eighth month ; The lateral incisors from the seventh to the ninth month ; The first molars from the twelfth to the fourteenth month ; The canines from the sixteenth to the twentieth month ; The last molars from the twentieth to the thirtieth month. During the fourth and fifth months of foetal life, in the progress of development of the dental sacs of the temporary teeth, a corresponding number of cavities4 are developed in the dental groove5 over them. These reserved cavities subsequently become the dental sacs of perma- nent teeth; those of the upper jaw receding behind and above the po- sition of the temporary teeth; those of the lower jaw receding behind and below the temporary teeth. The dental sacs just indicated are finally inclosed in osseous cavities of the jaws, communicating by canals6 with the margin of the latter. The canals contain a narrow pedicle,7 which is the closed and elongated neck of the dental sacs continuous with the gum behind the corresponding temporary teeth. The three permanent molar teeth on each side, above and below, origi- nate in succession from the posterior extremity of the dental groove. The permanent teeth are developed from their dental sacs and pulps in the same manner exactly as the temporary teeth. Calcification com- mences in the different ones from a period prior to birth up to the twelfth year subsequently. At six years, when the temporary teeth are usually still preserved, the 1 Organon adamantinae. * Cavities of reserve. 2 Teething; dentition; odontophyia. 5 Secondary dental groove 3 First dentition; odontia dentionis lactantium. 6 Itinera dentium. 7 Gubernaculum dentis. 294 THE ALIMENTARY APPARATUS. jaws contain besides, the crowns of all the permanent teeth except the last molars or wisdom teeth. The subsequent development of the fangs of the permanent teeth causes a gradual advancement of their crowns toward the gums. Those which come into contact with and press against the temporary teeth excite a gradual absorption of the fangs of the latter Continuing to advance, the permanent teeth detach the loosened crowns of the temporary set, and protrude from the gums in their place. The eruption of the permanent teeth1 and the shedding of the tempo- rary set commences between the fifth and seventh years after birth. The first permanent molars usually protrude before any of the temporary teeth are shed, and it is perhaps partly due to this circumstance that these teeth are usually the first to undergo decay. The course of eruption of the permanent teeth is commonly as follows, the lower ones preceding the upper :— The first molars from the fifth to the seventh year; The central incisors from the sixth to the eighth year; The lateral incisors from the seventh to the ninth year ; The first premolars from the eighth to the tenth year; The second premolars from the tenth to the twelfth year; The canines from the eleventh to the twelfth year; The second molars from the twelfth to the fourteenth year; The last molars or wisdom teeth from the seventeenth to the twenty- second year. THE PHARYNX. The Pha'rynx2 or throat is the funnel-like cavity occupying the gut- tural region of the skull, and extending from its base down to a level with the fifth cervical vertebra, where it terminates in the oesophagus. Behind it is the vertebral column, and on each side the great blood-ves- sels and nerves of the neck. Communicating with it in front, in succes- sion from above downward, are the nasal fossae, the mouth, and the larynx; and opening into it on each side of the nasal fossae is the Eu- stachian tube. Its upper extremity is attached to the basilar process of the occipital bone; and on each side it is attached in succession to the petrous portion of the temporal bone, the internal pterygoid process, the pterygo-maxillary ligament, the back part of the molar ridge of the lower jaw, the root of the tongue, the hyoid bone, and the larynx. With the surrounding parts it is connected by areolar tissue. 1 Second dentition; odontia dentionis pueiilis; dedentition. 2 Pharus; pharyngethros; fauces; gula; isthmos; laemos; ingluvics; gurges; os posterum; principium gulae; communis aeris et nutrimentorum via. THE ALIMENTARY APPARATUS. 295 The walls of the pharynx are musculo-membranous. Exteriorly it is provided with a thin, fibrous investment, which at its attachment to the base of the skull assumes a stronger and more aponeurotic character. Within this structure succeeds a moderately thick, muscular layer, sepa- rable into five pairs of distinct muscles, presently to be described. The lining mucous membrane of the pharynx is soft and red, and is con- nected with the muscular layer by a strong submucous tissue containing many glands. As low down as the floor of the nose the mucous mem- brane is furnished with a columnar ciliated epithelium, but in the lower portion of the pharynx it resembles that of the mouth, being furnished with minute papillae imbedded in a squamous epithelium. The pharyn'geal glands are of the racemose and follicular kind ; the latter variety being simple and compound, having the peculiar constitu- tion of the tonsils and follicular glands of the palate and tongue. The blood-vessels of the pharynx are derived from the pharyngeal, inferior palatine, and thyroid arteries. The nerves are supplied from the glosso-pharyngeal, pneumo-gastric, and sympathetic system. MUSCLES OF THE PHARYNX. The Pal'ato-pharyn'geal muscle1 originates in the soft palate, and descends within the posterior half arch of the palate to be inserted, in conjunction with the succeeding muscle, into the side of the pharynx and the upper part of the thyroid cartilage. The Sty'lo-pharyn'geal muscle2 arises from near the root of the sty- loid process of the temporal bone, and descends between the superior and middle constrictors of the pharynx, to expand upon the mucous membrane of the latter, and partially to be inserted into the upper part of the thyroid cartilage. The Superior Constric'tor of the Pharynx3 is a thin, quadrilateral muscle arising from the pterygo-maxillary ligament and the lower half of the internal pterygoid process. Proceeding backward, it conjoins the muscle of the opposite side, and is prolonged to be attached to the ba- silar process of the occipital bone. 1 M.palato-pharyngeus; m. pharyngo- Staphylinus; m. staphylino-pharyngeus; m. thyro pharyngo-staphylinus; m. hy- pero pharyngeus in part. 2 M. stylo-pharyngeus; m. stylo-thy- ro pharyngeus. 3 M. constrictor pharyngeus superior: m. cephalo-pharyngeus; m. glosso pha- ryngeus ; m. mylo-pharyngeus; m pte- rygo-pharyngeus; m. pterygo-syndesmo- staphili-pharyngeus. 290 THE ALIMENTARY APPARATUS. The Middle Constric'tor of the Pharynx1 is a fan-shaped muscle, arising from the great and small horns of the hyoid bone, from whence it radiates to conjoin the muscle of the opposite side in the posterior median line of the pharynx. The lower fibres of the muscle are concealed by the inferior constrictor; the middle ones are nearly horizontal; and the upper ones overlap the superior constrictor. Fig. 214. Fig. 215 Fig. 214. Posterior view of the muscles of the pharynx. 1, vertical section, transversely, of the base of the skull, just in advance of the cervical vertebra1; 2, 3, posterior border and angle of the lower jaw ; 4. internal pterygoid muscle; 5, styloid process giving attachment to 6, the stylo-pharyngeal mus- cle ; 7, larynx; 8, inferior constrictor of the pharynx; 9, middle constrictor; 10, superior constrictor. Fig. 215. Side view of the muscles of the pharynx. 1, trachea; 2, cricoid cartilage; 3, vocal membrane; 6, hyoid bone; 7, stylo-hyoid ligament; 8, oesophagus; 9, inferior constrictor of the pharynx; 10, middle constrictor; 11, superior constrictor; 12, portion of the stylo-pharyngeal muscle observed pass- ing into the interval between the superior and middle constrictors; 13, upper extremity of the pharynx; 14, pterygo-maxillary ligament; 15,buccinator muscle; 16,oral orbicular muscle; 17,mylo-hyoid muscle. The Inferior Constric'tor of the Pharynx2 arises from the upper one or two rings of the trachea, the side of the cricoid cartilage, and an oblique line of the thyroid cartilage. From this origin it curves back- ward, expanding in its course, and conjoins the muscle of the opposite side in the posterior median line of the pharynx. The inferior fibres of the muscle are horizontal, and inclose the com- mencement of the oesophagus; and the upper fibres ascend, gradually 1 M. constrictor pharyngeus medius ; m. hyo-pharyngeus; m. cerato-pharyn- geus ; m. chondro-pharyngeus ; m. syn- desmo-pharyngeus; m. hyo-glosso-basi- pharyngeus. 2 M. constrictor pharyngeus inferior; m. laryngo-pharyngeus; m. thyro- et crico-pharyngeus; m. crico-thyro-pha- ryngeus. THE ALIMENTARY APPARATUS. 297 increasing in obliquity, and overlap the lower part of the middle con- strictor. The muscles of the soft palate, fauces, and pharynx, together with those of the tongue and the elevators of the hyoid bone and larynx, are concerned in the action of deglutition, or swallowing. The genio-glossal muscles, drawing the tongue forward and upward, press the food against the hard palate, and from thence into the fauces. The stylo-glossal muscles now contract, narrowing the entrance of the fauces; and the stylo-glossal muscles draw the tongue backward and up- ward. The soft palate is drawn upward and backward, and made tense by the action of its elevators and tensors. At the same time, the palato- pharyngeal muscles cause the posterior half arches of the palate to ap- proach each other, leaving only a small interval, which is closed by the uvula, and thus the communication of the pharynx with the nasal cavi- ties is cut off. The pharynx and larynx are drawn up by the stylo- pharyngeal, stylo-hyoid, digastric, genio-hyoid, and mylo-hyoid muscles, through which action the former cavity is widened, and the latter is closed by pressure against the epiglottis. The food received into the pharynx is passed downward into the oesophagus by the action of its constrictors,1 after which the parts resume their ordinary position. THE (ESOPHAGUS. The Oesoph'agus or gullet2 is a musculo-membranous tube descending from the pharynx in a slightly flexuose course through the neck and pos- terior mediastinal cavity to the stomach. It commences on a level with the fifth cervical vertebra and the cricoid cartilage of the larynx, pro- ceeds downward in contact with the vertebral column, and opposite the ninth dorsal vertebra passes through the oesophageal orifice of the diaphragm. In the neck, the trachea is in front, and the primitive ca- rotid artery on each side of it; in the thorax, the pericardium is in front, the descending aorta to its left, and the azygos vein to its right. The oesophagus is about nine inches long, and rather less than an inch in diameter. It is narrowest at its commencement, gradually widens in its descent, but is slightly constricted as it passes through the diaphragm, after which it quickly expands into the stomach. In the state of rest it is flattened from before backward; but when distended, is cylindroid in shape. 1 Musculus sphincter gulae. 2Gula; fistula cibalis; f. ventriculi; infundibulum ventriculi; via stomachi et ventris; gluttus. 298 THE ALIMENTARY APPARATUS. The oesophagus is provided externally with a thin, fibrous investment, inclosing the oesophageal plexus of nerves, and adhering to the contigu- ous parts. Succeeding this investment is the muscular coat,1 which is about three-fourths of a line thick, and composed of two layers. The external layer consists of longitudinal fibres, which originate in three fasciculi from the cricoid cartilage and inferior constrictors of the pharynx, and surround the oesophagus uniformly to the stomach. The internal layer, thinner than the other, consists of transverse or circular fibres, continuous with the inferior constrictors of the pharynx, and ex- tending to the stomach. In the upper part of the oesophagus the muscular coat is exclusively composed of striated fibres, but in its descent unstriated fibres become mingled with the latter, and finally predominate. The mucous membrane lining the oesophagus is much paler than in the pharynx or mouth, though it has the same structure, being provided with minute papillae and a squamous epithelium which completely conceals the latter When the oesophagus is at rest, the mucous membrane is thrown into slight longitudinal folds, which disappear in the distended condition of the organ. Beneath the mucous membrane is a moderately thick layer of sub-mucous tissue, connecting it to the muscular coat, and con- taining some small, scattered, racemose glands, named from their position the cesophage'al glands.2 The blood-vessels of the oesophagus are derived from the inferior thy- roid and oesophageal arteries. The nerves are supplied by the pneumo- gastrics and the sympathetics. THE CAVITY OF THE ABDOMEN. The Cavity of the Abdomen, or of the belly,3 the most extensive space of the body, is occupied by the greater portion of the alimentary and uro-genital apparatus. It is lined with an extensive serous membrane, the peritoneum, which, from its relationship with the many viscera it invests, is very complex in its arrangement. The viscera of the abdominal cavity leave no unoccupied vacuity or space filled with air; they follow the movements of the muscular walls of the abdomen; and the enlargement or decrease of any one results in the displacement of those around. In consequence of the great extent of the abdomen, and the frequent necessity of referring to the relative position of the organs which occupy the different parts of its cavity, it is artificially divided into regions, 1 Tunica vaginalis gulae. 2 Glandula? oesophagealcs. s Cavum abdominis. THE ALIMENTARY APPARATUS. 299 Fig. 216. indicated by lines drawn on the abdominal walls. Transverse lines en- circling the body, one at the lower margin of the thorax, the other at the hips or crest of the ilium on each side, divide the abdomen into three zones. A vertical plane, ascending on each side from the anterior in- ferior spinous process of the ilium, will divide each zone into three parts, and in this manner nine re- gions will be defined. Of the middle regions, the upper one is the epi- gas'tric region;1 the suc- ceeding one, the umbil'ic- al region ;2 and the lowest, the hypogas'tric region.3 Of the lateral regions, the upper pair are the right and left hypochon'driac regions ;4 those succeed- ing, the lum'bar regions ;5 and the lowest, the il'iac regions.6 The different organs oc- cupying these regions are as follows:— The stomach occupies the left hypochondriac, epigastric, and a small part of the right hypo- chondriac regions. In a distended condition, with the small intestine empty, it encroaches on the umbilical region. The small intestine forms a convoluted mass, occupying the umbilical region and the contiguous borders of the surrounding regions. When Cavity of the abdomen laid open, with the viscera retained in their relative position. The straight lines indicate the regions of the abdomen, a, epigastric region; b, hypochondriac regions; c, umbilical region; d, lumbar regions; e, hypogastric region; /, iliac regions. 1, flaps of the abdominal wall turned aside; 2, 3, left and right lobes of the liver; 4, fundus of the gall-bladder; 5, round ligament of the liver; 6, part of the suspensory ligament of the liver; 7, 8, stomach; 9, commencement of the duodenum; 10, spleen; 11, great omentum; 12, small intestine; 13, crecum; 14, vermiform appendix^ 15, ascending colon; 16, transverse colon; 17, descending colon; 18, sigmoid flexure; 19, epiploic appendages; 20, ridges indicating the course of the remains of the urachus and umbilical arteries; 21, diaphragm. 1 Regio epigastrica ; r. cardiaca; r. stomachica; epigastrium. 2 R. umbilicalis ; r. mesogastrica; r. gastrica; mesogastrium. 8 R. hypogastrica; r. pubis: hypogas- trium ; rumen; venter parvus, or imus. 4 Regiones hypochondriacs?; r. sub- cartilagineae; hypochondria. 5 R. lumbares, or lumbales; lumbi; lendis ; psoae ; loins ; flanks ; reins ; la- para. 6 R. iliacae ; inania ; flanks. 300 THE ALIMENTARY APPARATUS. the viscera of the pelvis are empty, a portion of the small intestine descends into that cavity. The large intestine, commencing in the right iliac region, ascends through the corresponding lumbar into the right hypochondriac region. Thence crossing through the boundary of the epigastric and umbilical regions to the left hypochondriac region, it descends through the suc- ceeding lumbar and iliac regions, and enters the pelvis at its back part. The liver occupies the right hypochondriac region, and extends across the epigastric into the left hypochondriac region. The spleen is situated deeply in the left hypochondriac region. The pancreas extends from one hypochondriac region to the other, through the deep part of the epigastric region. The kidneys occupy the deep parts of the lumbar regions or loins. The urinary bladder occupies the pelvic cavity, but when distended rises into the hypogastric region. THE PERITONEUM. The Peritone'um,1 the most extensive of all serous membranes, lines the walls of the abdomen, and from them is reflected upon the viscera. Like all serous membranes, it forms a completely closed sac, except that in the female the Fallopian tubes communicate with its cavity. The viscera are not included within the latter, but are, as it were, thrust for- ward from the back part of the abdomen, and inclosed by inflections of the peritoneum projecting into its own cavity. It is to these numerous inflections inclosing the viscera that the peritoneum owes the complexity of its arrangement. That portion of the membrane investing the viscera is named the vis'ceral peritone'um,2 and that lining the abdominal walls is the parie'tal peritone'um;3 and both portions on the interior of the peritoneal cavity are in close contact with each other. Their opposed surfaces are smooth and shining, and are bathed with a serous liquid, which give the organs they invest a slippery feeling, and adapts them favorably to move on one another. The attached surface of the perito- neum adheres closely to the contiguous parts by thin, connective tissue.4 Its numerous doublings or folds,5 associated by connective tissue, often 1 Peritonaeum ; membrana abdominis; velamentum abdominale; tunica praeten- sa; operimentum praetensum; pagos; syphar; zepach. 2 P. viscerale, or intestinale. 3 P. parietale. 4 Textus cellulosus subperitonealis, or subserosus ; lamina externa peritonei; subperitoneal membrane; retro-perito- neal membrane. 5 Omenta; epiploones, ligaments, and mesenteries. Sing.: omentum; epiploon; rete; reticulum; dertron; gangamum; zirbus ; operimentum intestinorum; sac- cus epiploicus; sagena; caul. THE ALIMENTARY APPARATUS. 301 containing much fat, inclose and sustain the position of the viscera, and likewise include the blood-vessels, lymphatics, and nerves passing to and from the latter. In tracing the reflections of the peritoneum from the abdominal walls, and from one organ to another, in any direction, its complete continuity will be discovered. Thus the peritoneum, in ascending from the front and sides of the abdominal parietes, invests the diaphragm, and is "thence reflected to the liver, producing three folds, named the suspensory and lateral ligaments of the liver. After inclosing the liver, it is reflected as a doubling, the gas'tro-hepat'ic omen'tum, from the transverse fis- sure of the liver to the small curv- ature of the stomach. Envelop- ing the latter, the peritoneum then passes from its great curvature, and makes a quadruple fold, named the great omen'tum. This is suspend- ed as a broad, apron-like process in front of the intestines, and has its posterior division above, inclos- ing the transverse colon. Passing thence to the back of the abdomen, the doubling named the transverse mesocolon is produced. Of the two layers of this doubling, the upper one proceeds to the back of the liver, there forming the posterior part of its lateral ligaments. The other layer of the transverse meso- colon descends, and, passing off lat- erally, incloses the colon on each side and forms the ascending and descending mesoco'lon. The peri- toneum, from the intervening por- tions of the mesocolon reflected forward from the vertebral column to the small intestine, forms the extensive fold named the mes'en- tery. From the root of the latter the peritoneum descends to the rectum, and, binding this to the posterior part of the pelvis, forms the mesorec'tum. The peritoneum is then re- flected from the rectum to the bladder, or in the female to the uterus, and Diagram of the reflections of the peritoneum in a vertical section of the abdomen, the perito- neum represented by the thick, black line. 1, up- per segment of the sacrum; 2, first lumbar verte- bra; 3, dorsal vertebrae; 4, diaphragm; 5, liver; 6, Btomach; 7, transverse colon; 8, small intestine; 9, duodenum; 10, pancreas; 11, rectum; 12, vagina and uterus; 13, urinary bladder; 14, pubis; 15, greater cavity of the peritoneum; 16, lesser cavity; 17, section of a lateral ligament of the liver; 18, gastro-hepatic omentum : the arrow indicates the communication, at the right border of the latter, of the great and lesser cavities of the peritoneum ; 19, great omentum; 20, transverse mesocolon; 21, me- sentery; 22, recto-uterine pouch; 23, vesico-uterine pouch; 24, portion of peritoneum lining the ante- rior wall of the abdomen. 302 THE ALIMENTARY APPARATUS. thence to the bladder, and from this it ascends to the anterior wall of the abdomen. In figure 217, representing the course of the reflections of the peri- toneum, it would appear as if the latter formed a small cavity1 behind the stomach, distinct from the greater peritoneal cavity. This is, how- ever, not the case, as the two communicate by an aperture, named the foramen of Winslow,2 behind the right border of the gastro-hepatic omentum. A finger passed through this opening, and downward between the stomach and colon, gains access to the space between the two divisions of the great omentum, or if in the new-born child a blow-pipe be intro- duced at the aperture, the great omentum may be inflated, and then appears as a large and delicate sacculated vesicle. The experiment sub- sequently fails, as the omentum, in the progress of life, becomes per- forated. The folds of the peritoneum, from their importance, may now be sep- arately considered. The Suspen'sory ligament of the liver3 is a falciform doubling of the peritoneum, extending from the median line of the diaphragm to the upper surface of the liver, between its anterior notch and its posterior border, where it becomes continuous with the lateral ligaments. Its anterior extremity is extended from the liver to the umbilicus, and in- closes the obliterated umbilical vein. The Right and Left lateral ligaments4 of the liver are the peritoneal attachments of the posterior border of the liver to the diaphragm. The former is very short, and though of two layers, these are remote from each other, except at the right border of the liver. The other is longer, and suspends the left lobe of the liver loosely. The Suspen'sory ligament of the spleen5 is a doubling of peritoneum passing from the diaphragm to the upper part of the spleen; and it is continuous with the left lateral ligament of the liver. The Gas'tro-hepat'ic omen'tum6 is a thin doubling of the peritoneum, extended between the transverse fissure of the liver and the small curva- ture of the stomach. Its left border is short, and incloses the cardiac orifice. Its right border is long, bounds the foramen of Winslow, and incloses the common biliary duct, the portal vein, and. the hepatic artery. 1 Bursa omentalis; saccus retro-ven- tricularis; sac of the omentum. 2 F. Winslovii; hiatus of Winslow. 3 Ligamentum suspensorium hepatis ; broad ligament; 1. triangulare. * L. lateralia hepatis. 5 L. phrenico lienale; phrenico-splenic ligament. B Lesser omentum; omentum minus, or gastro-hepaticum; gastro-hepatic epi- ploon ; membrana macilentior; small epiploon. THE ALIMENTARY APPARATUS. 303 The Gas'tro-splen'ic omen'tum1 is a doubling of peritoneum passing from the cul-de-sac of the stomach to the hilus of the spleen, and con- tains the splenic blood-vessels. The Great omen'tum, or gas'tro-col'ic omen'tum,2 is a quadruple doubling of peritoneum suspended from the great curvature of the stomach and transverse colon downward in front of the small intestine, nearly to the pelvis. It is a broad, thin, apron-like process, with its four layers inseparably united in the adult. It frequently presents a perforated, lace-like appearance, crossed with reticular lines of fat, indi- cating the course of long, narrow vessels, which are branches of the gastro-epiploic arteries and veins. In fat persons it contains a large accumulation of fat. Not unfrequently it is found tucked up above the small intestine. The Mes'entery3 is a large doubling of the peritoneum, which is re- flected from the front of the vertebral column over the small intestine. Its root is about six inches wide, and extends obliquely from the left side of the second lumbar vertebra to the right iliac region. From the ver- tebral column the mesentery extends about four inches to its intestinal border, which corresponds in length with that of the small intestine it involves. Between the layers of the mesentery there are contained, besides areolar tissue and fat, the superior mesenteric blood-vessels and their accompanying plexus of nerves, the lacteals, and numerous lym- phatic glands. The Mesoco'lon4 is the portion of peritoneum which binds the colon to the back part of the abdomen. The transverse mesoco'lon5 is a wide doubling, the layers of which, in front, after inclosing the transverse colon, become continuous with the posterior layer of the great omentum; while behind they diverge over the position of the pancreas and duode- num. The ascending6 and descending mesoco'lon7 is for the most part so short, that its two layers do not come into contact behind the corre- sponding portions of the intestine, which, in consequence, are closely bound to the posterior wall of the abdomen. In the left iliac region, 1 Omentum gastro-lienale; o. gastro- splenicum; gastro-splenic epiploon; g. s. ligament. 2 Omentum majus; o. gastro-colicum; great, or gastro-colic epiploon; rete majus; peritonaeum duplicatum; zirbus adipinus. 8 Mesenterium ; mesaraeum; media- num; membrana pinguis intestinorum; medius intestinum ; lactes ; epichordis. * Mesenterium crassum. 5 Mesocolon transversum. 6 Right lumbar mesocolon; right liga- ment of the colon; colic omentum, or epiploon ; third omentum, or epiploon. 7 Left lumbar mesocolon and iliac mes- ocolon ; left ligament of the colon. 304 THE ALIMENTARY APPARATUS. however, it becomes so broad as to suspend the colon in a sigmoid flexure. The Meso-rec'tum is an extension of the descending mesocolon, con- necting the upper part of the rectum closely to the sacrum. The Rec'to-ves'ical folds,1 as expressed by the name, are two duplica- tures of peritoneum which extend between the sides of the rectum and bladder. They include between them a pouch of peritoneum, named the rec'to-ves'ical pouch, which extends downward between the rectum and bladder, nearly to the position of the prostate gland. When the bladder and rectum are empty, the recto-vesical folds form together a crescentic line, and a portion of the small intestine occupies the recto- vesical pouch. In the female, the pouch just mentioned is divided, by the presence of the uterus and vagina, into two portions, which are named, from their position, the rec'to-u'terine and ves'ico-u'terine pouches. The former is the deeper, extending downward between the rectum and the upper part of the vagina while the other extends between the body of the uterus and the bladder. Instead of the recto-vesical folds, their place in the female is substituted by the rec'to-u'terine2 and ves'ico-u'terine folds.3 The Broad ligaments of the uterus are two folds of peritoneum pass- ing from the sides of the uterus to those of the pelvis. They inclose the ovaries and the Fallopian tubes. From the summit and sides of the bladder a slight fold4 of peritoneum ascends to the umbilicus, and incloses the obliterated urachus and um- bilical arteries of the foetus. Likewise a pair of slight folds5 ascend to the umbilicus, over the position of the epigastric blood-vessels. The latter folds cross the course of the inguinal region, and divide it into two shallow fossae, called, from their relative position, the internal and external in'guinal fossae.6 The former corresponds in position with the external abdominal ring, the latter with the internal abdominal ring; and here the peritoneum often presents a short, conical pouch, which was once continuous with the vaginal tunic of the testicle. In the female, the pouch just mentioned is sometimes lengthened into a blind sac7 accompanying the round ligament of the uterus a short distance into the inguinal canal. 1 Posterior false ligaments of the bladder; plicae semilunares. 2 Posterior ligaments of the uterus; plicae semilunares. 3 Anterior ligaments of the uterus. * Plica vesico-umbilicalis media; liga- mentum suspensorium vesica': superior false ligament of the bladder. 5 Plicas vesico-umbilicales laterales; plicae epigastricae. 6 Fovea inguinalis interna et externa. 7 Canal of Nuck. THE ALIMENTARY APPARATUS. 305 THE STOMACH. The Stom'ach1 is a large musculo-membranous pouch, situated within the abdomen, and extending from the oesophagus to the small intestine. It is the most capacious portion of the alimentary canal, and is a re- ceptacle in which the food is sub- mitted to the chemical action of liquids elaborated in its walls. It occupies the left hypochondriac re- gion extending through the epigas- tric into a small part of the right hypochondriac region. Above it is the diaphragm and liver; below, the transverse colon ; in front, the abdominal wall; behind, the pan- creas ; to the right the liver, and to the left the spleen. In shape it is conical, curved upwardly on itself, and is extended obliquely from left to right. The different parts of the stom- ach, to which we usually refer in speaking of the organ, are its greater and lesser extremities, its greater and lesser curvatures, its anterior and posterior surfaces, and its cardiac and pyloric orifices. The greater extremity of the stomach is to the left, and commu- nicates with the oesophagus by the car'diac orifice ;2 the lesser ex- tremity, also named pylor'ic extremity,3 is to the left, and communi- cates with the small intestine by the pylor'ic orifice.4 The greater extremity of the stomach projects several inches to the left of the oesophagus, and in this position is named the fundus.5 The terminal portion of the lesser extremity, for about two inches of its The stomach and intestines. 1, stomach; 2. duodenum; 3, small intestine; 4, termination of the ileum; 5, caecum; 6, vermiform appendix; 7, ascending colon; 8, transverse colon; 9, descend- ing colon; 10, sigmoid flexure of the colon; 11, rectum; 12, spleen. 1 Stomachus; ventriculus; gaster; anocoelia; nedys; gluttupatens; maw. 2 Cardia; oesophageal orifice; upper, or left orifice; os ventriculi; ostium oesophageum. 3 Pars pylorica. * Pylorus; intestinal orifice, lower, or right orifice; ostium duodenale. 5 Cul-de-sac; great tuberosity. 20 306 THE ALIMENTARY APPARATUS. length, is slightly constricted from the rest, and is named the pyloric antrum.1 The lesser curvature2 of the stomach is directed upward and back- ward, and has attached the smaller omentum ; the greater curvature3 is directed forward and downward, and has attached the anterior division of the great omentum. The anterior surface of the stomach presents forward and upward; the posterior surface looks downward and backward, and is in contact with the diaphragm, pancreas, duodenum, and left kidney. The capacity of the stomach varies with the degree of distention, but ordinarily it will contain from one to two quarts, and measures from nine to twelve inches long, and from four to five inches in diameter where most capacious. The walls of the stomach are composed of four coats, named from their character serous, muscular, fibrous, and mucous, all of which adhere intimately together by means of connective tissue. The serous coat4 is the most external, and is derived from the perito- neum. It is a thin, transparent membrane closely investing the stomach, except along the curvatures, where it leaves a narrow interval occupied by the trunks of the blood-vessels, lymphatics, and nerves of the organ. The muscular coat5 is composed of three layers of pale-red, unstriated muscular fibres, pursuing different directions. The external layer con- sists of longitudinal fibres continuous with those of the oesophagus, from which they radiate on the stomach. They are most numerous along the curvatures, especially the lesser one, and are thinly scattered on the an- terior and posterior surfaces. The middle layer, more uniform and important than the former, consists of circular fibres. Commencing thinly at the fundus, they gradually accumulate toward the pyloric ex- tremity, and at the pyloric orifice form a thick fasciculus named the pylor'ic sphinc'ter.6 The internal layer consists of oblique fibres, con- tinuous with the circular fibres of the oesophagus. They form a wide band embracing the cardiac orifice on the left, and spreading obliquely downward and to the right on the anterior and posterior surfaces of the stomach. The fibrous coat7 is a thick, submucous tissue, forming an extensible layer upon which the strength of the stomach mainly depends. 1 Antrum pylori, or pyloricum; lesser cul-de-sac; lesser tuberosity. 2 Curvatura superior: superior, or dia- phragmatic margin. 3 Curvatura inferior; inferior, or colic margin. 4 Tunica serosa. 5 Tunica musculosa; stratum muscu- lar e. 6 Sphincter pylori. 7 Tunica fibrosa; t. nervosa, or nervea. THE ALIMENTARY APPARATUS. 307 The mucous coat1 or lining membrane of the stomach is soft and pulpy to the touch, and is of a pale-pinkish ash color. Under excitement it becomes more reddened, as during digestion; and in inflammation it assumes a deep-red hue. It is thin at the fundus, and gradually thickens Fig. 219. Wrinkled or rugous surface of the mucous membrane of the stomach. 1, wrinkles, or superficial folds: 2, mammillated surface. toward the pyloric extremity, where it is from three-fourths of a line to one line in thickness. In the latter position, ordinarily, it presents nu- merous contorted reticular ridges or wrinkles,2 the larger of which are longitudinal, and gradu- ally fade away toward the fundus of the stomach. These ridges multiply and increase in size with the extent of contraction of the organ, and decrease or even disappear with its distention. At the pyloric orifice a thick, circular fold, or sometimes a pair of cres- centic folds, acts the part of a valve, and hence is named the pylor'ic valve.3 It contains the thick mus- cular fasciculus constituting the pyloric sphincter. 1 Tunica mucosa; crusta villosa ventriculi; gastro-mycoderis. 2 Rugae; plicae. 3 Valvula pylori. Mammilla of the mucous membrane of the stomach, moder- ately magnified, exhibiting the orifices of the gastric glands. 308 THE ALIMENTARY APPARATUS. The free surface of the gastric mucous membrane exhibits a feebly mammillated appearance, well represented in figure 219; and it is everywhere minutely punctured by the orifices of glands. It is pro- vided with a columnar epithelium, which commences at the cardiac orifice and subsequently continues throughout the remainder of the ali- mentary canal. The gastric glands1 are tubular, and closely set upright in the thick- ness of the mucous membrane. They are generally simple, nearly straight or slightly tortuous, and gradually increase in length from the cardiac toward the pyloric orifice, to which circumstance is due the dif- ference in thickness of the mucous membrane in the same direction. Some of the glands, both in the vicinity of the cardiac and pyloric orifices, Fig. Fig. 222. Small portion of the mucous membrane of the stomach, with the imbedded gastric glands. 1, the glands; 2, orifices of the glands; 3, epithelium of the mucous membrane; moderately magnified. are compound, consisting of a main tube dividing at bottom in from two to four branches. Many of the gastric tubular glands are lined throughout with a columnar epithelium, not differ- ing from that of the mucous mem- brane of the stomach. Most of them,2 however, are provided in their deeper part with comparatively large, rounded or polyhedral cells,3 which gradually merge toward the orifices of the glands into columnar epithelial cells. Besides the tubular glands, the stomach contains at its pyloric end a few minute racemose glands ; and not unfrequently in the same position there may be detected a few small, rounded, whitish bodies, resembling the solitary glands of the intestines. A gastric gland, highly magnified. 1, large nucleated cells at the bottom of the gland, gradu- ally merging 2 into the columnar cells 3, at the upper part of the gland. Gastric follicles; glandulae gastricae. 2 Peptic glands. s Peptic cells. THE ALIMENTARY APPARATUS. 309 The stomach is very vascular, the blood-vessels reaching it along the line of attachment of its omenta. The gastro-epiploic arteries together form an arch along the greater curvature ; the coronary and pyloric arteries form a second along the lesser curvature, and the short gastric arteries reach the fundus. The branches from these vessels diverge to the surfaces of the stomach, and form together, between its coats, a vas- cular net, from which the capillary nets of the serous, muscular, and mucous coats originate. The veins correspond with the arteries and pursue the same course. The lymphatics are likewise numerous ; their trunks also running along the curvatures. The nerves are derived from the terminal portion of the pneumogastric and the solar plexus of the sympathetic nerves. The liquid elaborated by the glandular structure of the mucous mem- brane is named the gastric juice.1 Free from foreign matters derived from the food, it is a clear, colorless liquid, rendered slightly viscid from the mixture of mucus, and has a decidedly sour taste. It consists of water holding in solution a peculiar nitrogenized principle named pep- sin,2 free chlorohydric and lactic acids, and a number of chloride and phosphatic salts. Its operation consists mainly in the solution of albu- minoid substances, such as flesh, cheese, eggs, and the gluten of vege- tables. THE SMALL INTESTINE. The Small intes'tine3 is a cylindrical and much convoluted tube, occu- pying the umbilical region and continuous borders of the surrounding regions, and suspended by the mesentery from the vertebral column. It measures about twenty-five feet in length, and from one to one and three- quarters of an inch in diameter; becomes slightly narrower in its de- scent ; and terminates by joining the large intestine. It is divided into three portions: the duodenum, jejunum, and ileum, and although there is no distinct separation between these, each presents some pecu- liarity of character. The Duode'num,4 as expressed by the name, is about twelve fingers'- breadth in length, and it is the widest portion of the small intestine. Commencing at the pyloric orifice, it ascends to the right and backward, until it reaches the neck of the gall-bladder. It then abruptly turns 1 Succus gastricus ; menstruum, or fermentum ventriculi; gastric acid. 2Gasterase; chymosin; the digestive principle. 3 Intestinum tenue; i. gracile; intes- tines ; small gut; guts ; enteron. 1 Ventriculus succenturiatus; dodeca- dactylon ; portonarium; appendix, pro- cessus, or ecphysis ventriculi. 310 THE ALIMENTARY APPARATUS. downward in front of the right kidney, makes another turn to the rig!** side, opposite the second lumbar vertebra, and terminates in the jejunum. The ascending portion of the duodenum has the liver and gall-bladder in front and above it, and after death is usually found stained, with bile exuding from the latter. The descending portion has attached to it, on the left, the head of the pancreas; and into its lower part the duct of the latter, together with the common biliary duct, opens. The trans- verse portion is behind the transverse mesocolon, and is attached by areolar tissue to the crura of the diaphragm and vessels in front of the vertebral column. Along its upper border is the pancreas, and the su- perior mesenteric blood-vessels cross from beneath the latter over its termination. The Jeju'num1 and Il'eum2 are the remaining portions of the small intestine, and though they pass insensibly into each other, the former is viewed as consisting of two-fifths, the latter of three-fifths of the length of the tube. The jejunum is wider than the ileum, feels thicker between the fingers from the more folded condition of its mucous mem- brane, and is further generally characterized by the absence of agminated glands. The ileum terminates in the right iliac region, by joining the large intestine nearly at a right angle. Like the stomach, the small intestine has four distinct coats composing its walls : serous, muscular, fibrous, and mucous. The external or serous coat, derived from the peritoneum, adheres closely around the intestine, leaving only a narrow space along the attachment of the mesentery for the passage of vessels and nerves. The duodenum is invested with peritoneum only at its extremities; the de- scending and transverse portions, for the most part, being destitute of a serous covering. The muscular coat is composed of two layers of pale-red, unstriated fibres. The external layer consists of thinly-scattered, longitudinal fibres; the internal layer, thicker and quite distinct, consists of circular fibres. The fibrous coat, less thick than that of the stomach, is nevertheless a strong, extensible layer. The mucous coat, or lining membrane of the small intestine, is thinner and redder than that of the stomach, and, like it, possesses a columnar epithelium. It is thrown into numerous, transverse, crescentic folds or doublings, named val'vulae conniven'tes.3 These are widest and most abundant in the upper part of the small intestine, where they 1 Nestis. 2 Ileon ; intestinum circumvolutum. 3 V. c. Kerkringii; plicae conniventes; Kerkringian valves. THE ALIMENTARY APPARATUS. 3H even overlap at the edges. In descending, they gradually diminish in number and width; and in the ileum they become indistinct, and finally disappear. These folds are permanent, and not due to con- traction of the intestinal wall. They increase the extent of ab- sorbing and secreting surface, and further retard the passage of the food. The mucous membrane of the small intestine, including its valvulae conniventes, is everywhere pro- vided with minute elevations, named vil'li.1 These give to the surface a velvety appearance, which may be favorably observed, by examining a por- tion of intestine, after it is cleansed from mucus, beneath water. In the Fig. 224. Portion of the mucous membrane from the ileum, moderately magnified, exhibiting the villi on its free surface, and between them the orifices of the tubular glands. 1, portion of an agminated gland; 2, a solitary gland; 3, fibrous tissue. upper part of the small intestine the villi appear as fine, serpentine folds. frequently interrupted in their course, and often conjoined in a reticular manner. Descending the intestine, the fold-like villi become more fre- quently interrupted or broken, and finally, in the ileum, they appear as flattened, conical, or tongue-like processes. The villi are from one-fourth to one-third of a line high, and in struc- ture are processes of the intestinal mucous membrane. Provided with the columnar epithelium, they contain on their interior a capillary net of vessels, in the form of the villi. They likewise contain the commence- ment of those lymphatics called lacteals, but the manner in which these originate has not been satisfactorily determined. According to one Small portion of the mucous membrane from the upper part of the jejunum, moderately mag- nified. 1, villi, resembling valvulae conniventes in miniature; 2, tubular glands; their orifices, 3, open- ing on the free surface of the mucous membrane: 4, fibrous tissue. 1 Villi intestinales; flocculi. 312 THE ALIMENTARY APPARATUS. view, they commence as one or two caecal branches for each villus; and according to a second view, they commence in a reteform plexus. In function, the villi are most efficient organs in the absorption of the nutri- tive matter of the food. Four kinds of glands are found in the mucous membrane of the small intestine: the duode'nal, tubular, solitary, and ag'minated glands. Fig. 225. Diagram of the structure of the mucous membrane of the ileum, highly magnified. 1, epithelium forming the free surface of the mucous membrane; 2, basement membrane; 3, fibrous layer; 4, villi cov- ered with epithelium; 5, a villus deprived of one-half of its epithelium, and exhibiting through its base- ment layer the blood-vessels ; 6, a villus partially deprived of its epithelium; 7, vill\ totally deprived of their epithelium, but retaining their basement membrane; 8, tubular glands imbedded in the fibroua layer of the mucous membrane; 9, orifices of the tubular glands opening on the free surface of the mu- cous membrane between the villi; 10, section of a tubular gland, with its epithelial lining; 11, tubular glands stripped of the latter, but retaining their basement membrane; 12, one of the glands in section, without its epithelium ; 13, capillaries surrounding the orifices of the tubular glands; 14, an artery; 15, a vein; 16, lymphatics or lacteals; 17, commencement of the latter within the villi; 18, capillary blood- vessels of the villi. The Duode'nal glands1 (Brunner's) are small, racemose glands, occu- pying the submucous tissue, and opening into the duodenum. They are most numerous at the commencement of the latter, where they form a nearly continuous layer; gradually diminishing in number and size, they disappear altogether approaching its termination. The Tubular glands2 are the most numerous of those of the small in- testine, and are found throughout its whole tract. They are situated 1 Glands of Brunner; glandulae Brunneri; second pancreas. 2 Glands, or follicles of Lieberkiihn; glandulae, or cryptae Lieberkiihniamc; cryptac mucosae. THE ALIMENTARY APPARATUS. 313 upright in the thickness of the mucous membrane, and open in the inter- vals of the villi, to which spaces they give a perforated appearance. They are simple, straight glands, provided with a columnar epithelium; and secrete a clear liquid, called the intestinal juice.1 Fig. 226. Portion of the duodenum, viewed from without, natural size. 1, thickness of the duodenum; 2, 3, longitudinal and transverse layers of fibres of the muscular coat; 4, fibrous coat; 5, exterior of the mucous membrane, with the duodenal glands im- bedded. 1 Succus entericus. 2 Glandulae solitariae; incorrectly Brun- ner's glands; solitary follicles. 3 Peyer's glands ; glandulae Peyeri, or Peyerianae ; g. sociae Peyeri; g. agmina- taa; g. mucosae coagminatae ; g. muci- paras racematim congestae; g. intesti- Fig. 227. A vertical section of the duodenum, highly magnified. 1, a fold-like villus; 2, epithelium of the mucous membrane; 3, orifices of the tubular glands, 4; 5, orifice of a duodenal racemose gland, 6; 7, two vesicles of the latter, more highly magni- fied, exhibiting the epithelial cells lining their in- ternal surface. nales plexiformes; g. plexus intestinales; g. int. spurise ; g. in agmen congregatse ; corpuscula glandularium similia; ente- radenes; aggregate or aggregated glands; patches of Peyer; Peyer's plaques; ag- minae Peyeri. The Solitary glands2 are minute, whitish, oval or rounded bodies scattered singly throughout the small intestine. They are closed vesicles imbedded in the submucous tissue. In structure, they consist of an ex- terior fibrous capsule, containing rounded, nucleated cells, free nuclei, and granules ; and fine vessels penetrate into their interior. Their func- tion is unknown The Ag'minated glands3 (Peyer's) consist of vesicular bodies like those just described, arranged in elliptical patches. Ordinarily there are from fifteen to thirty of these patches, from half an inch to two inches in length, and about half an inch in breadth. Usually occupying the ileum, they are always situated opposite the attachment of the mesen- tery, with their length parallel to that of the intestine For the most part, the largest patches are the lowest in the ileum, and in ascending 314 THE ALIMENTARY APPARATUS. they become more distant, smaller, and more circular. When found in the jejunum, they are few in number, and small in size. Upon the inner surface of the intestine the agminated glands appear depressed below Fig. 228. Fig. 220. Portion of the ileum, viewed from without; the Berous and muscular coats removed over the posi- tion of an agminated gland. 1, exterior surface of the ileum; 2, cut edge of the serous and muscular coats; 3, exterior surface of the mucous membrane; 4, an agminated gland; 5, valvulae conniventes. Portion of the mucous membrane from the up- per part of the ileum, exhibiting very well the appearance presented to the naked eye when the specimen is floated in water. 1, 2, 3,4, an agmi- nated gland; 5, valvulae conniventes, becoming much contorted over the gland; the short lines everywhere covering the surface of the mucous membrane, including the valvulae and the gland, represent villi; 6, 7, solitary glands. the general level of the mucous membrane; but they give rise to a slight prominence externally. The valvulae conniventes, in approaching them, are usually interrupted, or if they pass upon them are reduced in size, and much contorted. Their function is unknown; and they are remarkable for the changes they undergo in certain diseases, as, for instance, typhoid fever. The arteries of the small intestine are numerous, and are derived from the pancreatico-duodenal, pyloric, and superior mesenteric arteries. Diverging from the mesentery upon the intestine, in the intervals of its coats they form vascular nets, from which are derived the three capillary nets of the mucous, muscular, and serous layers. The veins accompany the arteries. The lymphatics are numerous, and are derived from the three sources supplied by the arteries. The nerves are • furnished by the solar plexus of the sympathetic system. THE ALIMENTARY APPARATUS. 315 THE LAEGE INTESTINE. The Large intestine1 is a cylindrical tube, strikingly differing from the small intestine in its greater capacity and Sacculated appearance. It is about five feet in length, nearly encircles the abdomen in its course from the small intestine to the anus, and is retained in position by the mesocolon. Commencing in the right iliac region, it ascends in front of the right kidney to the under part of the liver, then crosses through the upper boundary of the umbilical region to the left hypochondriac region. Descending from the latter, in front of the left kidney to the left iliac region, it here forms an S-like convolution, and then dipping into the pelvis, passes down in front of the sacrum to terminate at the anus. It is divisible into three portions: the caecum, colon, and rectum. The Cse'cum or head of the colon2 is the most capacious portion of the large intestine, and consists of a large pouch occupying the right iliac region below the termination of the ileum. It is retained in po- sition by a fold of the peritoneum reflected in front, and by an attach- ment of loose connective tissue to the iliac fossa; though sometimes the peritoneum produces a doubling behind which renders the caecum less fixed than ordinarily. The caecum is about two and a half inches in length and breadth, and toward its bottom curves inwardly and backward, and is abruptly re- duced into a worm-like prolongation, named the verm'iform appen'dix.3 This is four or five inches long, as thick as a goose-quill, and is usually somewhat coiled, in which condition it is retained by a fold of peri- toneum. Its calibre is narrow, and its comparatively thick wall has the same structure as other portions of the large intestine. It is viewed as the rudiment of the much-elongated caecum of lower mammals. The Co'lon4 is the second and longest division of the large intestine, and extends from the caecum to the rectum. In the different parts of its course it is called the ascending, transverse, and descending colon, and the sigmoid flexure. It is most capacious at its commencement, 1 Intestinum crassum; megaloccelia. 2 Caecum; caput coli; monocolon; mo- nomacum ; typhlcenterum: typhloteron monocolon; initium intestinicrassi; sac- cus intestini crassi, or coli; prima cella coli; initium extuberans coli; the blind gut, 3 Appendix, or appendicula vermi- formis; processus, or tubus vermicula- ris; appendix ceeci; additamentum coli; ecphyas: digital appendix; vermiform, or vermicular process. 4 Colum; intestinum crassum et ple- num; i. majus; i. grande; i. laxum; i. cellulatum; colon caecum; monenterum; physce. 316 THE ALIMENTARY APPARATUS. where it is about two and a half inches in diameter, and gradually diminishes to its termination, where it is an inch less in breadth. It exhibits three ranges of saccules or pouches,1 alternating with as many equidistant longitudinal bands2 proceeding from the base of the vermi- form appendix. The constrictions between the saccules appear on the interior of the colon as crescentic doublings3 of its walls. The ascending colon4 occupies the right side of the abdomen, attached to its posterior wall by loose connective tissue, and further retained in position by the peritoneum passing over the sides and in front of the intestine. Behind, it is in relation with the quadrate lumbar muscle and kidney; in front with the small intestine. The transverse colon5 passes obliquely across the abdomen at the upper boundary of the umbilical region. It is closely attached to the back part of both hypochondriac regions, and arches forward toward its middle, where it is loosely suspended by the transverse mesocolon. Above it are the liver and the stomach ; below, the small intestine; and descend- ing from its outer border is the posterior fold of the great omentum. The descending colon6 occupies the left side of the abdomen, to the back part of which it is closely attached by connective tissue, and by the peritoneum passing over its sides and front. Its upper part is in contact with the spleen; behind it are the left kidney and quadrate lumbar muscle ; and in front is the small intestine. The sigmoid flexure of the colon7 is an S-like convolution of the in- testine attached by a wide fold of peritoneum to the left iliac fossa. It is the narrowest and least sacculated portion of the colon ; and termi- nates opposite the left sacro-iliac symphysis in the rectum. The Il'eo-col'ic valve. The ileum opens into the left side of the colon just above the caecum, the orifice being provided with a pair of semi- lunar folds, which constitute the ileo-colic valve.8 The folds are trans- verse, and project from the borders of the aperture toward each other into the colon. The free edges of the folds are concave, and their con- tiguous extremities coalesce and are prolonged a short distance as a narrow doubling on the interior surface of the colon. The aperture 1 Cellulae, haustra, or loculamenta coli. 2 Taeniae Valsalvae; taeniae, or fasciae ligamentosae coli; ligamenta coli. 3 Plicae sigmoideae. 4 Colon ascendens; c. dextrum; right lumbar colon. 5 Colon transversum; transverse arch of the colon. 6 Colon descendens; c. sinistrum; left lumbar colon. 7 Flexura sigmoidea; f. S romanum; iliac colon. 8 Ileo-caecal valve; valve of Bauhin, of Tulpius, of Fallopius, or of Varolius; valvula ilei; v. coli; v. caeci; opercu- lum ilei; sphincter ilei. THE ALIMENTARY APPARATUS. 317, Fig. 230. separating the folds is elliptical; but when closed, the free edges of the valve come into contact so as to prevent the return of matters from the large into the small intestine. The third division of the large intestine, the rectum, possesses so many peculiarities that its descrip- tion is reserved for a special section of our chapter. The caecum and colon, like the small intestine, have four coats holding the same relationship with one another. The serous coat, derived from the peritoneum, closely invests the colon except at the back part of the caecum, and of the ascending and descending colon. Along its course, it exhibits a series of ir- regular, pendulous pouches con- taining fat, and named the epip'- loic appendages.1 The muscular coat is composed of two layers of pale-red, unstriated fibres. The external longitudinal fibres, after forming a uniform layer to the vermiform appendix, are collected into three separate bands, which proceed equidistant from one another along the course of the caecum and colon. These bands are much shorter than the intestine would be if deprived of them, and serve to maintain its sacculated condition. The internal muscular fibres are circular, and form a continuous layer to the caecum and colon, dipping into the constrictions between their saccules, and into the folds of the ileo-colic valve. The fibrous coat is like that of the small intestine. The mucous membrane is soft, smooth, and of a pale-pinkish ash color. It is without villi or other doublings than those produced by the constrictions separating the saccules. Its free surface everywhere ex- hibits a finely-punctured or sieve-like appearance, with here and there small whitish spots. It is provided with a columnar epithelium and two Ihe cecum laid open, to expose the ileo-oecal valve, a, Termination of the ileum; b, slit-like orifice between the two folds of the ileo-caecal valve; c, caecum; d, vermiform appendix; e, ascending colon. 1 Appendices, or appendiculae epiploicae, or pinguedinosae; appendices coli adi- posae ; suplementa epiploica; fimbriae carnosae; omentula. 318 THE ALIMENTARY APPARATUS. kinds of glands, tubular1 and solitary glands,2 which are like those of the small intestine. The former are closely Fig. 231. set together in the thickness of the mucous ?»^@pfev membrane, and give to its free surface the *^^^J^»>\ punctured appearance ; the latter are indi- cated by the scattered whitish spots. The blood-vessels of the caecum and colon are branches of the mesenteric arteries and veins. The lymphatics communicate with Section of the mucous memdrane of the colon. i, free surface exhib- glands lying in the course of the former ves- iting the orifices of the tubular seigi The nerves are derived from the mesen- glands 2; 3, fibrous tissue; moder- ately magnified. tenc plexuses of the sympathetic systenv THE KECTUM. The Rec'tum,3 the terminal portion of the large intestine, proceeds from the sigmoid flexure of the colon, opposite the left sacro-iliac sym- physis, and descends along the middle of the sacrum and coccyx, to end at the anus. It follows the curvatures of the bones just mentioned, and from the point of the coccyx turns backward and downward. It is not sacculated like the colon, though it usually exhibits three constrictions, corresponding with crescentic folds on its interior. It is from six to eight inches long, and when distended is club-shaped, being narrow above and expanded just before it contracts to the anus. In front of it, in the male, are the urinary bladder, seminal vesicles, and prostate gland; in the female, the uterus and vagina. The a'nus4 is a dilatable aperture, situated about an inch from the end of the coccyx. It is encircled by a sphincter muscle, covered below by thin, dark-colored skin, gradually merging into the mucous membrane of the rectum. In the condition of rest, this skin is puckered or folded; but in the act of defecation the folds are expanded, and the mucous membrane at the verge of the anus is everted. The upper part of the rectum is invested by the peritoneum, which attaches it to the sacrum by a doubling named the mes'o-rec'tum. Subsequently the peritoneum extends down the sides, and finally only on the front of the rectum, and is thence reflected to the bladder of the 1 Glands or follicles of Lieberkuhn. * Podex ; archos; sedes ; cuius; proc- 2 Solitary follicles: glandulae simplices tos; molyne; dactylios; cathedra; cyr- majores. ceon; cysaros; cysthos; aphedra; he- s Intestinum rectum; longanon; ar- dra; the seat, fundament, or body. chos ; cysaros; princeps; enthyenteron; apenthysmenos. THE ALIMENTARY APPARATUS. 319 male, or the vagina and uterus of the female. The lower part of the rectum is destitute of a peritoneal investment, and is attached to the contiguous structures by areolar tissue, usually accompanied with much adipose tissue. In the male, the portion of the rectum unprovided with peritoneum is in contact in front with the base of the bladder, the seminal vesicles, and the prostate gland; in the female, it is in contact in the same position with the vagina. The muscular coat of the rectum is much thicker than elsewhere in the large intestine. Its external longitudinal fibres, continuous with the longitudinal bands of the colon, form a continuous and well-marked layer. The circular fibres likewise form a continuous layer, and gradu- ally increase in descending upon the rectum, and finally accumulate in a thick fasciculus, named the internal sphinc'ter of the a'nus.1 Between the two sphincters of the anus the longitudinal muscular fibres of the rectum terminate, except a few, which turn around the lower border of the internal sphincter and ascend a short distance between it and the mucous membrane. In the same position the rectum is embraced from each side by the insertion of the anal elevator muscles. The fibrous coat of the rectum is thicker than in other portions of the large intestine, and is strong and extensible. The mucous membrane of the rectum has the same structure as that of the colon, but is more vascular, and becomes bright red at the lower extremity. It exhibits many irregular wrinkles, which are obliterated on distention of the bowel. Approaching the anus, it is thrown into con- vergent longitudinal folds, named the columns of the rec'tum,2 which are often continuous below, so as to form small recesses between them, called the pouches of the a'nus.3 Corresponding in position with the three constrictions usually observed on the exterior of the rectum, its mucous membrane is provided with as many wide, crescentic folds, which may act the part of a valvular appa- ratus. The arteries of the rectum are the haemorrhoidal branches of the infe- rior mesenteric, internal iliac, and internal pudic arteries. The veins are numerous, and at the lower part of the rectum form an intricate net-work, named the hsemorrhoi'dal plexus, which returns its blood through the inferior mesenteric and internal iliac veins. Enlargement of the veins of the haemorrhoidal plexus at the verge of the anus constitute haemor- rhoids or piles. The lymphatics of the rectum proceed to the sacral and 1 Musculus sphincter ani internus, or superius. 2 Columnar carneaa Morgagni. 3 Sinus Morgagni; lacunas. 320 THE ALIMENTARY APPARATUS. lumbar glands. The nerves are numerous, and are derived from the hypogastric plexus of the sympathetic system and the contiguous spinal nerves. The muscles of the anus will be more particularly described in the account of the perineum. THE PANCREAS. The Pan'creas1 is a long, flat gland, situated behind the stomach, opposite the first lumbar vertebra. It extends from the descending por- tion of the duodenum in the right hypochondriac region, along the trans- verse portion of the duodenum through the epigastric region, and reaches the spleen in the left hypochondriac region. It closely adheres to the duodenum, and is loosely attached behind by connective tissue to the crura of the diaphragm, aorta, inferior cava, and superior mesenteric vessels. The latter are included in a groove of the gland, and some- times in a complete canal. In front, the pancreas is connected with the ascending layer of the transverse mesocolon; and its upper border is grooved to accommodate the splenic blood-vessels. The pancreas is pinkish white, and is less consistent and of looser texture than the salivary glands, which it resembles in composition. It is from six to eight inches long, is largest at the right extremity, named its head,2 and gradually narrows toward the left extremity, named its tail.3 Its average depth is about one and a half inches; its thickness about half an inch; and it weighs between two and three ounces. The head of the pancreas adheres closely to the inner side of the de- scending portion of the duodenum, and is frequently partially divided from the body of the gland, when it is named the lesser pan'creas.4 In structure the pancreas is a racemose gland, and consists of many polyhedral lobes and lobules loosely associated by connective tissue. The pancreat'ic duct5 usually possesses two principal branches, of which the longer and larger proceeds transversely through the body of the gland from left to right, and is joined near its termination by the smaller branch6 derived from the head of the pancreas. Upon emerging from the pancreas, the duct penetrates the wall of the duodenum, opening into it near to or in conjunction with the common biliary duct, about four inches from the stomach. 1 Sweetbread; pancratium; pancrene; callicreas; lactes; totum carnosum; pulvinar ventriculi; glandula salivalis abdominis. 2 Caput pancreatis. 3 Cauda. 4 Pancreas minus; pancreas of Asseli. 5 Ductus pancreaticus; d. Wirsungi- anus; canal, or duct of Wirsung. 6 Ductus Santorini. THE ALIMENTARY APPARATUS. 321 The arteries of the pancreas are derived from the pancreatico-duo- denal and splenic arteries. The veins join the splenic and superior mes- enteric veins. Its lymphatics communicate with the lumbar glands, and its nerves are branches from the solar plexus of the sympathetic system. The pancreat'ic juice1 is a clear, colorless, slightly viscid liquid, with a distinctly alkaline reaction. It contains a peculiar nitrogenized prin- ciple, named pancreatin, and is an important emulsifying agent of the fatty materials of the food. THE LIVER. The Liver2 is the largest true glandular organ of the body. It occu- pies the greater part of the right hypochondriac region, and extends through the epigastric into a small portion of the left hypochon- driac region. It is half ovoidal in shape, with its long diameter trans- verse, its convex surface accurately applied to the diaphragm, and its nearly flat or slightly concave surface in contact with the stomach, duo- denum, colon, and right kidney. In front, it is in relation with the ensi- form and costal cartilages, and behind, with the crura of the diaphragm. aorta, and inferior cava. It is suspended from the diaphragm by reflec- tions of the peritoneum named the suspensory, the right and left lat- eral ligaments, and by a further attachment of connective tissue at its posterior border. The right portion of the liver is much larger than the left, and is thicker, more fixed in position, and extends lowest in the abdomen as well as highest in the thorax. The posterior and right borders are thick and rounded; the anterior and left borders are thin and acute, and the most movable parts of the organ. The liver is of firm, solid texture, smooth on the surface, and of a reddish-brown color. It often has more or less of a yellowish hue, ap- parently dependent on the presence of fat in the hepatic substance, and sometimes exhibits superficial livid bluish or purplish patches and borders. It weighs between three and four pounds, and measures ten to twelve inches from right to left, about six inches from back to front, and about three inches at its thickest part. In the female it is usually about a fifth less in weight and size. The suspensory ligament, extending from the median line of the dia- phragm to the upper surface of the liver, together with the longitudinal fissure pursuing the same direction on the under surface, divide the organ into two unequal parts, named the right and left lobes. Succus, or liquor pancreaticus. 2 Hepar; jecur; jecinus. 21 322 THE ALIMENTARY APPARATUS. The right lobe of the liver,1 four or five times the size of the left, is square in outline, and is closely adherent at its posterior border, by con- nective tissue, to the diaphragm, be'tween the widely-separated reflections of the right lateral ligament. Its upper surface is convex; its lower surface is in contact with the right kidney, the pyloric extremity of the stomach, and the colon. At the fore part of its inferior surface the gall- bladder reposes in a fossa ;2 and to the left and back of this it presents two small subdivisions named the quadrate and caudate lobes. Inferior surface of the liver. 1, right lobe; 2, left lobe; 3, posterior margin; 4, anterior margin; 5, quadrate lobe; 6, caudate lobe; 7, isthmus, or caudate process, connecting the latter with the right lobe; 8, 9, longitudinal fissure; 10, transverse fissure; 11, portal vein; 12, hepatic artery; 13, common biliary duct formed by the union of the hepatic and cystic ducts; 14, gall-bladder; 15, inferior cava; 16, hepatic veins; 17, round ligament; 18, anterior part of the suspensory ligament. The left lobe of the liver3 is comparatively thin, trilateral in outline, and movably suspended by the left lateral ligament. Its lower surface is in contact with the anterior part of the stomach, and behind, it is in relation with the cardiac orifice of this organ. Besides the suspensory ligament and longitudinal fissure, the right and left lobes are separated at the anterior and posterior borders of the liver by notches. The anterior notch is acute, and continuous below with the longitudinal fissure; the posterior notch is broad and concave, and ac- commodates the vertebral column and the great blood-vessels in front of it. The inferior cava occupies a deeper portion of the posterior notch, excavated in the right lobe of the liver; and sometimes the hep^ic sub- stance extends around the vein so as to inclose it in a complete tube. 1 Lobus dexter; large, or colic lobe. 2 Fossa longitudinalis dextra. s Lobus sinister. THE ALIMENTARY APPARATUS. 323 Above the posterior notch, the two layers of the suspensory ligament diverge1 and become continuous with the anterior reflections of the lat- eral ligaments, leaving a triangular interval at which the liver is attached to the diaphragm by connective tissue. The Longitudinal fissure2 is a deep groove on the under part of the liver extending between the anterior and posterior notches, and separat- ing the right and left lobes. Its fore part3 is frequently crossed by a bridge4 of hepatic substance, and it contains a fibrous cord named the round ligament,5 which is the obliterated umbilical vein of foetal life. Its back part6 also contains a fibrous cord, which is the obliterated duc- tus venosus of the foetus. The Transverse fissure7 is a deep groove passing at a right angle from the longitudinal fissure, between the quadrate and caudate lobes, to ter- minate on the under part of the right lobe. This fissure is the position at which the blood-vessels and nerves enter the liver, and the lymphatics and excretory duct emerge. The Quadrate lobe of the liver8 is a square portion of hepatic sub- stance situated between the gall-bladder on the right and the longitudi- nal fissure on the left, and extending from the anterior border of the organ back to the transverse fissure. The Caudate lobe9 is a small blunt pyramidal mass of hepatic sub- stance behind the transverse fissure, extending to the posterior notch of the liver, and having to its left the longitudinal fissure, and to its right the groove for the inferior cava. A short isthmus or caudate process10 associates it, in front of the latter vessel, with the under surface of the right lobe. 1 This divergence is usually and incor- rectly described as if it were a distinct structure, under the name of the coro- nary ligament; 1. coronarium. 2 Great, or horizontal fissure, furrow, or sulcus; fossa umbilicalis; sulcus an- tero-posterior jecoris; sulcus sinister, or umbilicalis jecoris. 3 Fossa longitudinalis sinistra. * Pons^r isthmus hepatis.. 5 Ligame'htum teres. 6 Fossa ductus venosi. 7 Sulcus transversus; fossa transversa; sinus portarum; porta; p. hepatis, or jecoris; manus hepatis, or jecoris; prin- cipal fissure; fissure or fossa of the portal vein; portal fissure or fossa. 8 Lobulus quadratus; 1. anonymous; 1. accessorius anterior quadratus; ante- rior portal eminence; auriga anony- mous. 9 Lobulus Spigelii; the Spigelian lobe; lobulus porticus papillatus; tuberculum papillare; posterior portal eminence; small, duodenal, or pancreatic lobe. 10 Lobulus caudatus; lobus, or proces- sus caudatus; tuberculum caudatum. 324 THE ALIMENTARY APPARATUS. The liver derives its blood from two different sources, in this respect being quite peculiar among the organs of the body. It is supplied with red blood by a proportionately small vessel, the hepatic artery, and is provided with dark blood by a larger vessel, the portal vein. The two vessels together enter the transverse fissure of the liver, (the artery in front of the veir^, and both divide into two branches, which pass to the right and left lobes, and ramify through them in a divergent manner from below upward, and toward the borders of the organ. The bile ducts,1 originating in the hepatic substance, converge in the course of the vessels just mentioned, and emerge into the transverse fissure of the liver; a branch from the right and another from the left lobe conjoining to form the trunk of the hepat'ic duct. Numerous lymphatics, and nerves from the pneumogastrics and.sym- pathetics, pursue the same course as the above-mentioned blood-vessels and ducts, the whole together being enveloped by connective tissue.2 The hepat'ic veins collect the blood from the substance of the liver and return it to the general circulation. Commencing at the periphery of the organ, they emerge from before backward, and terminate, at the posterior notch of the liver, in two principal trunks which join the infe- rior cava. The relative position of the hepatic veins with the other vessels of the liver bears a resemblance to a prostrate tree whose boughs and branches are entangled among those of a clump of upright trees. STRUCTURE OF THE LIVER. The liver is closely invested with a serous coat derived from the peri- toneum, which everywhere covers it except along the posterior border, in the intervals of the suspensory and lateral ligaments, and at the bot- tom of its fissures. The subserous connective tissue3 is feebly developed, but a stronger and distinct extension of the same structure invests those portions of the liver which are destitute of peritoneum. In the trans- verse fissure the investing connective tissue of the liver is continuous with that enveloping the vessels and ducts. The material composing the liver, and named the hepat'ic substance,1 has a reddish-brown color tinged with yellow, and has a finely and uni- formly mottled aspect, which is much more evident in some of the infe- 1 Biliary ducts: pori biliarii; ductus biliarii. 2 Capsule of Glisson; c. communis Glissoni; vagina portae; v. Glissoni. 3 Tunica propria. * Parenchyma hepatis: parenchyma of the liver. THE ALIMENTARY APPARATUS. 325 rior animals than in man, as for instance in the hog. It is readily torn, and in this condition presents a coarsely granular appearance. The coarse granules corresponding with the distinct spots seen on the surface of the liver are polyhedral, from half a line to one line in diameter, and are named the lob'ules of the liver.1 Fig. 233. Fig. 233. Portion of the liver of the hog, exhibiting the lobular structure and the section of a he* patic vein, somewhat magnified, a, Large branch of the hepatic vein; the orifices belong to other branches; 6, branches exhibiting through their thin walls the outlines of the lobules; the dots in the centre of the latter are orifices of the veins commencing within the lobules. Fig. 234. Portion of the liver of the hoo, exhibiting the lobular structure. The large vessel is a branch of the portal vein, the outlines of the lobules being seen through its transparent wall. The ori- fices, large and small, seen in the portal vein, are fine branches sent between the lobules. The two vessels lying to the left of the portal vein are branches of the hepatic artery and duct. In tracing the relation of the hepatic lobules with the blood-vessels and ducts of the liver, it is found that an extreme branch2 of the hepatic veins commences in the axis of every lobule, and emerges at its base to join a larger branch.3 This arrangement of the hepatic lobules and veins resembles the attachment of leaves by their midribs and stems to the branches of a tree. The portal vein, hepatic artery, and hepatic duct, associated together by connective tissue,4 ramify through appro- priate canals5 of the hepatic substance, pursuing the same general course 1 Acini. * Capsule of Glisson. 2 Intra-lobular vein ; vena centralis. 5 Portal canals. 8 Sub-lobular vein. 326 THE ALIMENTARY APPARATUS. in relation with the branches of the hepatic veins which has been indi- cated in the account of the arrangement of their trunks. Finally, the portal vein, hepatic artery, and the bile ducts ramify in the interspaces' of the lobules, forming plexuses,2 and associating the latter together In the human liver, these interven- Fig. 235. ing vessels are the chief connection of the lobules with one another; but in some of the lower animals, as for instance the hog, they are accompanied with a much greater quantity of connective tissue, which renders the outlines of the lobules more defined. Between the terminal branches3 of the portal vein and hepatic ar- tery, occupying the intervals4 of the lobules and the commencing branches5 of the hepatic veins in the axis of the latter, intricate ca- pillary vascular nets6 intervene. Thus the blood which enters the liver by the portal vein and hepatic artery pursues its course until it arrives in the intervals of the lob- ules, when it meanders through the capillary nets to the commencement of the hepatic veins in the interior of the lobules. The meshes or interspaces of the capillary vascular nets are occupied by the proper secreting substance of the liver, constituting the hepatic cells.7 These are irregularly polyhedral, from the 1T*UT) to the 1T*w of an inch in diameter, with soft granular contents, some minute oil glob- ules, and a nucleus. Generally, two hepatic cells are about equal to the diameter of the meshes they occupy, though frequently a single cell is observed extending across the interval. From the description given, it may be readily comprehended that the hepatic lobules are composed of capillary vascular nets, intercaVated Section of several lobules of the liver of the rabbit, the vessels injected, and the preparation magnified. The intricate capillary net-works are formed from the portal veins between the lobules, and the hepatic veins within them. 1 Interlobular spaces. 2 Interlobular veins, arteries, and ducts. 3 Interlobular veins and arteries. 4 Interlobular spaces. 5 Intralobular veins. 6 Lobular plexuses. 7 Liver cells; hepatic corpuscles. THE ALIMENTARY APPARATUS. 327 with hepatic cell-nets, as represented in the diagram, figure 237. So far, anatomists concur in their observations on the structure of the liver; but in regard to the exact relationship of the hepatic cell-nets with the bile ducts1 there exists much conflict of opinion. According to one view, the hepatic cell-nets are solid, and the bile ducts originate at the bound- aries of the lobules. In a second view, intercellular passages of the hepatic cell-nets communicate with the commencement of the bile ducts in the interspaces of the lobules. According to a third view, a third net, composed of very fine tubes of basement membrane, is intercal- lated with the capillary vascular, and hepatic cell nets, and joins the bile ducts in the interspaces of the lobules. Finally, in a fourth view, as in other true glands, the hepatic cells are considered as lining tubes of basement membrane, from which the bile ducts originate'in the intervals of the lobules. Polyhedral epithelium, exemplified by secret- ing cells of the liver. The arrangement is ideal. 1, space occupied by a blood-vessel; 2, isolated cells. Fig. 237. Fig. 237. DIAGRAM REPRESENTING the section of a lobule of the liver, exhibiting the relative position of the hepatic cell-nets with the vascular nets. 1, section of a hepatic vein in the centre of a lobule; 2, branch of the portal vein at the cir- cumference of the lobule ; 3, capillary net formed between the portal and hepatic veins; 4, branch of the hepatic artery; 5, hepatic cell-net in the inte- rior of the lobule; 6, a bile duct at the boundary of the latter. Fig. 238. Fig. 238. Diagram representing a transverse SECTION OF ONE OF THE CORDS OF THE HEPATIC CELL- NET, showing how a few cells may form a hollow tube. 1, large cell; viewed from this side the tubes would appear to be the breadth of a single cell; 2, two cells the diameter of the tube; 3, passage-way for the bile. 1 Interlobular ducts ; pori biliarii. 328 THE ALIMENTARY APPARATUS. BILIARY DUCTS AND GALL-BLADDER. The Hepat'ic duct,1 commencing by two branches in the transverse fissure of the liver, descends within the right border of the gastro- hepatic omentum, in advance of the portal vein and to the right of the hepatic artery. It is about two inches in length, and terminates, by joining with the cyst'ic duct from the gall-bladder, to form the common bil'iary duct. The Gall-bladder,2 the receptacle of the bile, is a pyriform sac, par- tially lodged in a fossa on the under part anteriorly of the right lobe of the liver. Its fundus or base projects beyond the anterior border of the latter, in the vicinity of the tenth costal cartilage; and its body or main portion extends in a backward direction. Its neck forms an S-like con- volution, and terminates at the transverse fissure by becoming the cyst'ic duct. The gall-bladder is attached in its fossa of the hepatic substance by connective tissue, and its free part, including the fundus, is covered by the peritoneum. Independent of the latter membrane, its wall is pro- vided with a strong layer of fibrous tissue, and a thin, diffuse stratum of pale unstriated muscular fibres. Its lining mucous membrane, stained yellow from the bile, is uniformly covered with fine reticular folds, and has a columnar epithelium. The gall-bladder is supplied with blood by the cystic artery, a branch of the hepatic. Its veins terminate in the portal vein. The Cyst'ic duct3 is about an inch in length, and descends to the left to join the hepatic duct at an acute angle. Its lining membrane is thrown into a series of oblique folds, forming a sort of spiral valve,4 which retards the flow of the bile. The Common bil'iary duct,5 formed by the conjunction of the hepatic and cystic ducts, is about three inches long, and of the diameter of a large goose-quill. Continuing along the right border of the gastro- hepatic omentum, it pursues its course behind and to the inner side of the descending portion of the duodenum, and terminates in the latter, about four inches from the stomach. Its lower portion is involved in the head of the pancreas, and then perforates the wall of the duodenum 1 Ductus hepaticus. 2 Vesicula bilis; v. or folliculus fellis; vesica fellea; v. biliaria; cystis fellea ; cholecystis. 3 Ductus cysticus; meatus cysticus. 4 Valvulus spiralis Heisteri. 5 Ductus communis choledochus; d. choledochus; d. hepato-cysticus; chole- dochus ; common bile duct. THE ALIMENTARY APPARATUS. 329 obliquely. Its orifice is narrowed, and opens at the summit of a slight papillary eminence. The common biliary, cystic, and hepatic duct and its branches have the same structure. They have a strong fibrous coat, with a few unstri- ated muscular fibres, and a lining mucous membrane. The latter is pro- vided with many minute racemose glands; and it has a columnar epithe- lium, except in the small bile ducts, where the epithelium assumes the tesselated form. The secretion of the liver, named the bile,1 as obtained from the human gall-bladder, is a thin, glairy, dark, yellowish-brown liquid, of bitter taste, and nearly neutral in reaction when fresh. It is exceed- ingly complex in chemical composition; and though an abundant se- cretion, and a very constant one in animals, its uses have not yet been satisfactorily determined. THE SPLEEN. The Spleen2 is a half-ovoidal body, deeply situated in the left hypo- chondriac region. It is of comparatively soft consistence, and of a livid, purplish color. Its long diameter is vertical, with the larger extremity upward and attached to the diaphragm by a doubling of peritoneum, the suspensory ligament. Its external convex surface is directed toward the left side, and is in contact with the diaphragm opposite the three or four dower ribs. Its internal surface, slightly depressed in front and behind and elevated toward the middle, is directed to the right side, and applied to the fundus of the stomach, to which it adheres by the gastro- splenic omentum. Its posterior border is thick and rounded, and rests against the contiguous kidney and the diaphragm; its anterior border is thinner, and at the lower part usually exhibits one or two notches or clefts. Along the middle of the internal surface of the spleen, usually indi- cated by a slight groove named the hilus,3 the splenic vessels and nerves pass to and from the organ. The spleen is very variable in size, even in the condition of health, and is liable to great changes in this respect in certain diseases. Ordin- arily it is four or five inches long, three or four broad, and from one to one and a half thick; and weighs about six ounces. The spleen is provided with two coats, of which the outer is serous, 1 Bilis; cholos ; fel; the gall. -Lien; splen ; hepar sinistrum ; h. adulterinum; fomes ventriculi; milt. 3 Porta lienis. 330 THE ALIMENTARY APPARATUS. and the inner one fibro-elastic. The serous coat derived from the peri- toneum is thin, transparent, smooth, and tightly adherent to the contigu- ous structure beneath. The fibro-elastic coat1 is a moderately strong, extensible layer, com- posed of interlacing bundles of fibrous tissue mingled with fibres of elastic tissue. At the hilus it becomes continuous with a similar investment to the splenic blood-vessels as they ramify through the organ. The spleen is easily torn ; its lacerated surface presenting a deep red- dish-black, or brown, pulpy appearance, resembling coagulated blood or dark currant-jelly. This dark substance, named the splenic pulp,2 may be scraped from the torn surface, or it may be removed from portions of the spleen by maceration or repeated washings, leaving a spongy mass, composed of the splenic blood-vessels, associated with numerous bundles of fibro-elastic tissue. These bundles, named trabec'ulae, spring from the interior surface of the fibro-elastic coat of the spleen, and form an intricate net-work or sponge-like arrangement which supports the splenic blood-vessels and contains within its meshes the splenic pulp. The pulp of the spleen, examined with the microscope, is found to consist of the following elements: 1, numerous blood-corpuscles, for the most part unchanged, but many apparently exhibiting various condi- tions of disintegration; 2, finely granular matter, partly colorless, but mostly of various shades of red passing into brown ; 3, numerous iso- lated nuclear bodies ; 4, colorless nucleated cells; 5, a few cells contain- ing blood-corpuscles apparently in a state of disintegration; and 6, occasionally red acicular crystals, derived from the decomposition of blood-corpuscles. The arrangement of these different elements of the splenic pulp, in their relationship with one another and with the blood-vessels, has not yet been determined in a satisfactory manner. Adhering to the sides of the smallest arteries of the spleen, and im- bedded in the pulp, there exist certain small, rounded, whitish bodies, named splenic corpuscles.3 These are variable in number and size, usually measure about one-sixth of a line in diameter, and resemble, in composition, the solitary glands of the intestines. In proportion to its size, the spleen is the most vascular organ of the body. The splenic artery divides into a half dozen or more branches, which diverge along the hilus and enter the spleen. Spreading through the organ in numerous ramifications, those of the different principal branches not anastomosing, they finally break up into a multitude of 1 Tunica propria; t. albuginea. 2 pulpa lienis. 3 Corpuscles of Malphighi; Malphighian bodies. THE ALIMENTARY APPARATUS. 331 pencil-like bundles of delicate vessels, which terminate in the capillaries of the splenic pulp. The veins return in the course of the arteries, with which they correspond in number, but are larger. The lymphatics are few in comparison with those of the other abdominal viscera. The nerves are derived from the solar plexus of the sympathetic system. The function of the spleen, though the subject of numerous and laborious investigations, yet remains unknown. It has been supposed that the spleen acts as a reservoir or diverticulum to the blood during the state of rest of the digestive organs, and during those conditions in which the blood retires from the surface toward the interior of the body. It has also been looked upon as being the position in which the blood-corpuscles, after having fulfilled their function in the economy, undergo dissolution, yielding their chemical elements to the circulating liquor sanguinis. Further, it has been supposed to be the organ in which the blood-corpuscles have their origin. CHAPTER VII. THE VASCULAR SYSTEM. The Vas'cular system consists of the heart, blood-vessels, lymphatics, and their contained liquids, the blood and lymph. The heart is a power- ful muscular organ, and is the chief agent in the circulation of the blood. The blood-vessels consist of branching tubes, named arteries and veins, and an intermediate set of tubes, called capillaries. The lymphatics consist of vessels and peculiar bodies, named lymphatic glands. GENERAL CHARACTERS OF THE ARTERIES. The Ar'teries1 are cylindrical, membranous tubes, which commence in two great trunks, the aorta and pulmonary artery. They undergo divi- sion as in the branching of a tree, and distribute the blood throughout the body, terminating in the capillaries. Their branches mostly come off at acute angles, are commonly of uniform diameter in each case, but successively diminish after and in consequence of division; and in this manner gradually merge into the capillary system. As a general rule, the combined area of the branches is greater than that of the vessel from which they emanate, and hence the collective capacity of the arterial system increases with its distribution. This arrangement facilitates the circulation; for the increasing capacity of the vessels in their course compensates for the retarding influence of friction. Arteries have comparatively thick walls, and even when emptied, as is usually the case after death, they for the most part maintain their open calibre. Generally they pursue a straight course, but are often curved, and are sometimes tortuous, especially in positions liable to frequent change of volume, or of expansion and contraction; as in the lips, the urinary bladder, the uterus, etc. The larger arteries are generally deeply situ- ated, and frequently pursue their course along the bones, where they are protected from undue extension. In the limbs they occupy the sides of 1 Sing.: arteria; pi.: arterioe. (332) THE VASCULAR SYSTEM. 333 flexion, where they are less exposed to a variety of accidents than if situated on the sides of extension. Arteries, in their course of distribution, form intercommunications, named anastomo'ses,1 which become more frequent as the vessels diminish in size. Even in many large vessels anastomoses are numerous, where it is important that the blood should be incessantly supplied to organs, as in the case of the arteries of the brain; or where the vessels are constantly exposed to the liability of pressure, as in the arteries of the hand and foot, those around the joints, and those of the abdominal viscera. The arteries are highly elastic, being extensible and retractile both in length and breadth. During life, from their being provided with mus- cular tissue, they are also contractile. The walls of the arteries are composed of three coats, which vary in vessels of different sizes. Fig. 239. Transverse section of the walls op the aorta, treated with acetic acid, and magnified. 1, internal coat: a, epithelium and basement membrane ; b, c, layers of elastic tissue. 2, middle coat: d, layers of elastic tissue: e, muscular and connective tissue. 3, external coat, composed of fibrous tissue and fine nets of elastic tissue. The external coat2 is comparatively thin in the largest arterial trunks; increases to half the thickness of the walls in the medium-sized arteries; becomes relatively thicker in the smaller branches; but finally disappears in those which merge into the capillaries. It is mainly com- posed of fibrous tissue, the bundles and filaments of which pursue a spiral direction, crossing one another from opposite sides of the vessel. Its exterior portion is of looser texture, and adheres to the surrounding parts; its interior portion is intimately blended with the middle coat. It contains fine nets of elastic tissue, which are most abundant toward the interior. To this coat the arteries chiefly owe their tenacity. 1 Interosculations; inosculations; reuniones vasorum; exanastomoses ; concursi. 2 Tunica adventitia; t. externa; t. cellularis ; vagina cellularis. 334 THE VASCULAR SYSTEM. The middle coat1 forms the principal thickness of the walls of the largest arterial trunks, gradually diminishes in their branches, and finally disappears. In the largest arteries it is of a yellowish color, and is mainly composed of elastic tissue, with a small proportion of unstriated muscular tissue and some connective tissue. In the medium-sized and smaller arteries it is of a reddish hue, and chiefly consists of muscular tissue, with a small proportion of elastic and connective tissue. In the smallest arteries the middle coat consists alone of muscular tissue. Fig. 240. Elastic tissue from the middle coat of the popliteal artery, highly magnified. The dark reticular lines indicate a narrow net of elastic tis- sue ; the other part of the figure represents a layer of perforated membrane, which is a variety of the same tissue. Unstriated muscular fibres from the middle coat of the arteries, highly magnified. 1, from the popliteal artery: a, without, and 6, treated with acetic acid; 2, from a branch of the anterior tibial artery : a, pointing to the centre in all the figures, indicates the nucleus. The elastic and muscular tissues are arranged in layers varying in number according to the thickness of the coat, and their fibres pursue a circular course around the vessels. The muscular fibres are fusiform, with elongated oval nuclei. The elastic tissue exhibits all varieties of form, from fine nets to broad-banded ones, constituting the so-called perforated or fenes'trated membranes. To the middle coat arteries owe their contractility, most of their elasticity, and much of their strength; though it is of such a brittle character that the application of a ligature cuts or breaks it through. The internal coat2 of the arteries is the thinnest, most transparent, and elastic. It is composed of a lining epithelium, a basement membrane, 1 T. media; t. elastica. 2 Tunica intima; t. glabra; endangitd*. THE VASCULAR SYSTEM. 335 and layers of elastic tissue. The epithelium consists of a single layer of elongated, lozentfe-shaped cells, which are narrowest in the smallest arteries. The basement membrane is homogeneous and elastic, and is the last structure of the arteries becoming continuous with the capillaries. The elastic tissue consists of fibres, nets, and the so-called perforated membranes, pursuing a longitudinal direction, and intimately associated with the middle coat. The larger arteries have their walls furnished with nutrient vessels, which are derived from small neighboring arteries, and not from the trunks they supply. The nutrient vessels form a net-work of capillaries, from which veins arise to empty into the contiguous larger venous branches. The arteries are accompanied by many nerves, chiefly from the sympathetic system, but to what extent their walls are supplied by them has not been satisfactorily determined. The elasticity of the arteries allows them to dilate as each impulse of the heart sends an additional supply of blood to their circulating current. The dilatation moves rapidly onward in a wave-like manner, and insen- sibly decreases until it is entirely lost in the smallest arteries. It is followed by contraction of the arterial walls upon their contents, both in consequence of their elasticity and the excitation of their muscular structure. The alternation of dilatation and contraction of the arteries constitutes pulsation or the pulse.1 GENERAL CHARACTER OF THE VEINS. The Veins2 are branching tubes like the arteries, but are generally larger, more numerous, and consequently more capacious. They com- mence in the capillary vessels, gradually converge in a reverse course mostly along side of the arteries, and, with one exception, terminate in the heart by seven trunks. Four of the latter are the pulmonary veins; the two largest ones are the superior and inferior cava, and the smallest is the coronary vein, derived from the walls of the heart itself. The ex- ception is the portal vein, which derives its branches from the bowels, and is distributed through the liver. The larger veins consist of a superficial and deep series; the former unassociated with arteries, and running immediately beneath the skin, the latter usually accompanying the arteries, and thence named com- panion veins.3 The arterial trunks and their large branches generally 1 Pulsus ; pulsatio; ictus, or incursus arteriarum. 2 Sing.: vena; pi.: venae; phlebs. 3 Venae satellites; v. comites; v. concomites. 336 THE VASCULAR SYSTEM. have one companion vein; but the medium-sized and smaller arteries usually possess a pair, arranged one on each side of the artery. Anastomoses between veins of comparatively large size are much more frequent than among corresponding arteries ; and in some positions they form coarse, intricate nets, named venous plexuses. The veins have much thinner, but relatively stronger, walls than the arteries, and, after death, according to the quantity of their remaining contents, are found collapsed. Many of the larger ones are provided with valves, which are so arranged as to prevent the reflux of blood. The valves are usually in pairs, opposite each other, and consist of crescentic doublings of the lining membrane of the veins, strength- ened with some intervening fibro- elastic tissue. The convex border of the valves is attached; the con- cave border is free, and directed from the periphery of the body toward the heart. Behind each valve the vein is dilated into a pouch or sinus, which prevents the adherence of the valve to the side of the vein when the blood pursues its proper course. If the vein is compressed, the blood driven back enters the sinus and presses the valve inward, so as to meet the opposite one in the middle of the channel, and thus close it. The pulmonary veins throughout possess no valves, and this also is the case with the superior and inferior cava, the portal vein and its branches, the hepatic, renal, uterine, and spinal veins, and most of those of the head and neck. They are more abundant in the veins of the lower than in those of the upper extremities. In certain membranes and some other organs, channels exist lined with an extension of the internal coat of the blood-vessels, and serving the function of veins. These channels are usually termed venous sinuses, as the sinuses of the dura mater, those of the bones, and of the uterus. The walls of the veins, as in the arteries, are composed of three coats, having the same general character. The external coat is the thickest, and gradually increases in this respect from the smallest to the largest veins. As in the arteries, it con- sists of fibrous tissue, with longitudinal nets of elastic tissue. In the Fig. 242. A B C Diagrams exhibiting the arrangement of the valves of veins. A, vein laid open, showing the valves in pairs; B, longitudinal section of a vein, indicating the mode in which the valves, by appo- sition of their free edges, close its calibre. The di- lated condition of the walls behind the valves is also seen. C, vein distended, showing how the sinuses behind the valves become dilated. THE VASCULAR SYSTEM. 337 larger veins of the abdominal cavity it is also provided with unstriated muscular tissue, the lamina of which pursue a longitudinal direction. The middle coat is best developed in the medium-sized veins, and dis- appears altogether in the smallest ones. As in the arteries, it consists of unstriated muscular, elastic, and connective tissue, the elements of which usually pursue a circular direction, though laminae of the elastic tissue also have a longitudinal direction. In the largest veins the middle coat contains a large proportion of connective tissue, and is sparingly provided with muscular tissue. The internal coat, like that of the arteries, consists of a lining epithe- lium, an elastic basement membrane, and longitudinal lamina? of elastic tissue, which, however, do not form fenestrated membranes. The walls of the veins are furnished with nutritive vessels. A few nerves have been traced only in the larger veins. Both arteries and veins are insensible to painful impressions in a condition of health. The acute pain often evinced in the ligation of an artery is due to the inclu- sion of accompanying nerves. THE CAPILLARIES. The Cap'illaries1 are minute blood-vessels usually arranged in the form of nets among the proper tissue elements of the organs of the body. They communicate with the termination of the arteries and the commencement of the veins, but are otherwise closed, or never commu- nicate by open orifices with the structures in which they are distributed. The proper tissue elements are in all cases exterior to the capillary ves- sels, or occupy the meshes of the capillary nets; and they obtain their nutritive material simply by imbibition through the walls of the capil- laries. In any special structure the capillaries are remarkable for the general uniformity of their size, but in the different structures of the body they range from the j--^C) to the T-oU of a line in diameter. The smallest ad- mit the passage of blood corpuscles, though but a short time has elapsed since the opinion universally prevailed that in all structures of the body capillaries2 existed which only transmitted the liquor sanguinis. In structure the capillaries consist of tubes of transparent, elastic, structureless membrane with scattered oval nuclei. There is no lining epithelium, but only the single layer of membrane just described, which Vasa capillaria; micrangia; trichangia. 2 Vasa serosa. 22 338 THE VASCULAR SYSTEM. Fig. 243. is continuous with the basement layer of the internal coat of the arteries and veins. The form of the capillary nets is in a measure dependent upon the ar- rangement of the proper elements of the tissues they supply. Thus, in the lungs, the nets accommo- date themselves to the form of the air-cells; in the muscles, they have elongated meshes, most of the vessels pursuing the course of the muscu- lar fibres, and being con- nected by short ones crossing the latter, etc. In many instances, es- pecially within papillary eminences, the capillaries form loops, as in the pa- pillae of taste and of touch. The greater the vital activity of an organ, the more dense or close is the capillary net; or, in other words, the greater is its degree of vascularity. The clei of structureless membrane; 2, 3, 4, capillaries composed of Capillary net Or pleXUS is structureless membrane (a) with scattered nuclei (d). ^^ ^ ^ ^^ ^ glands, especially the liver and kidneys, the skin and mucous membranes, the muscles, and the gray nerve substance. In the fibrous tissues and the bones the nets have wide meshes, and, of course, comparatively few vessels. THE BLOOD. The Blood1 constitutes the circulating contents of the heart, arteries, capillaries, and veins. It is a highly complex liquid, furnishing nutritive material to all the tissues of the body. It is somewhat viscid, and heavier than water—its specific gravity being about 1055. When fresh, it appears to the naked eye perfectly homogeneous, and of a more or A small artery gradually passing into the structure of the ca- pillary vessels. 1, artery with transverse muscular fibres: a, struc- tureless membrane; 6, nuclei of transverse muscular fibres; c, nu- 1 Sanguis; cruor; haema; lapis animalis. THE VASCULAR SYSTEM. 339 less deep-red hue. It has an alkaline reaction, a saline taste, and a feeble peculiar odor. Its color varies in different vessels, and according to its degree of accumulation. A thin stratum always appears light red, and the color is deepened by an increase in the thickness of the stratum. In the pulmonary veins, the renal veins, the aorta and its branches, it appears bright red; in the superior and inferior cava? and their branches generally, in the portal veins and the pulmonary arteries, it resembles in color the pulp of the black-heart cherry, or is of a deep- maroon hue. The amount of blood in the adult varies with the bulk and organic activity of the individual, but may be stated to be about equal in weight to one-tenth of the body. When the blood is examined by means of the microscope, spread in a thin layer on a plate of glass, or while circulating in the capillaries, it is observed to consist of a color- less liquid, named the liquor sang'- uinis, and a multitude of minute circular bodies called blood cor'- puscles.1 These are of two kinds, red and colorless corpuscles, of which the former very greatly pre- dominate and give to the blood its color. The red blood cor'puscles2 are so exceedingly small and numerous that a single drop of blood a couple of lines in diameter con- tains about 100,000,000 of them. They are biconcave disks with rounded borders, resembling in shape the familiar article of food commonly known as the water cracker. They vary in diameter, but average about the roo- of a line in breadth, with about a fourth of that thickness. They are elastic, and appear homogeneous, presenting no trace of gran- ular contents or nucleus. Isolated, they appear of a yellowish hue, and it is only by their accumulation that they give rise to the decided red color of the blood. Through evaporation of the containing liquid, as exposed upon the slip of glass on which the blood corpuscles are observed, they assume a 1 Blood globules, or vesicles; globuli, vesiculae, sphaerulse, corpuscula, folliculi, cellulae, particulae, or granula sanguinis. 2 Blood disks Fig. 244. Bed blood corpuscles, highly magnified. 1, cor puscles seen on their broad surface; 2, seen on their edge; 3, rolls of corpuscles, indicating the manner in which they are frequently observed to arrange themselves. The remaining figures more highly magnified: 4, corpuscle seen on its broad surface; 5, seen on its edge; 6, a series of corpuscles; 7, a corpuscle in section, indicating its biconcave dis- coidal form. 340 THE VASCULAR SYSTEM. tuberculated and irregular stellated appearance. In water they swell up, become paler and spherical, and finally burst, exuding a faintly-colored liquid, and leaving a structureless membrane of extreme tenuity behind. When viewed in any quantity on a glass slide beneath the microscope, the blood corpuscles are frequently observed with a disposition to ar- range themselves into piles or columns, a tendency which becomes more marked in the blood of inflammation. The size, form, and constitution of the red blood corpuscles vary in different animals. In all mammals except the camel tribe, they are cir- cular, and have the same constitution as in man, but are generally smaller. In the elephant they are larger, though there is no general relationship between the size of the corpuscles and that of the animal; thus, they are larger in the rat than in the horse, and are smallest in the musk deer. In the camel tribe, birds, reptiles, and fishes, they are elliptical, and are provided with a nucleus. In the batrachian reptiles they are larger than in any other animals; thus, in frogs they measure the g'0 of a line long; in salamanders, ^ ; and in the proteus, ^ of a line. The colorless blood corpuscles1 are comparatively few in number—not more than one to several hundred of the red corpuscles. They are larger than the latter, and measure about the -.ji-- of a line in diameter, are spherical, and have faintly granular contents and a nucleus. Most of the colorless corpuscles are derived from the lymph, which, as will hereafter be seen, pours into the blood-vessels; but some of them also appear to originate in the spleen. According to the observations of T. W. Jones, their nuclei finally become red blood corpuscles. The liquor sang'uinis,2 or blood liquor, is a pale, amber-colored liquid which holds the blood corpuscles in suspension. It is remarkable for its tendency to coagulate or assume the solid condition upon removal from the circulating current, which change depends on its holding fibrin in solution. It is highly important as being the nutritive liquid which is imbibed from the capillaries by all the tissues of the body. When blood is removed from the circulation it ordinarily coagulates or solidifies in a few moments. The coag'ulum or clot3 then slowly con- tracts, and expresses from the mass a clear amber-colored liquid, called the serum, in which the remainder of the clot floats. The se'rum4 is the liquor sanguinis deprived of its fibrin, which in 1 White globules ; leucocytes ; lymph corpuscles. - Plasma; coagulable lymph; plastic lymph; haematoplasma; mucago ; mu- cilage ; intercellular fluid. 3 Crassamentum; cruor; insula; thrombus; placenta sanguinis, or cru- oris; hepar sanguinis. * Ichor sanguinis; haemydor. THE VASCULAR SYSTEM. 341 coagulation entangles the blood corpuscles and thus forms the clot. The relation of the different constituents of liquid and coagulated blood may be understood by reference to the following plan :__ (Corpuscles............................ ■» -j Liquor sanguinis... {™™ ........ * ......... | Coagulated blood. The coagulated fibrin of the blood, examined with the microscope, ex- hibits a fibrillated appearance, thus apparently indicating that the ready coagulation of this material is a step toward organization, or the pro- duction of definite form in a living body. The blood of the hepatic veins, and that which escapes from the torn vessels of the uterine mucous membrane during the menstrual period, ordinarily does not coagulate, thus indicating the absence of fibrin. The composition of the blood varies in the quantity of its chemical ingredients not only in different sexes, ages, individuals, and conditions of health, but also in different parts of the body. A thousand parts of blood by evaporation are found to contain on an average about 790 parts of water and 210 parts of solid materials. The same quantity of blood consists of about 513 parts of blood cor- puscles and 4^7 parts of liquor sanguinis. The chemical constituents of these, according to recent analyses, appear to be as follows :— 513 parts of blood corpuscles contain: contain: Water..................................................... 350 Globulin with Iron..................................... 151 Haematin with Iron................................... 8 Chloride of potassium; phosphates of potasssa, soda, lime, and magnesia; soda, and sul- phate of potassa................................................ 4 f Water..................................................... 440 Albumen................................................. 40 Fibrin..................................................... 3 Chloride of sodium and potassium; phosphates of soda, lime, and magnesia; soda, and sul- phate of potassa.................................... 4 THE HEART. The Heart,1 the great central power of the circulation of the blood, is situated within the cavity of the thorax, inclosed by a fibro-serous sac, the pericardium. It lies between the lungs, resting upon the dia- phragm, and encroaches more on the left than on the right side. Its shape is conical, and its position oblique. It is everywhere free or un- Cor; cardia. 342 THE VASCULAR SYSTEM. attached except at the base, by which it is suspended, through means of the blood-vessels emanating therefrom, to the front of the vertebral column. Fig. 245 Fig. 246. Fig. 215. Front view of the heart, a, base of the ventricles; 6, apex; c, auricular appendage of the right auricle; d, superior cava; e, longitudinal groove separating the ventricles; /, aorta; k, pulmonary artery; ?, right ventricle; to, right auricle; n, left auricle; o, its auricular appendage; the second letter o below indicates the left ventricle. Fig. 246. Posterior or lower surface of the heart. 6, apex of the heart; c, the four pulmonary veins; d, left auricular appendage; e, termination of coronary vefn into the right auricle; /, aorta; k, right and left pulmonary arteries; I, right ventricle; m, right auricle; n, left auricle; o, left ventriclej r, orifice of the inferior cava. The base of the heart is directed upward, backward, and to the right, and reaches from about the fourth to the eighth dorsal vertebra. The apex or point1 is directed downward, forward, and to the left, and is opposite the sixth costal cartilage. The anterior surface is convex, and directed upward and forward; the posterior surface is flattened, and in contact with the diaphragm. Of the two sides or borders the left one2 is the more obtuse, and is directed obliquely upward ; the right one3 is the longer, and is directed obliquely downward. The heart is a hollow muscular organ with a membranous investment and lining. It is brown in color, marked with white membranous streaks or patches, often rendered yellow from the presence of adipose tissue. Its average weight is about ten ounces; its length about five inches, and its breadth about three and a half inches. Its surface exhibits a longi- tudinal and a transverse groove4 which indicate a division of the organ into four parts, named auricles and ventricles. 1 Mucro. 2 Margo obtusus. s Margo acutus. 4 Sulcus longitudinalis, and circularis, or coronalis. THE VASCULAR SYSTEM. 343 The Au'ricles1 are thin-walled cavities forming the basal portion of the heart, and are so called from their fore part being prolonged into an auricular or ear-like appendage. They are separated by a partition,2 and are connected with the great venous trunks—the cavse and pulmo- nary veins, through which they receive the blood from all parts of the body. They communicate with the ventricles, each by a large aperture, the auric'ulo-ventric'ular orifice,3 which is furnished with a remarkable mechanism of valves, allowing the transmission of the blood from the auricles into the ventricles, but preventing it in a reverse course. The Ven'tricles4 are thick-walled cavities, forming the more massive portion of the heart toward the apex. They are separated by a parti- tion,5 and are connected with the great arterial trunks—the pulmonary artery and aorta—by which they send the blood to all parts of the body. Another remarkable arrangement of valves at the mouths6 of the vessels just named prevents the reflux of the blood into the ventricles. The Right Au'ricle7 consists of an oblong portion, the si'nus,8 with a triangular, somewhat indented auric'ular appendage,9 which projects forward to the outer side of the origin of the aorta. Its walls are thin and translucent, but are more thickened at the fore and outer part, and in the auricular appendage, by means of isolated fleshy fasciculi named pectinate muscles.10 When these are present, the interior surface of the auricle is rendered uneven by their prominence, but elsewhere it is smooth. Into the back part of the right auricle the superior and inferior cavse open with a direction forward, and thus produce between them an obtuse angle,11 which is slightly prominent on the interior of the auricle. The orifices of the two veins are unprotected by valves, but from the direc- tion of the two vessels their currents of blood are not opposed, but cross each other as they enter the auricle. On the interior surface of the right auricle, corresponding with the partition separating it from the left auricle, there exists a shallow oval fossa12 or depression, surrounded by a prominent border.13 The fossa 'Atria; sinus; cor venosum; cor membranosum; cavitates innominatae. 2 Septum atriorum. 3 Ostium atrio-ventriculare; 0. ven- triculi venosum; ostium venosum. 4 Ventriculi; cor arteriosum; cormus- culosum; specus cordis. 5 Septum ventriculorum. 6 Ostia arteriosa. 7 Atrium dextrum; a. anterius; a. ve- narum cavarum. 8 Sinus dexter cordis; sinus, or saccus venarum cavarum ; sinus venosus. 9 Auricula cordis dextra. 10 Musculi pectinati; trabecule car- neae. 11 Tuberculum Loweri. 12 Fossa, or fovea ovalis. 13 Annulus ovalis; limbus foraminis ovalis; isthmus Vieussenii. 344 THE VASCULAR SYSTEM. indicates the position during foetal life of an orifice, named the oval fora- men,1 by which the two auricles communicate. The thin, translucent bottom of the fossa, in the foetus, forms a valve2 which prevents a reflux of blood through the oval foramen. Not unfrequently the upper part of the fossa is found to have an oblique slit remaining as part of the free communication of the auricles in foetal life. Anterior to birth, a crescentic, membranous fold, named the Eusta'- chian valve,3 extends from the right of the orifice of the inferior cava, along its anterior border to the oval foramen, and serves to direct the current of blood from that vessel through the foramen. In the adult, the remains of this valve, usually more or less perforated in a reticular manner, are still observable. Between the left extremity of the Eustachian valve and the auriculo- ventricular orifice is situated the aperture4 of the coronary vein, pro- tected by a crescentic valve.5 A number of apertures" of small veins are also to be detected at various points of the interior surface of the right auricle. The right auric'ulo-ventric'ular orifice7 is placed in advance and to the left of that of the inferior cava. It is oval, about an inch in diameter, and has a smooth, slightly prominent border,8 giving attach- ment to the tricuspid valve. The Left Auricle9 has a cuboidal sinus10 and an elongated, indented auricular appendage, projecting forward to the left of the origin of the pulmonary artery. Its walls are thicker, and not so translucent as in the right auricle. The interior surface is smooth, except within the auricular appendage,11 which is provided with pectinate muscles. At the back part of the left auricle the four pulmonary veins open, two on each side; and their orifices are unprotected by valves. At the lower fore part of the cavity is situated the left auriculo-ventricular orifice,12 which is constructed like that in the right side of the heart. The Right Ven'tricle13 is pyramidal, with its base upward and back- 1 Foramen ovale; f. Botale; f. of Bo- tal. 2 Valvula foraminis ovalis. 3 Valvula Eustachii; valvula forami- nis ovalis anterior. 4 Orificium venae magnae coronarioa. 5 Valvula Thebesii. 6 Foramina Thebesii. 7 Ostium atrio-ventriculare dextrum; ostium venosum dextrum. X\nnulus fibro-cartilagineus; tendo cordis venosus; circulus callosus Hal- leri. 9 Atrium sinistrum. 10 Sinus sinister cordis; s. pulmonalis; s., or saccus venarum pulmonalium; s. arteriosus ; atrium cordis sinistrum. 11 Auricula cordis sinistra. 12 Ostium venosum sinistrum. 13 Ventriculus dexter; v. anterior; v. pulmonalis; v. primus; cor venosum; cor pulmonale. THE VASCULAR SYSTEM. 345 Fig. 24' ward, and joined to the corresponding auricle; its apex is downward and forward, and does not quite reach the point of the heart. It occupies more of the front surface of the heart than the left ventricle ; and its walls, much thinner than in the latter, are about the fourth of an inch in thickness. The left wall, which forms the partition1 between the ventricles, bulges into its cavity, so that this ap- pears crescentic in a trans- verse section. The interior surface of the right ventricle is ren- dered exceedingly uneven by numerous projecting, rounded, fleshy fasciculi, named the carneous col- umns.2 These are of va- rious sizes, and pursue different directions — springing from one part of the walls, sinking into another, and producing an intricate interlace- ment. Some of them, larger than the others, and named from their shape pap'illary muscles,3 project from the ven- tricular wall and end in narrow tendinous cords, which are inserted into the free borders of the tricuspid valve. rt The right auric'ulo-ventric'ular orifice4 opens into the ventricle at the lower back part of its base. From its boundary projects a broad membranous fold, irregularly divided into three parts, and named, from this circumstance, the tricus'pid valve.5 The free borders and View of the heart, with the anterior portions of the ven- tricles removed. 1, interior of the right ventricle, exhibiting its carneous columns; 2, left ventricle; 3, right auricle; 4, left auricle; 5, aorta; 6, 7, 8, tricuspid valve; 9, papillary muscles at- tached by tendinous cords to the tricuspid valve; 10, mitral valve; 11, pulmonary artery laid open; 12, one of the semilunar valves: the other two are seen in section on each side of the former: 13, sinus or dilatation of the artery behind one of the semilunar valves. 1 Septum ventriculorum. 2 Columnar carneae; trabeculae carnese; columnar, trabeculae, trabes, funes, fasci- culi teretes, lacerti, or lacertuli cordis. 3 Musculi papillares. * Ostium atrio-ventriculare dextrum. 5 Valvula tricuspidalis; valvulae tri- cuspides; v. trisulcae ; v. triglochines. 346 THE VASCULAR SYSTEM. contiguous under surface of the valve are attached by numerous tendin- ous cords,1 as above indicated, to the papillary muscles, and also to inter- vening points of the interior surface of the ventricle. When the valve is open, the divisions project into the cavity of the ventricle in contact with its sides. In structure, both the tricuspid valve and tendinous cords consist of doublings of the lining membrane of the heart, strengthened by included fibrous tissue. From the anterior angle of the base of the right ventricle, the pul- monary artery has its origin. The orifice2 of this vessel is provided with three semilunar valves, and the interior surface of the ventricle conducting to it is smooth, so that no impediment is presented to the current of blood in its passage to the artery. The semilunar valves3 of the pulmonary artery, as expressed in the name, are three crescentic membranous doublings arranged in a circle. Their convex border is attached around the boundary of the orifice of the artery, and their free border is directed into the latter. Behind each valve the artery is dilated into a shallow pouch or sinus,4 which pre- vents the valve, when open, from adhering to the side of the artery, and allows the blood in its reflux to get behind the valve and press it down, so as to meet the others and thus close the orifice. The semilunar valves are doublings of the vascular lining membrane, strengthened by included fibrous tissue. The latter forms a nodule5 at the middle of the free border of the valves, which serves as a common central point of contact when they are closed. Between the nodule and the ends of each valye, just within the position of the free border, there exists a pair of thin lunated spaces,6 arising from a deficiency of the fibrous basis of the valve. When the valves are shut, these spaces are applied by their opposed surfaces to one another, and completely pre- vent the entrance of blood into the ventricle; while the force of the reflux is sustained by the stronger portions of the valves. The Left Ven'tricle7 is conical, with its base connected to the corre- sponding auricle, and its apex forming the point of the heart. It is longer, and contributes more to the posterior surface of the heart than 1 Chordae tendinea?. 2 Ostium arteriosum dextrum. 3 Valvulae semilunares; v. sigmoideae; processus sigmoides. 4 Sinus of Valsalva; sinus pulmonalis. 5 Corpusculus, globulus, or nodulus Arantii. or Morgagni; corpusculuin sesamoideum. 6 Lunulae. 7 Ventriculus sinister; v. aorticus; v. posterior; v. secundus ; cor arteriosum: c. aorticum. THE VASCULAR SYSTEM. 347 the right ventricle. Its walls are three times as thick as those of the latter, and its transverse section is circular. Its interior surface is fur- nished with more numerous and stronger carneous columns, which further have a more complex arrangement; and its two or three pap'- illary muscles are also more robust. , The left auric'ulo-ventric'ular orifice,1 placed at the back part of the *igt*t ventricle, is provided with a pair of membranous folds, constituting the mi'tral valve.2 This has the same mechanism and purposes as the tricuspid valve, but is stronger. In advance and to the right of the orifice just indicated, is the origin of the aorta, which is provided with semilunar valves, identical in character with those of the pulmonary artery, and differ only in being stronger. STEUCTURE OF THE HEART. As previously mentioned, the heart is muscular, with an exterior in- vestment of serous membrane derived from the pericardium, and with its cavities lined by the endocar'dium. This is a thin, translucent membrane, continuous with that of the blood-vessels. Doublings of the endocardium, thickened with intervening fibrous tis- sue, constitute the various valves of the interior of the heart and the vascular orifices communicating therewith. In structure the endocar- dium consists of an epithelium and a fibro-elastic layer. The epithe- lium is composed of a layer of elongated, flattened, polygonal, pave- ment-like cells. The fibro-elastic layer adheres closely to the muscular structure beneath, and appears to be defined next the epithelium by an exceedingly delicate basement membrane. At the auriculo-ventricular orifices, and those of the pulmonary artery and aorta, the fibro-elastic tissue forms a slightly prominent ring,3 which gives attachment to the valves, and affords a point4 of departure for most of the muscular fibres of the heart. The muscular structure of the heart is composed of transversely striated fibres, which exhibit the peculiarity of anastomosing, or of being connected by means of numerous short oblique offsets, as rep- resented in figure 248. The muscular fibres are much smaller than those of the voluntary muscles, and are not collected into bundles as in 1 Ostium atrio-ventriculare sinistrum; ostium venosum sinistrum. 2 Valvula mitralis; v. bicuspidalis; valvulae mitrales; v. bicuspidatae; v. episcopates. 3 Tendo cordis venosus et coronarius; annulusfibro-cartilagineus; circulus cal- losus Halleri. 4 Punctum fixum. 348 THE VASCULAR SYSTEM. Striated muscular tissue of the heart, highly magnified. the latter, but are closely approximated with comparatively little inter- vening connective tissue. The arrangement of the muscular fibres of the heart is exceedingly complex. In the auricles a thin layer of transverse muscular fibres encircles both together. Beneath this layer is another, thicker in the left than the right auricle, consist- ing of loop-like fibres crossing the direction of the former, and at- tached by their ends to the fibrous rings of the auriculo-ventricular orifices. Other muscular fibres are arranged in circles around the origin of the great veins and the auricular appendages. In the ventricles, some of the muscular fibres are common to both, while others belong exclusively to each—the left one possessing many more than the right one. Most of the muscular fibres may be traced from the fibrous rings of the auriculo-ventricular orifices, and those of the pul- monary artery and aorta. Those seen on the fore part of the heart pursue a course downward, from right to left; while those on the back of the heart take a more longitudinal course in the opposite direction. At the apex of the heart they penetrate in a whorl to the interior of the ventricles, where they terminate in the carneous columns, some of them forming the papillary muscles, and others ascending to the point from which they started, thus describing in their course a twisted loop like the Greek letter «. The arteries supplying the structure of the heart are the right and left coronary. The course of their trunks will be given hereafter. Their branches are numerous, and the capillaries in which they termi- nate generally pursue a course parallel to the direction of the mus- cular fibres, as in other muscular structures. Most of the returning blood is emptied directly into the right auricle by the great coronary vein, and the remainder is returned to the same cavity by a number of minute veins. The lymphatics are numerous, the principal ones following the direc- tion of the coronary veins along the grooves of the heart. Those of the right and front of the heart for the most part join the anterior mam- mary lymphatic glands; those of the left and back of the heart join the bronchial glands. The nerves of the heart are numerous but small, and are derived from the cardiac plexuses of the pneumo-gastric, spinal, and great sympa- thetic nerves. THE VASCULAR SYSTEM. 349 THE PERICARDIUM. The Pericar'dium1 is the fibro-serous sac inclosing the heart, and is attached by connective tissue to the pleura of each side, and the tendin- ous centre of the diaphragm below. It has the form of the heart, a bluish-white color, and consists of two layers. The exterior fibrous layer2 is a strong inextensible membrane com- posed of interlacing bundles of fibrous tissue, generally pursuing a lon- gitudinal course. It embraces the origin of the great blood-vessels at the base of the heart, and becomes continuous with their external tunic. The internal serous layer3 of the pericardium has the general ar- rangement and constitution of serous membranes generally. One por- tion closely invests the heart and the commencement of the great blood- vessels at its base, from which it is reflected on the interior of the fibrous layer of the pericardium. The cavity of the pericardium presents smooth, opposed surfaces, bathed with a serous fluid, the pericardial liquor,4 which facilitates the movements of the heart. MECHANISM OF ACTION OF THE HEART. The heart, by alternate contraction5 and dilatation,6 is the motive power in the circulation of the blood, though there are also several other means which facilitate the latter. The motive power of the heart resides in its muscular walls, which, in the different cavities, correspond in strength with the distance to which the blood is to be sent. Thus, as the auricles transmit the blood only into the adjacent cavities, they possess thin walls, while those of the right ventricle, which sends the blood to the lungs, are thick—and those of the left ventricle are thickest, because this por- tion of thejieart transmits the blood to the remotest parts of the body. TheTpeciiWe' muscles and carneous columns are accessory powers to the general walls, but are always so situated as not to interfere by their 1 Pericardion; capsule, or sac of the heart; peribole; membrana cor circum- flexa; involucrum, area, arcula, capsa, capsula, camera, indumentum, pannicu- lus, membrana, theca, saccus, sacculus, scrotum, vagina, vesica, thalamus rega- lis, bursa, or amphiesma cordis. 2 Fibrous pericardium. 3 Serous pericardium. 4 Liquor pericardii; aqua, humor, lympha, or urina pericardii; hydrocar- dia. 5 Systole; systalsis, contractio, con- strictio, augustatio, submissio, or mica- tio cordis. 6 Diastole; relaxatio, or remissio cor- dis ; motus cordis diastalticus. 350 THE VASCULAR SYSTEM. projection with the course of the currents of blood passing through the heart. Thus the spaces between the two cavae and the four pulmonary veins are smooth, as are, likewise, the approaches to the auriculo-ventricular orifices, the pulmonary artery, and aorta. The uniform direction of the circulation of the blood is maintained by the admirable mechanism of valves situated in the heart, at the origin of the great arterial trunks, and in the veins. The auricles dilate and receive the blood simultaneously1—the right one through the two cavae and the coronary vein, the left one through the four pulmonary veins. The auricles then contract together, and transmit the blood through the auriculo-ventricular orifices into the ven- tricles. These becoming distended now contract2—the right one sending dark blood through the pulmonary artery to the lungs, the left one sending bright red blood through the aorta to the body generally. In the contraction of the ventricles the auriculo-ventricular orifices are closed by the tricuspid and mitral valves, which are pressed with their edges together by the reflux of blood, and are kept stretched by the tendinous cords, just as the sail of a boat is kept stretched against the wind by the sheet line. While the ventricles contract the auricles are refilling.3 The blood forced by the ventricles into the pulmonary artery and aorta pushes onward the column of blood which already fills these vessels, and likewise causes their expansion. The arteries subsequently react or contract upon their contents, and thus continue the onward impulse of the current of blood, while its re- flux closes the semilunar valves and prevents regurgitation into the ven- tricles. This alternate expansion and contraction of the arteries con- stitutes their pulsation, or the pulse. The number of dilatations and contractions of the auricles and ventricles corresponds with the pulsations of the arteries — in the healthy adult amounting to from sixty to eighty in the minute. The action of the heart gives rise to an impulse which may be felt on the left side of the thorax below the nipple, opposite the interspace of the fifth and sixth costal cartilages. In the circulation of the blood from the heart to the lungs and body generally, and then back again, it performs two circles. The smaller of these, named the lesser or pulmonary circulation, is from the right ven- tricle through the pulmonary artery to the lungs, and back again by the pulmonary veins to the left auricle. The larger circle, named the greater 1 Synchronous action of the auricles. 8 Isochronous action of the ventricles 2 Synchronous action of the ventricles. and auricles. THE VASCULAR SYSTEM. 351 or systemic circulation, is from the left ventricle through the aorta to all parts of the body, and thence back by the two cavae to the right auricle. Following the course of the blood in succession, and starting from the right auricle, this receives the dark blood of the body through the supe- rior and inferior cava. Contracting, the right auricle sends the blood into the corresponding ventricle, which in turn sends it through the pul- monary artery to the lungs. Here acquiring a bright-red hue, the blood returns through the four pulmonary veins to the left auricle, which then transmits it to the left ventricle, to be propelled through the aorta to all parts of the body, from whence it regains the heart by the two cavae. THE ARTERIES. The Ar'teries consist of two great trunks and their branches. One of these trunks is the aorta, by whose branches blood is conveyed to all parts of the body for the nutrition of the organs; the other is the pul- monary artery, which distributes the blood through the lungs to be aerated. THE AORTA. The Aor'ta1 is the main trunk of the arterial system supplying blood to the body. It springs from the left ventricle of the heart, ascends and arches obliquely from the right to the left of the vertebral column, upon which it then descends to the fourth lumbar vertebra, and there divides into the common iliac arteries. The first portion of its course is named the arch of the aorta; and the descending portion2 is named, from the cavities through which it passes, the thoracic and abdominal aorta. THE ARCH OF THE AORTA. The Arch of the Aorta3 ascends from the heart with a slight incli- nation toward the right side, curves obliquely backward to the left side over the right pulmonary artery and left bronchus, and descends to the left side of the third dorsal vertebra, where it becomes the thoracic aorta. Its commencement is concealed by the root of the pulmonary artery and right auricular appendage, and when exposed is observed to present a bulbous appearance,4 due to the dilatations5 behind the semilunar valves. 1 Arteria magna; a. maxima; a. eras' sa; haemal axis. 2 Aorta descendens. 8 Arcus aortae. * Bulbus aortae. 5 Sinuses of Valsalva; lesser sinuses of Valsalva. 352 THE VASCULAR SYSTEM. The ascending portion1 of the Fig. 249. The aorta. 1, arch of the aorta; 2, thoracic aorta; 3, abdominal aorta; 4, innominate artery; 5, right common carotid; 6, right subclavian; 7, left common carotid; 8, left subclavian; 9, bron- chial artery, a small branch of the aorta; 10, oeso- phageal arteries; 11, intercostal arteries of the right side ; 12,of the left side; 13, phrenic arteries; 14, cceliac axis; 15, coronary artery; 16, splenic artery; 17, hepatic artery; 18, superior mesenteric artery; 19, supra-renal arteries ; 20, spermatic ar- teries ; 21, inferior mesenteric artery; 22, lumbar arteries; 23, common iliac arteries; 24, middle sa- cral artery, a, aortic orifice of the diaphragm; 6, articulation of the head of the ribs; c, anterior scalene muscle. of the semilunar valves, and supply arch is in relation behind with the right pulmonary artery and veins, to the right with the superior cava, and to the left with the trunk of the pul- monary artery. The transverse portion of the arch rests in the bi- furcation of the pulmonary artery; is in relation above with the left innominate vein, behind with the division of the trachea, and in front with the upper part of the sternum. The descending portion of the arch is in relation with the oesophagus and thoracic duct to the right, and with the root of the left lung to the left and in front. Frequently the right portion of the aortic arch exhibits a conspicu- ous dilatation,2 resembling an in- cipient aneurism, but which is a natural condition, though not a constant one. From the summit of the arch of the aorta spring forth the large vessels which supply the head and upper extremities, and much reduce the diameter of the descending por- tion of the arch. The branches given in succession from the arch of the aorta are as follow:— The right coronary artery. The left coronary artery. * The innominate artery. *> j The right common carotid artery. The right subclavian artery. The left common carotid artery. The left subclavian artery. The coronary arteries arise from the aorta, just above the position the walls of the heart. The other 1 Aorta ascendens. 2 Sinus of Valsalva; greater sinus of Valsalva. THE VASCULAR SYSTEM. 353 three branches spring from the summit of the arch in close succession, and are the large vessels which supply the head and upper extremities. THE CORONARY ARTERIES. The Right Cor'onary artery1 arises from the aorta just above its right semilunar valve, and winds along the groove between the right auricle and ventricle, until it reaches the posterior median groove of the ventri- cles, along which it proceeds to the apex of the heart, and anastomoses with the left coronary artery. It supplies the right side of the heart and the posterior portion of the left ventricle. The left Cor'onary artery2 arises from the left side of the aorta and passes forward between the pulmonary artery and the left auricular ap- pendage, and divides into two branches. One of these descends the anterior median groove of the ventricles to the apex of the heart, where it anastomoses with the right coronary artery. The other branch winds along the groove between the left auricle and ventricle to the back of the heart, where it anastomoses with the right coronary artery. THE INNOMINATE ARTERY. The Innom'inate artery3 is the first of the three large vessels spring- ing from the summit of the arch of the aorta, and corresponds with the other two in supplying branches to one-half of the head and neck, and one upper extremity. It is about an inch and a half in length ; ascends obliquely toward the right side, in front of the trachea and behind the left innominate vein, and divides into the right subclavian and right common carotid arteries opposite the right sterno-clavicular articula- tion. As an occasional variation, the innominate artery gives off the left common carotid artery ; more frequently it is represented by its ordinary divisions springing directly from the aorta, as in the case of the corre- sponding arteries of the left side. 1 Arteria coronaria dextra. - A. coronaria sihistra. 3 A. innominata; a. annonyma; a. brachio-cephalica; truncus brachio-cephalicus; right subclavian artery. 23 354 THE VASCULAR SYSTEM. THE COMMON CAROTID ARTERY. The Right Common Carot'id artery1 is one of the divisions of the innominate artery, and ascends the neck to the upper border of the larynx, where it divides into the external and internal carotid arteries. The Left Common Carot'id artery2 is derived from the arch of the aorta next in succession to the innominate artery. It is longer, deeper, and more vertical in its ascent than the former, and divides in the same position and manner. Fig. 250. Left common carotid dividing into the external and internal carotid arteries. 1, common carotid artery; 2, internal carotid; 3, external carotid; 4, superior thyroid; 5, lingual; 6, pharyngeal artery; 7, facial; 8, inferior palatine and tonsillar arteries; 9, submaxillary; 10, submental; 11, occipital; 12, posterior auricular; 13, parotid branches; 14, internal maxillary; 15, temporal artery; 16, subclavian artery ; 17, axillary; 18, vertebral artery; 19, thyroid axis; 20, inferior thyroid giving off the ascending cervical; 21, transverse cervical; 22, supra-scapular; 23, internal mammary artery. The Common Carot'id arteries,3 in ascending the neck, rest upon the muscles in front of the cervical vertebrae. At their inner side the tra- chea, larynx, and oesophagus are situated; at their outer side is the 1 A. carotis communis dextra; a. c. tides; a. caroticae; a. capitales; a. ce- primitiva dextra. phalicoe ; a. jugulares; a. soporales; a. 2 A. c. c. sinistra; a. c. p. sinistra. somniferae ; a. lethargicae ; a. apoplecti- 3 Primitive carotid arteries; a. caro- cae. THE VASCULAR SYSTEM. 355 internal jugular vein, which is inclosed in the same sheath, with the pneumogastric nerve interposed. Behind them is the great sympathetic nerve; and in front they are crossed by the omo-hyoid muscle, and cov- ered by the sterno-mastoid muscle. They give off no branches until they reach the upper margin of the larynx, where they divide into the external and internal carotid arteries. THE EXTERNAL CAROTID ARTERY. The External Carot'id artery1 on each side supplies all the parts of the head, with the exception of the brain and the contents of the orbits. Commencing opposite the upper border of the larynx, it ascends nearly vertically to the space between the neck of the lower jaw and the auditory meatus, where it divides into the temporal and internal maxillary arteries. It lies in front and to the inner side of the internal carotid artery, close to the pharynx. In the first part of its course it is covered only by the cervical fascia, subcutaneous cervical muscle, and skin; then is crossed by the stylo-hyoid and digastric muscles and the hypoglossal nerve; and afterwards passes through the substance of the parotid gland, in which it is crossed by the facial nerve. The branches given off by the external carotid artery are as follow :— 1. Superior thyroid artery. 2. Lingual artery. 3. Pharyngeal artery. 4. Facial artery. 5. Occipital artery. 6. Posterior auricular artery. 7. Muscular branches. 8. Parotid branches. 9. Temporal artery.. 10. Internal maxillary artery. 1. The Superior Thy'roid artery2 comes off from the front of the ex- ternal carotid, just above its commencement, and descends obliquely for- ward and inward, to the thyroid body, in which it is mainly distributed; anastomosing with the other arteries of that organ. In its course it is crossed by the omo-hyoid muscle, and gives off the following named branches:— a. Hyoid branch. b. Muscular branches. c. Laryngeal artery. 1 A. carotis externa; a. carotis facialis; a. pericephalica. 2 A. thyroidea superior; a. laryngea superior; a. gutteralis superior. 356 THE VASCULAR SYSTEM. a. The Hy'oid branch1 is a small vessel running along the side of the hyoid bone, and supplying the contiguous parts. It is frequently a branch of the lingual artery. b. The Muscular branches2 are distributed to the sterno-mastoid muscle and the depressors and elevators of the hyoid bone and larynx. c. The Larynge'al artery3 pierces the thyro-hyoid membrane, and supplies the small muscles and mucous membrane of the larynx. 2. The Lin'gual artery,4 larger than the preceding branch of the carotid, comes off next to it, on a line with the side of the hyoid bone. After advancing just above the great horn of the latter, it ascends between the hyo-glossal muscle and the middle constrictor of the pharynx, to the under part of the tongue, along which it proceeds to the tip. Its branches are as follow :— a. Dorsal lingual artery. b. Sublingual artery. c. Ranine artery. a. The Dorsal lin'gual artery,5 frequently represented by several small branches, supplies the root of the tongue. b. The Sublin'gual artery6 passes between the mylo-hyoid muscle and the sublingual gland, and supplies both with branches. c. The Ran'ine artery7 is the continuation forward of the lingual, between the hyo-glossal kand genio-glossal muscles, to the tip of the tongue. It has a tortuous course ; and at the side of the fraenum of the tongue is covered only by the mucous membrane. 3. The Pharynge'al artery8 is a long, narrow vessel, derived from the inner side of the external carotid artery, nearly on a level with the pre- ceding branch. It lies concealed in the ordinary view of the vessels, and ascends deeply in the neck, on the surface of the pharynx, to the base of the skull. In its course it supplies branches to the pharynx,9 soft palate, and tonsils, the muscles in front of the cervical vertebrae, and the nerves which pass through the jugular foramen. It also gives small branches10 to the dura mater through the jugular and lacerated foramina. 1 Ramus hyoideus. 2 R. musculares. 3 R. laryngea; r. 1. superior. 4 A. lingualis. 5 A. dorsalis linguae. 6 A. sublingualis. 7 A. ranina; a. profunda linguae. 8 A. pharyngea; a. pharyngea ascen- dens, or inferior. 9 Rami pharyngei. 10 A. meningeal posteriores THE VASCULAR SYSTEM. Fig. 251. The external carotid artery and its branches. 1, right common carotid ; 2, internal carotid ; 3, ex- ternal carotid; 4, superior thyroid; 5, lingual; 6, facial; 7, submental; 8, inferior coronary; 9, superior coronary; 10, muscular branches; 11, lateral nasal artery; 12, angular artery; 13, occipital artery; 14, descending cervical; 15, muscular branch; 16, posterior auricular artery; 17, parotid branches; 18, in- ternal maxillary; 19, temporal; 20, transverse facial; 21, anterior auricular; 22, supra-orbital; 23, middle temporal; 24, anterior temporal; 25, posterior temporal artery. 4. The Fa'cial artery1 comes from the external carotid just above the lingual, and is about the same size as this. It passes upward and forward through the submaxillary gland, curves over the base of the lower jaw in advance of the insertion of the masseter muscle, and ascends upon the face in a tortuous manner to the angle of the mouth, and thence to the inner angle of the eye. Below the jaw it passes beneath the stylo-hyoid and digastric muscles; at the base of the jaw is only covered by the skin and subcutaneous cervical muscle; and at the angle of the mouth is beneath the depressor of the oral angle and the zygomatic muscles. Its principal branches are as follow :— a. Inferior palatine artery. b. Tonsillar artery. c. Submaxillary branches. d. Submental artery. 1 A. facialis; a. maxillaris externa; a. labialis; a. angularis; a. palato-labialis. 358 THE VASCULAR SYSTEM. e. Inferior coronary artery. /. Superior coronary artery. g. Muscular branches. h. Lateral nasal artery. i. Angular artery. a. The Inferior pal'atine artery1 ascends at the side of the pharynx, and gives branches to the internal pterygoid muscle, the styloid muscles, the tonsil, Eustachian tube, and muscles and mucous membrane of the soft palate. It is sometimes a branch of the pharyngeal artery. 6. The Ton'sillar artery2 ascends at the side of the pharynx to the fauces and tonsil. c. The Submaxillary branches3 are small vessels which supply the submaxillary gland. d. The Submen'tal artery,4 larger than any of the preceding branches, passes forward between the digastric and mylo-hyoid muscles, and winds over the chin to anastomose with the inferior coronary artery. In its course it supplies the contiguous muscles, the submaxillary gland, and the chin. e. The Inferior cor'onary artery5 is derived from the facial as it ap- proaches the angle of the mouth. Passing forward and upward, beneath the depressor of the oral angle, it enters the orbicular muscle of the lower lip, and pursues a tortuous course to join its fellow of the opposite side. /. The Superior cor'onary artery6 comes from the facial at the angle of the mouth, and pursues a tortuous course in the upper lip to join the corresponding vessel of the other side. Besides supplying the lip, it gives a branch to the partition of the nose.7 g. The Muscular branches8 are small and variable vessels supplying the depressor of the oral angle, the masseter, buccinator, zygomatic, and other muscles. h. The Lateral na'sal artery,9 frequently represented by several smaller branches, passes inward, and supplies the side of the nose. i. The Angular artery,10 the termination of the facial, inosculates with branches of the ophthalmic artery. 1 A. palatina inferior, or ascendens; a. pharyngo-palatina. 2 A. tonsillaris. s Rami submaxillares; r. glandulares. * A. submentalis. 5 A. coronaria inferior; a. labialis in- ferior. 6 A. coronaria superior; a. labialis su- perior. 7 A. septi narium. 8 Rami musculares; r. buccales, mas- seteric^ etc. 9 A. nasalis lateralis, or externa and ra- mi pinnales and dorsales nasi. 10 A. angularis. THE VASCULAR SYSTEM. 359 5. The Occip'ital artery1 springs from the back part of the external carotid, about as high as the former branch, and passes backward beneath the muscles attached to the mastoid process of the temporal bone. Pursuing its course between the splenius and complex muscles, at the back of the neck, it pierces the cranial attachment of the trapezius muscle, and ascends beneath the skin of the occipital region, where it divides into many branches, which anastomose with the posterior auric- ular and temporal arteries. In its course it gives off the following branches:— a. Muscular branches. b. Descending cervical artery. c. Meningeal branch. a. The Muscular branches2 go to the sterno-mastoid, digastric, and other muscles. 6. The Descending cer'vical artery3 passes down the back of the neck, and divides into branches which supply the complex, splenius, and other muscles. c. The Menin'geal branch4 is a small vessel ascending through the jugular foramen to be distributed to the dura mater. 6. The Posterior Auric'ular artery5 is a small vessel which comes off from the external carotid a short distance above the former branch. It ascends between the lower part of the parotid gland and the mastoid process to the side of the head behind the ear, where it divides into branches supplying the latter, and anastomosing with the occipital artery. In its course it gives off a small but important branch, as follows :— a. The Sty'lo-mastoid artery,6 which enters the foramen of that name, and ascends to supply the tympanum and its contents, and the mastoid sinuses. 7. The Muscular branches7 of the external carotid, irregular in size and disposition, supply the sterno-mastoid, masseter, and pterygoid muscles. 8. The Parot'id branches8 are small vessels given to the parotid gland in the course of the carotid artery through it. 1 A. occipitalis. 2 Rami musculares; r. cervicales; r. sterno-mastoideus, etc. 3 A. cervicalis descendens; a. cervicalis superior profunda and superficialis; a. princeps cervicis. 4 A. meningea; a. m. posterior externa; ramus meningeus. 5 A. auricularis posterior. 6 A. stylo-mast oidea. 7 Rami musculares; ramus sterno-mas- toideus, massetericus, etc. 8 R. parotidei. 360 THE VASCULAR SYSTEM. 9. The Tem'poral artery,1 the apparent continuation of the external carotid, ascends through the parotid gland in front of the ear to the temple, where it is situated between the skin and temporal fascia. A short distance above the zygoma it divides into two branches, which ramify on the side of the head immediately beneath the integument. The branches of the temporal artery, including the terminal ones, are as follow :— a. Transverse facial artery. b. Anterior auricular arteries. c. Supra-orbital artery. d. Middle temporal artery. e. Anterior temporal artery. /. Posterior temporal artery. a. The Transverse fa'cial artery2 arises from the temporal, while it is involved in the parotid gland, and passes across the masseter muscle, between the zygoma and parotid duct, to the upper part of the cheek. It supplies the parotid gland, masseter, palpebral orbicular, and other muscles, and anastomoses with branches of the ophthalmic and facial arteries. It is often represented by several smaller branches. b. The Anterior auric'ular arteries3 are several small vessels dis- tributed to the front of the ear and the auditory meatus. c. The Supra-orb'ital artery4 arises above the zygoma and ascends to the supra-orbital margin, where it anastomoses with branches of the ophthalmic and anterior temporal arteries. d. The Middle tem'poral artery5 perforates the temporal fascia, just above the zygoma, and is distributed to the temporal muscle. e. The Anterior tem'poral artery,6 one of the terminal branches of the temporal, curves forward and upward upon the temple and forehead, and divides into numerous branches, supplying the scalp and contiguous muscles, and anastomosing with branches of the ophthalmic and posterior temporal arteries. /. The Posterior tem'poral artery,7 larger than the former, turns upward and backward at the side of the head, and divides into numerous branches, anastomosing with the anterior temporal, posterior auricular, and occipital arteries. 1 A. temporalis; a. crotaphitica. s A. temporalis media. 2 A. transversa faciei. 6 \ temporalis anterior; a. t. superfi- 3 A. auriculares anteriores; a. auricu- cialis anterior; a t. frontalis ; a. t. in- lares anteriores inferiores, and a. auricu- terna. laris anterior superior. 7 A. temporalis posterior; a. t. superfi- * A. supra-orbitalis ; a. supra-orbitalis cialis posterior; a. t. occipitalis: a.t. ex- externa ; a. zygomatico-orbitalis. terna. THE VASCULAR SYSTEM. 361 10. The Internal Max'illary artery,1 the larger division of the exter- nal carotid, passes behind the neck of the jaw, horizontally forward be- tween the pterygoid muscles. It then ascends a short distance, and again turns forward and inward to the upper part of the pterygo-maxil- lary fossa, where it divides into two terminal branches—the descending palatine and the spheno-palatine arteries. Including the latter, the internal maxillary gives off the following branches:— a. Tympanic artery. b. Great meningeal artery. c. Small meningeal artery. d. Inferior maxillary artery. e. Muscular branches. /. Superior maxillary artery. g. Infra-orbital artery. h. Descending palatine artery. i. Spheno-palatine artery. a. The Tym'panic artery,2 a small vessel given from the internal maxillary near its origin, ascends behind the maxillary articulation and passes through the glenoid fissure to be distributed to the tympanum. 6. The Great menin'geal artery3 comes from the internal maxillary, a short distance from the preceding, and ascends to the spinous foramen of the sphenoid bone, through which it enters the middle cerebral fossa of the cranial cavity. It here curves forward and outward between the dura mater and the temporal bone, and divides into two branches, which ascend and ramify between the membrane just mentioned and the parietal bone. It produces the arborescent channels on the interior surface of the latter, and supplies both the dura mater and the cranial vault. In its course it gives branches to the elevator and tensor muscles of the palate, and to the semilunar ganglion of the trifacial nerve. c. The Small menin'geal artery,4 frequently a branch of the preced- ing, enters the cranium through the oval foramen, and supplies the dura mater of the middle cerebral fossa. d. The Inferior max'illary artery5 comes from the internal maxillary nearly opposite the meningeals, and descends, in company with the infe- rior dental nerve, to enter the dental canal of the lower jaw. In its 1 A. maxillaris interna: a. gutturo- maxillaris. 2 A. tympanica. 3 A. meningea magna; a. m. media; a. m. spinosa; a. spinosa; a. spheno- spinosa; a. dura? matris media maxima. 4 A. meningea parva. 5 A. maxillaris inferior; a. dentalis, or alveolaris inferior. 362 THE VASCULAR SYSTEM. Fig. passage through this canal it gives off the fine dental arteries1 to the teeth, and finally emerges at the mental foramen to terminate in the chin,2 where it anastomoses with the submental and inferior coronary arteries. Before entering the dental canal it gives off a branch3 which runs along the mo- lar ridge and supplies the gum and the mylo-hyoid muscle. e. The Muscular branches,4 given off be- tween the pterygoid mus- cles, usually consist of two5 to the latter, two6 to the temporal muscle, one7 to the masseter, and one8 to the buccinator. /. The Superior max'- illary artery9 is given off from the internal maxil- lary as it escapes from be- tween the pterygoid mus- cles. It descends upon the tuberosity of the max- illary bone, and gives off branches to the gum, and the posterior dental ar- teries which enter small foramina of the bone to supply the maxillary sinus and the molar teeth. g. The Infra-orb'ital artery10 arises near the preceding, and enters the infra-orbital canal, along which it runs to the face. In its course through the canal it gives off the anterior dental arteries to the front teeth, and small branches to the inferior straight and oblique muscles of the orbit. Internal maxillary artery. 1, right common carotid; 2, in- ternal carotid; 3, external carotid; 4, superior thyroid; 5, lin- gual; 6, facial; 7, occipital; 8, posterior auricular; 9, parotid branch; 10, temporal artery; 11, internal maxillary; 12, tym- panic; 13, the great and small meningeal arteries from a common branch; 14, inferior dental artery; 15, muscular branches; 16, superior maxillary artery giving off the posterior dental arteries; 17, 18, infra-orbital artery. 1 A. dentales; rami alveolares. 2 A. mentalis. 3 A. mylohyoidea. 4 Rami musculares. 5 A. pterygoidese. 6 A. temporales profunda; a. tempo- ralis profunda posterior and anterior. 7 A. masseterica. 8 A. buccinatoria; a. buccalis. 9 A. maxillaris superior; a. supra- maxillaris ; a. dentalis; a. alveolaris su- perior. 10 A. infra-orbitalis. THE VASCULAR SYSTEM. 363 On the face it gives branches to the lower eyelid and upper lip, and anastomoses with branches of the facial and ophthalmic arteries. h. The Descending pal'atine artery,1 one of the terminal branches of the internal maxillary, descends through the posterior palatine canal and is distributed to the soft and hard palate. One2 of its branches reaches the front of the hard palate, and anastomoses, through the ante- rior palatine foramen, with the arteries of the nose. Another branch,3 near the origin of the artery, turns back through the pterygoid canal and reaches the top of the pharynx. i. The Spheno-pal'atine artery,4 the second division of the internal maxillary, passes into the cavity of the nose through the spheno-pala- tine foramen, and, after sending a small branch5 backward through the pterygo-palatine canal to the upper part of the pharynx, divides into two branches. One6 of these is distributed to the lateral wall and floor of the nose, and to the maxillary sinus. The other branch7 descends upon the partition of the nose to which it is distributed, anastomosing, through the anterior palatine foramen, with a branch of the descending palatine artery. THE INTERNAL CAROTID ARTERY. The Internal Carot'id artery,8 the second division of the common carotid artery, destined to supply the brain and contents of the orbit, ascends in a nearly straight line to the carotid canal of the tem- poral bone. Winding through this canal, it enters the cranial cavity above the lacerated foramen, and proceeds forward along the side of the body of the sphenoid bone to the anterior clinoid process, where it turns upward to the fissure separating the anterior and middle lobes of the brain, and divides into the anterior and middle cerebral arteries. In the neck the internal carotid gives off no branches, and rests against the muscles in front of the cervical vertebrae. To its inner side is the pharynx; in front of it the external carotid artery; and externally and behind are the internal jugular vein and the last four cerebral nerves. At the side of the body of the sphenoid bone, it is inclosed in the lower wall of the cavernous sinus, and at the anterior clinoid process pierces the dura mater to reach the brain. 1 A. palatina descendens; a. palatina superior; a. pterygo-palatina. 2 A. palatina anterior. 3 A. Vidiana. 4 A. spheno-palatina; a. nasalis pos- terior. 5 A. pharyngea suprema, or descen- dens. 6 A. nasalis posterior externa, or late- ralis. 7 A. septi narium posterior. H A. carotis interna; a. carotis cere- bralis ; a. cerebralis; a. encephalica. 364 THE VASCULAR SYSTEM. The branches of the internal carotid artery are as follow :— 1. Ophthalmic artery. 2. Posterior communicating artery. 3. Choroid artery. 4. Anterior cerebral artery. 5. Middle cerebral artery. 1. The Ophthal'mic artery1 springs from the internal carotid, within the position of the anterior clinoid process, immediately after it pierces Fig. 253. Arteries op the interior of the cranium. 1. internal carotid arteries; 2, ophthalmic artery; 3, pos- terior communicating arteries; 4, anterior cerebral arteries; 5, anterior communicating artery; 6, mid- dle cerebral arteries; 7, lachrymal; 8, short ciliary arteries piercing the back part of the eyeball; 9, cen- tral retinal piercing the optic nerve to reach the interior of the eyeball; 10, muscular artery; 11, frontal and nasal artery; 12, vertebral arteries; 13, posterior meningeal artery;. 14, posterior spinal artery; 15, anterior spinal arteries conjoining in a single one; 16, inferior cerebellar arteries, 17 basilar artery formed by the union of the vertebrals; 18, internal auditory; 19, superior cerebellar; 20, posterior cerebral arteries. the dura mater, and passes through the optic foramen beneath and to the outer side of the optic nerve. Within the orbit it pursues a tortuous course above the optic nerve and along the inner wall, and di- vides into two terminal branches—the frontal and nasal. The branches of the ophthalmic artery, including the latter, are as follow:— 1 A. ophthalmica; a. orbitalis. THE VASCULAR SYSTEM. 365 a. Lachrymal artery. b. Central retinal artery. c. Long ciliary arteries. d. Short ciliary arteries. e. Muscular arteries. /. Supra-orbital artery. g. Posterior ethmoidal artery. h. Anterior ethmoidal artery. i. Palpebral arteries. j. Frontal artery. k. Nasal artery. a. The Lach'rymal artery1 passes along the outer part of the orbit to the lachrymal gland, in which it is mainly distributed. Some of its branches supply several of the contiguous muscles ; others pass through the foramina of the malar bone to anastomose with branches of the facial and internal maxillary arteries ; some pierce the sclerotic tunic as ciliary arteries, and, finally, others2 pass from the outer canthus of the eye to the eyelids. b. The Central ret'inal artery3 penetrates the optic nerve, and through it enters the eyeball to ramify in the inner layer of the retina. In the foetus a branch of it passes through the axis of the vitreous humor to reach the capsule of the crystalline lens. c. The Long cil'iary arteries,4 two in number, pierce the back of the eyeball and run forward, one on each side, between the choroid and scle- rotic coat, to the iris, in which they are distributed. d. The Short cil'iary arteries,5 three or four in number, pierce the back of the sclerotic coat, and are distributed to the choroid. e. The Muscular arteries6 are given off to all the muscles of the eye- ball. From these arise the anterior ciliary arteries,7 which consist of from five to ten minute branches penetrating the front of the sclerotic coat to be distributed to the iris. /. The Supra-orb'ital artery8 passes along the roof of the orbit, and through the supra-orbital foramen, to the skin and muscles of the eye- brow and forehead. g. The Posterior ethmoid'al artery9 enters the corresponding fora- men, and is distributed to the posterior ethmoidal sinuses and the dura mater. 1 A. lachrymalis. 2 A. palpebralis externa superior and inferior. 3 A. centralis retinae ; a. c. Zinnii. 4 A. ciliares posticae longse; a. iridis. 5 A. ciliares posticae breves; a. uveales. 6 A. musculares. 7 A. ciliares anteriores. 8 A. supra-orbitalis; a. superciliaris. 9 A. ethmoidalis posterior. 366 THE VASCULAR SYSTEM. h. The Anterior ethmoid'al artery1 enters the corresponding foramen, and gives off a menin'geal branch2 to the dura mater, and the anterior nasal artery,3 which enters the nose, through the most anterior of the foramina of the cribriform plate, to be distributed to the front part of the nose and the anterior ethmoidal and frontal sinuses. i. The Pal'pebral arteries4 come from the ophthalmic at the inner canthus, and are distributed one to each eyelid. j. The Front'al artery,5 one of the terminal branches of the ophthal- mic, passes from the orbit at the inner canthus and ascends upon the forehead beneath the muscles, to which and the skin it is distributed, k. The Na'sal artery,6 the remaining branch of the ophthalmic, passes from the orbit above the internal palpebral ligament, and descends upon the bridge of the nose, where it anastomoses with the angular artery. 2. The Posterior Communicating 'artery7 is a small branch of the internal carotid proceeding backward at the side of the infundibulum to join the posterior cerebral artery. 3. The Cho'roid artery,8 the smallest branch of the internal carotid, ascends on the outer side of the cerebral cms, and enters the descending horn of the lateral ventricle to be distributed to the choroid plexus. 4. The Anterior Cer'ebral artery,9 a terminal branch of the internal carotid, ascends the longitudinal fissure of the cerebrum, across which it is connected with the corresponding artery of the other side, by a trunk not more than a line or two long, called the anterior communicating artery.10 It then turns over the front of the corpus callosum, and runs backward between this and the cerebral hemisphere, in its course giving off numerous branches, and anastomosing with the posterior cerebral artery. 5. The Middle Cer'ebral artery,11 the remaining branch of the internal carotid, ascends the fissure separating the anterior and middle cerebral lobes, and divides into branches which supply the latter. 1 A. ethmoidalis anterior. 6 a. nasalis ; a. dorsalis nasi. 2 A. meningea anterior. 7 A. communicans posterior; a. c. 3 A. nasalis anterior. Willisii. 4 A. palpebrales; a. palpebralis inter- » \ choroidea. na superior et inferior. These form with » A. cerebri anterior; a. corporis cal- the palpebral branches of the lachrymal losi. artery the arcus tarseus superior and in- 10 A. communicans anterior. ferior. u A. cerebri media; a. c. transversa; a. 5 A. frontalis; a. supra-orbitalis. fossae Sylvii; a. Sylviana. THE VASCULAR SYSTEM. 367 THE SUBCLAVIAN ARTERIES. The Right Subcla'vian artery1 springs from the innominate artery, and curves outwardly to the interval of the anterior and middle scalene muscles, between which it passes over the first rib and assumes the name of axillary artery. It commences opposite the right sterno-clavicular articulation; and is in relation in front with the union of the internal jugular and subclavian veins, and is crossed in the same position by the pneumogastric nerve. Behind and above it are the brachial plexus and the great sympathetic nerve. The Left Subcla'vian artery2 is the third vessel arising in succession from the summit of the aortic arch. In consequence of its direct origin from the latter, it is longer than the right subclavian, and is also more deeply situated. It ascends vertically to a distance equal with the length of the innominate artery, and then pursues a similar course to the right subclavian. Its ascending portion is in relation with the left common carotid and the trachea on its right; and it has the pneumogastric nerve in front. In the rare cases in which the innominate artery is represented by its ordinary divisions, the right subclavian commonly springs from the arch of the aorta after all the other branches, and reaches its usual destina- tion by passing to the right side between the oesophagus and the cervi- cal vertebrae. No branches are given off by the ascending portion of the left subcla- vian artery, but in the subsequent part of its course, as in the, case of the right subclavian, the following arise :— 1. Vertebral artery. 2. Thyroid axis. 3. Inferior thyroid artery. 4. Supra-scapular artery. 5. Transverse cervical artery. 6. Ascending cervical artery. 7. Internal mammary artery. 8. Superior intercostal artery. 1. The Vert'ebral artery,3 the largest branch of the subclavian, passes behind the common carotid artery, and enters the foramen in the transverse process of the sixth cervical vertebra. Ascending through 1 A. subclavia dextra. - A. subclavia sinistra. 3 A. vertebralis; posterior cerebral artery. 368 THE VASCULAR SYSTEM. the foramina of the other transverse processes, it winds backward around the upper articular process of the atlas, perforates the dura mater, and enters the cranium through the occipital foramen. It then proceeds up- ward and forward, turns around the side of the medulla oblongata, and converges to join its fellow at the lower border of the pons, forming by this conjunction the basilar artery. Occasionally the vertebral artery arises directly from the arch of the aorta, especially the left one. The branches of the vertebral artery are as follow :— a. Muscular branches. b. Spinal branches. c. Posterior meningeal artery. d. Posterior spinal artery. e. Anterior spinal artery. /. Inferior cerebellar arteries. a. The Muscular branches,1 derived from the vertebral artery in the neck, are small vessels which supply the muscles attached to the cervical transverse processes. b. The Spinal branches,2 also derived from the vertebral artery in the neck, are small vessels which pass through the neighboring intervertebral foramina to supply the spinal cord and its membranes. c. The Posterior menin'geal artery3 is given off between the atlas and occipital foramen, and passes through the latter to the dura mater of the cerebellar fossa. d. The Posterior spi'nal artery,4 the first branch of the vertebral within the cranium, descends on the posterior surface of the spinal cord, anastomosing in its course with the spinal branches derived from the vertebral artery in the neck. e. The Inferior cerebellar arteries,5 usually two in number, wind around the upper part of the medulla oblongata to the under surface of the cerebellum, to which they are distributed. /. The Anterior spi'nal artery,6 the last branch of the vertebral, unites with its fellow of the opposite side in front of the medulla oblongata, and the common vessel thus formed descends in a tortuous manner in front of the spinal cord, to which it is distributed. The Bas'ilar artery,7 formed by the union of the two vertebrals, rests 1 Rami musculares. 2 Rami spinales. 3 A. meningea posterior. * A. spinalis posterior; posterior me- dian artery. 5 A. cerebelli inferiores; a. c. inferior posterior and anterior; inferior cerebel- lous arteries. 6 A. spinalis anterior ; ant. median ar- tery. 7 A. basilaris; a. cervicalis; a. meso- cephalica. THE VASCULAR SYSTEM. 369 in the median furrow of the pons, to which it gives small branches, besides sending off the following in pairs :— a. Internal auditory arteries. b. Superior cerebellar arteries. c. Posterior cerebdiiiiir arteries. a. The Internal aud'itory artery1 is a small vessel which accompa- nies the auditory nerve in the corresponding meatus, and is distributed, in company with the nerve, to the labyrinth. o. The Superior cerebellar artery2 passes outwardly at the fore part of the pons to the upper surface of the cerebellum, to which it is dis- tributed. c. The Posterior cer'ebral artery3 results from the division of the basilar artery. Diverging from its fellow of the opposite side, it receives the posterior communicating artery from the internal carotid, and winds around the cerebral crus outward and backward to the under part of the posterior lobe of the cerebrum. In this position it divides into many branches, supplying the latter and anastomosing with the other cerebral arteries. In the early part of its course, the posterior cerebral artery sends a small branch4 beneath the back part of the corpus callosum to the inter- posed velum of the pia mater and the choroid plexus. The union of the anterior cerebral arteries by the anterior communi- cating artery, and the union of the internal carotids with the posterior cerebrals by the posterior communicating artery, produce together an ar- terial circle at the base of the brain, around the position of the pituitary fossa. This remarkable series of anastomoses, known as the circle of Willis,5 associates the circulating currents of the internal earotid and vertebral arteries in such a manner that if any one of these vessels becomes obstructed, those remaining are still able to convey blood to all parts of the brain. 2. The Thy'roid axis6 is a short, thick vessel springing from the fore part of the subclavian artery near the anterior scalene muscle. Imme- diately after its origin it divides into the inferior thyroid, supra-scapular, transverse cervical, and ascending cervical arteries. Occasionally another 1 A. auditiva interna. * A. choroidea posterior. 2 A. cerebelli superior; superior cere- 5 Circulus arteriosus Willisii; arterial bellous artery. hexagon. ' A. cerebri posterior; a. profunda ce- 6 Truncus thyro-cervicalis; a. thyroi- rebri; a. cerebri inferior. dea inferior 24 370 THE VASCULAR SYSTEM. branch comes from the axis ; and any of the branches indicated may arise independently from the subclavian artery. 3. The Inferior Thy'roid artery1 ascends obliquely behind the com- mon carotid to the lower part of the thyroid body, to which it is distrib- uted, anastomosing freely with the superior thyroid. It likewise gives small branches to the trachea, larynx, and oesophagus. 4. The Supra-scap'ular artery2 passes outwardly behind the clavicle and between the sterno-mastoid and scalene muscles to the upper border of the scapula, over which it turns to the supra-spinous fossa. In this it lies close to the bone, and is chiefly spent on the supra-spinous muscle. In its course it gives a small branch3 to the subcutaneous surface of the acromion; and a larger branch descends behind the neck of the scapula to the infra-spinous muscle. Occasionally the supra-scapular comes directly from the subclavian artery, or from some of its other branches ; and sometimes it arises from the axillary artery. 5. The Transverse Cer'vical artery4 passes outwardly above and par- allel to the preceding, and crosses the scalene muscles and brachial plexus of nerves beneath the trapezius muscle to the upper angle of the scapula. Occasionally it is a branch directly of the subclavian artery; and it divides into the following branches : — a. Superie* cervical artery. b. Posterior scapular artery. a. The Superficial cer'vical artery,5 often a branch of the ascending cervical, passes upwardly beneath the outer border of the trapezius muscle, and supplies this, the elevator of the scapular angle, the sterno- mastoid muscle, the contiguous lymphatic glands, and the skin. o. The Posterior scap'ular artery6 descends along the base of the scapula under the rhomboid muscle, and supplies this, the great serrated, and latissimus muscles, and anastomoses with the supra- and subscapular arteries. 1 A. thyroidea inferior; ramus thy- reoideae thyroideus. 2 A. supra-scapularis ; a. transversa scapula?; ramus transversus scapularis. 3 Ramus acromialis ; r. supra-acromi- alis. 4 A. transversa cervicis, or colli; a. cervico-scapularis. 5 A. superficialis cervicis ; a. cervicalis posterior. 6 A. scapularis posterioris; a. dorsalis scapulae. THE VASCULAR SYSTEM. 371 6. The Ascending Cer'vical artery,1 a small vessel derived from the thyroid axis, or the inferior thyroid artery, or less frequently from one of the other branches of the subclavian, passes up the neck in front of the origin of the scalene muscles, to which, and other contiguous muscles, and the lymphatic glands, it is distributed. 7. The Internal Mam'mary artery2 is given from the subclavian, op- posite the thyroid axis. It descends behind the clavicle and costal car- tilages, a short distance from the sternum, and near the lower end of the latter divides into the musculo-phrenic and superior epigastric arteries. The branches derived from this vessel in its course, together with the terminal ones, are as follow:— a. Mediastinal arteries. b. Superior phrenic arteries. c. Perforating arteries. d. Anterior intercostal arteries. e. Musculo-phrenic artery. /. Superior epigastric artery. a. The Medias'tinal arteries3 are minute branches supplying the parts of the anterior mediastinal space, including the thymus gland, bronchus, pericardium, pleura, sterno-costal muscle, and sternum. b. The Superior phren'ic artery4 is a thread-like vessel descending in company with the phrenic nerve to the diaphragm. c. The Perforating arteries5 consist of five or six small vessels per- forating the corresponding upper intercostal spaces near the sternum, to supply the origin of the great pectoral muscle and the contiguous skin. In the female, the intermediate three or four vessels are larger than in the male, and contribute to supply the mammary gland. During lacta- tion they increase in size. d. The Anterior intercos'tal arteries,6 usually two in each intercostal space, arise together from the mammary, or separately, or in common with the perforating arteries. Proceeding outwardly in the upper five or six intercostal spaces, they anastomose with the aortic intercostal arteries, and supply the intercostal and pectoral muscles, the mammary gland, and the skin. 1 A. cervicalis ascendens ; a. c. ante- rior : a. dorsalis suprema; ramus thy- roideae ascendens. 2 A. mammaria interna; a. sternalis; a. substernalis; a. thoracica interna. 3 A. mediastinicae ; a. thymicae, bron- chialis anterior, pericardiacae, et ster- nales. 4 A. phrenica superior; a. pericardia- co-phrenica. 5 A. perforantes et mammariee exter- na? ; mammary arteries. 6 A. intercostales anteriores. 372 THE VASCULAR SYSTEM. e. The Mus'culo-phren'ic artery,1 the outer of the terminal pair of branches of the mammary artery, inclines downward and outward behind the costal cartilages of the lower ribs to the last intercostal space. In its course it gives branches to the lower five intercostal spaces and to the attachments of the diaphragm and abdominal muscles. /. The Superior epigas'tric artery2 continues in the direction of the mammary artery to the abdominal parietes back of the straight muscle, to which it is mainly distributed, anastomosing also with the epigastric branch of the external iliac artery, and with others supplying the abdom- inal walls. 8. The Superior Intercos'tal artery3 arises from the back part of the subclavian, descends in front of the neck of the first rib, and divides into two branches, which supply the first pair of intercostal spaces. 9. The Profound Cer'vical artery,4 frequently originating in common with the preceding vessel, penetrates beneath the transverse process of the last cervical vertebra to the back of the neck, where it ascends between the transverse and spinous processes to supply the contiguous muscles. THE AXILLARY ARTERY. The Ax'illary artery5 is the continuation of the subclavian from the outer border of the first rib to the lower margin of the axilla, after which it assumes the name of brachial artery. In its course through the armpit it rests on the great serrated, subscapular, latissimus, and greater terete muscles, and is under cover of the pectoral muscles. In front of it is the axillary vein; and the brachial plexus at first is behind, and after- wards surrounds it. The most important deviation from the ordinary arrangement of the axillary artery consists in its giving off a large branch, which corresponds with the radial artery of the forearm, or less frequently with the ulnar artery, or rarely with the interosseous artery. In some instances the large branch is the common source of several or all of the smaller ones, commonly derived separately from the axillary and brachial arteries. Besides several small and inconstant twigs6 to the contiguous muscles 1 A. musculo-phrenica. 2 A. epigastrica superior. 3 A. intercostalis superior, or supre- ma; a. i. subclavia. * A. profunda cervicis; a. cervicalis posterior ; a. transversalis colli; a. tra- chelo-cervicalis. 5 A. axillaris. 6 Muscular branches and axillary tho- racic artery; a. thoracica axillaris, or alaris; a. ultima thoracicarum. THE VASCULAR SYSTEM. 373 and lymphatic glands of the armpit, the axillary artery usually gives off in succession the following branches:— 1. Superior thoracic artery. 2. Acromial thoracic artery. 3. Long thoracic artery. 4. Subscapular artery. 5. Anterior circumflex artery. 6. Posterior circumflex artery. 1. The Superior Thoracic artery,1 sometimes substituted by two branches, and frequently arising in common with the succeeding artery, passes between the sub- clavian and small pectoral muscles to supply the lat- ter, the great pectoral muscle, and the mammary gland. 2. The Acro'mial Tho- racic artery2 ascends to the space above the small pectoral muscle, and di- vides into branches, which supply the pectoral and deltoid muscles, the shoul- der joint, and the subcu- taneous surface of the acromion. In the latter position it anastomoses with branches of the su- pra-scapular artery, forming together a fine vascular net.3 3. The Long Thoracic artery4 descends along the small pectoral muscle, and is distributed to the mammary gland, both pectoral, and the great serrated muscles. 1 A. thoracica superior; a. t. externa 3 Rete acromiale. superior; first thoracic artery. * A. thoracica longa ; a. t. inferior; a. 2 A. thoracica acromialis; a. t. hume- t. externa inferior; a. mammaria exter- ralis; a. acromialis; external scapular, na: second thoracic artery. or third thoracic artery. Fig. -!-j4. View of the axillary artery, portions of the pectoral and del- toid muscles removed. 1, axillary artery; 2, superior thoracic; 3, acromial thoracic; 4, long thoracic; 5, subscapular; 6, anterior circumflex; 7, posterior circumflex; 8,brachial artery; 9, superior profound artery. 374 THE VASCULAR SYSTEM. 4. The Subscapular artery,1 the largest branch of the axillary, de- scends along the outer border of the scapula, and is distributed to the subscapular, great serrated, greater terete, and latissimus muscles. In its course it gives off a large branch, as follows:— a. The Dorsal scap'ular artery.2—This passes between the greater terete and subscapular muscles around the outer border of the scapula to the infra-spinous fossa, to the muscle of which it is distributed, and anastomoses with the supra- and posterior scapular arteries. 5. The Anterior Circum'flex artery3 is a small branch winding for- ward and outward around the humerus below its tuberosities, supplying the shoulder joint and inosculating with the succeeding artery. 6. The Posterior Circum'flex artery,4 much larger than the preceding, turns backward between the triceps extensor and the humerus to the deltoid muscle, which it supplies, also giving branches to the shoulder joint, and anastomosing with the anterior circumflex, the supra-scapular, and acromial thoracic arteries. THE BRACHIAL ARTERY. The Bra'chial artery,5 the continuation of the axillary, extends from the outer border of the axilla along the inner side of the arm. It com- mences opposite the tendons of insertion of the latissimus and greater terete muscles, and, about a finger's-breadth below the bend of the elbow joint, divides into the radial and ulnar arteries. In its course it lies on the coraco-brachial, triceps extensor, and brachial muscles. The median nerve is at first on its outer side, and then crosses in front to its inner side. The ulnar nerve is in the latter position, but gradually diverges in approaching the elbow. The brachial artery is accompanied by two companion veins, which lie in close contact with it; and the basilic vein is placed over it. In nearly its whole length it is only covered by the brachial fascia and skin, and in an operation may readily be exposed without cutting the neighboring muscles. In front of the elbow joint it dips between the terete pronator and long supinator, and is covered by the offset from the tendon of the biceps flexor to the fascia of the forearm. 1 A. subscapulars; a. scapularis infe- rior ; a. s. communis; a. s. internus; a. thoracica axillaris, or alaris. 2 A. dorsalis scapulae ; a. circumflexa scapulae. 3 A. circumflexa anterior; a. articula- ris anterior. 4 A. circumflexa posterior; a. articu- laris posterior. 5 A. brachialis ; a. humeralis. THE VASCULAR SYSTEM. 375 As an important variation from the ordinary arrangement of the brachial artery, it may divide into its two principal branches in any posi- tion along the arm. The number of branches of the brachial artery and the order of their succession is variable, but usually they will be found to ac- cord with the following series:— 1. Superior profound artery. 2. Inferior profound artery. 3. Medullary artery. 4. Muscular arteries. 5. Anastomotic artery. 6. Radial artery. 7. Ulnar artery. 1. The Superior Profound ar- tery,1 the largest branch of the brachial except its ultimate divi- sions, accompanies the musculo- spiral nerve between the triceps extensor and the humerus to the outer part of the arm, where it de- scends between the long supinator and brachial muscle to the elbow. In its course it supplies the coraco- brachial, triceps extensor, brachial, and long supinator muscles, and at the elbow anastomoses with the radial, interosseous and ulnar re- current, the inferior profound, and anastomotic arteries. Fig. 255. View of the axillary and brachial artery. portions of the pectoral and deltoid muscles re- moved. 1, axillary artery; 2, brachial artery; 3. superior thoracic artery; 4, acromial thoracic; 5. long thoracic; 6, subscapular; 7, anterior circum- flex; 8, posterior circumflex; 9, superior profound. the first branch of the brachial artery; 10, inferior profound; 11, anastomotic; 12, radial; 13, ulnar: 14, interosseous; 15, recurrent radial; 16, recurrent ulnar artery. 2. The Inferior Profound ar- tery,2 a small vessel from near the middle of the brachial, descends along the inner side of the triceps ex- tensor, in company with the ulnar nerve, to the interval of the internal condyle and olecranon. It supplies the brachial muscle, and anastomoses with the ulnar recurrent and anastomotic arteries. 1 A. profunda superior ; a. p. major humeri; a. p. brachii; a. collateralis magna; a. c. externa; a. spiralis; great muscular artery of the arm. 2 A. profunda inferior ; a. p. minor ; a. collateralis prima; a. c. superior: large communicating ulnar artery ; pro- funda-ulnar artery. 376 THE VASCULAR SYSTEM. 3. The Med'ullary artery,1 a small vessel from near the middle of the brachial, or from one of its other branches, proceeds through the medul- lary foramen of the humerus to the marrow, which it supplies. 4. The Muscular arteries2 consist of several small branches to the coraco-brachial, biceps flexor, triceps extensor, and brachial muscles. 5. The Anastomotic artery,3 from the lower part of the brachial, descends to the internal condyle, and there anastomoses with the ulnar recurrent and profound arteries. The anastomotic and profound branches of the brachial artery form, with the recurrent branches of the radial, ulnar, and interosseous arteries, a fine vascular net,4 which envelops and supplies the elbow joint and the spongy extremities of the bones. THE RADIAL ARTERY. The Ra'dial artery,5 the smaller of the ultimate divisions of the bra- chial, from its direction appears as if it were a continuation of the latter. It proceeds along the outer side of the front of the forearm, between the long supinator and radio-carpal flexor to the lower end of the radius. It then turns around the outer side of the wrist beneath the extensor tendons of the thumb, to the back of the carpus, where, reaching the interval of the first pair of metacarpal bones, it penetrates to the palm of the hand, and ends in the deep palmar arch. In the early part of its course it rests on the tendon of the biceps flexor and the insertion of the rounds pronator, and is overlapped by the fleshy part of the long supinator. Subsequently it rests on the long flexor of the thumb, the quadrate pronator, and the radius, and is covered alone by the fascia and skin. Xear the wrist, during life, this artery is found very convenient, to determine the condition of the circu- lation as indicated by the pulse. It is accompanied by a pair of com- panion veins, and part of the way by the radial nerve. In those cases in which the radial artery is derived from the brachial above its ordinary source, it passes along the inner side of the latter, and then crosses to its outer side. Reaching the elbow, it usually pierces the brachial fascia, and proceeds between it and the skin down the outer 1 A. nutritia humeri. 2 Rami musculares. 3 A. anastomotica; ramus anastomoti- cus magnus; a. collateralis internus; a. c. ulnaris secunda; a. c. u. inferior. 4 Rete articulare cubiti. 5 A. radialis ; a. externa cubiti. THE VASCULAR SYSTEM. 377 Fig. 256. side of the forearm; or, less frequently, from the position of the elbow it pursues the ordinary course. The branches of the radial artery are as follow:— 1. Radial recurrent artery. 2. Muscular branches. 3. Anterior carpal artery. 4. Volar artery. • 5. Posterior carpal artery. 6. Metacarpal artery. 7. Principal artery of the thumb. 8. Radial index artery. 9. Deep palmar arch. 1. The Ra'dial Recur'rent artery,1 derived from near the commencement of the radial, ascends between the long and short supinators to the external condyle. It supplies the con- tiguous parts of the supinator and extensor muscles, and anastomoses with the superior profound artery. 2. The Muscular branches are small vessels given to the neighboring muscles in the course of the radial artery. 3. The Anterior Car'pal artery2 is a small branch from the lower part of the radial, de- scending to the front of the radio-carpal artic- ulation, where it forms an anastomosis3 with a similar branch from the ulnar artery, and sup- plies the wrist joint. 4. The Volar artery,4 very variable in its size and arrangement, is usually a small vessel derived from the radial just before it turns to the back of the carpus. Descending in front of the ball of the thumb, it supplies the small muscles of the latter, and contributes to form the superficial palmar arch. Arteries of the forearm. 2, brachial artery; 3, anastomotic ar- tery ; 4, radial artery; 5, ulnar ar- tery ; 6, recurrent ulnar; 7, inter- osseous ; 8, anterior carpal; 9, su- perficial volar; 10, anterior carpal branch of the ulnar; 11, superficial palmar arch; 12, principal artery of the thumb; 13, radial index ar- tery; 14, digital arteries; 15, re- current branches. 1 A. recurrens radialis; recurrent ar- tery of the epicondyle. 2 A. carpea anterior; a. c. volaris ; a. radio-carpalis; a. transversa-carpi ante- rior. 3 Anterior carpal arch; rete carpi volare. * A superficialis volas: superficial vo- lar artery ; ramus volaris ; a. radio-pal- maris; external superficial artery of the palm. 378 THE VASCULAR SYSTEM. 5. The Posterior Car'pal artery1 is a small branch from the posterior portion of the radial, which crosses the back of the carpus beneath the extensor tendons, to join with a similar branch of the ulnar artery. From this conjunction2 twigs supply the wrist joint; and branches3 pro- ceed to the outer three metacarpal interspaces, each dividing into a pair,' which descend along the contiguous sides of the backs of the fingers. 6. The Metacar'pal artery5 is a small vessel descending upon the first metacarpal interspace, and dividing into three branches,6 which pro- ceed along the sides of the thumb and the approximate side of the index finger. 7. The Principal artery of the Thumb7 is derived from the radial just after it reaches the palm of the hand. It descends along the first metacarpal bone, and divides into two digital arteries,8 which proceed along the opposite sides of the thumb to its extremity. 8. The Ra'dial Index artery9 arises close to the preceding and descends along the radial border of the index finger to its extremity. 9. The Deep Pal'mar Arch10 is formed by the conjunction of the termi- nating portion of the radial with the communicating artery from the ulnar. It lies transversely across the upper part of the metacarpus, beneath the flexor tendons, and gives off the following branches:— a. Recurrent branches. b. Perforating branches. c. Interosseous arteries. a. The Recurrent branches11 ascend and anastomose with the anterior carpal arteries. b. The Perforating branches12 pass through the upper part of the in- terosseous spaces and join the branches of the posterior carpal arteries. c. The Interos'seous arteries13 supply the corresponding muscles, and anastomose with the digital branches of the superficial palmar arch. 1 A. carpae posterior; a. c. dorsalis; a. transversa carpi-dorsalis; a. dorsalis carpi-radialis. 2 Posterior carpal arch; rete carpi dorsale; r. carpeum posterius. 3 A. interossese dorsales. 4 A. digitales dorsales. 5 A. interosseae dorsalis prima. 6 A. dorsalis pollicis et indicis; a. dor- salis pollicis radialis et ulnaris, et indi- cis radialis. 7 A. princeps pollicis; a. magna polli- cis ; a. pollicaris. 8 A. volaris pollicis radialis and ulna- ris. 9 A. radialis indicis ; a. volaris indicis radialis. 10 Arcus palmaris profundus ; a. vola- ris profundus; profound, or radial pal- mar arch. 11 Rami recurrentes; r. retrogradi. 12 Rami interossei perforantes; r. per- forantes superiores. 13 A. interosseae volares. THE VASCULAR SYSTEM. 379 THE ULNAR ARTERY. The Ul'nar artery,1 the second division of the brachial, turns inwardly beneath the muscles springing from the internal condyle, and descends on the inner side of the forearm between the ulno-carpal and superficial flexor of the fingers to the wrist. Passing over the anterior annular liga- ment at the side of the pisiform bone to the palm of the hand, it termin- ates in the formation of the superficial palmar arch. In the early part of its course it rests on the insertion of the brachial muscle, and afterwards on the deep flexor of the fingers. It is accompanied by two companion veins, and in the greater part of its course by the ulnar nerve. In those anomalous instances in which the ulnar artery comes from the brachial above its ordinary position, as it approaches the elbow it in- clines inwardly, and passes over the heads of the flexor muscles instead of beneath them, and then pursues the usual course down the forearm. The branches given from the ulnar artery are as follow :— 1. Ulnar recurrent artery. 2. Common interosseous artery. 3. Muscular branches. 4. Posterior carpal artery. 5. Anterior carpal artery. 6. Communicating artery. 7. Superficial palmar arch. 1. The Ulnar Recur'rent artery,2 frequently substituted by a pair of branches, comes from the ulnar just below the elbow, and ascends beneath the muscles arising from the internal condyle. It supplies the heads of the flexor muscles, and anastomoses with the inferior profound, anasto- motic, and other arteries about the elbow joint. 2. The Common Interos'seous artery3 comes from the ulnar near the tuberosity of the radius, and shortly afterwards divides into the anterior and posterior interosseous arteries. Occasionally the common interosse- ous artery is a branch of the brachial; and when the ulnar artery de- rives its origin above the usual position, the common interosseous and radial arteries appear as the terminal divisions of the brachial. a. The Anterior interos'seous artery4 descends in front of the inter- 1 A. ulnaris ; cubital artery ; a. cubi- talis. 2 A. recurrens ulnaris; a. r. u. ante- rior and posterior; a. r epitrochleae ; a. r. cubitalis anterior and posterior. 3 A. interossea communis; a interos- sea antibrachii communis; a. interossea. * A. interossea anterior, or interna. 380 THE VASCULAR SYSTEM. osseous membrane as far as the quadrate pronator, when it pierces the former and passes to the back of the wrist, where it anastomoses with the posterior carpal arteries. In its course it gives branches to the neighboring muscles. b. The Posterior interos'seous artery1 passes to the back of the fore- arm through the opening at the upper part of the interosseous membrane, and descends beneath the common extensor of the fingers to the wrist, supplying in its course the contiguous muscles, and anastomosing with the anterior interosseous and posterior carpal arteries. At its upper part it gives off the Interosseous recur'rent artery,2 which ascends be- neath the short supinator and anconeus muscles to the interval of the olecranon and external condyle, and anastomoses with the superior pro- found and radial recurrent arteries. 3. The Muscular branches of the ulnar artery are small vessels given to the neighboring muscles. 4. The Posterior Car'pal artery,3 of variable size, comes from the lower part of the ulnar artery and turns beneath the tendon of the ulno- carpal flexor to the back of the wrist. It sends a metacarpal branch to the inner side of the hand and little finger, and terminates by joining the corresponding branch of the radial artery. 5. The Anterior Car'pal artery,4 smaller than the preceding, passes outwardly to the front of the wrist, where it joins the anterior carpal branch of the radial artery. 6. The Communicating1 artery5 is derived from the ulnar just after passing the pisiform bone, and dips between the short flexor and abduc- tor of the little finger to contribute in the formation of the deep palmar arch. 7. The Superficial Palmar arch,6 the terminating portion of the ulnar artery, curves internally in the palm of the hand, upon the flexor tendons and beneath the palmar fascia, and joins the volar artery of the radial. The branches given from the arch are four digitals.7 1 A. interossea posterior, or externa; a. perforans suprema. 2 A. interossea recurrens; a. recurrens olecranea; a. r. radialis posterior. 3 A. carpea posterior; ramus dorsalis. 4 A. carpea anterior. 5 A. communicans; a. cubitalis manus profunda. G Arcus palmaris superficialis; arcus volaris sublimis; a. v. superficialis; ra- mus volaris superficialis. T A. digitales volares; a. d. communes. THE VASCULAR SYSTEM. 381 The first Digital artery runs along the ulnar side of the hand and little finger to its extremity. The remaining Digital arteries descend along the metacarpal inter- spaces, except the first, to the roots of the fingers, where each divides into two branches1 which run along the contiguous sides of the fingers to their tips. The arteries of the hand exhibit frequent varia- tions in their arrange- ment. In some instances the contribution of the ul- nar artery to the super- ficial arch is much reduced, and that from the radial artery is in a correspond- ing degree increased. In other instances the con- tributions of both are re- duced, even to a want of continuity in the super- ficial arch, and each supplies its own side of the hand; or the deep arch is larger, and then appears mainly to supply the hand and fingers. Arteries of the hand; palmar surface. 1, radial artery; 2, ulnar; 3, communicating branch with the deep palmar arch; 4, superficial palmar arch; 5, superficial volar artery; 6, digital ar- teries of the thumb; 7, radial index artery; 8, digital artery to the little finger; 9, common digital arteries; 10, digitals to the fingers. THORACIC AORTA. The Thoracic Aor'ta2 commences with the termination of the arch of the aorta on the left side of the third dorsal vetrebra. Descending on the left of the vertebral column, in the lower part of its course it gradu- ally inclines toward the median line, which it nearly reaches opposite the last dorsal vertebra, and there passes through the aortic orifice of the diaphragm to assume the name of abdominal aorta. It is situated in the posterior mediastinal space behind the pericardium and the root of the left lung. It is in relation on the right with the oesophagus, azygos vein, and thoracic duct; on the left with the corresponding pleura and lung. 1 Collateral digital arteries. 2 Aorta thoracicus. 382 THE VASCULAR SYSTEM. The branches of the thoracic aorta are all of small size, and come off in succession, as follow:— Fig. 2-">8. The aorta. 1, arch of the aorta; 2, thoracic aorta; 3, abdominal aorta; 4, innominate artery : 5, right common carotid; 6, right subclavian; 7, left common carotid; 8, left subclavian; 9, bron- chial artery, a small branch of the aorta; 10, oeso- phageal arteries; 11, intercostal arteries of the right side ; 12, of the left side; 13, phrenic arteries; 14, coeliac axis; 15, coronary artery; 16, splenic artery; 17, hepatic artery; 18, superior mesenteric artery; 19, supra-renal arteries ; 20, njiniiMiiitic ar- teries ; 21, inferior mesenteric artery ; 22, lumbar arteries; 23, common iliac arteries; 24, middle sa- cral artery, a, aortic orifice of the diaphragm; b, articulation of the head of the ribs; c, anterior scalene muscle. Qj6 > £y = ; n '■-' • ! 1. Pericardiac arteries. 2. Bronchial arteries. 3. (Esophageal arteries. 4. Mediastinal arteries. 5. Intercostal arteries. 1. The Pericar'diac arteries' consist of a few fine vessels rami- fying on the contiguous portion of the pericardium. 2. The Bron'chial arteries,2 two or three in number, occasionally originating in one trunk, apply themselves to the bronchi and ac- company them in their ramification through the lungs. Sometimes the right bronchial artery is derived from the corresponding third inter- costal artery. 3. The Oesophage'al arteries,3 four or five in number, supply the oesophagus. 4. The Medias'tinal arteries4 consist of a number of fine ves- sels distributed on the neighboring pleurae and lymphatic glands. 5. The Intercos'tal arteries,5 of which there are ten on each side, including the one below the last rib, come off from the back of the aorta opposite the vertebral bodies. Those of the left side are shorter than the right ones in consequence of the position of the aorta on the left of the median line. They pass 1 A. pericardiac® ; a. pericardiacse posteriores. 2 A. bronchiales; a. b. posteriores 3 A. oesophageal 4 A. mediastinicae. 5 A. intercostales ; a. aorticae. i. inferiores, or THE VASCULAR SYSTEM. 383 from their origin upward and outward to the commencement of the inter- costal spaces, and divide into an anterior and a dorsal branch. a. The anterior branch1 passes outwardly beneath the pleura, enters between the two intercostal muscles, and then runs along the lower bor- der of the uppermost rib. In its course it gives branches to thejnter- costal, pectoral, and great serrated muscles; a moderate-sized one^which descends and runs along the border of the rib below; and others which anastomose with the anterior intercostal branches of the internal mam- mary artery, and the thoracic branches of the axillary artery. The lower three of the anterior branches extend into the abdominal muscles, where they anastomose with the epigastric arteries. In the female, the anterior branches from the third to the sixth give off considerable twigs2 to supply the mammary gland. 6. The dorsal branch3 of the intercostals, after transmitting a branch4 through the intervertebral foramina to the contents of the spinal canal, passes backward between the transverse processes of the vertebrae, and is distributed to the muscles of the back. ABDOMINAL AORTA. The Abdominal Aor'ta5 commences in the termination of the thoracic aorta as it emerges through the aortic orifice of the diaphragm opposite the last dorsal vertebra. Descending in front of the vertebral column with a slight inclination to the left side, opposite the fourth lumbar ver- tebra it divides into the two common iliac arteries. In front it is in relation with the liver, splenic vein, pancreas, duodenum, left renal vein and peritoneum; and to its right is the inferior cava, with the right crus of the diaphragm, commencement of the thoracic duct and azygos vein interposed above. The branches of the abdominal aorta are numerous, and many of them of large size. Four of them are symmetrical and median in their origin ; the others are in pairs. The symmetrical branches are as follow :— Cceliac axis. Superior mesenteric artery. Inferior mesenteric artery. Middle sacral artery. The branches in pairs are as follow:— 1 Ramus anterior, or intercostalis. 4 R. spinalis; r. vertebralis. 2 Rami mammarii externi. ° Aorta abdominalis; abdominal por- s R. dorsalis ; r. posterior. tion of the descending aorta. THE VASCULAR SYSTEM. Phrenic arteries. Supra-renal arteries. Renal arteries. Spermatic arteries. Lumbar arteries. THE CCELIAC AXIS. The Cceliac axis1 is a short, thick trunk, projecting forward from the commencement of the abdominal aorta. It is in relation below with the pancreas, and with the semilunar ganglion on each side. It divides into three diverging branches as follow:— 1. Coronary artery. 2. Hepatic artery. 3. Splenic artery. Fig. 259. Distribution of the cojliac artery. 1, liver turned upward, and showing its lower surface; 2, trans- verse fissure; 3, gall-bladder; 4, stomach; 5, oesophagus; 6, 7, 8, duodenum; 9, pancreas; 10, spleen; 11, aorta- 12, cceliac artery; 13, coronary artery; 14, hepatic artery; 15, pyloric artery; 16, gastrc-duodenal artery; 17, right gastro-epiploic artery; 18, pancreatico-duodenal artery; 19,hepatic artery dividing into the right and left branches for the liver; 20, splenic artery; its courso indicated behind the stomach by dotted lines; 21, left gastro-epiploic artery; 22, pancreatic branch; 23, gastric branches; 24, superior mesenteric artery, emerging from between the pancreas and duodenum. 1. The Cor'onary artery,2 the smallest of the divisions of the cceliac axis, turns upward and to the left side toward the cardiac orifice of the 1 A. cceliaca; tripus Halleri; a. epis-togastricus. 2 A. coronaria; a. c. ventriculi; a. c. v. sinistra; a. gastrica major; a. g. sinistra superior; a. stomogastrica. THE VASCULAR SYSTEM. 385 stomach, and then runs along its lesser curvature. Situated between the layers of the lesser omentum, it divides into numerous branches, which supply the lower part of the oesophagus1 and both sides of the stomach,2 and anastomose with all the other arteries of the latter. 2. The Hepat'ic artery,3 the second in size from the cceliac axis, in- clines upwardly within the right border of the lesser omentum, and divides into two branches which enter the transverse fissure of the liver. Behind it is the portal vein, and to its right the bile duct. Its branches, including the terminal pair, are as follow :— a. Pyloric artery. b. Gastro-duodenal artery. c. Pancreatico-duodenal artery. d. Right gastro-epiploic artery. e. Right branch. /. Cystic artery. g. Left branch. a. The Pylor'ic artery4 is a small branch which turns downward and runs along the lesser curvature of the stomach from right to left, anasto- mosing with the coronary artery. b. The Gas'tro-duode'nal artery,5 a large branch, descends behind the pylorus, and divides into the following two vessels :— c. The Pancreatlco-duode'nal artery6 passes between the head of the pancreas and the duodenum, and supplies both with branches.7 d. The Right gas'tro-epiploic artery8 runs along the greater curva- ture of the stomach from right to left, and terminates by conjunction with the left gastro-epiploic. It gives many branches9 to both surfaces of the stomach which anastomose with those from the lesser curvature, and it also sends long thread-like vessels10 downward to the great omentum. e. The Right branch11 of the hepatic artery enters the right side of the transverse fissure of the liver, and divides into two or three branches, which penetrate into the right lobe of the liver. /. The Cys'tic artery,12 a branch of the preceding, turns forward to supply the gall-bladder. 1 Rami oesophagei inferiores. " Rami pancreatici dextri and r. duode- 2 Rami cardiaci and gastrici. nales. 3 A. hepatica. 8 A. gastro-epiploica dextra; a. coro- 4 A. pylorica; a. p. superior; a. coro- naria dextra inferior; a. c. ventriculi, naria dextra; a. c. ventriculi; a. gas- or gastrica dextra inferior. trica dextra superior. 9 Rami gastrici. 5 A. gastro-duodenalis. "> Rami epiploici. 6 A. pancreatico-duodenalis. " A. hepatica dextra. 25 12 A. cystica. 386 THE VASCULAR SYSTEM. g. The Left branch1 of the hepatic artery, smaller than the other, enters the left of the transverse fissure to be distributed to the corre- sponding lobe of the liver. 3. The Splenic artery,2 the largest branch of the cceliac axis, passes toward the left side in a tortuous manner along the upper border of the pancreas to the hilus of the spleen. Its branches are as follow:— or.. Pancreatic arteries. 6. Left gastro-epiploic artery. c. Short gastric arteries. d. Splenic branches. a. The Pancreatic arteries,3 variable in size and number, are given from the splenic in its course along the pancreas. 6. The Left gas'tro-epiploic artery* runs from left to right along the greater curvature of the stomach, and terminates by joining the right gastro-epiploic, like which it is also distributed. c. The Short gas'tric arteries,5 three to six in number, are directed from the termination of the splenic artery, or some of its branches, to the fundus of the stomach, where they anastomose with the other arteries of that organ. d. The Splenic branches,6 five or more in number, diverge from the parent vessel and enter the hilus of the spleen. THE SUPERIOR MESENTERIC ARTERY. The Superior Mes'enteric artery,7 a large vessel, springs from the front of the aorta just below the coeliac axis, and supplies the small in- testine and the right portion of the large intestine. It descends behind the pancreas and in front of the duodenum, and then proceeds within the mesentery in a curved line, at first downward and to the left, and then toward the right iliac region, where it inosculates with its own ileo- colic branch. The superior mesenteric artery gives off the following branches:— 1. Duodenal artery. 2. Jejunal and ileal arteries. 3. Ileo-colic artery. 4. Right colic artery. 5. Middle colic artery. 1 A. hepatica sinistra. 2 A. splenica; a. lienalis. 3 A. pancreatica?. * A. gastro-epiploica sinistra; a. co- ronaria sinistra inferior; a. c. ventriculi, or gastrica sinistra inferior. 5 A. gastrica? breves; vasa brevia. 6 Rami splenici; r. lienales. T A. mesenterica superior; a. mesara ica sup. THE VASCULAR SYSTEM. 387 1. The Duode'nal artery1 turns back along the course of the duode- num, and gives branches both to it and the pan- creas. Fig. 260. 2. The Jeju'nal and Il'eal arteries,2 fifteen or more in number, diverge from the convexity of the parent vessel, and supply almost the whole length of the small intestine. In their course within the mesentery they divide,and the contiguous branches conjoin so as to form a series of arches. From these spring forth a greater number of branch- es, which subdivide, and, in the manner just indi- cated, form a second se- ries of arches, and from these again a third series is formed. Each series of arches becomes succes- sively more numerous and smaller, and from the last series originate a multitude of intestinal branches which diverge upon the sides of the jejunum and ileum, where they freely anastomose with one another. 3, 4, 5. The Il'eo-colic,3 Right Colic,4 and Middle Colic arteries5 arise in succession from the right side or concavity of the superior mes- enteric artery. Each divides into two branches, of which those contigu- ous, together with the termination of the parent vessel and the upper branch of the left colic artery, conjoin so as to form four large arches. Upon these, in the manner indicated in the account of the preceding arteries, a more numerous and smaller row of arches is formed, from Distribution of the superior mesenteric artery. 1, superior mesenteric artery; 2, jejunal and ileal arteries; 3, ileo-colic ar- tery; 4, right colic; 5, middle colic artery; 6, duodenal artery. a, small intestine turned to the left; 6, large intestine; c, pan- creas. a. pancrea- 1 A. duodenalis inferior; tico-duodenalis inferior. 2 A. jejunales et ileae; a. intestinales; vasa intestini tenuis. 3 A. ileo-colica; a. colica dextra infe- rior; a. ceecalis. * A. colica dextra; a. c. d. media; a. media anastomotica. 5 A. colica media; a. colica dextra su- perior; a. mesocolica. 388 THE VASCULAR SYSTEM. which emanate many branches to supply the termination of the ilium, the caecum, and the ascending and transverse colon. THE INFERIOR MESENTERIC ARTERY. The Inferior Mes'enteric artery1 springs from the front of the aorta about two inches below the superior mesenteric, and is destined to sup- FlG 261. Ply ^he descending colon and the rectum. It de- scends toward the left iliac region and gives off the following branches:— 1. Left colic artery. 2. Sigmoid artery. 3. Superior haemorrhoidal artery. 1. The Left Colic ar- tery,2 directed to the left side, divides into two branches, of which one joins the middle colic ar- tery, and the other joins the sigmoid artery, thus contributing to form a pair of arches. Upon these a series of irregular and smaller arches is formed, from which branches proceed to the descending colon. Distribution of the inferior mesenteric artert. 1, aorta; 2, inferior mesenteric artery; 3, left colic artery; 4, sigmoid artery; 5, superior haemorrhoidal artery; 6, superior mesenteric artery; 7, middle colic artery anastomosing with the left and the right (8) colic arteries; 9, branches to the small intestine; 10, left renal artery, a, small intestine turned to the right side; 6, large intestine; c, pan- creas. 2. The Sig'moid ar- tery3 sometimes originat- ing in common with the former, and sometimes represented by two branches, inosculates with the left colic and superior haemorrhoidal arteries, thus producing arches from which branches proceed to the sig- moid flexure of the colon. 3. The Superior haemorrhoidal artery,* the terminal portion of the 1 A. mesenterica, or mesaraica inferior. 2 A. colica sinistra; a. c. s. superior; a. c. sinistra magna and media. s A. colica sinistra inferior; a. c. s. parva. * A. haemorrhoidalis superior, or in- terna. THE VASCULAR SYSTEM. 389 inferior mesenteric, after anastomosing with the former, descends behind the rectum and divides into two branches, distributed on the sides of the latter, and anastomosing with the middle and inferior hemorrhoidal arteries. THE MIDDLE SACRAL ARTERY. The Middle Sac'ral artery1 is a small vessel descending from behind the bifurcation of the aorta along the middle of the sacrum and coccyx. It is really a rudimental termination of the aorta, and appears as a gradual prolongation of the latter in whales, snakes, and other animals in which hinder extremities do not exist or are feebly developed in com- parison with the tail. In its course it gives off branches which anasto- mose with the lateral sacral arteries. ARTERIES IN PAIRS FROM THE ABDOMINAL AORTA. The Phrenic arteries2 are two small vessels arising from the sides of the abdominal aorta near the cceliac axis, or from the latter itself. Di- verging on the crura of the diaphragm, the right one passes behind and to the outer side of the inferior cava, while the left one proceeds in like manner in relation with the oesophagus, and both divide into branches supplying the diaphragm, anastomosing with the phrenic branches of the internal mammary and the terminations of the intercostals. In their course they give small branches3 to the supra-renal bodies. The Lum'bar arteries* correspond very nearly with the intercostals in their manner of origin, direction, and distribution. There are four pairs of them, and they cross the bodies of the lumbar vertebrae beneath the origin of the crura of the diaphragm and the psoas muscles, to the inter- spaces of the transverse processes, where they divide into an anterior and a posterior branch. The anterior branch5 passes outwardly behind the quadrate lumbar muscle, ramifies in the broad abdominal muscles, and anastomoses with the epigastric arteries. The posterior branch,6 after giving off a spinal branch,7 through the intervertebral foramina, to the spinal cord and membranes, is distributed to the muscles and skin of the back. 1 A. sacralis media; a. s. anterior; * A. lumbares, a. lumbales. median-artery of the sacrum. 5 Ramus lumbaris, or abdominalis. 2 A. phrenicoe: a. p. inferiores, or mag- 6 Ramus dorsalis. nae; a. diaphragmaticae. 7 R. spinalis. 3 A supra renales superiores. ggQ THE VASCULAR SYSTEM. The Supra-re'nal arteries1 are two small vessels coming from the aorta on a level with the superior mesenteric artery, and proceed out- ward to be distributed to the supra-renal bodies. The Re'nal arteries2 are two large vessels coming from the sides of the aorta, a short distance below the position of the superior mesenteric artery. The right one is usually a little lower than the left one, and is longer in consequence of the position of the aorta on the left side of the vertebral column. Passing directly outward and backward in front of the crura of the diaphragm, they divide into four or five branches, which enter the sinus of the kidney and are distributed through the organ. They also give small branches to the supra-renal body,3 the kid- ney fat,* and the pelvis and ureter. The Sperma'tic arteries5 are long, slender vessels which spring one from each side of the front of the aorta, a short distance below the renal arteries Each descends outwardly upon the psoas muscle, in company with the ureter, but leaves the latter at the brim of the pelvis, and pro- ceeds to the internal abdominal ring, where it becomes one of the con- stituents of the spermatic cord, and descends to be distributed to the testicle. It gives fine twigs to the ureter; near the testicle, becomes quite tortuous, and gives branches to the vaginal tunic of the organ. The Ova'rian arteries6 of the female correspond with those just de- scribed of the male. They have the same origin, and, likewise, the same course as the spermatic arteries to the brim of the pelvis, after which they proceed in a tortuous manner between the folds of the broad liga- ment to the ovary, the Fallopian tube, and the uterus. THE COMMON ILIAC ARTERIES. The Common Il'iac arteries7 are the terminal branches of the abdom- inal aorta, and are given off opposite the body of the fourth lumbar vertebra, slightly to the left of the median line. The two vessels diverge on the sides of the fifth lumbar vertebra; and just above the sacro-ibac symphysis each divides into the internal and external iliac arteries. iA. supra-renales; a. s. mediae, or * A. spermatic*; a. s. intern*; a. aorticae ; a. capsulares; a. atrabilariae. prseparantes; a. testiculares. » A renales; a. emulgentes. 6 A. ovariana; a. spermatica. 3 A supra-renales inferiores. 7 A. iliacae communes ; a. i. primitive * A. adiposse. primitive or primary iliac arteries; a. pelvicrurales.. THE VASCULAR SYSTEM. 391 The common iliacs are about two inches in length, and are covered by the peritoneum and intestines. The right one crosses over both common iliac veins as these converge to the inferior cava. VlIW OP THE LEFT 8IDE OF THE PELVIS, THE BLADDER, UTERUS, VAGINA, AND RECTUM, turned downward SO as to exhibit the distribution of the internal iliac artery. 1, aorta; 2, right common iliac artery; 3, left common iliac; 4, middle sacral; 5, external iliac; 6, circumflex iliac; 7, epigastric; S, internal iliac; 9, ilio-lumbar; 10, lateral sacral arteries; 11, gluteal artery passing from the pelvis, above the pyriform muscle, at the upper part of the great sacro-sciatic foramen; 12, superior vesical artery; the branch cut off is extended into the remains of the umbilical artery; 13, obturator artery; 14, inferior vesical artery giving off the uterine artery to the vagina and uterus; 15, middle haemorrhoidal artery; 16, internal pu- dic artery, seen emerging from and again entering the pelvis; 17, ischiatic artery, a, iliac muscle; 6, pBoas muscle; c, symphysis of the pubis; d,sacrum; e, pyriform muscle; /, internal obturator muscle ; g, sacro-sciatic ligaments; h, rectum; i, uterus and vagina; j, Fallopian tube; k, bladder. THE INTERNAL ILIAC ARTERY. The Internal Il'iac artery1 is a short, stout vessel which descends from the common iliac into the pelvis, the contents of which, the but- A. iliaca interna ; a. i. posterior; a. hypogastrica; a. pelvica. 392 THE VASCULAR SYSTEM. tocks, and the generative apparatus it supplies. It extends in front of the sacro-iliac symphysis toward the great sacro-sciatic foramen, and di- vides into two portions, which usually give off branches in the following order:— From the posterior division:— 1. Ilio-lumbar artery. 2. Lateral sacral arteries. 3. Obturator artery. 4. Gluteal artery. From the anterior division:— 5. Vesical arteries. 6. Internal pudic artery. 7. Ischiatic artery i In addition, in the female there come off from the anterior division the uterine and vaginal arteries. 1. The Illo-lum'bar artery1 passes outward beneath the psoas muscle, and divides into two branches. Of these, one2 ascends and sup- plies the psoas and quadrate-lumbar muscles, and anastomoses with the lumbar arteries; the other3 crosses the iliac fossa to the crest of the ilium and supplies the iliac muscles, and anastomoses with the circumflex iliac artery. 2. The Lateral Sac'ral arteries,* usually two, sometimes arising in common, descend in front of the sacral plexus of nerves, anastomose with the middle sacral artery, and supply the pyriform, coccygeal, and anal elevator muscles. Branches derived from these arteries enter the sacral foramina and supply the contained nerves and membranes, and in part pass out at the posterior foramina to terminate in the neighboring muscles and skin. 3. The Obtura'tor artery£often a branch of the anterior division of the internal iliac, passes forward along the side of the pelvis to the ob- turator foramen, through which it emerges and divides into two branches. Of these, the internal branch6 is distributed to the adductor, pectineal, and gracilis muscles, and anastomoses with the internal circumflex artery. The external branch7 is distributed to the obturator, quadrate femoral, 1 A. ilio-lumbaris; a. ilia parva. 2 Ramus ascendens ; r. lumbaris. 3 R. transversalis; r. iliacus. 4 A. sacrales laterales. 5 A. obturatoria; a. sub-pubio-femo- ralis. B Ramus internus ; r. anterior. 7 R. externus; r. posterior. THE VASCULAR SYSTEM. 393 and geminous muscles, to the hip joint, and to the heads of the flexors attached to the tuberosity of the ischium. Within the pelvis the obtura- tor artery gives small branches to the iliac, internal obturator, and anal elevator muscles. Frequently the obturator artery arises, in common with the epigastric, from the termination of the external iliac artery, in which cases it de- scends behind the pubis to the obturator foramen, from whence it pursues the ordinary course. 4. The Glu'teal artery,1 the continuation of the posterior division of the internal iliac, turns out of the pelvis at the upper part of the great sacro-sciatic foramen, and divides into two branches. The superficial branch runs backward between the middle and great gluteal muscles, which it supplies, together with the skin of the gluteal and sacral regions. The deep branch passes forward between the middle and small gluteal muscles, diverging into many branches,2 which supply the latter and anastomose with the ischiatic and circumflex arteries. 5. The Vesical arteries3 are generally two in number. The superior vesical artery* extends through the remains of the umbilical artery of the foetus to the side of the urinary bladder, to which it is distributed. In its course it gives the deferent artery to the spermatic duct, and a branch to the ureter. The inferior vesical artery5 proceeds to the lower part of the bladder, and also supplies the prostate gland and seminal vesicles. 6. The Internal Pu'dic artery,6 one of the terminal branches of the anterior division of the internal iliac, descends to the lower part of the great sacro-sciatic foramen, and thence passes from the pelvis. Winding around the spine of the ischium, it again enters the pelvis through the small sacro-sciatic foramen, ascends along the inner side of the rami of the ischium and pubis, and divides into the cavernous and dorsal arteries of the penis. Its branches, including the terminal ones, are as follow:— a. Middle haemorrhoidal artery. b. Inferior haemorrhoidal artery. c. Perineal artery. d. Bulbo-urethral artery. e. Cavernous artery. /. Dorsal artery of the penis, or clitoris. 1 A. glutaea; a. g. superior ; a. iliaca posterior. 2 Deep superior and inferior branches. 3 A. vesica? ; a. vesicales. 1 A. v. superior. 5 A. v. inferior. , , „ ,. X,. axis flbre of the nerve fibre; 8, about the ^ of a line m diameter, discovered portion of a digital nerve with in the conjunctiva of the eyeball, the mucous Pacinian corpuscles attached, of . . , the natural size. membrane Of the root of the tongue and soft palate, and the skin of the glans penis and clitoridis. They are filled with a soft, transparent, homogeneous substance, and have entering into them one or two branches of a nerve fibre. GENERAL CHARACTER AND STRUCTURE OF THE SYMPA- THETIC NERVES. The nerves of the sympathetic system are mostly reddish gray3 or grayish white,3 a few of the larger trunks being white, as in the case of the cerebro-spinal nerves. They are generally much smaller than the 1 Corpuscula tactus; tactile corpuscles of Wagner, or of Meissner; Wagner- Meissner'schen Tastkorperchen!; axile bodies; touch corpuscles. 2 Corpuscles of Krause; Krause'schen Endkolben. 3 Nervi molles ; n. grisei; fasciculi nervosi molles. 512 THE NERVOUS SYSTEM. latter, and are associated with many ganglia, from which the sympathetic has likewise been called the gan'glion'ic system of nerves. In their course to the organs they supply, they usually follow the blood-vessels, upon which they form exceedingly intricate plexuses. The sympathetic nerves are composed of nerve fibres, like those of the cerebro-spinal system in association with others of peculiar charac- ter, called gray fibres.1 The white nerve fibres are generally much finer than those of the cerebro-spinal nerves, are most numerous in the white trunks of the sympathetic system, and are compar- atively few in the reddish- gray nerves. The gray fibres1 are far more numerous than the white ones in the red- dish-gray and grayish- white sympathetic nerves. They exist in the form of bands, averaging the 3J0 of a line in breadth. In structure they appear faintly granular, indistinctly striated or homogeneous, and are provided with elongated oval nuclei. Whether the gray fibres are a peculiar ele- ment of the nervous structure, or whether they are to be viewed as a variety of connective tissue, is a much-disputed question. Elements of the sympathetic system. A, portion of a nerve highly magnified: a, nerve fibres; b, gray fibres with nuclei. B, three nerve cells from a ganglion. GENERAL CHARACTER AND STRUCTURE OF THE GANGLIA. The Gan'glia, or gan'glions,2 are rounded bodies situated in the course of many of the nerves. Thus, several belong to the trifacial, glosso-pharyngeal, and pneumogastric nerves ; one exists on the pos- terior root of each spinal nerve; and a numerous series are found on the sympathetic nerves. They are mostly elliptical or spheroidal, but present many varieties of form. The ganglia are viewed as sources of nerve power, and hence, like the brain and spinal cord, are frequently called nerve centres. The term is likewise often applied to the collections of gray substance of the cerebro- spinal axis. 1 Fibres of Remak; gelatinous fibres. 2 Ganglia nervorum: nervous gan- glions ; ganglia, gangliones, nodi, noduli, or tubercula nodosa nervorum; tumores, or plexus ganglioformes; diverticula spirituum animalium; ganglia of in- crease; formative ganglia. THE NERVOUS SYSTEM. 513 The ganglia are reddish gray or grayish white, and of firm consistence. They appear like knots or swellings in the course of the nerves, and are furnished with a tightly-adherent membrane continuous with the sheath of the latter. In structure they consist of a mass of nerve cells imbedded in a stroma of connective tissue, and are traversed by nerve fibres associated with gray fibres. The nerve cells of the ganglia resemble those of the gray sub- stance of the cerebro-spinal axis, but are more uniformly of large size, ranging from about the y^ou to the 3 J 0 of an inch. They are globular or oval, and generally unipolar or bipolar, though both apolar and multipolar cells also appear to exist. The processes of the nerve cells are continuous with the nerve fibres passing to and from the ganglion. In the ganglia of the cerebro- spinal nerves, the cells are generally larger than in those of the sympa- thetic system. The nerve fibres partly traverse the ganglia without forming any at- tachment to the cells, while others are continuous with them. The gray fibres of the ganglia are like those of the sympathetic nerves, and are especially abundant in the sympathetic ganglia, in which they occupy the position of a stroma to the nerve cells. The stroma of the cerebro-spinal nerves appears as a homogeneous or feebly striated connective tissue furnished with nuclei, and on isolated nerve cells looks like an especial investment to them. Like other nerve centres, the ganglia are abundantly furnished with capillary blood-vessels. THE CEREBRO SPINAL AXIS, OR BRAIN AND SPINAL CORD. The Cer'ebro-spinal axis consists of the brain, which occupies the cavity of the cranium, and the spinal cord, which is a prolongation of the former extending downward into the vertebral canal. Besides the 33 Fig. 325. Nerve cells from the semilunar ganglion of the trigeminal nerve of a cat, highly magnified. 1, nerve cell exhibiting the origin of a nerve fibre: a, sheath of the cell and nerve fibre with nuclei; 6, the nerve cell within; c, the nerve fibre within its sheath: 2, cell with the origin of a nerve fibre de- prived of its sheath; 3, nerve cell without sheath or nerve fibre. 514 THE NERVOUS SYSTEM. skull and vertebral column, the cerebro-spinal axis is further enveloped in three membranes, the dura mater, arachnoid, and pia mater. From it originate the cerebro-spinal nerves, or the cer'ebral nerves and the spinal nerves. It is symmetrical, the two halves being in contact, and united along the median line by commissures of nerve substance. The term com'missure,1 frequently employed in anatomy, generally im- plies the union of symmetrical parts. In the nervous system it applies to the conjunction of two parts of the brain or spinal cord ; the union of two nerves in the median line of the body, to nerves between two or more ganglia; and to the fibres uniting nerve cells. THE BRAIN. The Brain,2 the seat of the intellect, the will, the sensations, and the emotions, is the great nervous mass which, with its enveloping mem- branes, completely fills the cavity of the cranium. The size and weight of the brain varies with the race, sex, age, and individual. It is largest in the white race ; and, all other circumstances being equal, such as race, sex, age, size of body, and health, its bulk bears a general relationship with the development of intellect. Its weight in the adult white male averages near fifty ounces avoir- dupois; in the female, forty-five ounces. In its relation with the weight of the body, the difference between the two sexes is very little. In relation with the size of the body at birth, the brain bears the propor- tion of one to twenty; in the adult, of one to thirty-five. The human brain is larger than in any other animal except the species of elephants and whales; but in relation with the size of the nerves given off from its base, it is larger than in any animal without exception. In relation with the size of the body, the brain is larger in some small mammals and birds than in man, as for instance, in the little monkey Oustiti, the field mouse, and the canary bird. In the infant the brain is of a soft, pulpy consistence, but gradually assumes the firmness, in the adult, of newly-pressed cheese. Its specific gravity is about equal to or a very little greater than water. It is for the most part of a reddish-ash color on the exterior, and is generally ovoid in form, with the broader extremity posterior. Its upper part is uniformly convex, but its lower part, called the base, is uneven. It exhibits four well-marked divisions of unequal size, named the cere- brum, cerebellum, pons, and medulla oblongata. 1 Commissura. 2 Encephalon; cerebrum. THE NERVOUS SYSTEM. 515 THE CEREBRUM. The Cer'ebrum1 forms about six-sevenths of the mass of the brain, and extends the whole length and breadth of its upper part. It is half ovoid, with the narrow extremity forward, the convex side upward, the base downward, and the broadest part opposite the parietal protuber- ances. A deep cleft, the great longitudinal fissure,2 extends the entire length of the upper part of the cerebrum, and the whole depth of its fore and back part. It accommodates the cerebral falx, and along its upper boundary the superior longitudinal sinus. The lateral halves of the cerebrum are named its hemispheres.3 These form vertical planes next the longitudinal fissure, have their outer sur- face convex, and their under part forming the three pairs of cer'ebral lobes. The anterior lobes4 of the cerebrum occupy the anterior fosses of the base of the cranium, and therefore rest above the position of the orbits. The middle lobes5 occupy the middle fossae of the cranial cavity, and are the deepest portions of the cerebrum. They are separated from the anterior lobes by the Syl'vian fissure,* which curves outwardly, and^ receives the small wings of the sphenoid bone^ The posterior lobes7 have no dividing line from those in advance, and are constituted by the portions of the cerebrum resting upon the tento- rium, or situated above the cerebellum. In the upper view of the brain they completely conceal the latter, and their under surface is somewhat hollowed, to accommodate the prominent upper part of the cerebellum. The cerebral hemispheres have their surface everywhere thrown into winding eminences called convolutions,8 separated by deep fissures,9 which receive processes of the pia mater. 1 Cerebrum magnum ; encephalon; the brain; the great brain. 2 Superior longitudinal sinus; fissura,. or scissura cerebri longitudinalis; f. c. 1. superior, inferior, et horizontalis poste- rior; interlobular fissure. 3 Hemisphaeria cerebri; h. c. et pars media cerebri. 4 Lobi anteriores; 1. minores. 5 Lobi medii; 1. descendentes. 6 Fissura, or fossa Sylvii; fissura an- terior ; f. a. inferior et externa; f. infe- rior; f. transversa. 7 Lobi posteriores. The middle and posterior together named lobi poste- riores; 1. majores; 1. temporo-occipitales. 8 Cerebral circonvolutions; gyri; pro- cessus enteroidei cerebri. 9 Sulci; anfractuosities. 516 THE NERVOUS SYSTEM. The Convolutions of the cerebrum are nearly of uniform diameter, and are rounded at the borders of the fissures separating them, but are rather flattened at the summit. Their course is, however, not symmetrical on the two hemispheres, nor are they alike in two individuals, though there is sufficient correspondence in their position and general direction to permit of their being identified. One1 of the most characteristic of these convolutions arches over the corpus callosum on each side ; another,2 less well-marked, borders the great longitudinal fissure; and a third3 borders the Sylvian fissure, and incloses a small group of convolutions' concealed within the latter. The exterior of the cerebrum is composed of gray substance called, from its position, cortical,5 while the interior consists of white substance named, in contradistinction, medullary.6 In a horizontal section of the cerebral hemispheres, they exhibit a central oval surface7 of white sub- stance spotted with minute red points arising from the division of blood- vessels. The circumference of the plane of white substance is observed to form many processes corresponding with the divided convolutions, These processes are further noticed to be everywhere inclosed by the cortical gray matter, which forms a layer of uniform thickness, and fol- lows the course of all the convolutions and fissures of the cerebral hemi- spheres. In a section of the hemispheres, on a level with the corpus callosum, this appears as a bridge of white substance associating the oval centres8 of the same material of the cerebrum. In a view of the base of the brain, the posterior lobes of the cerebrum are concealed by the cerebellum. In advance of this are the medulla oblongata and pons, and in front of the latter, along the median part of the cerebrum, the following are observed in succession: the cerebral crura, the mammillary eminences, the infundibulum, the pituitary body, the optic nerves and commissure, and the olfactory nerves. The Crura of the cer'ebrum9 are two large cylindroid bodies diverg- 1 Great convolution of the corpus callo- sum ; internal convolution of the hemi- spheres ; gyrus fornicatus; processus cristatus. 2 Great convolution of the circumfer- ence of the hemispheres; marginal con- volution of the longitudinal fissure. 3 Convolution of the Sylvian fissure. * Island of Reil; insula; i. Reilii; gyri operti. 5 Cineritious, or vesicular substance. 6 Tubular, or fibrous substance; me- dulla cerebri. 7 Centrum semi-ovale; c. ovale Vieus- senii; c. ovale minus; lesser oval centre of Vicq-d'Azyr. 8 Greater oval centre; centrum ovale Vieussenii. 9 Crura cerebri; pedunculi cerebri; processus medullares cerebri; caudex cerebri; crura anteriora medulhc ob- longatae ; peduncles of the brain; cere- bral peduncles. THE NERVOUS SYSTEM. 517 ing from the fore part of the pons into the cerebral hemispheres, at the inner side of their middle lobes. They are longitudinally striated, and composed, on the exterior, of white substance. On the interior they con- tain a collection of gray substance,1 which appears as a crescentoid layer in a transverse section through them. Fig. 326. Base of the brain. 1, anterior lobes of the cerebrum; 2, middle lobes; 3, posterior lobes; 4, 5, ante- rior and posterior extremities of the great longitudinal fissure; foSylvian fissure; 7, anterior perforated Bpace; 8, infundibulum; 9, mammillary eminences; 10, posterior perforated space; 11, crura of the cere- brum; 12, pons; 13, medulla oblongata; 14, pyramidal bodies; 14*, decussation of the pyramids; 15, oli- vary body; 16, restiform body; 17, hemispheres of the cerebellum; 18, vermiform process at the bottom i of the fissure separating the latter; 19, crus of the cerebellum; 20, pneumogastric lobule of the cerebel- lum; 21. fissure which accommodates the olfactory nerve, 22; 23, bulb of the olfactory nerve; 24. optic commissure; 25, oculo-motor nerve; 26, pathetic nerve; 27, trifacial nerve; 23, abducent nerve; 29, facial nerve; 30, auditory nerve; 31, glosso-pharyngeal nerve; 32, pneumogastric nerve; 33, accessory nerve; 34, hypoglossal nerve. The interval2 separating the crura at its fore part includes the mam- millary eminences and the infundibulum. At its posterior angle it forms a deep pit, which is separated from the third ventricle by some mingled 1 Locus niger; substantia nigra; stratum nigrum. 2 Interpeduncular space. 518 THE NERVOUS SYSTEM. gray and white substance perforated by a number of small blood-vessels, and hence named the posterior perforated space.1 The Mam'millary eminences2 are two small, white, spherical bodies, in contact with each other, immediately in advance of the space just mentioned. Thev are connected above with the anterior crura of the fornix, and contain some gray substance.3 The Infundib'ulum,4 as expressed by the name, is a funnel-shaped body included between the mammillary eminences behind, and the optic commissure in front. It is composed of gray substance, is hollow, and forms part of the bottom of the third ventricle. Its broad base5 narrows to a tubular process, which is directed obliquely downward and forward, and is closed at the extremity. The Pitu'itary body6 occupies the corresponding fossa of the sphe- noid bone, and is connected with the end of the infundibulum. It is reddish gray, of firm consistence, and presents an anterior transversely reniform lobe, and a smaller posterior rounded one. Its structure con- sists of a stroma of connective tissue, with many capillary blood-vessels mingled with granular matter, nuclei, and nucleated cells. The Optic com'missure,7 situated in front of the infundibulum, is formed by the conjunction of the optic tracts converging from the outer side of the cerebral crura. It and its connections will be more particularly de- scribed in the account of the optic nerves. Between the optic commissure and the roots of the olfactory nerves, 1 Substantia perforata postrema, pos- terior, or media: basis ventriculi tertii; antrum; pons Tarini. 2 Eminentiae mammillares, candican- tes, glandulosae, papillares, or medulla- res; bulbi fornicis; bulbs of the'fornix; b. priorum crurum fornicis; globuli medullares; g. albi; corpora alba, mam- millaria, albicantia, or glandularia; pro- tuberantiae crurum medullae oblongatae; p. glandulosae; p. orbiculares; tuber- cula mammillaria, hemispherica, or pisi- formia; prominentia? albicantes ; glan- dulae sub-infundibulo ; g. candicantes ; processus glandulos: protensiones gran- dulares ; testiculi cerebri; mammae mu- liebres. 3 Nucleus griseus. 4 Funnel; funnel of the middle ven- tricle ; pelvis, choana, cyathus, concha, scyphus, lacuna, aquaeductus, embolum, labrum, concavitatis conchularis, or pro- cessus orbicularis cerebri; tubercine- reum cum infundibulo. 5 Tuber cinereum; substantia perfo- rata media posterior. 6 Glandula pituitaria, pituitosa, or basilaris ; hypophysis, appendix, or ap- pendicula cerebri; caput rosae ; colato- rium; labrum ; lacuna; infusorium; concha; pelvis; p. colatoria; sentina en- cephali. 7 Chiasma opticum; chiasm of the op- tic nerves; chiasma nervorum optico- runi. THE NERVOUS SYSTEM. 519 on each side, are the anterior perforated spaces,1 so called from their presenting numerous small apertures for vessels which penetrate to the interior of the cerebrum. On pressing apart the cerebral hemispheres, at the bottom of the great longitudinal fissure, a convex white body, the corpus callosum, is observed to connect the former, and extend for several inches along the latter. The Corpus callo'sum,2 or great cer'ebral com'- missure, in a section of the brain on a level with it, appears as a bridge of white substance, about three inches long and three-fourths of an inch wide, uniting the central white masses of the cere- bral hemispheres. It reaches farther forward than backward, and is narrower anteriorly. Its upper surface3 arches in the length, and is trans- versely striated,* but ex- hibits on each side of the median line5 a narrow tract of longitudinal striae.6 Its anterior and posterior borders are thick and rounded, and are separated by fissures from the contiguous gray substance of the cere- bral hemispheres. In a vertical section of the brain, along the great longitudinal fissure, Transverse section op the hemispheres of the cerebrum on a level with the corpus callosum. 1, white substance of the hemispheres, dotted with divided capillary vessels; 2, gray sub- stance on the convoluted exterior; 3, corpus callosum, with the direction of its fibres indicated by transverse striae; 4, longitud- nal median striae; 5, anterior and posterior portions of the groat longitudinal fissure. 1 Substantia perforata anterior; s. cribrosa anterior ; lamina cribrosa cere- bri; substantia perforata antica media, et partes laterales substantiae perforatae anticae. 2 Commissura magna, or maxima cere- bri ; trabs cerebri; t medularis; co- pula alba, or magna cerebri: great com- missure of the brain; mesolobe. 3 Facies, or superficies superior, or libera. i Striae, or chordae transversales Wil- lisii. 5 Raphe*; r. externa; linea, or chorda longitudinalis. 6 Striae longitudinales Lancisii, in- terna?, or liberae ; nerves of Lancisi. 520 THE NERVOUS SYSTEM. the corpus callosum is observed to be a thick layer of white substance passing beneath an arching convolution of each cerebral hemisphere. Its anterior part1 appears doubled on itself producing a thick fold, the Fig. 328. Section of the brain along the ore it longitudinal fissure. 1, medulla oblongata; 2, pons; 3, cms of the cerebrum; 4, arborescent appearance in section of the fundamental portion of the cerebellum; 5, left hemisphere of the cerebellum; 6, inner surface of the left hemisphere of the cerebrum; 7, corpus callosum; 8, pellucid septum; 9, fornix; 10, anterior crus of the fornix descending to join the correspond- ing mammillary eminence; 11, fissure through which the interposed voUimi 12 is introduced into the third ventricle; 13, pineal gland; 14, its peduncle; 15, rests on the thalamus within the third ventricle; 16, posterior commissure of the latter; 17, middle commissure; 18, anterior commissure; 19, foramen of communication between the third and lateral ventricles; 20, optic nerve; 21, pituitary body; 22, infun- dibulum; 23, mammillary eminence; 24, oculo-motor nerve; 25, posterior perforated space; 26, fourth ventricle; 27, valve of the brain; 28, quadrigeminal body; 23, entrance from the third to the fourth ven- tricle; 30, 31,32, anterior, middle, and posterior lobes of the cerebrum. under portion2 of which becomes continuous with a thin lamina3 curving downward to the optic commissure, and closing the front of the third ventricle. The posterior part4 is seen to reach the base of the cerebrum, just above the position of the quadrigeminjal body and the most promi- nent portion of the cerebellum. '7 In structure the corpus callosum consists of a thick stratum of nerve fibres diverging through the white substance of the cerebral hemispheres to their cortical gray substance. 1 Genu corporis callosi. 2 Rostrum corporis callosi; apex genu. 8 Lamina genu ; lamina cinerea et pe- dunculi corporis callosi. * Splenium, or tuber corporis callosi. THE NERVOUS SYSTEM. 521 FORNIX. Continuous with the back part of the corpus callosum, and arching forward beneath nearly to its anterior part, is a thin layer of white sub- stance, the fornix.1 Viewed from above or below it is triangular. Its upper surface along the middle is continuous with the corpus callosum and pellucid septum, and on each side forms part of the floor of the lateral ventricles. Its lower vaulted surface2 is longitudinally and trans- versely striated, and forms the roof of the third ventricle. The apex of the fornix divides into two portions, its anterior crura,3 which descend with a slight divergence to the mammillary eminences. The basal angles are prolonged, as its posterior crura,* into the middle horns of the lateral ventricles, and become continuous with the fimbri- ated body. PELLUCID SEPTUM. The interval between the corpus callosum and fornix, in the median line of the brain, is occupied by the pellucid septum,5 a thin partition of nerve substance separating the lateral ventricles. It includes a nar- row cavity or fissure, the fifth ventricle,6 which is closed at all points, and is lined with a delicate serous membrane. The pellucid septum is composed of gray substance on its exterior surface, and of white substance on the surface next the fifth ventricle. LATERAL VENTRICLES. Beneath the corpus callosum on each side is a cavity with prolonga- tions extending into the three lobes of the cerebral hemispheres. The cavities are the lateral ventricles;7 the prolongations are named the horns.8 1 Fornix cerebri, trilateralis, or tri- cuspidalis ; arcus medullaris ; camera; comix; corpus psalloides; c. camera- turn ; trigonum cerebrale ; testudo ; com- munionis cerebris. 2 Lyra; psalterium; corpus psalloi- deum; lamina medullaris; 1. triangularis; membrana medullaris inter crura poste- riora fornicis. 3 Crura or cornua anteriora fornicis; cornua fornicis ; columna? fornicis ; an- terior pillars or pillar; crus, or columna fornicis. * Crura posteriora fornicis; crura for- nicis ; posterior pillars. 5 Septum pellucidum, or lucidum; diaphragma cerebri; d* ventriculorum lateralium; speculum; corpus specu- lare; mediastinum ; septum medium; s. tenue; tympanum; septum medullare triangulare. 6 Ventriculus quintus; ventriculus, camera, or sinus septi pellucidi; inci- sura septi; cavitas Vieussenii, Sylvii, Duncani, prima, or quinta. * Ventriculi laterales ; v. anteriores ; v. magni; v. majores; v. priores; v. su- periores ; v. tricornes ; sinus anteriores. 8 Cornua; c. laterales; partes late- rales. 522 THE NERVOUS SYSTEM. Each lateral ventricle has for its Transverse section of the cerebral hemi- spheres, THE CORPUS CALLOSUM REMOVED, AND THE lateral vextricles exposed. 1, white substance of the interior of the cerebral hemispheres; 2, gray substance of the exterior convoluted surface; 3, 4, anterior and posterior extremities of the cor- pus callosum; 5, anterior horn of the left lateral ventricle; 6, middle or descending horn; 7, poste- rior horn; 8, striated body; 9, pellucid septum; 10, fifth ventricle; 11, fornix; 12, posterior crus of the fornix; 13, attachment of the fornix to the under part of the corpus callosum; 14, hippocam- pus; 15, fimbriated body; 16, ergot; 17, semicir- cular line; 18, choroid plexus; 19, edge of the thalamus.-j,o ^-.-avvviw* JlV«.-«". • '.X/ roof1 the corpus callosum, its floor the fornix, its inner wall the pellu- cid septum, and its outer wall the striated body. The anterior horn2 of the lat- eral ventricle, less conspicuous than the others, is simply the ex- tension of the cavity around the anterior extremity of the striated body. The middle horn3 curves down- ward into the middle cerebral lobe. From the inner part of its floor projects a thick convex ridge, in- dented at its lower end,4 and named the hippocam'pus.5 The upper border of the ridge is provided with a white band, named the fim- briated body,6 which is continuous with the posterior crus of the for- nix. The hippocampus is composed of white substance7 on the sur- face, of gray substance within, and the latter appears superficially as a dentated band8 on the inner or concave side of the hippocam- pus. The posterior horn9 curves in- wardly as it passes into the pos- 1 Tegumentum cellae lateralis; t. ven- triculi lateralis. 2 Cornu anterius. 3 Cornu medium, inferius, descendens, magnum, or laterale; sinus inferior hip- pocampi ; s. cornu Ammonis; ventricu- lus inferior hippocampi; v. bombycinus. 4 Digiti cornu Ammonis; colliculi fissi interni; uncus; pes hippocampi. 5 Hippocampus major; pes hippocam- pi; p. h. major ; cornu Ammonis; c arietis; vermis, or appendix bombyci- nus; bombyx; processus cerebri late- ralis; protuberantia cylindroides; pes hippopotami major. 6 Fimbria, or taenia hippocampi; lim- bus, or corpus fimbriatum; c. f. Sylvii. 7 Lamina medullaris superficialis cor- nu Ammonis. 8 Fascia dentata ; margo denticulatus Tarini. 9 Cornu posterius; cavitas digitalis; c. ancyroidea; diverticulum. THE NERVOUS SYSTEM. 523 terior cerebral lobe. From its inner side projects a white, spur-like ridge, named the ergot.1 The lateral ventricles communicate with each other and with the third ventricle by a foramen2 beneath the anterior crura of the fornix. In all other positions they are closed, and are lined throughout with a delicate serous membrane. CORPORA STRIATA, OR STRIATED BODIES. Projecting into each lateral ventricle from the outer wall is a half- pyriform prominence, named, from its appearance in section, the cor'pus stria'tum, or striated body.3 Its larger portion* is anterior, and its narrower portion5 curves backward to the outer side of the thalamus. Some depth from the ventricular surface it is composed of gray substance,6 beneath which is a layer of white substance,7 succeeded by a lenticular nucleus8 of gray substance. The latter is penetrated by the diverging fibres of the cerebral crus, giving to it in section a striated appearance. Below the fore part of the lenticular nucleus is a smaller accumulation of gray substance,9 and to its outer side is another collection.10 On the floor of each lateral ventricle is a remarkable vascular append- age of the pia mater, named the choroid plexus. This extends from the foramen beneath the anterior crura of the fornix along the side of the latter, and descends to the bottom of the middle horn of the lateral ventricle. It is continuous beneath the fornix with the interposed velum of the pia mater, and is separated from the cavity of the lateral ventricle by its lining membrane. THIRD VENTRICLE. Beneath the fornix is the third ventricle11 of the brain. This is a narrow triangular cavity, with its apex forward and its base correspond- ing with the fissure between the posterior border of the corpus callosum 1 Hippocampus minor; calcar; c. avis; unguis; u. avis ; u. Halleri; ocrea; pes hippocampi minor; eminentia minor digitata; e. unciformis; ocrea; collicu- lus. 2 Foramen of Monro ; f. Monroi; f. anterius; vulva. s PI.: corpora striata; eminentiae stria- tae; e. pyriformes; e. similes coxis hu- raani; e. lenticulares ; prominentia? len- tiformes; apices medullae oblongatae; processus anteriores medullae oblonga- tae ; ganglia magna superiora cerebri; g. cerebralia anteriora ; colliculi nervo- rum ethmoidalium; apices crurum me- dullae oblongatae. * Caput. 5 Cauda 6 Nucleus caudatus ; n. intraventricu- laris. 7 Capsula medullaris nuclei lentifor- mis; capsula externa. 8 Nucleus lentiformis; n. extraven- tricularis. 9 Nucleus amygdalae. 10 Claustrum ; nucleus taeniaeformis. 11 Ventriculus tertius ; v. medius cere- bri. 524 THE NERVOUS SYSTEM. and the quadrigeminal body. Its fore part is closed by the anterior descending portion of the corpus callosum. Its floor is formed in suc- cession from before backward by the optic commissure, infundibulum,1 mammillary eminences, posterior perforated space, and cerebral crura. Behind the latter and beneath the quadrigeminal body it communicates' with the fourth ventricle by a narrow passage,3 the sides of which are coated with gray substance.4 As previously mentioned, beneath the anterior crura of the fornix it opens on each side into the lateral ven- tricles. At the fissure,5 between the posterior border of the corpus callosum and the cerebellum, a process of pia mater, the interposed velum,6 is introduced along the under surface of the fornix, which forms the vaulted roof of the third ventricle. THALAMI. The outer walls of the third ventricle are formed by a large, oval prominence, the thal'amus,7 which is supported on the inner side of the diverging cerebral crus. Its ventricular surface, for the most part, is composed of white substance,8 but on the inner side exhibits some gray substance. Its interior is composed of mingled white and gray sub- stance.9 In front and to the outer side the thalamus is separated from the stri- ated body by a narrow semicircular band10 of white substance. The anterior and posterior more prominent portions of the thalamus are named its tubercles.11 Beneath the posterior tubercle are two convex white eminences, the genic'ulate bodies,12 which give partial origin to the optic tracts. 1 Aditus ad infundibulum. 2 Aditus ad aquaaductum Sylvii; in- troitus. 3 Iter e tertio adquartum ventriculum; aquaeductus Sylvii; fistula sacra; ven- triculus subter nates et testes; transi- tus ad ventriculum quartum; aquae emissorium; canalis medianus; incile, or canalis tuberculorum; c. corporum quadrigeminorum. 4 Substantia feruginea superior. 5 Transverse fissure of the cerebrum. 6 Velum interpositum ; tela choroidea. 7 Optic thalamus ; pi.: thalami nervo- rum opticorum; ganglia magna inferiora cerebri; g. cerebri media ; g. c. postica; protuberantiae striatae; eminentiae mag- nae cerebri; corpora striata superna pos- teriora; c. s. posteriora interna; colli- culi nervorum opticorum; capita, or crura medulla? oblongata?; juga crurum medullarium ; secundum par tuberculo- rum ; secunda sectio crurum medulla- rium. 8 Stratum zonale. 9 Nuclei cinerei. 10 Taenia semicircularis; t. terminalis; lamina cornea; centrum geminum semi- circulare ; stria cornea. In part: acies, flabellum, and penicillus. 11 Tuberculum superius anterius and t. s. posterius, or pulvinar. 12 Corpus geniculatum internum and c g. externum ; corpora geniculata. THE NERVOUS SYSTEM. 525 QUADRIGEMINAL BODY. At the back part of the third ventricle is situated a quadrate, white mass, divided on its upper surface by a crucial gutter1 into four emi- Fig. 330. Striated bodies, thalami, quadrigeminal body, and cerebellum. 1, quadrigeminal body; 2, valve of the brain; 3, superior peduncle of the cerebellum; 4, superior portion of the middle peduncle; 5, supe- rior portion of the crus of the cerebrum; 6, posterior tubercle of the thalamus; 7, anterior tubercle; 8, fundamental portion of the cerebellum ; 9, process of gray substance resting on the valve of the brain; 10, posterior commissure of the third ventricle; 11, middle commissure; 12, anterior commissure; 13, pineal gland turned forward; 14, its peduncle; 15, thalamus; 16, hemispheres of the cerebellum; 17, dentated body; 18, semicircular h««; 19, vein of the striated body; 20, anterior crura of the fornix; 21, striated body; 22, fifth ventricle between the layers of the pellucid septum. nences, from whence it derives the name of quadrigem'inal body or bodies.2 It extends obliquely from the thalami toward the cerebellum, with which it is connected by the superior peduncles. At the sides it is 1 Sulcus longitudinalis et s. transver- sus corporum quadrigeminorum. 2 Corpora, or tubercula quadrigemina; c. bigemina; c. anteriores; protuberan- tiae ; processus natiformes et testiformes; tubercula; t. anteriora et posteriora; prominentia?; p. orbiculares ; p. ence- phalali; nates et testes; prominentias, eminentia?, or corpora superiores et in- feriores, majores et minores, or nati- formes et testiformes ; pons Sylvii. 526 THE NERVOUS SYSTEM. attached to the thalami and geniculate bodies; and by means of a band1 of white substance joins the back part of the pons between the crura of the cerebrum and cerebellum. Between it and the posterior border of the corpus callosum is the fissure through which the interposed velum of the pia mater is introduced along the roof of the third ventricle. Beneath it is the entrance from the latter to the fourth ventricle. PINEAL (iLAND. Upon the anterior pair of eminences of the quadrigeminal body there reposes a small cone of gray substance, named the pine'al gland.2 It is remarkable for containing a quantity of sand-like grains,3 having nearly the same composition as bone earth. From the front of the pineal gland a pair of narrow tracts of white matter, named its pedun'cles,4 diverge, like the prongs of a fork, to the inner sides of the thalami. COMMISSURES OF THE THIRD VENTRICLE. The anterior com'missure5 appears as a small transverse cylinder of white substance at the front part of the third ventricle, between the anterior crura of the fornix and the descending portion of the corpus callosum. It is a cord of white nerve fibres extending through the lower part of the striated bodies into the cerebral hemispheres. The middle commissure6 is a rounded isthmus of gray substance con- necting the thalami across the centre of the third ventricle. The posterior commissure7 is a thin lamina of white substance ex- tended between the back part of the thalami, and connecting the quadri- geminal body with the pineal gland. THE CEREBELLUM. The Cerebel'lum8 forms about one-eighth of the bulk of the brain, and occupies the posterior fossae of the cranial cavity, beneath the ten- 1 Lemniscus; fillet; laqueus; fascicu- lus triangularis lateralis; ribbon of Reil. 2 Glandula pinealis; conarium; pinus; penis; cerebral epiphysis ; corpus co- noides; c. turbinatum; turbo cerebri; virga. 3 Cerebral sand; acervulus cerebri; concrementa pinealia; sabulous matter; brain sand; pineal sand; sabulum co- narii; lapilli glandulae pinealis. * Pedunculi conarii; striae, or taeniae medullares; habenula; reins. 5 Commissura anterior. 6 Commissura media ; c. mollis; chor- dae AVillisii; unio thalamorum nervorum opticorum. 7 Commissura posterior. 8 Cerebrum parvum; c. posterius; ap- pendix ad cerebrum ; encranion; epen- cranis; parencephalum; encephalium; micrencephalum ; encephalus opisthius; little brain; after brain. THE NERVOUS SYSTEM. 527 torium, which separates it from the posterior lobes of the cerebrum. Like the latter, it consists of two lateral portions, named hemispheres,1 which are separated behind and below by a wide, deep groove, named the valley.2 The hemispheres are associated by an intermediate or fundamental portion,3 which is not distinctly evident above, but appears at the bottom of the valley as a thick, worm-like ridge, whence it receives the name of the verm'iform process.4 The superior cerebellar surface5 is moderately convex, is most prom- inent at its anterior portion,6 and inclines from the median line of union' of the hemispheres to their lateral border. The lower and outer sur- faces8 are prominently convex. The exterior of the cerebellum presents the same gray color as that of the cerebrum, and is divided by numerous fissures9 into nearly par- allel laminae,10 having a general transverse direction. When the constitution of the hemispheres is examined, it is found that each consists of an interior prismoid trunk11 of white substance, from the sides of which emanate about a dozen broad, thin, divergent lamiuas of the same material. These divide into a second series of thinner laminae, which in many cases subdivide. Around the laminar divisions of white substance the cortical gray substance of the cerebellum is folded, the intervals of the folds corresponding with fissures of the cerebellar surface. In consequence of this arrangement, a vertical sec- tion of the hemispheres exhibits an arborescent appearance,12 while a transverse section simply presents a broad surface of the medullary white substance bordered by gray substance. The fundamental portion of the cerebellum exhibits the same arrange- ment of structure as the hemispheres, and differs only in accordance with the comparative size of the part. At the anterior extremity of the valley, the hemispheres form a pair of rounded eminences, including between them a more prominent por- 1 Hemisphaeria cerebelli; pontes late- rales. 2 Yallis; vallecula ; scissura cerebelli longitudinalis. 3 Ambitus vermis; vermiform pro- cess. * Inferior vermiform process; the worm; vermis inferior; protuberantia vermiformis; pyramid of Malacarne; pyramid, uvula, and nodulus. 5 Superficies cerebelli superior. 6 Culmen; monticulus. 7 Monticulus; superior vermiform pro- cess; vermis superior; protuberantia vermiformis superior. s Superficies cerebelli inferior. 9 Sulci. 10 Gyri; convolutions; circonvolutions. 11 Stratum medullare; meditullium la- terale. 12 Arbor vitae. 528 THE NERVOUS SYSTEM. tion of the vermiform process, which together, from their resemblance in relative position, have been named tonsils1 and uvula. Above the tonsils anteriorly, and separated from them by a fissure2 proceeding from the cerebellar crura outwardly, each hemisphere presents the pneu- mogas'tric lobule,3 so named from its vicinity to the corresponding nerve. DENTATED BODY. Within the trunk of white substance of each hemisphere of the cere- bellum there is a plicated pouch-like layer4 of gray substance. In sec- tion this appears as an indented nucleus of white substance5 bordered by gray substance, whence its name of the dentated body.6 The gray layer is open at its upper and inner part, in which position the nerve fibres of the white substance gain admission to its interior surface. CRURA OF THE CEREBELLUM. At the base of the brain, the pons extends laterally as a pair of cylindroid processes of white substance, diverging posteriorly, and enter- ing the hemispheres of the cerebellum. These processes are the crura, or middle pedun'cles of the cerebellum.7 They are longitudinally striated, and consist of large bundles of nerve fibres proceeding from the pons to the white substance of the cerebellar hemispheres. Behind the crura are situated the superior and inferior peduncles of the cerebellum. The Superior pedun'cles8 are two flattened, cylindrical, white bands, ascending obliquely in a converging manner from the interior white sub- stance of the hemispheres of the cerebellum to the quadrigeminal body. The triangular interval of these peduncles, and the fundamental portion of the cerebellum, is closed by a thin lamina of white matter, incorrectly 1 Tonsillae ; amygdalae ; lobi medulla3 oblongatae ; lobi interni cerebelli. 2 Sulcus horizontalis ; s. perpendicu- laris ; s. magnus cerebelli. 3 Lobulinervi-pneumogastrici; appen- dices lobulares anteriores; flocculi; sub- peduncular lobes. 4 Fascia dentata cinerea, or fimbriata. 5 Medulla centralis, or ciliaris. 6 Corpus dentatum, denticulatum, rhomboideum, ciliare, or mixtum; nu- cleus dentatus, rhomboidalis, lenticula- tus, fimbriatus, or centralis; ganglion ciliare; g. cerebelli; substantia rhom- boidea. 7 Crura cerebelli; c. c. ad pontem; c. media ; c. lateralia; c. posteriora; bra- chia pontis. 8 Anterior peduncles; crura, or bra- chia cerebelli ad corpora quadrigemina; crura superiora; c. anteriora; c. ad- scendentia; commissura cerebelli et cerebri; brachia conjunctoria, or copu- lativa; processus cerebelli ad testes; processus ad testes; columna? valvulae Vieussenii; oblique intercerebral com- missures. THE NERVOUS SYSTEM. 529 named the valve of the brain.1 This so-called valve is attached at all its borders, and is situated over the fourth ventricle. Upon its upper surface a tongue-like process2 of gray substance, transversely ridged, is extended from the cerebellum. The Inferior peduncles of the cerebellum,3 smaller than the others, are two narrow, white bands, which proceed from the interior of the hemispheres, and descend to become continuous with the restiform bodies of the medulla oblongata. THE PONS. The Pons* is a quadrate white body, situated back of the middle of the base of the cerebrum, and in advance of the cerebellum. It rests on the upper part of the basilar process of the occipital bone, and the de- clivity of the sphenoid bone. Its under surface is convex and trans- versely striated,5 and its anterior and posterior borders are rounded. Along the median line of the under surface it presents a shallow groove,6 which accommodates the basilar artery, and also exhibits small perfora- tions transmitting branches of the latter. The superficial or lower portion of the pons is composed of transverse nerve fibres, which at the sides diverge as the crura or middle peduncles of the cerebellum. The association of the hemispheres of the cerebellum through its middle peduncles is the origin of the name pons, signifying a bridge, though the term is extended in its application to the deeper parts, or those within the superficial portions of the structure. The latter, which constitutes a transverse commissure conjoining the hemispheres of the cerebellum, depends on these for its existence; and therefore in birds, in which the cerebellar hemispheres do not exist, the transverse commis- sural portion of the pons is absent. 1 Valvula cerebelli; v. Vieussenii; v. * Pons Varolii; p. cerebelli; nodus Willisiana; v. cerebri; v. magna cere- encephali; n. cerebri; protuberantia bri; velum medullare anterius; v.Vieus- annularis; p. a. Willisii; p. basilaris; senii; v. interjectum cerebelli; v. apo- annular protuberance; processus, emi- physi vermiformi obtentum; lacunar nentia, or prominentia annularis; tuber ventriculi quarti superior. annulare; corpus annulare ; commissura 2 Lingula; linguetta laminosa. hemisphaeriorum cerebelli; c. cerebelli; 3 Pedunculi cerebelli sensu strictiori; mesocephalon; Varoli's bridge; cerebral crura cerebelli ad medullam oblongatam; protuberance. c. c. ad medullam spinalem; crura infe- 5 Sulci transversi; s. obliqui; s. mi- nora; c. posteriora. nores pontis. 6 Sulcus basilaris. 34 530 THE NERVOUS SYSTEM. From the front of the pons, the crura of the cerebrum appear to emerge, and this is found actually to be the case on removal of the superficial portion of the pons; for within this, longitudinal fasciculi of fibres, intermingled with gray matter, extend from the medulla oblongata upward to become continuous with the cerebral crura. THE MEDULLA OBLONGATA. The Medul'la oblonga'ta1 is the smallest of the four divisions of the brain, and is a white, pyriform body, situated in front of the cerebellum, and extending from the pons to the spinal cord, with which it is con- tinuous. It is a little over an inch in length, and rests in the groove of the basilar process of the occipital bone. It is divided into two lateral portions by an anterior and a posterior median fissure, continuous below with the corresponding fissures of the spinal cord. The medulla oblongata is further divided on each side into the pyram- idal, olivary, and restiform bodies, and the posterior pyramids. The Pyram'idal bodies2 appear on each side of the anterior median fissure as a club-shaped, white mass, continuous below with the anterior and lateral columns of the spinal cord. Their upper and thicker ex- tremity is rounded, and is connected with the pons. At the lower part of the median fissure portions of the white sub- stance of the pyramidal bodies cross from side to side, producing the decussation of the pyramids.3 In structure the pyramidal bodies are three-sided prismatic bundles of nerve fibres, ascending from the anterior and lateral columns of the spinal cord to the pons. The inner fibres ascend from the lateral columns of the cord, and cross to the opposite side, thus producing the decussa- tion above mentioned; the lateral fibres ascend from the anterior col- umns of the spinal cord of the same side. The Ol'ivary bodies4 appear as oval, white prominences to the outer side of the pyramidal bodies. They are composed of white substance, and contain a plicated, pouch-like layer of gray substance. In section 1 Bulbusrachidicus; caudex encephali communis; medulla respiratoria; ob- long medulla; cerebrum elongatum; centrum vitale. 2 Corpora pyramidalia; c. p. anteri- ora; c. p. interna; eminentia? pyramid- ales ; e. oblongae; e. mediana? interna?. 3 Decussatio pyramidum; decussation of Mistichelli. * Corpora olivaria; eminentiae oliva- res; e. ovales ; e. o. laterales; olivse ; corpora ovata, or semiovalia; funiculi, or fasciculi ovales. THE NERVOUS SYSTEM. 5gi the latter gives the central mass of the olivary bodies the appearance of an indented oval nucleus, whence its name of the dentated bodyf An additional small accumulation of gray substance within the olivary bodies, distinct from the former, is named the accessory olivary nucleus. The white substance of the olivary bodies is continuous with that of the anterior columns of the spinal cord, and forms a fasciculus, which may be traced through the pons to the crura of the cerebrum and the quadrigeminal body. The Res'tiform bodies,1 situated to the outer side, posteriorly, of the olivary bodies, ascend from the spinal cord in a divergent manner, and become continuous with the inferior peduncles of the cerebellum. They are composed of white substance continuous with that of the spinal cord, and contain some gray substance2 continuous with the posterior horns of the latter. The Posterior pyramids3 are situated behind the preceding bodies, on each side of the posterior median fissure, and diverge at the sides of the fourth ventricle. They consist of two narrow fasciculi of white sub- stance, continuous with the posterior median columns of the spinal cord, and appear to merge in the inferior peduncles of the cerebellum. At the sides of the medulla oblongata, below the olivary bodies, or even crossing their lower part, there usually exist some arching fibres connecting the pyramidal and restiform bodies, and named arciform fibres.4 Other fibres also pass transversely from before backward, within the median fissures of the medulla oblongata, and are named septal fibres. FOURTH VENTRICLE. The triangular space included between the medulla oblongata and pons in front, and the cerebellum behind, is called the fourth ventricle.5 1 Corpora restiformia; pyramides laterales; fasciculi, or funiculi pyra- midales; fasciculi laterales et cuneati; corpora pyramidalia posteriora; pro- cessus a cerebelli ad medullam oblonga- tum; peduncles of the medulla oblongata; inferior peduncles of the cerebellum. 2 Nucleus, or corpus cinereus; par- tially the tubercula cinerea of Rolando. 3 Fasciculi graciles. 4 Fibra? transversa? arciformes; stra- tum zonale medulla? oblongatae ; ponti- culus. 5 Ventriculus quartus; v. Arantii: v. calami-script orii; v. rhomboidalis ; v. cerebelli; ventricle of the cerebellum. 532 THE NERVOUS SYSTEM. It communicates, by a narrow passage1 ascending beneath the quadri- geminal body, with the third ventricle, and is lined with a delicate serous membrane, continuous with that of the latter cavity, and opening below into the subarachnoid space of the spinal cord. The posterior sloping roof of the fourth ventricle is formed by the superior peduncles of the cerebellum, and the intervening "valve" of the brain. Its sides, posteriorly, are formed by the inferior peduncles of the cerebellum. The anterior part, or floor of the fourth ventricle,2 is formed by the back of the medulla oblongata and pons. It is lozenge shaped in out- line, and is bounded laterally above by the superior peduncles of the cerebellum; below by the inferior peduncles, the restiform bodies, and posterior pyramids. The sides of the floor incline to the posterior me- dian fissure,3 which is continuous below with that of the spinal cord, and becomes obsolete above. The surface of the floor is rendered uneven by several slight convex eminences,4 and is invested with a layer of gray substance5 continuous with that of the spinal cord. On each side it is crossed by a series of transverse white lines6 which are connected with the origin of the audit- ory nerves. At the lower angle7 of the floor is a small pit,8 which is the upper ex- tremity of a canal9 existing during foetal life along the centre of the spinal cord. The lower portion of the fourth ventricle is closed by the arachnoid membrane, but, as previously indicated, it communicates with the sub- arachnoid space of the spinal cord. 1 Meatus conjunctorius ventriculi quarti et tertii medii; aquaeductus Sylvii; iter e tertio ad quartam ventriculam. 2 Sinus, fovea, fossa, or cavitas rhom- boidalis; scrobs, or fovea ventriculi quarti; area, or semicanalis medullae oblongatae. 3 Sulcus, or fissura longitudinalis; s. or f. medius fossae rhomboidalis. 4 These comprise—1, the eminentiae teretes, semiteretes, perpendiculares, or longitudinales; funiculi, or fasciculi te- retes, or the corpora teretia; 2, the emi- nentiae cuneiformes cinereae ; alas cine- reae, or folia cinerea lanceolata. 5 Comprising the substantia cinerea ochracea; locus cinereus, or coeruleus, or substantia ferruginea; and the fasci- ola? cinereae. 6 Stria?, taeniae, or libra? medullares, or acusticae; fasciculi etfibrillae filiformes nervi acustici. 7 Calamus scriptorius. 8 Ventriculus Arantii. 9 Canalis medullae spinalis. THE NERVOUS SYSTEM. 533 THE SPINAL CORD. The Spinal cord,1 the centre of excito-motor impulses, with its mem- branes, occupies the vertebral canal. It is continuous with the medulla oblongata, and extends from the occipital foramen to the lower part of the first lumbar vertebra. In the embryo the spinal cord corresponds in length with the verte- bral column, but subsequent to the third month the latter grows more rapidly than the former, so that at birth the cord extends only as far as the third lumbar vertebra. The length of the spinal cord of the adult is from fifteen to eighteen inches, and its weight about an ounce and a half avoirdupois. In gen- eral form it is cylindrical, compressed from before backward, and it varies in diameter in different positions. In the region of the neck it presents the cervical enlargement2 extending from about the third cervical to the first dorsal vertebra. Below this position it is of nearly uniform diameter, until it forms the lumbar enlargement,3 which is opposite the last dorsal vertebra, and subsequently it tapers to a conical point.4 The cervical and lumbar enlargements correspond with the large nerves connected with these portions of the spinal cord. Where other nerves emanate from the latter, it exhibits slight enlargements, which give to the sides of the cord a somewhat undulating appearance. Exteriorly the spinal cord is composed of white nerve substance; in- teriorly, of gray substance—the former being the more abundant, espe- cially in the cervical region. In front and behind, the spinal cord is divided by fissures into lateral symmetrical halves. The anterior median fissure5 penetrates about one-third the thickness of the cord, but becomes deeper toward its lower extremity. The white substance at its bottom associating the two sides of the cord is named the anterior or white commissure.6 The posterior median fissure,7 narrower, and for the most part deeper than the anterior, becomes shallower toward its lower end. 1 Medulla spinalis ; spinal marrow; corda spinalis; medulla dorsalis; m. spina?; caudex dorsalis; funiculus spi- nalis ; cerebrum longum, or oblongum; nucha; myelus ; myelon; notomyelus; rhacites; rhachetrum; processus rachi- dianus; funis argenteus; sacra fistula; vertebral marrow. 2 Intumescentia cervicalis. 3 Intumescentia lumbaris, or cruralis. 4 Conus medullaris ; c. terminalis me- dulla? spinalis. 5 Fissura longitudinalis anterior, or mediana. 6 Commissura anterior. 7 Fissura longitudinalis posterior; sul- cus longitudinalis medianus; fis. long. post, superior et inferior. 534 THE NERVOUS SYSTEM. Fig. 331. From each side of the cord, the spinal nerves originate by a series of anterior and posterior roots, the attachments of which give rise to slight furrows named the anterior and posterior lateral fissures.1 Of these the posterior is the more evi- dent from the gray substance of the interior of the cord extending to its bottom, so as to isolate the white substance of the posterior part of the cord from the antero- lateral part. The fissures of the spinal cord have led to its division into col- umns. The portions included be- tween the anterior median fissure and the antero-lateral fissures con- stitute the anterior columns ;2 those at the sides between the lat- eral fissures or the roots of the spinal nerves are the lateral columns;3 and those between the posterior median and postero-lateral fissures are the posterior columns.4 In con- sequence of the feebly-marked character of the antero-lateral fissures, the anterior and lateral portions of the cord are usually referred to under the name of the antero-lateral columns. At the upper part of the cord, a pair of narrow, white tracts are ob- served separated by the posterior median fissure. These are named the posterior median columns,5 and are continuous with the posterior pyra- mids of the medulla oblongata. In a transverse section of the spinal cord, the gray substance is noticed to be arranged in the form of two irregular crescentoid bars, situated one on each side, with their convexities conjoined by a transverse bar. The extremities of the crescentoid bars are called horns,6 and the inter- vening transverse bar is the posterior or gray commissure.7 The anterior horns8 are short, broad, and obtuse, and are inclosed Segment of the spinal cord. 1, anterior median fissure; 2, posterior median fissure; 3, postero- lateral fissure; 4. antero-lateral fissure; 5, anterior column; 6, lateral column; 7, posterior column; 8, anterior commissure; 9, anterior horns of the gray substance: 10, posterior horns; 11, gray com- missure ; 12, anterior root of a spinal nerve spring- ing by a number of filaments from the antero- lateral fissure; 13, posterior root from postero- lateral fissure; 14. ganglion on the posterior root; 15, spinal nerve formed by the union of the two roots. 1 Fissura lateralis anterior et poste- rior. 2 Funiculi anteriora. 3 Funiculi lateralia. 4 Funiculi posteriora. 5 Fasciculi graciles. 6 Cornua; crura. 7 Commissura cinerea. Its central portion is the nucleus cinereus; centrum cinereum; commissura gelatinosa; sub- stantia grisea centralis; gray central nucleus; gelatinous central cord of the gray commissure. 8 Cornua anteriora. THE NERVOUS SYSTEM. 535 within the antero-lateral columns of the cord. The posterior horns1 are longer and narrower, and are capped at the extremity by a more trans- lucent portion of the gray substance, called the gelatinoid substance.2 They separate the antero-lateral from the posterior columns, and reach the bottom of the postero-lateral fissures. Toward the lower extremity of the spinal cord, the crescentoid appear- ance of the lateral bars of gray substance becomes indistinct, and the relative quantity of the white substance is diminished. MEMBRANES OF THE BRAIN AND SPINAL CORD. THE PIA MATER. The Pia mater3 is a delicate fibro-vascular membrane closely investing the brain and spinal cord, contributing to sustain their structure, and serving as a point of departure and termination to their numerous capil- lary blood-vessels. PIA MATER OF THE BRAIN. The branches of the internal carotid and vertebral arteries destined to supply the brain with blood, by frequent anastomosis form upon its sur- face an intricate net-work. This vascular net, in conjunction with numerous veins, and strengthened with delicate, interlacing bundles of fibrous tissue, constitutes the pia mater of the brain. Processes of the membrane extend into all the fissures of the brain, and its vessels supply and return the blood of the capillaries of the latter. When the pia mater is detached, the torn capillaries from the brain give its inner sur- face a flocculent appearance. A process of the pia mater, named the interposed velum,4 dips from between the cerebrum and cerebellum, beneath the posterior border of the corpus callosum, and above the quadrigeminal body, into the third ventricle. The velum extends along the under surface of the fornix, and has the same form. In the median line it incloses the two ventricular veins, which lie parallel to each other, and end in a short trunk5 which opens into the straight sinus of the dura mater. On each side the velum projects beyond the lateral borders of the for- 1 Cornua posteriora. '2 Substantia cinerea gelatinosa. 3 Pia meninx; mollis, or tenuis mater; tunica, or meninx interior, vasculosa, or choroides; membrana vasculosa cerebri; m. cerebri tenuis, mollis, or propria; inner lamina of the meninges; tunica cerebri et medullae spinalis propria. 4 Velum interpositum, triangulare, or choroides; tela choroidea; t. c. supe- rior; plexus choroideus medius; rete mirabile; r. choroideum. 5 Vena Galeni. 536 THE NERVOUS SYSTEM. nix, and forms the choroid plexuses of the lateral ventricles.1 These plexuses are two remarkable vascular appendages, which resemble in ap- pearance pieces of knotted red worsted cord. They extend from the foramen beneath the anterior crura of the fornix, along the floor of the lateral ventricles at the side of the latter, and descend to the bottom of the middle horns of the ventricles. Narrow at their commencement, they increase in bulk until they reach the middle horns of the lateral ventricles, and then decrease to their termination. In structure the cho- roid plexuses consist of portions of the interposed velum, furnished with many villous processes, and containing tortuous blood-vessels. The villous processes, in an advanced period of life, are frequently found more or less dilated into spherical bodies, from the size of a pin-head to that of a pea, and have been mistaken for hydatid parasites. On the under.surface of the interposed velum are situated the choroid plexuses of the third ventricle.2 These are two narrow, vascular ap- pendages, extending from those of the lateral ventricles backward along the course of the ventricular veins. The choroid plexuses of the fourth ventricle3 extend from the pneu- mogastric lobule of the cerebellum, join each other across the vermiform process, and are prolonged a short distance along the sides of the latter. Connected with the pia mater at the borders of the great longitudinal fissure, there is found a variable number of coarse, rounded granules, called Pacchionian bodies.4 These are usually collected in groups, and frequently protrude through openings of the dura mater into the longi- tudinal sinus. The openings just indicated appear to result from pres- sure of the Pacchionian bodies, and absorption of the contiguous osse- ous wall of the cranium is also occasionally produced by them. They were formerly supposed to be glandular in character, but as they do not exist at birth, they are perhaps to be viewed as a pathological produc- tion, notwithstanding their frequency. PIA MATER OF THE SPINAL CORD. The pia mater of the spinal cord has fewer vessels and more fibrous tissue entering into its composition than that of the brain, and therefore appears denser, stronger, and less vascular. Thin pro- cesses of the membrane dip into the anterior and posterior median 1 Plexus choroideus, or choroides; p. c. lateralis dexter et sinister: p. choroi- fornies; p. reticularis; p. reteformes; p. glandulares; vermes cerebri; retia mirabilia. 2 Plexus choroideus ventriculi tertii. 3 Plexus choroideus ventriculi quarti. 4 Glandula? Pacchionii; glands of Pac- chioni; glandulae dune matris; g. dura? meningis; tubercula parva; corpora glandiformia; cerebral granulations. THE NERVOUS SYSTEM. 537 fissures. In front it exhibits a longitudinal fibrous band,1 and on each side, between the roots of the spinal nerves, it forms the denticulate liga- ment.2 This is a projecting fibrous band deeply toothed in a saw-like manner at its outer part, the points of the dentations being attached to the dura mater in the intervals of the spinal nerves. From the lower end of the spinal cord the pia mater is continued, as a partially hollow, thread-like prolongation,3 to the termination of the vertebral canal, where it is attached to the dura mater. The hollow of the prolongation is apparently occupied by a continuation of the gray substance of the spinal cord. THE EPENDYMA. The Epen'dyma4 is the delicate, transparent, serous membrane, lining the ventricles of the brain and the central canal of the spinal cord of the embryo. At birth its epithelium consists of ciliated cells, but at a later period the cilia are obliterated. THE DURA MATER. The Dura mater,5 the exterior investment of the brain and spinal cord, is a dense, strong, inextensible bluish-white membrane, composed of an intertexture of bundles of fibrous tissue. DURA MATER OF THE BRAIN.6 This consists of two intimately adherent layers, of which the outer corresponds with the periosteum in other parts of the skeleton, while the inner alone corresponds with the spinal dura mater. The adhesion of the dura mater to the inner surface of the cranium depends on the many minute blood-vessels and fibrous processes passing between the two. The connection is closest along the sutures, and at the borders of the foramina, and is especially well marked at the base of the cranium. The inner layer of the dura mater has a smooth .internal surface closely invested by the arachnoid membrane. Between the cerebrum and cere- bellum and their hemispheres it sends strong partitions which contribute to sustain the mass of the brain. 1 Linea splendens Halleri. 2 Ligamentum denticulatum; 1. serra- tum; 1. dentatum ; membrana dentata. 3 Fiwum terminale ; nervus impar. 4 Endyma, or indumentum ventriculo- rum. 5 Dura meninx; meninx exterior; m. sclera; m. dermatodes; m. pacheia; crassa meninx; cuticularis membrana; membrana externa; m. dura; m. fibrosa. 6 Dura mater cerebri; d. m. sensu strictiori; d. membrana cerebrum am- biens. 538 THE NERVOUS SYSTEM. The Cer'ebral falx,1 one of the partitions just indicated, occupies the great longitudinal fissure, and separates the hemispheres of the cere- brum. Commencing at the ethmoidal crest, to which it tightly adheres, it extends along the course of the superior longitudinal sinus, gradually increasing in breadth until it joins the tentorium. It is thus shaped like a sickle, from whence its name is derived. The Cerebellar falx2 is a thick fold of the dura mater occupying the valley, and separating the hemispheres of the cerebellum. It extends from the tentorium downward to the occipital foramen. The Tentorium3 is a broad partition of the dura mater separating the cerebrum from the cerebellum. It is continuous along its median line with the cerebral falx, from which it inclines on each side downward, outward, and backward. It is attached along the horizontal limbs of the occipital cross, and the superior border of the petrous portion of the temporal bones, extending to the posterior clinoid processes. Its inner border includes a large oval space4 through which the cerebral crura diverge from the pons to the hemispheres of the cerebrum. Through separation of the layers of the dura mater in certain po- sitions, channels are formed named the sinuses of the dura mater. These perform the office of veins, and are lined with a continuation of the ordinary epithelium of blood-vessels. In them terminate the veins of the pia mater, which return the blood from the capillary vessels of the brain. The superior longitudinal, straight, and lateral sinuses are three sided, from their occupying the angular intervals along the lines of departure of the cerebral falx and tentorium. The remaining sinuses, smaller than those just mentioned, are generally cylindroid, and occupy the base of the cranial cavity. A description of the course of the sinuses of the dura mater is given in the account of the venous system, page 409. The meningeal arteries of the dura mater, which give rise to the ar- borescent channels on the interior surface of the cranium, not only sup- ply the membrane, but are also destined to supply the bones of the latter. 1 Falx cerebri, major, or magna; pro- cessus falciformis cerebri; septum, or mediastinum cerebri; vertical superior longitudinal process. 2 Falx cerebelli; f. minor; processus falciformis cerebelli; septum cerebelli; s. parvum occipitale; median septum of the cerebellum. 3 T. cerebelli; t cerebello super ex- tensum ; tentaculum cerebelli; septum encephali; diaphragma cerebri; inter- septa horizontalia Pacchioni; processus transversus; lateral processes; trans- verse septum. 4 Incisura tentorii. THE NERVOUS SYSTEM. 539 In the passage of vessels and nerves through foramina at the base of the cranium, the dura mater becomes continuous with their fibrous sheaths. DURA MATER OF THE SPINAL CORD.1 This corresponds alone with the internal layer of the dura mater of the brain, with which it is continuous through the occipital foramen. Firmly attached to the border of the latter, the spinal dura mater ex- tends to the end of the vertebral canal, and forms a loose sheath for the spinal cord and its nerves. It is unattached to the periosteum of the vertebral canal, except at the occipital foramen, the interval of the two membranous layers being occupied by the intra-spinal plexus of veins, together with some loose areolar and adipose tissue. Opposite the intervertebral foramina the dura mater is pierced sepa- rately by the roots of the spinal nerves, but prolongations of the mem- brane extend as sheaths of the latter and become firmly attached to the periosteum bordering the intervertebral foramina. THE ARACHNOID MEMBRANE. The Arach'noid membrane2 is a delicate, transparent, and colorless, serous tunic, intervening between the pia mater and the dura mater. Its reflected portion adheres closely to the internal surface of the latter membrane ; while its investing portion is connected with the pia mater without dipping into any of the fissures or depressions of the brain and spinal cord, except those which receive the cerebral falx, the cerebellar falx, and the tentorium. The arachnoid membrane is especially remarkable among serous mem- branes from its loose attachment to the structure beneath. Being con- nected with the pia mater by scattered bands of fibrous tissue and blood-vessels, an interval is left between the two membranes, called the subarachnoid space. This varies in extent in different positions, but is most capacious along the middle part of the base of the brain, at the bottom of the superior longitudinal fissure, and on the spinal cord. A serous fluid, the cer'ebro-spinal liquid, amounting to several ounces, occupies both the cavity of the arachnoid membrane and the subarachnoid space. The bottom of the fourth ventricle is closed by the arachnoid mem- brane, but the cavity of the former communicates with the subarachnoid space. 1 Dura mater spinalis; pars spinalis dura? matris. 2 Membrana, or tunica arachnoidea; m. media; t. mucosa; t. serosa; t. aranea; t. crystallina ; meninx media; m. serosa ; meningion. 540 THE NERVOUS SYSTEM. The roots of the cerebro-spinal nerves are loosely invested with tubu- lar sheaths of the arachnoid membrane, extending from the pia mater to their exit through the dura mater. THE NERVES OF THE BRAIN, OR THE CEREBRAL NERVES. The Nerves of the Brain, usually called the Cerebral nerves,1 consist of twelve pairs,2 and are either named numerically from before backward, or from their function, destination, or other special character. THE OLFACTORY, OR FIRST PAIR OF NERVES. The Olfac'tory nerves3 are situated beneath the anterior cerebral lobes, and appear rather as appendages of the brain than as true nerves. They are small in comparison with those of most lower mammals, in accordance with the less acute sense of smell in man. They occupy a groove a short distance from the longitudinal fissure, and rest in the ethmoidal gutters. Each nerve is a club-shaped body, with a three-sided handle or ped- icle, and an oval head or bulb. The pedicle of the olfactory nerve is composed of white substance or nerve fibres below, and of gray substance above. The nerve fibres orig- inate by a pair of roots4 converging from the sides of the anterior per- forated space at the inner part of the Sylvian fissure ; the gray substance communicates by a single root5 with the space just mentioned. The bulb6 forms the free extremity of the olfactory nerve anteriorly. It is oval, soft, and composed of gray substance. From it emanate many branches,7 which descend through the foramina of the cribriform plate of the ethmoid bone to be distributed to the mucous membrane of the upper part of the nose. 1 Cranial, or encephalic nerves. 2 Nine pairs of Willis. 3 Nervi olfactorii; n. odoratorii; pro- cessus mammillares; p. m. cerebri ad nares ; p. papillares ; carunculas mam- millares ; ethmoidal nerves ; par primum nervorum cerebri; first pair of encepha- lic nerves; nerves of smelling, or olfac- tion. 4 Radix externa, or longa, and radix interna, or brevis. 5 Radix media, grisea, or superior. 6 Bulbus olfactorius ; b. cinereus; ol- factory tubercle or lobe. ' Nervi olfactorii; rami bulbi. THE NERVOUS SYSTEM. 541 THE OPTIC, OR SECOND PAIR OF NERVES. The Optic nerves,1 among the largest of those of the brain, originate each in a white band, named the optic tract.2 This starts from the quadrigeminal and geniculate bodies, winds around the outer side of the crus of the cerebrum, and converges to join that of the opposite side in front of the base of the infundibulum. The conjunction of the tracts forms the optic commissure,3 from which the optic nerves diverge to pass through the optic foramina into the orbits. The optic tracts and commissure throughout their course intimately adhere to the contiguous structures of the brain, from which they receive additional nerve fibres. In the optic commissure some of the nerve fibres cross from one side to the other, or decussate; another set proceed directly from the optic tracts to the corresponding nerves; a third series, in the form of loops, appear to associate the tracts together; and a fourth series, in the same manner, conjoin the two nerves independently of the tracts. The optic nerves are those of vision, and terminate in the retina of the eyeball. THE OCULO-MOTOR, OR THIRD PAIR OF NERVES. The Oc'ulo-motor nerves4 ap- pear at the surface of the brain, springing from the inner side of the cerebral crura, just in advance of the pons. Their nerve fibres are OCULO-MOTOR AND ABDUCENT NERVE, the Upper part of the right orbit removed. 1, oculo-motor . nerrve; 2, 3, branch to the superior straight and ' i obliqWv.muscles; 4, 5, branches to the internal and inferior straight muscles; 6, branch to the inferior oblique muscle; 7, branch from the latter to the ophthalmic ganglion; 8, abducent nerve to the ex- ternal straight muscle; 9, communicating filaments between the abducent nerve and the carotid plexus of the sympathetic. To their outer side is the tri- facial nerve. 10, ciliary nerves perforating the sclerotic coat of the eyeball, and passing forward between it and the choroid to the ciliary muscle and iris. 1 Nervi optici; n. visorii; par secun- dum, opticum, or visorium; ocular nerves ; nerves of sight or vision. 2 Tractus opticus. 3 Chiasma, or commissura nervorum opticorum. Fig. 332. 4 Nervi oculo-motores: n. motores ocu- lorum; n. oculares communes; n. oph- thalmici externi; common oculo-muscu- lar nerves; par tertium. traceable to the gray substance in the interior of the crura of the cer- ebrum and the pons. 542 THE NERVOUS SYSTEM. Passing obliquely forward and outward, the oculo-motor nerve pierces the dura mater in front of the posterior clinoid process, and, after travers- ing the outer wall of the cavernous sinus, it divides into two branches, which enter the orbit through the sphenoidal foramen. Of the two branches, the upper and smaller is distributed to the pal- pebral elevator and superior straight muscles; while the lower one sup- plies the internal and inferior straight and the inferior oblique muscles, and is connected by a short branch1 with the ophthalmic ganglion. The name of the oculo-motor nerve indicates its function. THE PATHETIC, OR FOURTH PAIR OF NERVES. The Pathet'ic nerves,2 the smallest of those connected with the brain, start from the upper part of the "valve of the brain," immediately behind the quadrigeminal body. Their fibres are traceable to the gray substance of the pons and the floor of the fourth ventricle. Each pathetic nerve appears like a white thread winding around the outer side of the crus of the cerebrum. Piercing the dura mater just behind the oculo-motor nerve, it accompanies this through the outer wall of the cavernous sinus and the sphenoidal foramen into the orbit. It is motor in its function, and is distributed to the superior oblique muscle of the eye. THE TRIFACIAL, OR FIFTH PAIR OF NERVES. The Trifa/cial nerves3 are the largest of those derived from the brain. They arise by two roots of unequal size, which emerge from the side of the pons at its fore part inferiorly. The large root4 of the trifacial nerve, sensory in its function, consists of numerous bundles of nerve fibres, which may be traced through the pons into the restiform body and the gray substance of the floor of the fourth ventricle. The small root,5 motor in its function, though trace- able through the pons to the medulla oblongata, has not had its origin satisfactorily determined. The two roots of the trifacial nerve, the smaller concealed behind the large one, pass through an oval aperture of the dura mater, near the 1 Radix brevis ganglii ciliaris; short root of the ophthalmic ganglion. 2 Nervi pathetici; n. trochleares; n. oculo-musculares superior, minimi, or interni; par quartum. 3 N. trifaciales; n. trigemini; trigem- inal nerves; n. gustatorii; par quintum; par trigeminum; par trium funiculorum. Sing.: n. divisus ; n. trimellus; n. mix; tus; n. quintus; n. sympathetica me- dius ; n. anonymus ; n. innominatus. 4 Radix major, posterior, inferior, or longior. 3 Radix minor, anterior, or superior. THE NERVOUS SYSTEM. 543 apex of the petrous portion of the temporal bone. The large root terminates in the semilunar ganglion, which rests in a slight depression in front of the apex of the petrous portion of the temporal bone ; while the small root passes beneath the ganglion, and simply lies in contact with it. The semilunar ganglion1 of the trifacial nerve is a large crescentic body, with its concavity upward, and receiving the diverging fibres of the large root of the nerve. From its convexity emanate the ophthalmic and superior maxillary nerves, and a third branch, which joins the small root of the trifacial to form the inferior maxillary nerve. Fig. 333. THE OPHTHALMIC NERVE. This is the first division of the trifacial nerve, and the smallest branch from the semilunar gan- glion. After traversing the outer wall of the cavernous sinus, it di- vides into three branches, which pass through the sphenoidal foramen into the orbit. Trifacial nerve, the upper part of the orbit and temporal fossa re- moved. 1. semilunar ganglion; 2, ophthalmic nerve; 3, lachrymal nerve; i.frontal nerve; 5, 6, its two principal branches; 7, a branch passing from the orbit above the pulley of the superior oblique mus- cle; 8, nasal nerve; 9, its exter- nal nasal branch; 10, course of the internal nasal nerve from the orbit into the cranium, and nose; 11, 12, 13, temporal branches of the inferior maxillary nerve; 14, com- mencement of the auriculo-tempo- ral nerve; 15, greater petrosal nerve; I, olfactory nerve; II, optic nerves; III,oculo-motor nerve; IV, pathetic nerve to the superior ob- lique muscle of the eye; V. trifacial nerve; its small root visible beneath the cut end of the large root, which forms the semilunar ganglion dividing into the ophthalmic, superior and inferior maxillary nerves; VI, abducent nerve; VII, facial, included in a groove of the auditory nerve, VIII, both entering the auditory meatus; IX, glosso-pharyngeal, X, pneumogastric, and XI, accessory nerves emerging at the jugular foramen; XII, hypoglossal nerve. 1 G. semilunare; g. Gasseri: Gasserian ganglion; ganglion of Gasser; intumes- centia, or moles gangliformis; i. semilunaris; taenia nervosa Halleri; ganglion of the fifth nerve. 2 Nervus ophthalmicus ; n. orbito-frontalis. 544 THE NERVOUS SYSTEM. The Lach'rymal nerve,1 one of the branches of the ophthalmic, passes along the outer part of the orbit to be distributed to the lachrymal gland and upper eyelid. The Frontal nerve,2 the largest branch of the ophthalmic, passes along the roof of the orbit, and divides into two branches, of which one3 emerges at the supra-orbital foramen, the other4 between the latter and the pulley of the superior oblique muscle, and both are distributed to the skin and muscles of the forehead and upper eyelid. The Nasal nerve,5 the remaining branch of the ophthalmic, passes above the optic nerve and along the inner side of the orbit to the anterior ethmoidal foramen, where it divides into the internal and external nasal nerves. In its course within the orbit it is connected by an anastomotic filament6 with the ophthalmic ganglion, and gives off two or three ciliary nerves.7 The internal nasal nerve8 passes through the anterior ethmoidal fora- men and enters the cranium, when it proceeds forward to the most ante- rior of the foramina of the ethmoid bone, and descends to supply the mucous membrane at the fore part of the nose. The external nasal nerve9 passes from the orbit beneath the pulley of the superior oblique muscle, and is distributed to the eyelids with their muscle, the lachrymal sac, and the skin of the nose. THE OPHTHALMIC GANGLION.10 This is a small, reddish-gray body, situated at the back part of the orbit, between the optic nerve and the external straight muscle. It is imbedded in areolar and adipose tissue, and is connected by branches with the nasal nerve of the ophthalmic, the oculo-motor nerve, and the carotid plexus of the sympathetic. From its fore part emanate about a dozen cil'iary nerves.11 These, together with the two or three ciliary branches from the nasal nerve, pierce the back part of the sclerotic coat, and advance between it and the choroid coat to be distributed to the ciliary' muscle and iris. 1 Nervus lachrymalis. 2 N. frontalis; n. fronto-palpebralis. 3 N. supra-orbitalis; n. frontalis ex- ternus, or major. 4 N. supra-trochlearis; n. frontalis in- ternus, or minor. 5 N. nasalis ; n. nasarius ; n. naso-ci- liaris ; n. naso-ocularis. 6 Long root of the ophthalmic gan- glion. 7 Long ciliary nerves. 8 N. nasalis internus; n. ethmoidalis. 9 N. infra-trochlearis; n. nasalis ex- ternus. 10 Ganglion ophthalmicum ; g. ciliare ; g. lenticulare; g. semilunare; g. orbi- tale ; ciliary or lenticular ganglion. 11 Short ciliary nerves; nervi ciliares breves. THE NERVOUS SYSTEM. 545 OPHTHALMIC GANGLION—THE OUTER PART OF THE RIGHT ORBIT REMOVED. 1. optic nerve; 2, oculo-motor nerve; 3, branch to the superior straight <«*d oblique muscle*; 4. branch to the in- ferior oblique muscle; 5, abducent nerve to the external straight muscle; 6, trifacial nerve, its ganglion and three principal branches; 7, ophthal- mic nerve; N. nasal nerve; 9, ophthal- mic ganglion; 10, its communicating branch with the oculo-motor nerve; 11, do. with the ophthalmic nerve; 12, do. with the carotid plexus of the sympathetic; 13, the ciliary nerves; II, frontal nerve. Fig. 334. THE SUPERIOR MAXILLARY NERVE.1 This is the second division of the trifacial nerve, and is intermediate in size and position to the others. Starting from the middle of the Fig. 335. Superior maxillary nerve—the external wall op the left orbit and of the superior maxillary bone removed. I, superior maxillary nerve in its course through the infra-orbital canal; 2, 3, posterior dental nerves; 4, anterior dental nerve; 5, anastomosis between the dental nerves; 6,spheno-palatine ganglion; the branch from the superior maxillary nerve above is the commencement of the temporo-malar nerve; 7, pterygoid nerve ; 8, greater petrosal nerve joining the facial nerve; 9, deep petrous nerve join- ing the carotid plexus of the sympathetic; 10, abducent nerve with its communicating branches of the latter plexus; 11, superior cervical ganglion; 12, ascending branches to the carotid plexus; 13, facial nerve; 14, glosso-pharyngeal nerve; 15, the tympanic nerve; 16, branch to the carotid plexus; 17,18,19, branches to the round and oval windows and Eustachian tube; 20, branch to the smaller petrosal nerve, 21. semilunar ganglion as a flattened cord, it assumes a rounded form, and passes from the cavity of the cranium through the rotund foramen of the sphenoid bone. It then crosses the upper part of the pterygo-max- 1 Nervus maxillaris superior. 35 546 THE NERVOUS SYSTEM. illary fossa, and enters the infra orbital canal,1 through which it advances to the face. In its course it gives off the temporo-malar, spheno-pala- tine, dental, and infra-orbital nerves. The Temporo-ma'lar nerve2 enters the orbit through the spheno-max- illary foramen, and divides into filaments, which are transmitted by foramina of the malar bone to the skin of the temple and cheek. It anastomoses with the lachrymal and facial nerves. The Sphe'no-pal'atine nerves3 are two short branches descending to join the spheno-palatine ganglion. The Dental nerves4 consist of posterior and anterior branches. The posterior dental nerves,5 of which there are two or three, descend behind the tuberosity of the superior maxillary bone, and enter small canals in the outer wall of the maxillary sinus to supply the back teeth. One of the branches also supplies the upper gum. The anterior dental nerve6 comes off from the superior maxillary within the infra-orbital canal, and descends in the anterior wall of the maxillary sinus to supply the front teeth. The anterior and posterior dental nerves anastomose with one another, and also give branches to the lining membrane of the maxillary sinus. The Infra-orbital nerves7 are the terminal branches of the superior maxillary, emerging at the infra-orbital foramen to be distributed to the lower eyelid, the upper lip, the side of the nose, and the raucous mem- brane of the cheek. THE SPHENO-PALATINE GANGLION.8 This is a small, triangular body, situated in the pterygo-maxillary fossa, near the spheno-palatine foramen. It is joined by the spheno- palatine branches of the superior maxillary nerve, and besides giving small filaments9 to the upper part of the pharynx, sends off the nasal, palatine, and pterygoid nerves. 1 Within which it is usually called the infra-orbital nerve ; nervus infra-orb i- talis. 2 N. subcutaneus malae ; n. orbitarius. 3 Nervi spheno-palatini; n. pterygo- palatine 4 N. dentales; n. d. superiores; n. al- veolares superiores. 5 N. dentales, or alveolares superiores posteriores. 6 N. dentalis, or alveolaris superior anterior. 7 N. infra-orbitales. 8 G. spheno-palatinum; g. pterygo- palatinum; g. Meckelii; Meckel's gan- glion ; ganglion of Meckel; g. nasale; g rhinicum ; g. sphenoidale. 9 Rami pharyngei. THE NERVOUS SYSTEM. 547 The Nasal nerves1 consist of half a dozen or more small branches, which pass through the spheno-palatine foramen to supply the mucous membrane of the nose, including its partition, its outer wall, and the ethmoidal and sphenoidal sinuses. One2 of the branches, descending obliquely on the partition, passes through the naso-palatine canal to the roof of the mouth. Fig. 336. View of the spheno-palatine ganglion, the outer wall of the left nasal cavity, and the olfactory nerve. 1, olfactory nerve; 2, nasal branch of the ophthalmic nerve; 3,spheno-palatine ganglion; 4,5, 6, palatine nerves; 7, branch to the nose; 8, nasal nerve to the outer wall of the nose; 9, do. to the inner wall; 10, pterygoid nerve; 11, facial nerve; 12, deep petrous nerve joining the carotid plexus, 13; the other branch of the pterygoid is the larger petrosal nerve, which joins the facial. The Pal'atine nerves,3 of which there are usually three, descend through the posterior palatine canal and its divisions to be distributed to the hard and soft palate, the palatine arches, the uvula, and the tonsil. From the largest palatine nerve,4 in its course one or two branches5 are given off to the outer wall of the nose. The Pter'ygoid nerve6 proceeds from the spheno-palatine ganglion backward through the pterygoid canal of the sphenoid bone, and divides into two branches. One of these, the deep petrous nerve,7 pierces the cartilage occupying the lacerated foramen, and joins the carotid plexus of the sympathetic nerve. The other branch, named the greater petro- 1 N. nasales superiores anteriores et 4 N. palatinus anterior, or major. posteriores, et naso-palatinus. 2 N. naso-palatinus : n. naso-palatinus Scarpa?; n. septi narium. 3 N. palatini; n. p. anterior et medius, posterior, or minus posterior et mini- mus exterior. 5 N. nasales inferiores. 6 N. pterygoideus ; n. Vidianus; Vi- dian nerve; n. recurrens Vidianus. 7 Ramus sympatheticus; r. profundus nervi Vidiani. 548 THE NERVOUS SYSTEM. sal nerve,1 enters the cranial cavity through the cartilage of the lacerated foramen, and passes into a canal on the front of the petrous portion of the temporal bone to join the facial nerve. THE INFERIOR MAXILLARY NERVE.2 This is formed by the union of the small root of the trifacial nerve with the third branch of its semilunar ganglion. It is larger than the ophthalmic or superior maxillary nerve, and emerges from the cavity of the cranium through the oval foramen of the sphenoid bone. Imme- diately after its exit it separates into two divisions, of which the smaller receives nearly all the fibres of the small or motor root of the trifacial nerve; while the larger division receives most of the fibres emanating from the semilunar ganglion. The smaller division of the inferior maxillary nerve resolves itself into a number of muscular branches,3 of which two4 supply the tem- poral muscle, one5 the masseter, one6 the buccinator, and two7 the ptery- goid muscles. The larger or sensory division of the inferior maxillary nerve is con- nected on its inner side with the otic ganglion, and divides into the auriculo-temporal, lingual, and inferior dental nerves. The Auric'ulo-tem'poral nerve,8 the smallest of the three branches just indicated, is directed outwardly between the ear and the articulation of the lower jaw, and ascends to be distributed to the skin of the temple. In its course it gives branches to the external ear, the articulation of the lower jaw, and the parotid gland ; and it anastomoses with the facial nerve. The Lin'gual nerve9 curves downward and forward between the pterygoid muscles to the side of the tongue, along which it continues to the tip, beneath the sublingual gland and in contact with the mucous membrane of the mouth. In its course it is joined by the tympanic branch10 of the facial nerve, and gives small branches to the mucous 1 Greater superficial petrosal nerve; nervus petrosus superficialis major ; n. superior, or superficialis nervi Vidiani. 2 Nervus maxillaris inferior; n. crota- phitico-buccinatorius et maxillaris infe- rior; ramus tertius nervi quinti; third branch of the fifth, or trigeminal nerve. 3 Rami musculares. 4 N. temporalis profundus anterior et posterior. 5 N. massetericus. 6 N. buccinatorius. 7 N. pterygoideus internus et exter- nus. 8 N. auriculo-temporalis; n. tempora- lis superficialis; n. auricularis anterior. 9 N. lingualis; n. gustatorius ; gusta- tory nerve. 10 Chorda tympani. THE NERVOUS SYSTEM. 549 membrane of the mouth, sublingual gland, and the submaxillary gan- glion. Its terminal branches perforate the muscular structure of the tongue, and ascend almost vertically to end in the papilla? of taste. Fio. 337. Distribution op the inferior maxillary nerve. 1, muscular branch to the masseter muscle; 2, 5, 7. branches to the temporal muscle ; 3, branch to the buccinator, anastomosing with one from the facial at 4; 6, external pterygoid muscle; 8, auriculo-temporal nerve; 9, branches to the temple; 10, branches to the ear; 11, its anastomosis with the facial; 12, lingual nerve; 13, branch to the mylo-hyoid muscle from the inferior dental nerve, 14; 15, branches to the teeth; 16, terminal branches to the lower lip and chin. The Inferior dental nerve,1 a little larger than the lingual, descends in company with it, but diverges to enter the dental canal of the inferior maxillary bone. In its course through the canal it supplies the lower teeth ; and it finally emerges at the mental foramen to be distributed to the lower lip and chin. Before entering the dental canal it gives a branch2 to the muscles and skin of the floor of the mouth. 1 N. dentalis inferior; n. maxillaris inferior; n. mandibulars. 2 Ramus mylo-hyoideus. 550 THE NERVOUS SYSTEM THE OTIC GANGLION.1 This is a small, flattened, oval body, situated on the inner side of the sensory division of the inferior maxillary nerve, with which it is con- nected by several short filaments. Behind it is the great meningeal artery, and it is connected by a filament with the sympathetic plexus fol- lowing this vessel. It gives branches to the tympanic tensor and cir- cumflex palatine muscles, and an anastomotic filament to the auriculo- temporal nerve. From it emanates the small petro'sal nerve,2 which enters the cranium through a fine canal in the spinous process of the sphenoid bone, and then traverses a canal in the front of the petrous portion of the temporal bone, to join the facial nerve and the tympanic branch of the glosso-pharyngeal nerve. THE SUBMAXILLARY GANGLION.3 This is a minute body situated on the trunk of the lingual nerve, just above the submaxillary gland. It is conuected by filaments with the lingual nerve, which are partly traceable to the tympanic branch of the facial. It is also connected with the sympathetic plexus of the facial artery, and sends all its branches to the submaxillary gland. THE ABDUCENT, OE SIXTH PAIR OF NERVES. The Abdu'cent nerves4 appear at the surface of the brain, between the summits of the pyramidal bodies of the medulla oblongata and the pons. Their fibres, forming a large and small bundle, for the most part originate from the pyramidal bodies, a few being derived from the pons. The abducent nerve appears as a white thread, but is larger than the pathetic nerve. It proceeds forward, traverses the cavernous sinus, from the cavity of which it is separated by the lining membrane, and passes through the sphenoidal foramen into the orbit. In the cavernous sinus it lies at the outer side of the internal carotid artery, and is connected with its sympathetic plexus by a pair of filaments. In the orbit it passes between the two heads of the external straight muscle, to which it is distributed. 1 Ganglion oticum; g. auriculare; g. Arnoldi; ganglion of Arnold; otogan- glium; g. maxillo-tympanicum. 2 Small superficial petrosal nerve; nervus petrosus superficialis minor. 3 G. submaxillar; g. linguale ; g. mi- nus Meckelii; plexus gangliosus sub- maxillaris. 4 Nervi abducentes. Sing.: nervus abducens; n. oculomuscularus externus or posterior; n. ocularis externus; n. motor-oculi externus; n. timidus. THE NERVOUS SYSTEM. 551 THE FACIAL, OR SEVENTH PAIR OF NERVES. The Facial nerves1 emerge from the depression immediately back of the pons, between the olivary and restiform bodies. They have a large Fig. 338. The facial nerve. 1, trunk of the nerve emerging at the stylo-mastoid foramen; 2, its deep auricu- lar branch; 3, anastomosis of the latter with the great auricular nerve of the cervical plexus; 4, 5, 6, branches to the contiguous muscles; 7, 8, branches of the facial to the digastric and stylo-hyoid muscles ; 9, temporo-facial division of the nerve; 10, branch to the temple, anastomosing with the auriculo-temporal nerve; 11, temporal branches; 12, zygomatic branches; 13, infra-orbital branches; 14,15, cervico-facial division of the facial nerve; 14, buccal branches; 16, inferior maxillary branches; 17, cervical branches; 18, auriculo-temporal nerve; 19, 20, terminal branches of the frontal nerve; 21, terminal branch of the lachrymal nerve; 22, external nasal nerve; 23, branch of the temporo-malar nerve; 24, terminal branch of the internal nasal nerve; 25, infra-orbital nerves; 26, anastomosis between the buccal branch of the inferior maxillary nerve and the buccal branches of the facial nerve; 27, terminal branches of the infe- rior dental nerve; 28, great occipital nerve; 23, 31, branches of the great auricular nerve; 30, small occipital nerve; 32, superficial cervical nerve, anastomosing with the facial nerve. 1 Nervi faciales; par septimum; p. faciale. Sing.: portio dura nervi sep- timi; n. communicans faciei; n. primus paris septimi; n. sympathetica parvus or minor; ramus durior septimae conju- gations ; respiratory nerve of the face; portio dura nerve; portio dura of the seventh pair of nerves. 552 THE NERVOUS SYSTEM. root whose fibres are derived from the restiform body, and a small root from the floor of the fourth ventricle. The two roots together accom- pany the auditory nerve, lying in a groove on its upper part, and pass down the internal auditory meatus. At the bottom of this passage the facial leaves the auditory nerve and enters the Fallopian canal, through the winding course of which it pursues its way to the stylo-mastoid foramen. At the position in which the Fallopian canal turns backward, the facial nerve presents a gangliform enlargement,1 which is joined by the larger petrosal nerve, a branch of the smaller petrosal nerve, and a filament from the sympathetic plexus following the great meningeal artery. In the descending portion of the Fallopian canal the facial nerve sends a branch to the stapedius muscle, and gives off the tympanic nerve.2 This enters the tympanum through a foramen near the pyra- mid, and proceeds forward to emerge at the glenoid fissure, from which it descends between the pterygoid muscles to join the lingual nerve. In its course it lies in contact with the tympanic membrane, between this and the handle of the mallet, and is separated from the cavity of the tympanum by its lining mucous membrane. Below the stylo-mastoid foramen the facial nerve gives branches to the digastric and stylo-hyoid muscles, anastomotic filaments to the auric- ulo-temporal nerve, and sends off the deep auricular nerve.3 This ascends between the ear and the mastoid process, and is distributed to the muscles of the back of the ear and the occipital region. From the stylo-mastoid foramen the facial nerve turns forward through the parotid gland, and divides into numerous diverging branches,4 which anastomose with one another on the side of the cheek, and are distrib- uted over the face, extending from the temple to the upper part of the neck. The branches of distribution form two groups, named the tem- poro-facial and cervico-facial divisions of the nerve. The Temporo-facial division of the facial nerve ramifies on the side of the face from the temple to the vicinity of the mouth, forming an intricate plexus, and anastomosing with the contiguous terminal branches of the trifacial nerve. Its branches, mainly distributed to the muscles of the temple, forehead, eyelids, cheek, nose, and upper lip, are named, from their special position, temporal, zygomatic, and infra-orbital. 1 Intumescentia gangliformis; gan- 3 Nervus auricularis profundus; pos- glion geniculare. terior, or exterior. 2 Chorda tympani; funiculus tympani. 4 Pes anserinus; plexus parotideus. THE NERVOUS SYSTEM. 553 The Cervico-facial division of the facial nerve is distributed to the lower part of the face and the upper part of the neck. Its upper or buccal branches anastomose with the lower ones of the preceding division, and supply the muscles of the cheek, nose, and upper lip. The inferior maxillary branches supply the muscles of the lower lip and chin, and anastomose with the inferior dental nerve. The cervical branches anastomose with the upper cervical nerves, and supply the subcutaneous cervical muscle. The facial nerve is the motor nerve of the face, and is the avenue through which its muscles are acted upon by the emotions. A few sen- sory filaments which it contains are derived through anastomosis with the pneumogastric and trifacial nerves. THE AUDITORY, OR EIGHTH PAIR OF NERVES. The Aud'itory nerves1 have their origin in the transverse white striae of the floor of the fourth ventricle, and turn forward around the resti- form bodies, from which they also receive a few fibres. Each nerve is then directed outwardly, in company with the facial nerve, and passes into the internal auditory meatus, from whence it is distributed to the labyrinth. The auditory nerve is the special one of hearing, and is more particu- larly described in the account of the ear. THE GLOSSO-PHARYNGEAL, OR NINTH PAIR OF NERVES. The Glosso-pharynge'al nerves2 arise by about a half dozen cords from the restiform body, just behind the olivary body. They issue from the cavity of the cranium, in company with the pneumogastric and accessory nerves, through the jugular foramen. Within the latter foramen, some of the fibres of the glosso-pharyngeal nerve become mingled with nerve cells, forming a small ganglion,3 but its presence is inconstant. As it emerges from the jugular foramen, the glosso-pharyngeal nerve 1 Nervi auditorii. Sing.: n. audito- rius; n. acusticus; portio mollis paris septimi, or nervi auditorii; portio mollis nerve : portio mollis of the seventh pair of nerves ; acoustic nerve. 2 N. glosso-pharyngei; par nonum. Sing.: n. pharyngo-glossus; n. lingualis lateralis; n. sensualis linguae; n. gus- tatorius linguae; n. lingualis paris oc- tari; n. lingualis paris noni; n. lingua- lis pneumogastrici; first branch of the eighth pair of nerves. 3 Ganglion superius nervi glosso-pha- ryngei ; g. jugulare superius ; g. Ehren- ritteri; g. Miilleri; ganglion of Ehren- ritter. 554 THE NERVOUS SYSTEM. Fig. 339. enlarges into the petrous ganglion,1 which is connected by fine filaments with the pneumogastric and sympathetic nerves, and gives off an import- ant branch, named the tympanic nerve.2 This ascends through a fine canal of the petrous por- tion of the temporal bone to the tympanum, and ex- pands upon the promon- tory into a number of branches, which supply the lining membrane of the tympanum, the round and oval windows, and the Eustachian tube. It is also connected with the sympathetic plexus of the internal carotid artery, and with the smaller pe- trosal nerve. From the petrous gan- glion, the glosso-pharyn- The last four cerebral nerves, the facial nerve, the sympa- geal nerve be- passes thetic, and the upper two cervical nerves. 1, facial nerve; 2', tween the iuffular Vein anastomosis between branches of the facial and glosso-pharyngeal 'Jo nerve; 2, glosso-pharyngeal; 3, pneumogastric; 4 accessory, 5, anQ tne internal Carotid hypoglossal; 6, first cervical ganglion of the sympathetic; 7, first arterV aild descends in a and second cervical nerves; 8, carotid plexus of the sympathetic curve to the root of the tongue, on the inner side of the stylo-pharyn- geal muscle, and beneath the tonsil. In its course it is connected by anasto- motic filaments with the pneumogastric nerve and the carotid plexus of the sympathetic, and gives branches to the muscles and mucous membraue on the internal carotid artery; 9, tympanic nerve from the petrous ganglion of the glosso-pharyngeal; 10, its connection with the carotid plexus; 11, branch to the Eustachian tube; 12,13, branches to the round and oval windows of the ear; 14, 15, branches join- ing the small and greater petrosal nerves; 16, otic ganglion; 17, auricular branch from the jugular ganglion, connected by fila- ments with the petrous ganglion and the facial nerve; 18, anas- tomosis of the accessory with the pneumogastric; 10, anastomosis of the first cervical nerve with the hypoglossal; 20, anastomosis of the second cervical nerve with a branch of the accessory; 21, pharyngeal plexus; 22, superior laryngeal nerve; 23, its external branch; 24, second cervical ganglion of the sympathetic. 1 G. inferius nervi glosso-pharyngei; g. petrosum; g. Anderschii; neurono- dus petrosus; ganglion of Andersch. 2 Nerve of Jacobson; ramus tympani- cus; nervus tympanicus superior; ra- mus anastomoticus Jacobsonii; nervus Jacobsonii. THE NERVOUS SYSTEM. 555 of the pharynx. ' Its terminal branches are distributed to the tonsils and the mucous membrane of the root of the tongue, including the circum- vallate papillae. The glosso-pharyngeal nerve is sensory-motor in its function; and its terminal branches are by many believed to participate with the lingual nerve in the sense of taste. THE PNEUMOGASTRIC, OR TENTH PAIR OF NERVES. The Pneumogas'tric nerves1 extend from the cavity of the cranium, through the neck and thorax, into the abdomen, and are distributed to the organs of voice and respiration, the heart, and the alimentary canal from the pharynx to the stomach inclusively. They spring by from ten to fifteen cords from the groove behind the olivary body, and pass from the cranium, in company with the glosso-pharyngeal and accessory nerves, through the jugular foramen. From thence they descend within the sheath of the great blood-vessels of the neck, lying posteriorly be- tween the carotid arteries and jugular vein. At the bottom of the neck the right pneumogastric nerve enters the posterior mediastinal cavity between the corresponding subclavian artery and vein. It then descends behind the root of the right lung to the pos- terior surface of the oesophagus, which it accompanies to the stomach. The left pneumogastric nerve descends, in front of the left subclavian artery and the arch of the aorta, into the posterior mediastinal cavity, and passes behind the root of the left lung to the front of the oesopha- gus, along which it continues to the stomach. Within the jugular foramen the pneumogastric nerve presents an ovoidal, grayish body, the jugular ganglion.2 This resembles in appear- ance the ganglia of the spinal nerves, and like them it gives additional fibres to the trunk upon which it is situated. It gives off an auricular branch,3 which, after being joined by filaments from the petrous gan- glion and the facial nerve, is distributed to the external auditory meatus. Having emerged from the jugular foramen, the pneumogastric nerve re- ceives an accession of fibres from the accessory and hypoglossal nerves, and dilates into a fusiform enlargement called the gangliform plexus.4 This 1 Nervi pneumogastrici; par vagum; par undecimum. Sing.: nervus vagus; n. ambulatorius; n. decimus; n. sym- pathetica medius; second branch of the eighth pair of nerves. 2 G. jugulare nervi vagi; g. superius nervi vagi; g. nervi vagi. 3 Ramus auricularis; auricular nerve of Arnold. 4 Plexus gangliformis ; p. nodosus ; ganglion inferius nervi vagi; g. tunici nervi vagi. 556 THE NERVOUS SYSTEM. The pneumogastric nerve. 1, trunk of the pneumogastric; 2, gangliform plexus; 3,anastomosis of the latter with the accessory nerve; 4, anastomosis with the hypoglossal; 5, pharyngeal nerve; 6, supe- rior laryngeal nerve; 7, its external branch; 8, pharyngeal plexus; 9, inferior laryngeal nerve; 10,11, filaments to the cardiac plexus; 12, commencement of the oesophageal plexus; 13, pulmonary plexus; 14, lingual nerve; 15, lower 'part of the hypoglossal nerve; 16, glosso-pharyngeal nerve; 17, accessory nerve; 18,19, 20, second, third, and fourth cervical nerves; 21, commencement of the phrenic nerve; 22, 23, the lower four cervical nerves which with the first thoracic nerve form the brachial plexus; 24, 25, first and second cervical ganglia of the sympathetic; 26, third cervical united with the first thoracic ganglion; 27-30, second to the fifth thoracic ganglia. The gangliform plexus receives anastomotic branches from the glosso- pharyngeal nerve, the first cervical ganglion of the sympathetic, and the upper part of the cervical plexus, and it gives off the pharyngeal and superior laryngeal nerves. THE NERVOUS SYSTEM. 557 The Pharynge'al nerve or nerves,1 from one to three in number, de- scend upon the side of the pharynx, anastomose with the pharyngeal branches of the glosso-pharyngeal nerve, and supply the constrictor muscles and mucous membrane of the pharynx. The Superior Larynge'al nerve2 curves downward and forward to the side of the larynx. After giving a branch to the inferior constrictor of the pharynx, the crico-thyroid muscle, and the thyroid body, it pierces the thyro-hyoid membrane, and is expended in numerous filaments to the mucous membrane of the larynx. Descending the neck, the pneumogastric nerve gives off several fila- ments3 which join the cardiac nerves of the sympathetic, or descend the neck to the cardiac plexus. It also gives off an anastomotic branch to the descending cervical nerve of the hypoglossal. At the bottom of the neck it gives off a large branch, the Inferior Larynge'al nerve.4 This, on the right side, descends in front of the subclavian artery, and winds around it posteriorly from beneath ; on the left side, in the same manner, the nerve winds around the arch of the aorta. It then ascends the neck, in the interval laterally of the trachea and oesophagus, to the larynx. In its course it is connected by anastomotic filaments with the last cervical ganglion, and the cardiac plexus of the sympa- thetic, and gives branches to the trachea and oesophagus. Its terminal branches supply most of the muscles of the larynx, a few of them being distributed to the mucous membrane, and anastomosing with the superior laryngeal nerve. In the thorax the pneumogastric nerve gives off cardiac and pulmo- nary branches, and then with its fellow forms the oesophageal plexus. The cardiac branches5 are derived from the pneumogastric nerve be- low the inferior laryngeal. They anastomose with the cardiac branches of the sympathetic, and contribute to form the cardiac plexus of the latter. The pulmonary branches6 are numerous, and enter the root of the lung upon the bronchus, a few in front, but mainly at its back part. They are joiued by filaments from the upper thoracic ganglia of the sympathetic, and form on the bronchus the pulmonary plexus,7 from 1 Nervi pharyngei. 2 Nervus laryngeus superior. 3 Rami cardiaci. 4 Nervus laryngeus inferior, or recur- rens ; recurrent laryngeal nerve. 5 Rami cardiaci; r. c. profundi infe- riores. 6 Rami pulmonarii. 7 Plexus pulmonalis anterior et poste- rior. 558 THE NERVOUS SYSTEM. which the nerves follow the ramifications of the bronchial tubes through- out the lungs. After the origin of the pulmonary branches, the pneumogastric nerve of the right side applies itself to the back of the oesophagus, while that of the left side applies itself to the front. By division and reunion of branches, the two nerves form the intricate oesophage'al plexus,1 which surrounds the oesophagus and supplies its walls. The terminal branches2 of the right pneumogastric nerve, after leav- ing the oesophageal plexus, are distributed to the posterior part of the stomach, and are connected with the solar plexus of the sympathetics. The terminal branch^2 of the left pneumogastric nerve, descending from the oesophagus, supply the front surface and pyloric extremity of the stomach, and partly proceed along its lesser curvature to join the hepatic plexus of the sympathetics. The pneumogastric nerve is sensory-motor in its function, and presides over the general sensibility and muscular actions of the pharynx, oesoph- agus, stomach, larynx, trachea^ and lungs. .X U <': .-x THE ACCESSORY, OR TWELFTH PAIR OF NERVES. The Ac'cessory nerves3 are somewhat variable in extent and origin, and not unfrequently differ on the two sides. They arise by a series of filaments from the lateral columns of the spinal cord, and from the med- ulla oblongata, below and behind the olivary bodies. The filaments of origin may commence as low as from the third to the last cervical verte- bra, and are situated between the posterior roots of the spinal nerves and the denticulated ligament. They are successively collected into an ascending cord, which enters the cranium through the occipital foramen. The accessory nerve then passes through the jugular foramen, in com- pany with the glosso-pharyngeal and pneumogastric nerve, and divides into two branches. One of these joins the gangliform plexus of the pneumogastric nerve; the other branch turns outwardly behind the jugu- lar vein, and pierces the sterno-mastoid muscle above its middle. After supplying the latter with filaments, it proceeds through the supra-clavic- ular fossa to the trapezius muscle, in which it terminates. Besides its connection with the pneumogastric, the accessory nerve anastomoses with the upper four cervical nerves. Occasionally it pre- 1 Plexus oesophageus. 2 Rami gastrici. 3 Spinal accessory nerves; nervi ac- cessorii; par undecimum ; eleventh pair of encephalic nerves. Sing.: accessory of the par vagum, or eighth pair; ner- vus accessorius Willisii; n. a. ad par oc- tavum; n. spinalis; superior respiratory nerve; third branch of the eighth pair of nerves. THE NERVOUS SYSTEM. 559 sents a ganglion upon its trunk. In function it is a motor nerve, though it appears also to contain a few sensory fibres. THE HYPOGLOSSAL, OR TWELFTH PAIR OF NERVES. The Hypoglos'sal nerves,1 the last pair of the cerebral series, arise by a number of filaments from the fissure between the pyramidal and olivary bodies. The filaments converge into two bundles, which, after passing through the condyloid foramen of the occipital bone, unite in a rounded cord. From the condyloid foramen the hypoglossal descends behind the pneumogastric nerve, and then curves downward and forward to the outer side of the latter, between the internal carotid artery and jugular vein, to the under part of the tongue. It is here situated above the hyoid bone, on the outer side of the hyo-glossal muscle, and penetrates the genio-glossal muscle, to which, and the other muscular structure of the tongue, it is distributed. After its exit from the cranium, the hypoglossal nerve is connected by anastomotic filaments with the first cervical ganglion of the sympathetic, the gangliform plexus of the pneumogastric, and the upper two cervical nerves. Lower in its course it gives off the descending cervical nerve,2 which crosses to the outer side of the great blood-vessels of the neck, and, after being joined by filaments from the pneumogastric and cervical plexus of nerves, is distributed to the omo-hyoid, sterno-hyoid, and sterno-thyroid muscles. The hypoglossal nerve, as indicated by its distribution, is motor in function. THE SPINAL NERVES. Of Spinal nerves3 there are thirty-one pairs, divided, according to their relation with the vertebral column, into eight cervical, twelve tho- racic, five lumbar, five sacral, and one coccygeal nerve. Every spinal nerve originates by an anterior and a posterior root from the corresponding lateral grooves of the spinal cord. Each root is com- posed of a vertical series of flattened threads, which converge together from their origin. The anterior roots, except those of the upper two cervical nerves, are larger and composed of a greater number of threads than the posterior roots. 1 Nervi hypoglossi; par nonum; ninth pair cf nerves. Sing.: nervus lingualis; n. 1. medius; n. motorius linguae; n. sublingualis ; n. loqueus ; hypoglossus; myoglossus; gustatory nerve. 2 Descendens noni; ramus descendens. 3 Vertebral nerves; intervertebral nerves. 560 THE NERVOUS SYSTEM. The largest roots of the spinal nerves are those of the lower four cer- vical and the first thoracic nerve, which supply the upper extremities; and those of the lower three lumbar and upper two sacral nerves, which supply the lower extremities. The anterior and posterior roots converge and pass side by side through separate apertures of the dura mater, opposite the intervertebral and sacral foramina, but are accompanied by tubular sheaths of that membrane. In consequence of the comparative shortness of the spinal cord, the roots of the spinal nerves, in order to reach their place of exit from the dura mater, successively increase in length from the first to the last. From this arrangement they also incline more and more from a horizon- tal course, until they finally assume a vertical direction, and thus the roots of the lumbar, sacral, and coccygeal nerves are collected into a thick bundle1 occupying the lower part of the sheath of the dura mater. The posterior roots of the spinal nerves are provided with a reddish- gray, oval ganglion, which contributes additional fibres to the roots as they proceed from them. The ganglia, except those of the sacral and coccygeal nerves, are situated within the intervertebral foramina. Those of the sacral nerves are contained within the spinal canal, and that of the coccygeal nerve is even placed within the sheath of the dura mater of the spinal cord. The anterior root of the spinal nerves lies in contact with the ganglion of the posterior root, but neither contributes to nor receives fibres from it. Immediately beyond the ganglion, the two roots unite in a common trunk, which is a short, rounded cord, composed of an intermixture of the nerve fibres of both roots. The spinal nerves thus formed emerge from the intervertebral fora- mina, the sacral and coccygeal nerves excepted, which divide within the vertebral canal into anterior and posterior branches, and then escape through the corresponding sacral foramina. The nerves which pass through the intervertebral foramina imme- diately afterwards divide into an anterior and a posterior branch. With the exception of those of the first two pairs of spinal nerves, the anterior branches are much the larger, and are destined to supply the trunk in advance of the vertebral column, and the limbs; the posterior branches are distributed to the back of the trunk. The anterior roots of the spinal nerves are motor in function ; the posterior roots are sensory. The association of the two roots renders Cauda equina. THE NERVOUS SYSTEM. 561 the spinal nerves sensory-motor; and with this endowment the nerves are distributed to the muscles and skin of the body, from the head downward. THE CERVICAL NERVES. Of the Cer'vical nerves1 there are eight pairs, of which the first pair, or suboccip'ital nerves,2 emerge from the vertebral canal, between the occipital bone and atlas; and the last pair escape through the inter- vertebral foramina, between the last cervical and first dorsal vertebras. They increase successively from above downward, and, after passing from the vertebral canal, as already indicated, they divide into an ante- rior and a posterior branch. POSTERIOR BRANCHES OF THE CERVICAL NERVES. The posterior branch of the first cervical, or suboccip'ital nerve,2 is larger than the anterior branch. After issuing from between the arch of the atlas and the vertebral artery, it is expended in filaments on the contiguous straight, oblique, and complex muscles ; one of them de- scending to communicate with the second cervical nerve. The posterior branch of the second cervical nerve is the largest of the corresponding branches of the cervical series. Emerging from between the arches of the atlas and axis, it receives a communicating filament from the first cervical nerve, and then divides into two branches. Of these, the external branch is expended in the complex, splenius, and trachelo-mastoid muscles. The internal branch, or great occip'ital nerve,3 pierces the complex and trapezius muscles, and accompanies the occipital artery to be distributed to the muscle and skin of the occipital region. The posterior branches of the lower six cervical nerves, after pass- ing backward between the transverse processes of the vertebras, divide into external and internal branches. The external branches supply the ascending cervical, transverse cer- vical, and trachelo-mastoid muscles. The internal branches are larger than the preceding. These, from the third, fourth, and fifth cervical nerves, turn inwardly toward the spinous processes of the vertebras, and are then directed outwardly to be distributed to the skin; while those from the lower three cervical nerves terminate in the complex, semi- spinal, and multifid spinal muscles. 1 Nervi cervicales; n. cervicis; n. nuchse ; n. intervertebrales colli. 2 N. cervicalis primus; n. c. supremus ; n. infra-occipitalis. 3 N. occipitalis magnus or maximus. 36 562 THE NERVOUS SYSTEM. ANTERIOR BRANCHES OF THE CERVICAL NERVES. The anterior branches of the cervical nerves successively increase in size from first to last. They turn forward to the outer side of the verte- bral artery, except the first of the series, which is situated beneath the horizontal turn of that vessel above the atlas. The anterior branches of the upper four cervical nerves divide and anastomose with one another in such a manner as to form a series of loops, constituting the cervical plexus, which is situated in front of the attachment of the muscles to the transverse processes of the vertebras. The plexus is connected by anastomotic filaments with the superior cer- vical ganglion and trunk of the sympathetic, and with the pneumogas- tric, accessory, and hypoglossal nerves. It supplies an offset to the brachial plexus, and gives off numerous branches, which are mainly dis- tributed to the front and side of the neck. The anterior branches of the lower four cervical nerves are much larger than the preceding. Through anastomosis together, and with the anterior branch of the first thoracic nerve, they form the brachial plexus, mainly destined to supply the upper e_ytrcqu^. The nerves forming the brachial plexus communicate by filaments with the second and third cervical and first dorsal ganglia of the sympathetic. THE CERVICAL PLEXUS. The Cer'vical plexus,1 as above mentioned, is formed by division and anastomosis of the anterior branches of the upper four cervical nerves. It is situated beneath the sterno-mastoid muscle, and rests upon the middle scalene muscle and the elevator of the scapular angle, opposite the upper four cervical vertebrae. From the cervical plexus are derived the following nerves :— 1. Muscular branches. 2. The superficial cervical nerve. 3. The great auricular nerve. 4. The small occipital nerve. 5. The supra-clavicular nerves. 6. The phrenic nerve. 1. The Muscular branches supply the scalene and long cervical mus- cles, the anterior and lateral straight muscles, the elevator of the scap- ular angle, and the sterno-mastoid and trapezius muscles. Plexus cervicalis. THE NERVOUS SYSTEM. 563 2. The Superficial Cer'vical nerve,1 derived from the anastomosis of the second and third cervical nerves, is directed around the posterior border of the sterno-mastoid muscle, and passes forward between it and the subcutaneous cervical muscle. Dividing into ascending and descend- ing branches, the former supply the subcutaneous cervical muscle and the skin at the upper fore part of the neck, and anastomose with fila- ments of the facial nerve; the latter supply the skin of the lower fore part of the neck. 3. The Great Auric'ular nerve,2 from the cervical plexus, winds around the posterior border of the sterno-mastoid muscle, and ascends on its outer surface to be distributed to the external ear and the skin over the parotid gland and mastoid process. Some of its filaments anastomose with branches of the facial and pneumogastric nerves. 4. The Small Occip'ital nerve,3 derived from the second cervical nerve, ascends along the posterior border of the sterno-mastoid muscle, and is distributed to the skin and muscles of the occipital region, anas- tomosing with the great occipital and great auricular nerves. 5. The Supra-clavie'ular nerves,4 of which there are usually three, spring from the fourth cervical nerve, and descend in the interval of the sterno-mastoid and trapezius muscles to be distributed to the skin over the clavicle, the breast, and shoulders. 6. The Phrenic nerve,5 the most important branch of the cervical plexus, springs from the third and fourth cervical nerves, and further receives an offset from the fifth cervical nerve or the commencement of the brachial plexus. Descending upon the anterior scalene muscle, it enters the thorax between the subclavian artery and vein, and proceeds downward in front of the root of the lung, included between the pleura and pericardium until it reaches the diaphragm, to which it is distributed. In its course it receives anastomotic filaments from the lower two cervical ganglia of the sympathetic, and gives filaments to the pericardium. THE BRACHIAL PLEXUS. The Bra'chial plexus,6 which mainly supplies the upper extremity, is formed through anastomosis of the anterior branches of the lower four 1 N. superficialis colli; n. subcutane- ous colli superior, medius, et infimus. 2 N. auricularis magnus; n. a. pos- terior. 3 N. occipitalis minor. 4 N. supra-claviculares; n. s. c. anteri- ores, medii, et posteriores. 5 N. phrenicus ; n. diaphragmaticus ; n. respiratorius internus ; internal res- piratory nerve of Bell. 6 Plexus brachiales ; p. axillaris. 564 THE NERVOUS SYSTEM. cervical nerves, together with the corresponding branch of the first tho- racic nerve. It extends from the side of the cervical vertebrae to the axilla, and opposite the coracoid process separates into large offsets for the upper extremity. In its course it passes outwardly between the an- terior and middle scalene muscles, and descends obliquely beneath the The brachial plexus. 1, anastomosis between the descending cervical branch of the hypoglossal and a branch of the cervical plexus; 2, pneumogastric nerve; 3, phrenic nerve; 4-8, the lower four cervical, and the first thoracic nerves, forming the brachial plexus; 9, branch to the subclavian muscle giving a filament to the phrenic nerve; 10, posterior thoracic nerve; 11,13, anterior thoracic nerves; 14, anasto- mosis between the latter; 12, supra-scapular nerve; 15-17, subscapular nerves; 18, small cutaneous nerve; 19, anastomosis of a branch of the latter with the intercosto-humeral nerve, 20; 21, continuation of the small cutaneous nerve in company with the internal cutaneous, 22; 23, ulnar nerve; 24, median; 25, external cutaneous; 26, musculo-spiral nerve. clavicle into the axilla. It is at first situated above and partially be- hind the subclavian blood-vessels, then behind the axillary vessels, and finally, it surrounds the latter as it is about to expend itself in branches. In its modes of formation the brachial plexus is subject to variation, but the most frequent arrangement is that which follows. The fifth cer- THE NERVOUS SYSTEM 565 vical nerve descends obliquely and joins the sixth, and the trunk thus formed is shortly after joined by the seventh cervical nerve. The first thoracic nerve ascends obliquely to join the eighth cervical nerve. The two trunks thus produced then send off each a branch which joins with its fellow to form a third trunk. Of the three trunks, one is placed on the outer side of the axillary artery; another on the inner side; and the third behind the vessel; and from them diverge the branches to the limb. The branches given off from the brachial plexus above the clavicle are, for the most part, destined to supply the side of the thorax and shoulder; those given off below the clavicle are its terminal divisions, and mostly extend the length of the upper extremity. The branches of the brachial plexus are as follow :— 1. Muscular branches. 2. Supra-scapular nerve. 3. Thoracic nerves. 4. Subscapular nerves. 5. Small cutaneous nerve. 6. Internal cutaneous nerve. 7. External cutaneous nerve. 8. Circumflex nerve. 9. Median nerve. 10. Ulnar nerve. 11. Musculo-spiral nerve. 1. The Muscular branches given off from the commencement of the brachial plexus supply the scalene, long cervical, rhomboid, superior serrate, and subclavian muscles. 2. The Supra-scap'ular nerve,1 from the upper trunk of the brachial plexus, passes outward and backward, and proceeds through the supra- scapular foramen to supply the supra- and infra-spinous muscles. 3. The Thorac'ic nerves consist of posterior and anterior branches. The posterior or long thoracic nerve,2 larger than the others, is derived from the fifth and sixth cervical nerves, and descends along the fore part of the great serrated muscle, to which it is distributed. The anterior thoracic nerves,3 of which there are two, spring from the inner and outer trunks of the brachial plexus, and pass beneath the clavicle to supply the pectoral muscles. 1 N. supra scapularis; n. scapularis. 2 N. thoracicus posterior, or longus; n. respiratorius externus; external respira- tory nerve of Bell. 3 Nervi thoracici; n. pectorales anteriores. 566 THE NERVOUS SYSTEM. 4. The Subscap'ular nerves,1 of which there are three, originate by filaments from all the cords of the brachial plexus, except the first tho- racic nerve. The largest branch descends along the outer border of the subscapular muscle to be distributed to the latissimus muscle, some of its filaments reaching the inferior serrated muscle. The other two nerves enter the upper part of the subscapular and terete muscles, which they supply. 5. The Small Cuta'neous nerve,2 derived from the first thoracic nerve of the brachial plexus, descends along the inner side of the axillary and brachial blood-vessels to near the middle of the arm. It then pierces the fascia of the latter, and proceeds beneath the skin to the elbow be- tween the internal condyle and olecranon. Iu its course it anastomoses with the intercosto-humeral nerve, and it supplies the skin on the lower inner part of the arm. The remaining branches of the brachial plexus come off at the lower or outer part of the axilla, and appear as its terminal divisions, for the most part extending the length of the upper extremity. 6. The Internal Cuta'neous nerve,3 from the lower trunk of the bra- chial plexus, is its smallest terminal branch. It descends on the inner side of the brachial blood-vessels, near the middle of the arm, pierces the fascia, and divides into two branches. Of these the smaller branch descends to the inner side of the basilic vein and behind the internal condyle, to be distributed to the skin on the back of the forearm. The larger branch, apparently the continuation of the main nerve, descends along the inner front part of the arm and forearm, and is expended in the contiguous skin. At the bend of the elbow one of its branches usually passes above, and another beneath the median basilic vein, near the termination of this vessel in the basilic vein. 7. The External Cuta'neous nerve,4 larger than the preceding, and derived from the upper cord of the brachial plexus, perforates the coraco-brachial muscle, and passes between the biceps flexor and bra- chial muscle to the outer part of the arm. It here perforates the brachial fascia, and divides into two branches, of which one passes in 1 N. subscapulares. 2 N. cutaneus minor; n. c. internus minor; n. c. brachii internus; n. c. ul- naris AVrisbergii. 3 N. cutaneus internus; n. c. i. ma- jor; n. c. brachii medius. 4 N. cutaneus externus; n. musculo- cutaneus; n. perforans Casserii; ramus magnus nervi mediani. THE NERVOUS SYSTEM. 567 front, the other beneath the median cephalic vein, and both descend along the outer part of the forearm to the wrist. Cutaneous nerves of the upper extremity. 1, supra-clavicular nerves of the cervical plexus; 2, cutaneous branches of the circumflex nerve; 3, branch of the internal cutaneous nerve; 4, small cuta- neous nerve, with its anastomosis from the intercosto-humeral; 5, cutaneous branch of the musculo- spiral nerve; 6, internal cutaneous nerve piercing the brachial fascia; 7, posterior branch anastomosing with 8, the ulnar nerve, and 9, the anterior branch; 10, the internal cutaneous dividing into branches, some passing in front and others behind the median basilic vein; 11, external cutaneous nerve; 12, cutaneous branch of the musculo-spiral nerve; 13, branches of the internal cutaneous to the front of the forearm; 14, anastomosis of one of the latter branches with one from the ulnar nerve; 15, terminal branches of the external cutaneous nerve; 16, 17, anastomosis between the latter and the radial nerve; 18, superficial palmar branch of the median nerve; 19-25, digital nerves. In its course it gives branches to the coraco-brachial, biceps flexor, and brachial muscles, and its terminal branches supply the skin on the outer part of the forearm — some of them anastomosing with filaments of the radial and musculo-spiral nerves. 568 THE NERVOUS SYSTEM. 8. The Circumflex nerve1 accompanies the posterior circumflex blood- vessels around the upper extremity of the huincrus, and is distributed to the lesser terete and deltoid muscles, some of the branches also sup- plying the shoulder joint and the skin on the back of the arm. 9. The Median nerve2 commences by two roots embracing the axillary artery from the inner and outer trunks of the brachial plexus, and de- scends in contact with the brachial artery to the elbow. Crossing in front of the latter, the nerve passes beneath the terete pronator, and proceeds between the superficial and deep flexors of the fingers to the wrist, and then passes under the annular ligament to the palm of the hand. In its course it gives off the following branches :— a. Muscular branches to the muscles on the front of the forearm, except the ulno-carpal flexor. &. The anterior interosseous nerve,3 which follows the corresponding artery, and supplies the deeper muscles on the front of the forearm. c. The superficial palmar branch,4 which pierces the fascia of the fore- arm near the wrist, and proceeds to the skin of the palm of the hand. d. A muscular branch to the muscles of the ball of the thumb. e. The Digital nerves, of which there are five. Two proceed to the sides of the thumb; a third runs along the outer side of the index finger; and the remaining two pass down the second and third meta- carpal intervals, and divide each into branches, which supply the con- tiguous sides of the index, middle, and ring fingers. The fifth digital nerve receives a communicating branch from the ulnar nerve. At the bases of the first phalanges, the digital nerves give off a dor- sal branch, which runs along the border of the back of the fingers. At the ends of the latter the digital nerves divide into two branches, of which one supplies the tips, the other the part beneath the nail. 10. The Ulnar nerve,5 from the lower and &a£er trunks of the bra- chial plexus, is smaller than the preceding, and gradually diverges from it on the inner part of the arm to the interval of the olecranon and in- ternal condyle. In this position it may be compressed against the latter through the skin, giving rise to the sensation which has led the part commonly to be called the "crazy bone." Piercing the origin of the ulno carpal flexor, the ulnar nerve proceeds between this muscle and the deep flexor of the fingers to the wrist, where 1 N. circumflexus; n. axillaris; n. scapulo-humeralis. 2 N. medianus. 3 N. interosseus internus; n. i. pro- fundus. * N. palmaris superficialis; n. cuta- neus palmaris; n. c. p. longus 5 N. ulnaris; n. cubitalis; cubito-di- gital nerve. THE NERVOUS SYSTEM. 569 it passes over the annular ligament close to the pisiform bone, and reaches the palm of the hand. Its branches are as follow:— a. Articular, muscular, and cutaneous branches to the elbow joint, ulno-carpal and deep flexor of the fingers, and the skin on the inner part of the forearm. Fig. 344. Ft. R'o. External cutaneous, median, ulnar, and musculo-spiral nerves. 1, external cutaneous nerve; 2, 3, 4, muscular branches; 5, anastomotic filament from the median; 6, division of the external cutaneous nerve into branches to the forearm; 7, musculo-spiral nerve; 8, cutaneous branch of the latter; 9, inter- nal cutaneous nerve; 10, its branches to the forearm; 11, median and ulnar nerves; 12, median nerve; 13-16, muscular branches; 17. anterior interosseous nerve; 18, superficial palmar branch; 19, branch to the muscles of the ball of the thumb; 20-24, digital nerves of the thumb, index, middle, and one side of the ring finger; 25, ulnar nerve; 26, muscular branches; 27, 28, cutaneous and dorsal branches ; 30, 31, digitals to the little and ring fingers; 32, deep palmar branch; 33-36, muscular branches from the latter; 37, musculo-spiral nerve; 38, its posterior interosseal division; 39, a muscular branch of the latter; 40, radial nerve. b. A dorsal branch,1 which passes beneath the tendon of the ulno- carpal flexor to supply the skin on the back of the hand. 1 N. dorsalis manus; cubito-dorsal nerve. 570 THE NERVOUS SYSTEM. e. The deep palmar branch, which follows the corresponding blood- vessels, and supplies the small muscles of the little finger, the interosseal and lumbrical muscles. d. The Digital nerves, of which there are two. One of these sup- plies twigs to the short palmar muscle and the skin on the inner part of the hand, and then runs along the inner side of the little finger. The other passes along the last metacarpal interval, gives an offset to the last median digital nerve, and then divides into two branches, which supply the contiguous sides of the ring and little fingers. 11. The Musculo-spiral nerve,1 from the posterior trunk of the bra- chial plexus, is the largest branch of the latter. It winds in a half spiral around the back of the humerus, in company with the superior profound artery, between the triceps extensor and the bone, and descends in the interval of the long supinator and brachial muscle to the elbow, where it divides into the radial and posterior interosseal nerves. In its course through the arm it gives off muscular branches to the triceps extensor, anconeus, brachial, long supinator, and long radio-carpal ex- tensor muscles, and cutaneous branches to the skin on the inner side of the arm and forearm to the wrist. The Radial nerve, the smaller division of the musculo-spiral, runs along the outer part of the forearm, and passes beneath the tendon of the long supinator. It then pierces the fascia, and divides into branches which anastomose with the external cutaneous nerve, and are distributed to the skin on the outer back part of the hand, the back of the thumb, the index and middle fingers. The Posterior Interos'seal nerve passes through the short supinator muscle to the back of the forearm, where it divides into branches supply- ing the extensor muscles, except the long radio-carpal extensor. A term- inal branch descends on the interosseal membrane to the back of the wrist, which it supplies. THE THORACIC NERVES. There are twelve pairs of thorac'ic nerves,2 of which the first pair issue from the intervertebral foramina, between the upper two dorsal vertebrae, and the last pair between the last dorsal and first lumbar ver- tebra. The first pair is much the largest; the others are nearly of uni- form size. After escaping from the intervertebral foramina they divide into anterior and posterior branches. 1 N. musculo-spiralis; n. radialis; n. spiralis. 2 Dorsal nerves; nervi thoracicis, or dorsales. THE NERVOUS SYSTEM. 571 POSTERIOR BRANCHES OF THE THORACIC NERVES. The Posterior branches of the thoracic nerves, like those of the other spinal nerves generally, are smaller than the anterior branches. Turning backward between the transverse processes of the vertebrae, they divide into external and internal branches. The external branches successively increase in size from first to last, and appear in the interval of the longissimus and sacro-lumbar muscles, which they supply. The lower six of the series further give off cuta- neous branches, which pierce the inferior serrated and latissimus muscles to supply the skin contiguous to the angle of the ribs. The internal branches of the upper six thoracic nerves appear in the interval of the multifid and semi-spinal muscles, to which they give fila- ments, and then supply the skin in the vicinity of the spinous processes of the vertebrae. The corresponding branches of the lower six thoracic nerves terminate in the multifid spinal muscle. ANTERIOR BRANCHES OF THE THORACIC NERVES. The anterior branches of the thoracic nerves remain distinct from one another, or do not anastomose and form plexuses as in the case of the other spinal nerves. Near their commencement each communicates, by means of a pair of anastomotic filaments, with the contiguous tho- racic ganglia of the sympathetic. The anterior branch of the first thoracic nerve, much larger than the others, as previously indicated, ascends over the first rib to form part of the brachial plexus. In its course it gives off a small branch, the first intercostal nerve, which runs along the first intercostal space. The anterior branches of the succeeding thoracic nerves are of nearly uniform size, and, with the exception of the last one, pass out- wardly in the intercostal spaces as intercostal nerves. The anterior branch of the last thoracic nerve is situated below the last rib. After crossing the quadrate lumbar muscle, it advances between the internal oblique and transverse muscles in the same manner as the intercostal nerves. At its commencement it frequently sends an anasto- motic filament to the first lumbar nerve. THE INTERCOSTAL NERVES. The first intercostal nerve is a small branch given off from the ante- rior branch of the first thoracic nerve, and supplies the muscles of the corresponding intercostal space. 572 THE NERVOUS SYSTEM. The lower ten intercostal nerves1 are constituted by the anterior branches of the thoracic nerves, from the second to the eleventh inclusive, and pass outwardly in the lower ten intercostal spaces. They first rest against the external intercostal muscle, and proceed between the two in- tercostal muscles in company with the corresponding blood-vessels, below which they are situated. They then penetrate the internal intercostal muscle, and continue forward between it and the pleura. The upper intercostal nerves finally perforate the fore part of the intercostal spaces and the greater pectoral muscle, and terminate in the skin of the breast as the anterior cutaneous nerves of the thorax.2 The lower intercostal nerves pass over the cartilages of the ribs at the inferior margin of the thorax, and advance between the internal oblique and transverse muscles of the abdomen to the straight muscle. Penetrating this, they finally end near the median line as the anterior cutaneous nerves of the abdomen.2 In their course the intercostal nerves supply the contiguous muscles, and give off lateral cutaneous branches.3 These perforate the external intercostal muscles, and pass between the fasciculi of the great serrated muscle above and the external oblique muscle below, and are distributed to the skin on the side of the thorax and abdomen. The lateral cutaneous branch of the second intercostal nerve consti- tutes the intercosto-humeral nerve, which extends across the axillary space, anastomoses with the small cutaneous nerve, and is distributed to the skin on the inner part of the arm. THE LUMBAR NERVES. Of the five pairs of lumbar nerves,4 the first issue from the interver- tebral foramina, between the first and second lumbar vertebrae, and the last pair between the fifth lumbar vertebra and the sacrum. Like the cervical and thoracic nerves they divide into an anterior and a posterior branch. The posterior branches of the lumbar nerves decrease in size from above downward, and pass backward between the transverse processes of the vertebrae. Penetrating the interstice of the longissimus and sacro- lumbar muscles, they supply them with branches and send filaments to the contiguous skin. The anterior branches of the lumbar nerves successively increase in size; and at their commencement each communicates by a pair of anas- 1 N. intercostales: n. subcostales. 3 Rami cutanei laterales. 2 Rami cutanei interni; reflected * N. lumbares; n. abdominales. nerves. THE NERVOUS SYSTEM. 573 tomotic filaments with the neighboring lumbar ganglia of the sympa- thetic. They pursue an oblique course outward and downward, partly through and partly behind the psoas muscle. In this position each nerve above sends an offset to the one next below, and by this mode of anas- tomosis the upper four lumbar nerves, in conjunction with a filament from the last thoracic nerve, form the lumbar plexus. The offset from the fourth lumbar nerve joining the fifth, together1 form part of the sacral plexus. THE LUMBAR PLEXUS. The Lumbar plexus,2 formed, as above mentioned, by the anastomosis of the anterior branches of the upper four lumbar nerves with a filament from the last thoracic nerve, besides supplying the psoas and quadrate lumbar muscles, gives off the following branches :— 1. Ilio-hypogastric nerve. 2. Ilio-inguinal nerve. 3. Genito-crural nerve. 4. External cutaneous nerve. 5. Obturator nerve. 6. Anterior crural nerve. 1. The Ilio-hypogas'tric nerve3 springs from the first lumbar nerve, passes through the psoas muscle, and crosses the quadrate lumbar muscle to the crest of the ilium. It then perforates the transverse muscle of the abdomen, and proceeds between it and the internal oblique muscle to the inguinal canal, through which it descends, or it pierces the tendon of the external oblique muscle, to supply the skin over the pubis. 2. The Ilio-in'guinal nerve,4 from the same source as the preceding, passes through the psoas muscle and across the iliac muscle to Poupart's ligament. It then perforates the transverse muscle, and descends the inguinal canal to supply the skin of the penis and scrotum, or the labium of the female. This and the ilio-hypogastric nerve are of variable size, and usually a diminution of one is compensated by an increase of the other. 3. The Genito-crural nerve5 springs from the second lumbar nerve, and pierces the psoas muscle to descend on its anterior surface, upon 1 The lumbo sacral cord. 2 Plexus lumbaris. 5 N. ilio-hypogastricus; n. musculo- cutaneus superior. * N. ilio-inguinalis ; n. musculo-cuta- neus inferior. 5 N. genito-cruralis; n. pudendis ex- ternus ; n. spermaticus externus; n. in- guinalis externus. 574 THE NERVOUS SYSTEM. which it divides into two branches. Of these, the genital branch1 crosses to the inner side of the external iliac artery, and enters the in- guinal canal, through which it proceeds to be distributed to the sperm- atic cord and the coverings of the testicle, or in the female to the round ligament, mons veneris, and labium. The crural branch2 descends on the outer side of the external iliac artery, and passes beneath Poupart's lig- ament to supply the skin in front of the thigh. 4. The External cutaneous nerve,3 derived from the second and third lumbar nerves, crosses the iliac muscle to the notch below the anterior superior spinous process of the ilium, and thence escapes from the ab- domen. Piercing the femoral fascia below Poupart's ligament, it divides into two branches, of which one supplies the skin on the outer part of the thigh, while the other supplies the skin on the fore part as low as the knee. 5. The Obtura'tor nerve,4 larger than the preceding branches of the lumbar plexus, is derived from the second, third, and fourth lumbar nerves. Emerging from beneath the inner border of the psoas muscle, it runs along the side of the pelvis, and escapes, in company with the ob- turator blood-vessels, through the foramen of the obturator membrane. Reaching the thigh, it divides into two branches,3 of which one supplies the great adductor and external obturator muscles, and gives filaments to the hip joint, while the other supplies the long and short adductor, the pectineal, and gracilis muscles, and furnishes filaments to the skin on the inner side of the thigh. 6. The, Crural nerve,6 the largest branch of the lumbar plexus, is derived from the second, third, and fourth lumbar nerves. Passing from beneath the psoas muscle, it descends in the groove between this and the iliac muscle, and emerges from the pelvis under Poupart's ligament. In this position it is situated a short distance to the outer side of the fem- oral artery, beneath the femoral fascia, and divides into numerous branches. Within the pelvis it supplies the iliac muscle ; externally it gives muscular branches to the quadriceps extensor, the sartorius, and pecti- neal muscles, besides which it gives off the following:— 1 Ramus pudendus externus; n sper- maticus externus. 2 Ramus lumbo-inguinalis. 3 Nervus cutaneus externus ; n. c. an- terior. * N. obturatorius; n. cruralis poste- rior; n. c. internus. 5 Ramus anterior et posterior. B N. cruralis; n. c. anterior ; the ante- rior crural nerve; n. femoratis; n. mus- culo-cutaneus femoris. THE NERVOUS SYSTEM. 575 a. The Middle cutaneous nerve,1 which perforates the sartorius muscle and femoral fascia to supply the skin on the front of the thigh as low as the knee. Fig. 346. Fig. 347. Fig. 340.—Cutaneous nerves of the front of the thigh. 1, external cutaneous nerve; 2,-middle cuta- neous nerve; 3, 4, 5, 6, 7, internal cutaneous nerve and its branches; 8, cutaneous filaments to the inner part of the thigh; 9,10, branches of the long saphenous nerve. Fig. 347.—Lumbar plexus and its branches. 1, crural nerve; 2, 3, branches to the iliac and psoas muscles; 4, the cutaneous nerves cut away; 5, 6, small muscular filaments to the pectineal and adductor muscles; 7, origin of the cutaneous filaments seen in the preceding figure on the inner part of the thigh; 8, cutaneous filament descending to the inner part of the knee; 9,10,11, muscular branches of the crural to the quadriceps extensor; 12, long saphenous nerve; 13, branch to the knee; 14, branch descending the leg in company with the saphenous vein; 15, obturator nerve; 16,17, IS, 19, branches to the adductor and gracilis muscles; 20, branch of the fourth lumbar nerve, with the fifth lumbar nerve descending to join the first sacral nerve, 21; 22, lumbar and sacral ganglia of the sympathetic; 23, external cutaneous nerve. 1 N. cutaneus medius; n. perforans. 576 THE NERVOUS SYSTEM. 6. The Internal cutaneous nerve,1 which descends inwardly across the femoral blood-vessels, and perforates the fascia to supply the skin on the inner part of the thigh to the knee. c. The Long Saphenous nerve,2 which is the largest of the cutaneous branches of the anterior crural nerve. It accompanies the femoral blood-vessels until these are about passing through the opening of the great adductor muscle, when it leaves them, and descends under the sartorius muscle to the knee. It then pierces the fascia between the ten- dons of the sartorius and gracilis muscles, and accompanies the long saphenous vein down the inner side of the leg to the foot. Above the knee it gives off a considerable branch, which perforates the sartorius muscle and the fascia, and is distributed to the skin over the knee. In the remainder of its course it is expended in branches to the skin on the inner side of the leg and foot. THE SACRAL AND COCCYGEAL NERVES. There are five pairs of sacral,3 and one pair of coccyge'al nerves,4 which successively diminish in size; and they differ from other spinal nerves by undergoing division into anterior and posterior branches within the vertebral canal. The posterior branches of the upper four sacral nerves emerge at the corresponding sacral foramina; the posterior branches of the fifth sacral and the coccygeal nerve from the end of the vertebral canal. They anastomose with one another, forming a series of loops, and give off filaments which supply the commencement of the dorsal extensor and multifid-spinal muscle, and the contiguous skin. The anterior branches of the upper four sacral nerves emerge at the corresponding sacral foramina, and, in conjunction with the fifth, and part of the fourth lumbar nerve, form the sacral plexus. The anterior branch of the fifth sacral nerve is small, and emerges from the end of the vertebral canal. It divides into two branches, of which one joins with a filament of the fourth sacral nerve to end in the hypogastric plexus of the sympathetic, and the other joins the coccygeal nerve. The anterior branch of the coccygeal nerve, smaller than the pre- ceding, also emerges at the end of the vertebral canal. Being joined by a branch of the last sacral nerve, it perforates the coccygeal muscle and the great sacro-sciatic ligament, to terminate in the contiguous skin of the buttock. 1 N. cutaneus internus; n. saphenus minor. 3 N. sacrales. 2 N. saphenus longus; n. s. major. ■ \ . ^ * N. coccygei. THE NERVOUS SYSTEM. 577 THE SACRAL PLEXUS. The Sacral plexus,1 as previously mentioned, is formed by the con- junction of the anterior branches of the upper four sacral nerves with the anterior branch of the fifth and part of that of the fourth lumbar nerves. These converge from their respective foramina into a broad, flat cord, which passes from the cavity of the pelvis through the great sacro-sciatic foramen, and mainly ends in the great sciatic nerve. The sacral plexus is triangular, rests against the pyriform muscle, and is separated from the internal iliac blood-vessels and the neighboring viscera by the pelvic fascia. Its upper divisions, formed by the lowest lumbar and upper sacral nerves, are of large and nearly uniform size. The division formed by the third sacral nerve is considerably smaller than those above, and that formed by the fourth sacral nerve is less than half the size of the preceding. Besides giving off small branches, chiefly from the lower part of the plexus, to the hypogastric plexus of the sympathetic, the pyriform, in- ternal obturator, elevator and sphincter anal, geminous, and quadrate femoral muscles, it terminates in the following branches :— 1. Superior gluteal nerve. 2. Pudic nerve. 3. Small sciatic nerve. 4. Great sciatic nerve. 1. The Superior Gluteal nerve2 is derived from the upper part of the sacral plexus, and passes from the pelvis in company with the gluteal blood-vessels at the upper part of the great sciatic foramen. Dividing into two branches, these advance between the middle and small gluteal muscles, to which, and the tensor of the femoral fascia, they are dis- tributed. 2. The Pudic nerve3 leaves the lower part of the sacral plexus, and passes from the pelvis through the great sciatic foramen below the pyri- form muscle. Turning behind the spine of the ischium, it re-enters the pelvis through the small sciatic foramen, and accompanies the internal pudic artery along the outer part of the ischio-rectal fossa. Its branches are as follow :— a. The inferior haemorrhoidal nerve,4 which is given off near the Plexus sacralis; p. ischiaticus; p. 3 N. pudendus; n. spermaticus com- femoralis inferior. munis. 2 Nervus glutseus superior. * N. haemorrhoidalis imus. 31 578 THE NERVOUS SYSTEM. commencement of the pudic, or sometimes directly from the sacral plexus. Accompanying the trunk of the pudic through the small sci- atic foramen, it descends to the extremity of the rectum, and terminates in the sphincter of the anus and the adjacent integument. b. The perineal nerve.1 This divides into superficial branches, which are distributed to the skin of the perineum ; and deep branches, which supply the muscles of the perineum and penis, and the posterior part of the scrotum. In the female, in correspondence with the latter parts, it supplies the muscles of the vagina and clitoris, the vestibule, the nymphae, and the labia. c. The dorsal nerve of the penis,2 or of the clitoris.3 This accom- panies the corresponding artery between the cavernous and spongy bodies to the back of the organ, along which it proceeds to the glans. It supplies the cavernous and spongy bodies, the glans and prepuce, the skin of the penis, or the upper part of the nymphae. 3. The Small Sciat'ic nerve4 is derived from the lower part of the sacral plexus, through the union of two or three narrow offsets. Pass- ing from the cavity of the pelvis through the great sciatic foramen, be- low the pyriform muscle, it descends upon the back of the thigh and leg. At the upper part of its course it is under the great gluteal muscle, and gives off the inferior gluteal and pudendal nerves. It then proceeds downward beneath the femoral fascia, and is resolved into many small cutaneous branches, which pierce the latter and supply the contiguous skin of the thigh and leg. The inferior gluteal nerves,5 usually two in number, come from the commencement of the small ischiatic nerve or directly from the sacral plexus close to it, and are distributed to the great gluteal muscle. The pudendal nerve,6 a large, cutaneous branch of the small sciatic, curves forward below the tuberosity of the ischium, and is distributed to the scrotum, or the labia. 4. The Great Sciat'ic nerve7 appears as a prolongation of the sacral plexus, and is the largest nerve of the body. It escapes from the pelvis 1 N. pudendus inferior; n. spermati- ds inferior; n. ovaricus inferior; n. o. internus. 2 N. pudendus superior; n. spermati- ds superior; n. ovaricus superior; n. o. externus ; n. dorsalis penis. 3 N. clitoridis. * N. glutseus inferior et n. cutaneus posterior; n. ischiadicus minor. 5 N. glutaei inferiores. 6 N. cutaneus femoris posterior; n. pudendalis longus inferior; inferior pu- dendal nerve. 7 N. ischiadicus major; n. ischiadi- cus ; great femoro-popliteal nerve. THE NERVOUS SYSTEM. 579 through the great sciatic foramen, below the pyriform muscle, descends through the middle of the interval between the tuberosity of the ischium and the great trochanter, and continues along the back of the thigh to its lower part, where it divides into the external and internal popliteal nerve. The division of the sciatic nerve may occur at any point be- tween the ordinary one just stated and its commencement in the sacral plexus In its course down the thigh the great sciatic nerve gives articular filaments to the hip joint, and muscular branches to the flexors and great adductor. The External Poplite'al nerve1 is the smaller terminal division of the great sciatic. Descending obliquely along the outer part of the popli- teal space to the fibula below its head, it passes between that bone and the long peroneal muscle, and divides into the anterior tibial and mus- culocutaneous nerves. In its course it gives off several articular branches to the knee joint, a couple of cutaneous branches2 to the skin on the outer part of the leg, and the peroneal communicating branch,3 which descends the back of the leg to join the short saphenous nerve. The anterior tibial nerve4 passes beneath the long extensor of the toes, and reaches the fore part of the interosseal membrane, to accom- pany the anterior tibial vessels down the leg. In its course it furnishes filaments to the contiguous muscles, and in front of the ankle joint divides into two branches, of which one supplies the short extensor of the toes, and the other follows the dorsal pedal artery, and supplies the inner part of the foot. The musculo-cutaneous nerve5 descends between the peroneal muscles and the long extensor of the toes, giving them branches, and reaches the lower third of the front of the leg, where it perforates the fascia and be- comes subcutaneous. Continuing its descent, it divides into two branches, which supply the skin on the back of the foot and toes. The Internal Poplite'al nerve,6 the larger of the terminal divisions of the great sciatic nerve, is continued in the direction of the parent trunk. It occupies the middle of the popliteal space, more superficially than the blood-vessels, and at the lower margin of the popliteal muscle assumes the name of the posterior tibial nerve. It gives off two or three ar- 1 N. popliteus externus; n. peroneus; n. fibularis ; n. ischiadicus minor. 2 Peroneo-cutaneous nerves. 3 N. communicans fibularis. ' 4 N. tibialis anterior; n. peroneus pro- fundus; n. interosseus. 5 N. musculo-cutaneus; m. peroneus superficialis. 6 N. popliteus internus; n. tibialis. 580 THE NERVOUS SYSTEM. ticular branches to the knee joint, and muscular branches to the gas- trocnemius, soleus, plantar, and popliteal muscles. It also gives off the short saphenous nerve,1 which descends between the gastrocnemius Fig. 348. Fir.. 340. Fig. 318. External popliteal nerve and its branches. 1, external popliteal nerve; 2, cutaneous branch to the outer part of the leg; 3, peroneal communicating branch anastomosing with the short saphe- nous nerve 4 5; 6, 7, 8, terminal branches of the latter to the outer part of the foot; 9, musculocutane- ous nerve- 10,11,12, terminal branches to the back of the foot; 13, anterior tibial nerve; 14, terminal branch of the latter anastomosing with branches of the musculocutaneous nerve; 15, muscular branches. Fig. 349. Popliteal nerves. 1, internal popliteal nerve; 2, 3, 4, muscular branches; 5, short saphe- nous nerve; 6, external popliteal nerve; 7, cutaneous branch; 8, peroneal communicating branch joining the short saphenous nerve; 9, common trunk of the peroneal communicating and saphenous nerves to the outer part of the foot; 10, branch to the heel; 11, cutaneous branch from the posterior tibial nerve; 12, 13, branches of the long saphenous nerve. 1 N. saphenus externus; n. s. brevis; n. communicans tibialis; ramus commu- nicans nervi tibici; n. cutaneus longus cruris et pedis. THE NERVOUS SYSTEM. 581 muscle and the fascia, and about the middle of the leg perforates the latter and becomes subcutaneous. It then usually receives the peroneal communicating branch1 of the external popliteal nerve, and descends, in company with the short saphenous vein, to the outer side of the foot, to which it is distributed. The Posterior Tibial nerve is the continuation of the internal pop- liteal nerve from the lower margin of the popliteal space. It descends the back of the leg, in company with the posterior tibial vessels, supply- ing in its course muscular branches to the posterior tibial and long flexor muscles of the toes, and a cutaneous branch to the skin of the heel. Behind the inner ankle it divides into the two plantar nerves. The Internal plantar nerve2 accompanies the corresponding artery in the sole of the foot, in its course giving branches to the short flexor of the toes, the abductor of the great toe, and the skin of the sole. At the back part of the metatarsus it divides into four digital nerves, of which one courses along the inner side of the great toe, while the other three pass forward in the succeeding three metatarsal intervals, and bi- furcate to supply the contiguous sides of the corresponding toes. These digital nerves also supply the short flexor muscle of the great toe and the contiguous lumbrical muscles. The External plantar nerve,3 the smaller of the terminal divisions of the posterior tibial, passes between the short digital and accessory flexors to the outer side of the foot. In its course it gives muscular branches to the short and accessory flexors of the toes, the muscles of the little toe, the adductor of the great toe, and the interosseal, trans- verse, and outer lumbrical muscles. It also gives cutaneous filaments to the outer part of the sole, and terminates in two digital nerves, which supply the outer side of the little toe and the contiguous sides of this and the adjoining toe. THE SYMPATHETIC SYSTEM OF NERVES. The Sympathetic system of nerves4 is mainly devoted to supply the viscera of the great cavities of the body, though the respiratory organs, the heart, and the extremities of the alimentary canal also receive nerves from the cerebro-spinal system. The nerves of the sympathetic system are generally much smaller, less strong, and less distinctly observable 1 N. communicans fibularis. 2 N. plantaris internus. 3 N. plantaris externus. ♦Great sympathetic nerves; tri- splanchnic nerves; ganglionic nerves; organic nervous system; nervous sys- tem of the automatic functions; nerves of organic life; great intercostal nerves; vertebral nerves; vaso-motor nerves. 582 THE NERVOUS SYSTEM. than those of the cerebro-spinal system. Usually they possess a more or less grayish aspect, closely adhere to contiguous structures by a pro- fusion of connective tissue, and are connected with many ganglia. Like the cerebro-spinal system, the sympathetic system is double. It consists of a gangliated cord, extending on each side of the body the entire length of the vertebral column, intercommunicating with the neighboring cerebro-spinal nerves by means of anastomotic filaments,1 and sending off numerous branches, which form intricate plexuses often associated with additional ganglia, and usually following the course of the blood-vessels to the viscera. The gangliated cords of the two sympathetics lie nearly parallel to each other as far down as the sacrum, upon which they gradually con- verge and conjoin in a single minute ganglion resting on the coccyx. The ganglia of each cord correspond in number, and nearly in position with the segments of the vertebral column, except in the neck, where there are but three. These ganglia intercommunicate with the contigu- ous cerebro-spinal nerves by means of short, narrow cords, composed of an interchange of nerve fibres of the two systems, which thus become closely associated. Many of the nerves from the gangliated cords at once follow the course of the contiguous blood-vessels to their ultimate destination; but the greater number and larger ones contribute to the formation of three most intricate plexuses common to the two sympathetic nerves. These symmetrical plexuses are situated in front of the vertebral column, within the thorax, abdomen, and pelvis, and are successively named the cardiac, solar, and hypogastric plexuses. With them are associated many ganglia, and they are resolved into smaller plexuses, which accom- pany the contiguous blood-vessels to the neighboring organs. The gangliated cord of the sympathetics, from the different positions it occupies in its course, for description is conveniently divided into the cervical, dorsal, lumbar, and sacral portions. These, with the three great symmetrical plexuses above indicated, will be separately considered. (For the upper part of the sympathetic nerve see figures 339, 340.) CERVICAL PORTION OF THE SYMPATHETIC NERVE. In the neck the gangliated cord of the sympathetic nerve rests upon the muscles in front of the cervical vertebras, behind the great blood- vessels. It posseses three ganglia, which are called, from their relative position, superior, middle, and inferior. Rami communicantes. THE NERVOUS SYSTEM. 583 The Superior cer'vical ganglion1 is the largest of the cervical series, and is usually fusiform. It rests on the greater straight muscle in front of the second and third cervical vertebrae and behind the internal carotid artery. It is connected by intervening filaments with the upper four spinal nerves, the petrosal ganglion of the glosso-pharyngeal, the ganglia of the pneumogastric, and with the hypoglossal nerve. Besides the cord of communication with the second cervical ganglion, it gives off an ascending branch, vascular branches, pharyngeal nerves, and the superior cardiac nerve. 1. The Ascending branch2 of the superior cervical ganglion appears as the continuation of the sympathetic accompanying the internal carotid artery through the carotid canal of the temporal bone. It divides into two branches, which subdivide and communicate with one another around the artery, and thus form the carotid plexus. This plexus, by means of one or two filaments, joins the abducent nerve; and, through the deep pe- trosal branch of the pterygoid nerve, it joins the spheno-palatine ganglion. The continuation of the plexus upon the same artery in the cavernous sinus constitutes the cavernous plexus, and this communicates through fine filaments with the semilunar ganglion of the trifacial nerve, with the oculo-motor, the pathetic, and the ophthalmic nerves, and with the oph- thalmic ganglion. From the carotid and cavernous plexuses fine fila- ments are given off, which accompany all the branches of the internal carotid artery. 2. The Vascular branches3 of the first cervical ganglion apply them- selves to the external carotid artery, and form plexuses upon it and its ramifications. By means of the plexuses on the facial and internal max- illary arteries, the sympathetic nerve is brought into communication with the submaxillary and otic ganglia. 3. The Pharynge'al nerves,4 of which there are two or three, descend to the side of the pharynx, and, in conjunction with the branches derived from the glosso-pharyngeal and pneumogastric nerves, form the pharyn- geal plexus, which supplies the mucous membrane and constrictor muscles of the pharynx. 4. The Superior cardiac nerve5 is derived from the first cervical gan- glion and the cord below it by two or three filaments, and descends the 1 Ganglion cervicale superius. 2 Ramus ascendens; cranial branch. 3 Nervi molles. * Rami pharyngei. 5 Nervus cardiacus superficialis, supe- rior, supremus, or magnus. 584 THE NERVOUS SYSTEM. neck behind the great blood-vessels, to enter the thorax. On the right side it passes either in front of or behind the subclavian artery, and then along the innominate artery to the back of the arch of the aorta, where it ends in the deeper part of the cardiac plexus. On the left side, the nerve follows the carotid artery to the arch of the aorta, and usually ends in the superficial part of the cardiac plexus. In its course down the neck, the superior cardiac nerve receives branches from the pneumogas- tric nerve, and it gives filaments to the inferior thyroid artery. The Middle cervical ganglion1 is small, and is connected with the third ganglion by several branches. Sometimes it is indistinct, and appears to be associated with the third ganglion. It rests against the inferior thyroid artery, opposite the fifth cervical vertebra, and is usually con- nected by intervening filaments with the fifth and sixth spinal nerves. Besides giving branches to the inferior thyroid artery, following that vessel to the thyroid body, it gives off the Middle cardiac nerve.2 This descends to the root of the neck, communicates with the superior and inferior cardiac and pneumogastric nerves, and ends in the deeper part of the cardiac plexus. The Inferior cervical ganglion,3 irregularly crescentic in form, is situ- ated between the transverse process of the last cervical vertebra and the first rib, behind the vertebral artery. It is connected with the first tho- racic ganglion by several branches, some of which pass in front and some behind the subclavian artery. It communicates by short cords with the seventh and eighth spinal nerves. Besides sending filaments to con- tribute in the formation of the plexus accompanying the vertebral artery, it gives off the Inferior cardiac nerve,4 which, after communicating with the middle cardiac and inferior laryngeal nerves, terminates in the deeper part of the cardiac plexus. It sometimes receives a contribution from the first thoracic ganglion; and on the left side is often blended with the middle cardiac nerve. THE CARDIAC PLEXUS. The Cardiac plexus5 of the sympathetic nerve is situated behind and beneath the arch of the aorta, and' is formed from the three cardiac nerves derived from the cervical ganglia, together with branches derived from the first thoracic ganglia and pneumogastric nerves. Beneath 1 Ganglion cervicale medium; g. thy- roideum. 2 Nervus cardiacus medius, profundus, or magnus. 3 Ganglion cervicale infinum, inferius, ultimum, thyroideum, vertebrale, stella- tum, or cardiacum tertium. 4 Nervus cardiacus inferius. 5 Superficial and deep cardiac plexus; plexus cardiacus superficialis et magnus profundus. THE NERVOUS SYSTEM. 585 the arch of the aorta, above the point of division of the pulmonary artery, the plexus contains one or two small ganglia,1 called cardiac from their position. From the cardiac plexus prolongations accompany the coronary arteries, and are named the coronary plexuses. THORACIC PORTION OF THE SYMPATHETIC NERVE. In the thorax the gangliated cord of the sympathetic nerve is situated at the side of the vertebral column, along the line of the heads of the ribs, and is covered by the pleura. The ganglia, twelve in number, rest on the heads of the ribs. They are irregularly triangular, and are gen- erally associated, each by means of two narrow cords, with the nearest intercostal nerve. The first thoracic ganglion joins the last cervical ganglion, as previously stated; the last one communicates through the diaphragm with the first lumbar ganglion. The upper six thoracic ganglia give off small branches to the aorta, the intercostal blood-vessels, and the oesophageal and pulmonary plexuses of the pneumogastric nerve. The lower six ganglia, besides furnishing filaments to the aorta, give off branches which conjoin to form the three splanchnic nerves. The Great Splanch'nic nerve2 derives its roots from the sixth to the tenth thoracic ganglia. Descending obliquely over the bodies of the dorsal vertebrae, it perforates the crus of the diaphragm, and terminates in the semilunar ganglion. The Small Splanchnic nerve3 derives its roots from the tenth and eleventh thoracic ganglia, and accompanies the preceding nerve through the diaphragm, and terminates in the solar plexus. The Third Splanchnic nerve4 comes from the twelfth thoracic gan- glion, and, after piercing the diaphragm, ends in the renal plexus. Its place is sometimes supplied by a branch from the preceding nerve. THE SOLAR PLEXUS. The Solar plexus5 is the most extensive of those of the sympathetic system, and is so named from the multitude of filaments radiating there- 1 Ganglion cardiacumWrisbergii; g. c. magnum; g. c. inferius; g. thoracicum rami cardiaci superioris. 2 N. splanchnicus maximus, major, superior, or primus. 3 N. splanchnicus medius, minor, or inferior. 4 N. splanchnicus inferior, inferius, or minimus; least splanchnic nerve. 5 Plexus Solaris ; p. epigastricus; cen- trum commune. 586 THE NERVOUS SYSTEM. from. It is situated behind the stomach, in front of the aorta and the crura of the diaphragm, surrounding the cceliac and commencement of the superior mesenteric artery, and extending between the supra-renal bodies. It is composed of a highly intricate intertoxture of nerves associated with ganglia ; and on both sides it receives the great and small splanchnic nerves, together with some filaments from the pneumo- gastric nerves. Among the ganglia, which are variable in size and num- ber, generally there is one on each side of the plexus conspicuous for its size and shape, named the semilunar ganglion.1 This is situated at the side of the cceliac and superior mesenteric arteries, and receives the great splanchnic nerve. From the solar plexus emanate a multitude of nerves, which pursue the course of the neighboring arteries, form plexuses upon them, and partake in their ultimate distribution to the viscera. These secondary plexuses are as follow :— The Phrenic plexus,2 accompanying the corresponding artery on each side to the diaphragm. The Coronary, Hepatic, and Splenic plexuses, pursuing the like- named arteries to the stomach, liver, pancreas, and spleen. The Supra-renal plexus to the supra-renal body. This is large in * comparison with the organ it supplies, and usually contains a ganglion.3 The Renal plexus, which accompanies the renal artery to the kidney. It receives the third splanchnic nerve, and contains several small gan- glia. An offset, pursuing the course of the spermatic artery, constitutes the spermatic plexus. The Superior mesenteric plexus, following the corresponding artery and its branches to the intestines. With its commencement several small ganglia are associated. The Aortic plexus, which is the continuation of the solar plexus, de- scending upon the aorta. It is intimately associated with the renal plexus on each side, receives branches from the lumbar ganglia, and terminates below in the hypogastric plexus. From it is derived the Inferior mesenteric plexus, which follows the corresponding artery to the large intestine. 1 Ganglion semilunare; g. magnum ; g. medium; g. splanchnicum; g. solare; g. transversale; g. abdominale maximum; cerebrum abdominale; centrum nerv- osum. 2 Diaphragmatic plexus. 8 Ganglion splanchnico-supra-renale. THE NERVOUS SYSTEM. 587 LUMBAR AND SACRAL PORTIONS OF THE SYMPATHETIC NERVES. The gangliated cord of the sympathetic nerve in the lumbar region, continued from that in the thorax, rests at the side of the lumbar verte- brae along the front edge of origin of the psoas muscle. Its four or five ganglia are oblong, oval, and small, and are situated at the sides of the vertebrae. Each is connected by a pair of communicating filaments with the nearest lumbar nerve, and gives off branches to the neighboring aortic plexus and the hypogastric plexus. The sacral portion of the gangliated cord lies to the inner side of the anterior sacral foramina, and terminates in front of the coccyx in a small ganglion common to the two sympathetic nerves. Besides the latter, it usually possesses four ganglia, which successively decrease in size. The sacral and coccygeal ganglia are each connected with the con- tiguous spinal nerves by a pair of communicating filaments, and they give off branches to the hypogastric plexus. THE HYPOGASTRIC PLEXUS. The Hypogastric plexus,1 more intricate than the preceding great plexuses of the sympathetic, is situated between the common iliac blood- vessels, and extends2 downward on each side of the rectum. It is formed from the termination of the aortic plexus in conjunction with branches from the lower lumbar ganglia, the sacral ganglia, the lower two or three sacral nerves, and the inferior mesenteric plexus. It is mingled with much loose connective tissue, contains a number of minute inconspicuous ganglia, and gives off the following secondary plexuses :— The Vesico-prostat'ic plexus,3 which extends to the sides of the bladder, the prostate gland, and the seminal vesicles. The Vesico-vag'inal plexus,4 which represents the preceding in the female, and extends to the sides of the vagina and bladder. The Uterine plexus,5 which extends between the layers of the broad ligament to the uterus. 1 Plexus hypogastrics; p. h. superior, communis, uterinus, medius, or impar; inferior aortic plexus ; plexus divisionis aortoe. 2 The extensions on each side down- ward are the inferior hypogastric plex- uses; p. hypogastrics inferior; p. h. lateralis inferior; p. ganglionus infe- rior ; pelvic plexus. 3 Plexus vesicalis et prostaticus, et vesiculae seminalis. * Plexus vesicalis et vaginalis. 5 Plexus uterina. CHAPTER XII. THE ORGANS OP SPECIAL SENSE. THE NOSE. The Nose1 is the special organ of the sense of smell, though it par- ticipates in oth^r functions, as those of respiration, and the voice. For convenience of description the term is restricted to the pyramidal emi- nence of the face, extending from the forehead to the upper lip, while the other portions of the organ are separately considered as the nasal cavities. THE NOSE. The nose2 varies in its exact shape and size in different races, sexes, and individuals, and forms one of the most expressive features of the face. Its upper part, firm and immovable, has for its basis the nasal bones and the nasal processes of the superior maxillary bones; its lower part, quite movable, is sustained by cartilages and tough fibrous membrane. Externally the nose is covered by the skin, and is furnished with muscles, and internally is lined by an extension of the mucous membrane of the nasal cavities. The upper extremity of the nose, forming an indentation below the forehead, is its root;3 the convexity between the eyes is the bridge, from which the back4 extends to the tip5 and the sides, terminated below by con- vex prominences named the wings.6 At the lower part of the nose are the nostrils or anterior nares,7 a pair of elliptical orifices directed down- ward, and separated by a thick ridge named the column of the nose.8 The skin of the nose is thin above, and readily movable on the parts beneath; but is much thicker below, and firmly adherent to the carti- lages, and other subjacent structures. As elsewhere, generally, it is fur- nished with perspiratory and sebaceous glands and hairs. The seba- 1 Nasus; organonolfactorium; emunc- 5 Lobulus; lobe; globulus1; apex; torium cerebri. point of the nose. 2 Nasus; rhin; promonitorium faciei; 6 Alae ; pinnae. snout. 7 Nares; aperturae nasi externae; 3 Radix. rhines; narium aditus. * Dorsum ; rachis. 8 Columna nasi. (588) THE ORGANS OF SPECIAL SENSE. 589 ceous glands are comparatively large and numerous at the lower part of the nose, more especially along the groove above the wing. The hairs for the most part are exceedingly minute, except within the margin of the nostrils, where they are well developed and project from all sides, and in some measure serve the purpose of a sieve in preventing the entrance of dust. The muscles of the nose have already been described in the general account of the muscles of the face, to which the student is referred, pages 186, 188, 189. They are the nasal pyramidal, nasal compressor, nasal dilator, labio-nasal elevator, and the labio-nasal depressor muscles. Fig. 350. Partition of the nose. 1, cartilage of the partition; 2, its junction with the nasal plate of the eth- moid bone; 3, its junction with the nasal bones; 4," margin of continuation with the upper lateral carti- lage; 5, fibrous membrane connecting the cartilage of the partition with the lower lateral cartilage; 6, inner portion of the left lower lateral cartilage; 7, anterior border of the vomer; 8, an accessory carti- lage- 9 prolongation of the cartilage of the partition, in a groove between the vomer and nasal plate of the ethmoid bone; 10, naso-palatine canal of the right side opening into the anterior palatine foramen, 11. The cartilages of the nose are the main support of the lower part of the organ, and are situated in front of the anterior nasal orifice of the skull. They consist of a cartilage to the partition, and two pairs of lateral cartilages, besides several small accessory pieces. The cartilage of the partition1 of the nose occupies the angular in- •tilagineum; cartilage of the septum; cartilago septi narium. 590 THE ORGANS OF SPECIAL SENSE. terval between the nasal plate of the ethmoid bone and the vomer. It is continued forward along the median line of the nasal bones ; below these^is continuous with the upper lateral cartilages, and inferiorly con- tributes to form the column of the nose. It is trapezoidal in outline, and constitutes about one-third of the partition of the nose. The upper lateral cartilages1 are continuous with the anterior border of the cartilage of the partition, and are reflected one on each side out- wardly to be attached along the margin of the nasal bone and the nasal process of the superior maxillary bone. They are triangular, and are connected with the tip and wings of the nose by tough fibrous membrane. The lower lateral cartilages2 form the basis of the tip, and contrib- ute to the column and wings of the nose. Each consists of an elongated plate bent upon itself so F,G- 351- as to form a triangle, with its apex directed to the tip, and its open base directed backward. The inner portion of the plate is narrow, extends along the column of the nose, and is attached to that of the opposite cartilage and the lower border of the cartilage of the par- tition by loose fibrous tis- sue. The outer portion is oval, and extends out- ward and backward upon the tip and upper portion of the wing. Its upper border and posterior ex- tremity are attached by tough fibrous membrane to the upper lateral car- tilage and the margin of the nasal process of the maxillary bone. Between the two lower lateral cartilages, which adhere to each other Cartilages of the nose. 1, upper lateral cartilage; 2, its ante- rior border; 3, anterior margin of the cartilage of the septum appearing between the lateral cartilages; 4, small accessory carti- lage ; 5, lower lateral cartilage, back of which is the wing of the nose; 6, accessory cartilages; 7, tip of the nose where the lower lateral cartilages are bent inwardly along the column. 1 Cartilagines nasi laterales; c. laterales superiores; c. triangulares. 2 Cartilagines alarum nasi; c. pinnalles; c. laterales inferiores; oval cartilages. THE ORGANS OF SPECIAL SENSE. 591 by fibrous tissue, an angular cleft is left at the tip of the nose, in which the skin often appears depressed. The accessory cartilages1 consist of two or three small pieces2 im- bedded in the fibrous membrane behind the posterior extremity of the outer portion of the lower lateral cartilages—occasionally a small nod- ule above the latter—and a small slip3 on each side of the lower margin posteriorly of the cartilage of the partition. The cartilages of the nose are composed of pure cartilage, and are enveloped in a perichondrium continuous with the periosteum of the contiguous bones The cartilage of the septum forms a continuous structure with the upper lateral car- tilages, the vomer, and the nasal plate of the ethmoid bone. The wings of the nose4 are the convex prominences bounding the nostrils externally, and separated from the sides above by a furrow. They are composed of a doubling of thick skin containing a mass of tough connective tissue mingled with adipose tissue and muscular fibres forming part of the insertion of the nasal muscles. The cartilages and wings of the nose give to the lower part of the organ its flexibility, and while they ordinarily preserve the open con- dition of the nostrils, they permit their contraction and expansion. THE NASAL CAVITIES. The Nasal cavities5 are two narrow but extensive and complex spaces, communicating with the exterior in front by the anterior nares, and with the pharynx behind by the posterior nares. Their roof is formed by the nasal bones, the cribriform plate of the ethmoid bone, and the body of the sphenoid bone ; their floor is formed by the palate pro- cesses of the superior maxillary and palate bones. They are separated from each other by the nasal partition ;6 their outer wall supports the turbinated processes and bone, between which are the three meatuses; and with them communicate the sphenoidal, ethmoidal, frontal, and maxillary sinuses. The mode of construction of the nasal cavities by the surrounding bones has already been described in the account of the skull, page 92. The anterior nares are placed below the level of the floor of the nose, 1 Cartilagines sesamoideae; c. epac- tiles; c. accessorii. 2 C. sesamoideae ; c. quadratae. 3 Vomer cartilagineus dexter et sinister. 4 Alae nasi; pinnae. 5 Fossae nasales; nasus internus: cavi narium; caverna narium. 6 Nasal septum. 592 THE ORGANS OF SPECIAL SENSE. at the most advanced position of the organ, and are directed downward. The posterior nares occupy the posterior inferior extremity of the organ, and are directed backward and downward. Inspired currents of air describe a semicircle in passing through the nasal cavities, ascending from the nostrils to the roof, and descending to the posterior nares. The turbinated processes break up the currents, and the air passes through the meatuses and into the various sinuses, so that all parts of the nasal surfaces may receive odorous particles conveyed into the nose. Fig. 352. Outer wall of the left nasal cavity. 1, superior turbinated process; 2, superior meatus; 3, inferior turbinated process; 4, middle meatus; 5, portion of the turbinated processes of the ethmoid bone, removed to exhibit the orifice of communication 6, with the anterior ethmoidal sinuses; 7, communication with the frontal sinus; 8, left frontal sinus; 9, part of the unsymmetrical partition which separates the frontal sinuses; 10, turbinated bone; 11, inferior meatus; 12, lachrymo-nasal duct exposed by removing a por- tion of the bones; 13, its termination; 14, edge of the upper lateral cartilage; 15, outer part of the-left nostril; 17, cut edge of the cartilage of the partition; 18, inner portion of the left lower lateral cartilage; 19, sphenoidal sinus; 20, its orifice; 21, pharynx; 22, orifice of tho Eustachian tube. The nasal cavities are lined throughout with a highly vascular mucous membrane intimately adherent to the subjacent periosteum and peri- chondrium. At the nostrils it gradually merges into the skin, at the posterior nares is continuous with the mucous membrane of the pharynx, and through the lachrymo-nasal duct and lachrymal canals with the conjunctiva. THE ORGANS OF SPECIAL SENSE. 593 The nasal mucous membrane1 is red, but varies in thickness, vascu- larity, and special structure in different positions. It is thickest and most vascular upon the turbinated processes, but especially on the tur- binated bone ; and at their inferior borders and posterior extremities it forms quite thick doublings, which much increase the extent of the nasal surface. On the partition it is also moderately thick, but in other positions is thinner; and in the sinuses it is so delicate and transparent as to assume more the appearance of a serous membrane. The foram- ina communicating with the sinuses are much reduced in size, from what they appear in the macerated skull, by the reflection of the mucous membrane at their edges. Approaching the anterior nares the mucous membrane is compara- tively dry, and is provided with a squamous epithelium. In other po- sitions, including the sinuses but excluding the olfactory region, it is provided with a ciliated columnar epithelium, and is furnished with mi- nute racemose glands,2 which are most numerous where the membrane is thickest. In the olfac'tory region,3 which corresponds with the convex surface of the turbinated processes and the surface of the nasal plate of the ethmoid bone, the mucous membrane4 has a columnar epithelium devoid of cilia, and is furnished with simple tubular glands.5 The principal arteries which supply the nasal mucous membrane are the spheno-palatine branches of the internal maxillary, but it also re- ceives the ethmoidal branches of the ophthalmic, branches from the descending palatine and dental arteries of the internal maxillary, and branches from the superior coronary and lateral nasal arteries of the facial. The veins of the nasal mucous membrane are larger and more numerous than the arteries, and form a plexus between the membrane and the periosteum, which is especially well developed upon the turbin- ated processes and bone, and the partition. They communicate with veins pursuing the course of the spheno-palatine artery, and by eth- moidal branches with the ophthalmic vein. The nerves of the nasal mucous membrane are numerous, and are of two kinds—those of general, and those of special sensibility. The for- mer are the nasal branches of the spheno-palatine ganglion, a branch from one of the palatine nerves, and the internal nasal division of the nasal nerve of the ophthalmic, besides filaments from the superior dental nerves. 1 Schneiderian membrane ; pituitary 2 Glandulae muciparae aggregatae. membrane; membrana pituitaria: m. ol- 3 Regio olfactorio. factoria; m. mucosa nasi; m. Schneide- 4 Olfaetory mucous membrane. riana. 5 Bowman's glands. 38 594 THE ORGANS OF SPECIAL SENSE. The olfactory nerves are those of special sensibility. The branches of each pass through the foramina of the cribriform plate of the ethmoid bone in two groups, of which one is destined to the inner, the other to the outer wall of the nasal cavity. At first the branches de- scend in grooves of the surfaces of the bones beneath the nasal mucous Fig. 353. Nerves of the partition of the nose. I, olfactory nerve; 1, its branches descending to the nasal mu- cous membrane; 2, internal nasal branch of the nasal nerve of the ophthalmic; 3, nasal branches from the spheno-palatine ganglion. II, optic nerve; III, oculo-motor; IV, pathetic; V, trifacial; VI, abdu- cent; VII, facial; VIII, auditory; IX, glosso-pharyngeal; X, pneumogastric; XI, accessory; XII, hypo- glossal. 4. cavernous plexus of the sympathetic; 5, filaments of communication with the semilunar ganglion of the trifacial; 6, filaments of communication with the oculo-motor nerve; 7, branches of the sympathetic following the internal carotid artery; 8, branch connected with the superior cervical gan- glion ; 9,10, filaments forming a plexus upon the internal carotid artery; 11, petrous ganglion of the glosso-pharyngeal; 12, jugular ganglion of the pneumogastric nerve; 13,14,15, anastomotic filaments between the sympathetic, the glosso-pharyngeal, pneumogastric, accessory, and hypoglossal nerves. (For the nerves of the outer wall of the nose see figure 336, page 547.) membrane, and then penetrate into the fibrous layer of the latter. The inner group subdivide into flattened tufts of filaments, which spread laterally in a fan-like manner, but appear not to descend below the nasal plate of the ethmoid bone. The outer group subdivide, and, through frequent anastomoses, produce a plexus or net-work which covers the external surface of the turbinated processes of the ethmoid bone. THE EYE. The Eye,1 or organ of sight, includes the eyeball and the surrounding structures, named its appendages,2 which consist of the muscles of the eyeball, the eyebrows and eyelids with their muscles, and the lachrymal apparatus. 1 Oculus; ophthalmus; ops; organum visus. 2 Tutamina oculi. THE ORGANS OF SPECIAL SENSE. 595 THE EYEBROWS. The Eyebrow1 is the arching prominence resting upon the superciliary ridge and supra-orbital margin, between the forehead and upper eyelid. It is composed of skin thickly provided with hairs, some subcutaneous connective and adipose tissue, a portion of the palpebral orbicular, and the superciliary muscle. The hairs of the eyebrow are stiff, compressed, and pointed, project very obliquely from the skin, so as to lie in contact with it, and are gen- erally directed along the line of the arch from within outwardly. THE EYELIDS. The Eyelids2 are a pair of horizontal curtains placed in front of the eye or of the orbit, are separated by the palpebral fissure, and are fringed at their free margins by the eyelashes. The upper eyelid3 is larger than the lower one,4 and is more movable, in consequence of its being provided with a special muscle, the pal'pe- bral elevator. The pal'pebral fissure5 varies in length, and thus mainly gives rise to the apparent difference of size of the eye in different races and individ- uals. The extremities are named the angles of the eye,6 of which the external7 is acute and the internal8 is prolonged and rounded. The edges of the eyelids9 are straight, so that when they are closed the pal- pebral fissure appears as a transverse slit fringed with a double row of eyelashes. Where the palpebral fissure commences to be prolonged to form the internal angle, the border of each eyelid presents a slight mammillary eminence, named the lach'rymal papilla.10 At the summit of this is a minute aperture, the lach'rymal orifice,11 which is the commencement of the corresponding lachrymal canal. In structure the eyelids consist of skin, the palpebral orbicular muscle, the palpebral cartilages and glands, and a portion of the conjunctiva. 1 Supercilium; ophrys. 2 Palpebrae; opercula. 3 Palpebra superior; p. major; epi- ccelis. * Palpebra inferior; p. minor; hypo- coelis. 5 Fissura palpebrarum. 6 Anguli; canthi. 7 External, lesser, or temporal can- thus. 8 Internal, greater, or nasal canthus; canthus ; epicanthus; angulus ocularis; fons lacrymarum. 9 Margo palpebrarum. 10 Papilla lacrymalis; tuberculum la- crymale. 11 Punctum lacrymale. 596 THE ORGANS OF SPECIAL SENSE. The skin of the eyelids is thin, delicate, semitransparent, and without subcutaneous adipose tissue ; and at the edges of the lids it becomes continuous with the conjunctiva. Subjacent to the skin is the palpebral orbicular muscle, which in this position is thin and pale, and specially concerned in the act of winking. The Pal'pebral cartilages,1 succeeding the muscle just indicated, are two thin plates of fibro-cartilage, which give form and firmness to the eyelids. They are thickest at their free margin, and have the conjunc- tiva intimately adherent to their inner surface. By their orbital margin they are continuous with an extension2 of the periosteum of the orbit and face. Their inner extremity is attached by a round fibrous cord, the internal pal'pebral ligament,3 with the inner border of the orbit; Fig. 354. TnE left eyelid and lachrymal gland, turned forward and inward SO AS TO see their inner sur- face. 1, upper and lower part of the orbit; 2, portion of the palpebral orbicular muscle; 3, attachment of this muscle to the inner margin of the orbit; 4. perforation for the passage of the external nasal nerve; 5, offset described as the tensor muscle of the eyelids; 6,palpebral glands; 7. posterior, and 8, an- terior portions of the lachrymal glands; 9,10, ducts; 11, orifices opening on the inner surface of the upper eyelid; 12,13, the lachrymal orifices at the summits of the lachrymal papillae. and their outer extremity is connected with the contiguous border of the orbit by a somewhat thickened extension of the periosteum, named the external pal'pebral ligament.4 The upper pal'pebral cartilage5 is the larger, has the shape of the 1 Tarsi; tarsal cartilages or fibro-car- tilages ; coronae, chelae, crepidines, or ungulae palpebrarum. 2 Ligamenta tarsorum superius et in- ferius; superior and inferior palpebral ligaments. 3 Ligamentum palpebrale, interpalpe- brale, or angulare internum; tendo pal- pebralis. 4 L. palpebrale, interpalpebrale, or angulare externum. 5 Tarsus superior. THE ORGANS OF SPECIAL SENSE. 597 long half of an oval, and is about five lines wide at the middle. Into its upper convex border the broad, thin tendon of the palpebral elevator muscle is inserted. The lower pal'pebral cartilage1 is a band about a line in width, and has its borders nearly parallel. The Pal'pebral glands,2 about twenty to each eyelid, are situated between the palpebral cartilages and the conjunctiva, through which they appear as vertical, parallel bodies, of a yellowish color and gran- ular aspect. They are sebaceous glands lodged in grooves of the palpebral cartilages, with the depth of which they correspond in length. Each gland consists of a series of pyriform pouches communi- cating with a median duct extending the length of the gland and open- ing at the margins of the eyelids. They secrete an oleaginous matter,3 which prevents the overflow of the tears from the margins of the eyelids. The Eyelashes4 are the stiff, curved hairs projecting from the borders of the eyelids along the line of union of the skin with the conjunctiva. Those of the upper lid are more numerous and longer, and have their convexity directed downward; those of the lower lid have their convex- ity directed upward. Associated with the roots of the eyelashes are numerous minute sebaceous glands, distinguishable as yellowish granules along the edges of the eyelids. The muscles of the eyebrows and eyelids are the palpebral orbicular, superciliary, and palpebral elevator muscles, which are described in the account of those of the face, page 187. THE CONJUNCTIVA. The Conjuncti'va5 is the mucous membrane which lines the eyelids, and is thence reflected over the front of the eyeball. It is provided with a squamous epithelium, but otherwise varies in character in different positions. The palpebral portion6 of the conjunctiva is red and highly vascular, and is closely adherent to the inner surface of the palpebral cartilages. 1 Tarsus inferior. 2 Glands of Meibomius; Meibomian glands; glandulae Meibomian^; g cili- ares ; folliculi ciliares; glandulae seba- cae palpebrarum; g. s ciliares; intesti- nula Meibomii; lacunae palpebrarum. 3 Gum ; eye-gum; lippitudo ; lema; sebum palpebrale. * Cilia; epicaelides; pili palpebrarum; bletharides; winkers. 5 Conjunctival membrane; membrana, or tunica conjunctiva; tunica adnata; circumcaulalis. 6 Conjunctiva palpebrarum. 598 THE ORGANS OF SPECIAL SENSE. It is furnished with minute conical papilla?, and is the most sensitive portion of the membrane. At the inner angle of the eye the conjunctiva covers a group of seba- ceous glands, which together form the lach'rymal car'uncle.1 This is the soft, red eminence occupying the interval of the internal angle. It is furnished with minute hairs, and secretes an oleaginous material, which bathes the lachrymal papillae. At the outer side of the caruncle the conjunctiva forms a narrow, red doubling, the semilunar fold,2 which is a rudiment of the third eyelid, or nictitating membrane of lower animals. From the eyelids the conjunctiva is reflected over the front part of the sclerotica and cornea of the eyeball. Along the line of reflection at the bottom of the eyelids it contains a few small racemose glands. The sclerotic portion3 of the conjunctiva is thin, transparent, devoid of papillae, and less vascular than the palpebral portion. It adheres loosely to the sclerotica, which, seen through the transparent mem- brane, constitutes the white of the eye. The few large vessels ordina- rily observed in the sclerotic portion of the conjunctiva are branches of the ophthalmic artery, which terminate in a fine capillary net-work bor- dering the cornea, but not extending beyond it in a state of health. The corneal portion4 of the conjunctiva is non-vascular, highly trans- parent, and adheres so intimately to the cornea as to appear to be a part of its structure. THE LACHRYMAL APPARATUS. The Lach'rymal apparatus5 consists of the lachrymal gland, the lachrymal canals, the lachrymal sac and its continuation the lach- rymo-nasal duct. The lachrymal gland secretes the tears, which moisten the conjunctiva, an excess ordinarily finding its way through the lachrymal canals and sac into the nose. Under the emotion of grief the gland is excited to an inordinate flow of tears, which then trickle over the edges of the eyelids. The Lach'rymal gland6 is situated at the upper outer part of the orbit, and consists of two portions, of which the posterior7 is about the size and form of an almond kernel; the anterior8 is thinner and irreg- 1 Caruncula lacrymalis. 2 Plica, valvula, or membrana semilu- naris ; palpebra tertia. < 3 Conjunctiva scleroticae. * Conjunctiva corneae. 5 Organa lacrymalia. 6 Glandula lacrymalis. 7 G. 1 superior; g. innominata Galeni. 8 G. 1. inferior Rosenmiilleri; g. congre- gates Monroi. THE ORGANS OF SPECIAL SENSE. 599 ularly square. Its upper surface applied to the roof of the orbit is convex ; while its lower surface, accommodating itself to the eyeball, is concave. It is a lobulated, racemose gland, of a pinkish hue, and is provided with a transverse series of about half a dozen ducts,1 which proceed forward to open at the outer part of the reflection of the con- junctiva from the upper eyelid to the eyeball. The Lach'rymal canals,2 which ordinarily convey the tears from the front of the eye, commence at the summit of the lachrymal papillae3 by a minute aperture, named the lachrymal orifice or point.4 The upper canal ascends within the corresponding eyelid; the lower one descends, and both then abruptly converge inwardly and terminate by separate apertures into the lachrymal sac. The canals expand after their origin, and are composed of an exterior fibrous tunic and a lining mucous membrane. They include between them the lachrymal caruncle, and are covered in front by the palpebral orbicular muscle. Fig. 355. 3 ' U23i The left eve, with a portion of the eyelids removed, to exhibit the lachrymal canals and sac. 1, lachrymal canals; 2, commencement of these at the summit of the lachrymal papilla?; 3, palpebral cartilages; 4, edges of the eyelids; 5, lachrymal sac ; 6, internal palpebral ligament; 7, its point of divi- sion in front of the lachrymal canals; 8, branches of the ligament giving attachment to the fibres of the palpebral orbicular muscle. The Lach'rymal sac5 is the commencement of the passage which con- ducts the tears from the front of the eye to the nose. It occupies the 1 Ductus lacrymales. 2 Canaliculi lacrymales; c 1. superior et inferior; c. limacum ; canales, or duc- tus lacrymales; d. 1. laterales; d. or col- liciae punctorum lacrymalium; cornua lacrymalia; c. limacum; spiracula; hir- qui; lachrymal ducts. 3 Papilla lacrymalis; tuberculum la- crymale. 4 Punctum lacrymale; spiramen pal- pebrae. 5 Saccus lacrymalis; sinus, or lacus lacrymalis; utriculus lacrymarum; in- fundibulum lacrymale; lacrycystis. 600 THE ORGANS OF SPECIAL SENSE. fossa between the lachrymal and superior maxillary bones, and is about half an inch in length. It is cylindrical, with a rounded, closed summit projecting a short distance above the entrance of the lachrymal canals. The Lach'rymo-nasal duct1 is formed by the lachrymal, superior max- illary, and turbinated bones, and is about half an inch in length. It is lined by a continuation of the lachrymal sac, and descends to terminate at the anterior extremity of the inferior meatus of the nose. The lachrymal sac and lachrymo-nasal duct together have a nearly vertical direction, but in their descent incline slightly inward and back- ward. They are lined with mucous membrane intimately adherent to the subjacent periosteum, and continuous above with the mucous membrane of the lachrymal canals, below with that of the nose. The membrane is pale red, is provided with a columnar, ciliated epithelium, and sometimes has one or two slight transverse folds. THE EYEBALL. The Eyeball2 is situated in the fore part of the orbit, protected in front by the eyelids, and resting behind in what may be viewed as the excavated base of a conical cushion of adipose and areolar tissue. It is maintained in position by the cushion just indicated, by the optic nerve and eyelids, but mainly by the muscles which surround and serve to move it in various directions. Its shape is nearly spherical, with a diameter a little less than an inch. Viewed in profile, it presents parts of two spheres, of which the posterior and larger corresponds with the sclerotica, and the smaller is formed by the cornea projecting from the front of the larger sphere. The eyeballs have their axes3 nearly parallel, but the diverging optic nerves join the balls posteriorly to the inner side of their axes, and are thus brought several lines nearer the internal than the external border of the cornea. In composition the eyeball consists of a series of concentric tunics in- closing three perfectly transparent and colorless media, named the hu- mors of the eye. The tunics in succession are, firstly, the sclerotica and the cornea; secondly, the choroid coat and the iris; and thirdly, the retina. The humors are the aqueous humor, the crystalline lens, and the vitreous humor. 1 Ductus naso-lacrymalis; d. lacry- malis; d. nasalis; d. n. orbitae; d. ad nasum; nasal canal or duct; lachrymal duct; canalis lacrymalis; c. 1 membra- naceus ; c. orbitae nasalis. 2 The eye ; ball, globe, or bulb of the eye; bulbus oculi. 3 Visual axes. THE ORGANS OF SPECIAL SENSE. 601 MUSCLES OF THE EYEBALL. The Straight muscles1 of the eyeball, of which there are four, are named from their rela- u- 4.1. a Fig. 356. tive position the Supe- rior,2 Inferior,3 Exter- nal,* and Internal.5 They arise tendinously around the optic foramen, and di- verge forward equidistant from each other, to be in- serted by tendons into the sclerotica a short distance from the cornea. The external straight muscle has its origin di- dided into two parts, be- tween which pass the ocu- lo-motor and abducent nerves and the nasal branch of the ophthalmic. The superior and infe- rior straight muscles of the two eyes act together, and draw the balls upward or downward. The external straight muscle draws the eyeball outward; the internal draws it inward, but the external muscle of one eye acts in conjunction with the internal muscle of the other eye. The united action of the straight muscles draws the eyeball toward the bottom of the orbit, which action, in a measure, is antagonized by the oblique muscles. The Superior Oblique muscle6 arises tendinously above the optic fora- Muscles of the eye. 1, the palpebral elevator muscle ; 2, the superior oblique; 3, the pulley through which the tendon of inser- tion plays; 4. superior straight muscle; 5, inferior straight muscle; 6, external straight muscle; 7, 8, its two points of origin; 9, in- terval through which pass the oculo-motor and abducent nerves; 10, inferior oblique muscle; 11, optic nerve; 12, cut surface of the malar procoss of the superior maxillary bone; 13, the nasal ori- fice. A, the eyeball. 1 Musculi recti oculi 2 Musculus rectus superior; m. attol- lens oculi; m. levator oculi; m. super- bus; m. oculum movens tertius; elevator muscle of the eyeball. 3 M. rectus inferior; m depressor ocu- li ; m. deprimens ; m. humilis; m. timi- dus; m. oculum movens quartus; de- pressor muscle of the eyeball. 4 M. rectus externus; m. abductor oculi; m. indignabundus ; m. indignato- rius; m. iracundus ; m. oculum movens secundus; abductor muscle of the eye- ball. 5 M. rectus internus; m. adductor ocu- li; m. adducens oculi; m. bibitorius; m. oculum movens primus; adductor muscle of the eyeball. 6 M. obliquus superior oculi; m. o. major oculi; m. trochlearis; m. trochlea- tor; m. amatorius; m. circumductionis opifex ; m. longissimus oculi. 602 THE ORGAN'S OF SPECIAL SENSE. men, and advances along the upper and inner part of the orbit. Term- inating in a round tendon, this passes through a fibro-cartilaginous ring or pulley,1 situated in a depression just within the inner extremity of the supra-orbital margin. The tendon then turns backward and out- ward beneath the superior straight muscle, and is inserted into the eye- ball, midway between the latter and the external straight muscle, the cor- nea and the optic nerve. To facilitate movement, the tendon as it passes through the pulley is invested with a synovial bursa. The Inferior Oblique muscle2 arises from the superior maxillary bone within the lower margin of the orbit and just external to the lachrymal fossa. Proceeding outward and backward below the inferior straight muscle, it is inserted into the outer part of the eyeball a little back of its middle. The oblique muscles antagonize the straight muscles by protruding the eyeball, and they also rotate it on its axis in opposite directions. THE SCLEROTICA. The Sclerot'ica, or sclerot'ic coat,3 forms the posterior four-fifths of the exterior wall of the eyeball It is a strong, white, opaque, inextensible membrane, composed of interlacing bundles of fibrous tissue, and is adapted to give form and solidity to the eyeball. Its front part, seen through the conjunctiva, is commonly called the white of the eye.4 It is thickest posteriorly, and gradually becomes thin- ner anteriorly, in which position the tendons of the straight and ob- lique muscles are inserted. Its back part admits the optic nerve through a funnel-shaped opening; and the sheath of the nerve becomes continuous with the sclerotica. Into a circular aperture at its fore part the cornea is inserted, in the manner of a watch-crystal in its frame. The margin of the aperture is beveled inwardly, so as to inclose the cor- responding margin of the cornea. In the vicinity of the optic nerve and near the cornea, the sclerotica is pierced by the ciliary blood-vessels and nerves. Its inner surface is brownish, and is attached to the choroid tunic by a small quantity of delicate connective tissue.5 The sclerotica is supplied with blood from branches of the ciliary arteries; and its veins join the choroid and ciliary veins. 1 Trochlea. 2 M. obliquus inferior oculi; m o. mi- nor oculi. 3 Tunica sclerotica; t. albuginea ; t. dura, durior, crassior, alba, extima, Candida, or innominata oculi; cornea opaca. * Album, or albumen oculi; lonchades. 5 Lamina, or membrana fusca. THE ORGANS OF SPECIAL SENSE. Fig. 357. 603 Vertical section antero-posteriorly of the eyeball. 1, optic nerve; 2, sclerotica; 3, its posterior thicker portion; 4, sheath of the optic nerve continuous with the sclerotica; 5, the nerve within the sheath; 6, insertion of the straight muscles into the sclerotica; 7,8, superior and inferior straight muscles ; 9, cornea; 10, its conjunctival surface; 11, membrane of the aqueous humor; 12,13, beveled edge of the cornea fitting into the sclerotica; 14, circular sinus of the iris; 15, choroidea; 16, the anterior portion of the same, constituting the ciliary body; 17, the ciliary muscle; 18, the ciliary processes; 19, retina; 20, its origin; 21, its anterior border; 22, central retinal artery; 23, vitreous humor; 24, 25, hya- loid tunic; 26, 27, its separation into two lamina?, which inclose the crystalline lens, 28; 29, iris; 30, pupil; 31, posterior chamber, and 32, anterior chamber occupied by the aqueous humor. THE CORNEA. The Cor'nea1 is the transparent membrane at the front of the eyeball, the exterior wall of which it constitutes the most prominent fifth part. By a beveled margin it fits into the circular aperture adapted to it in the sclerotica. Externally the conjunctiva2 is reflected over it; and inter- nally it is lined by an equally transparent layer named the membrane of the aqueous humor.3 Independently of the two layers just mentioned, the cornea4 is composed of a fibrous tissue much resembling in appear- ance and chemical constitution that not unfrequently observed in the matrix of cartilages. The fibrous tissue has a lamellar arrangement, so that the cornea may be dissected into a number of layers, varying with the delicacy of manipulation. At the conjunction of the cornea and sclerotica the two become intimately associated, and in this position inclose a venous channel, called the circular sinus of the iris.5 1 C. pellucida, lucida, or transparens; membrana cornea; sclerotica ceratoides; ceratoides ; membrana ceratoides; cera- tomeninx; the sight. 2 Conjunctival portion of the cornea. 3 Membrana, tunica propria, vagina, or capsula humoris aquei; m. Descemeti; m. Demoursii; m. Duddeliana; m Demu- riana; proper membrane of Descemet; posterior elastic lamina of the cornea; capsula aquea cartilaginosa; c. praea- quosa. * Cornea propria. 5 Canalis Schlemmii; c. Fontanae ; si- nus venosus Hovii; circulus venosus orbiculi iridis, or ciliaris. 604 THE ORGANS OF SPECIAL SENSE. The cornea in a healthy condition is non-vascular, but is pervaded with a system of branching lacunae which resemble those of the bones, and serve to convey colorless nutritive liquid throughout the membrane It is supplied with delicate filaments from the ciliary nerves. On the approach of old age the circumference of the cornea usually becomes more or less dull or opaque by the deposit of fatty matter in its tissue, constituting the so-called arcus senilis.1 Fig. 358. Fig. 359. Fig. 358.—The choroidea and iris. 1, ciliary arteries situated at the sides of the optic nerve; 2, the long ciliary arteries; 3, the same after having pierced the sclerotica; 4, 5, the main divisions of the same vessels; 6, the ciliary muscle; 7, the anterior ciliary arteries; 8, the short ciliary arteries to the choroidea; 9, the iris supplied by the long and anterior ciliary arteries; 10, the pupil. Fig. 359.—Veins of the choroidea and iris. 1, sclerotica; 2, choroidea; 3, ciliary muscle, of which a portion has been removed to exhibit the ciliary processes, 4; 5, the iris; 6, pupil; 7, 8, trunks of the cho- roid veins; 9,10, vorticose vessels; 11, their conjunction with the veins of the ciliary processes; 12, anas- tomosis between the groups of vorticose vessels. THE CHOROIDEA. The Choroi'dea, or choroid coat,2 is a thin, black, and highly vascular membrane succeeding the sclerotica and separating it from the retina. It is perforated behind for the passage of the optic nerve, and terminates 1 Gerontoxon; macula corneae arcuata; leucoma gerontotoxon. 2 The choroid; tunica or membrana choroidea; t. vasculosa; t. aciniformis; t. rhagoides; uvea. THE ORGANS OF SPECIAL SENSE. 605 in front in the ciliary muscle and body. Its outer surface,1 of a brownish- black hue, is attached to the sclerotica, loosely at the fore part, more intimately behind, by delicate connective tissue and blood-vessels. The inner surface is smooth, shining, intensely black, and is simply applied to the contiguous surface of the retina. Fig. 3G0. Fig. 361. View from behind of the anterior part of the eyeball. 1, sclerotica; 2, choroidea; 3, retina; 4, its anterior border; 5, ciliary processes; 6, the crystalline lens placed back of the iris and pupil. The same view, with the crystalline lens and retina removed. 1, sclerotica; 2, choroidea; 3, ciliary body; 4, line at which the retina ceases; 5, ciliary processes; 6, iris; 7, cornea seen through the pupil. The cil'iary muscle2 is a whitish zone connecting the anterior part of the choroidea with the circumference of the iris and the conjuction of the sclerotica and cornea. It is composed of pale, unstriated muscular fibres, and is abundantly supplied with nerves and blood-vessels. Within the position of the ciliary muscle the choroidea constitutes the so-called ciliary body,3 of which the fore part4 is thrown into about sixty convergent folds,5 named ciliary processes.6 These are received into corresponding grooves of the vitreous humor in advance of the retina, and serve to retain it in position. Their anterior extremities7 are free, suspended behind the iris, and are bathed in the aqueous humor of the posterior chamber of the eye. In structure the choroidea consists of a vascular lamina lined on the interior with a pigmentary layer. 1 Lamina fusca: 1. supra-choroidea; 1. cellulosa: 1. arachnoidea chorioideae ; 1. villoso-glandulosa. 2 Musculus ciliaris; ciliary ligament; Iigamentum ciliare; 1. sclerotico-chorioi- dale; 1. iridis ; annulus, circulus, orbi- culus, or plexus ciliaris; interstitium ciliare, or iridis; tensori chorioideae; circulus chorioideae; annulus cellulosus; commissure of the uvea; ciliary circle, or ring. 3 Corpus ciliare ; corona ciliaris; orbi- culus ciliaris; tunica ciliaris; ciliary disk. 4 Pars plicata corporis ciliaris. 5 Plica? ciliares; ciliary folds. 6 Processus ciliares; plicae ciliares; p. corporis ciliaris; radii ciliares; striae ciliares, ligamenta ciliaria; fibrae palli- da?. 7 Processus ciliares. 606 THE ORGANS OF SPECIAL SENSE. The vascular lamina1 Segment of the choroidea and iris, seen on its inner surface, magnified four diameters. 1, ciliary processes; 2, their free extremities behind the iris; 3, 4, commencement of the processes; 5, interven- ing reticular folds; 6, veins of the ciliary processes; 7. posterior margin of the ciliary body; 8, choroi- dea with its veins; 9, iris; 10, its outer border; 11, the pupillary border; 12, radiating fibres of the iris; 13, circular fibres, is composed of blood-vessels mingled with a stroma of fusiform and stellate cells, apparently an incipient form of connective tissue. The arterial branches of the vascular lamina are derived from the short ciliary arteries, which pierce the sclerotica in the vicinity of the optic nerve, and, after repeated branching, end in a fine capillary net-work.2 The veins derived from the latter form an intricate and remarkable plexus exterior to it, and are named, from their peculiar whorled arrange- ment, the vorticose vessels.3 These form four groups,4 and converge in curving lines to four equidistant trunks, which perforate the scle- rotica midway between the cornea and optic nerve, and end in the ophthalmic vein. The ciliary processes are equally vascular with other portions of the choroidea. The arteries proceed- ing from the latter into the pro- cesses become convoluted, inoscu- late, and finally terminate in veins which pursue a reverse course to join the vorticose vessels. The ciliary muscle is supplied by terminal branches of the short ciliary and the anterior ciliary arteries. The pigmen'tary layer5 of the inner surface of the choroidea also en- velops the ciliary processes. It consists of flattened, regularly hexahe- dral nucleated cells, filled with brownish-black granular contents, which give to the choroidea its intensely black color. In albinoes the pig- mentary granular matter is absent, and the choroidea presents a red color, due to its vascularity. In many of the lower animals the inner surface of the choroidea at its back part exhibits a patch of metallic color and brilliancy, named the 1 Tunica vasculosa Halleri; t. chorioi- dea propria; external layer; proper vascular layer. 2 Membrana chorio-capillaris; m. Ho- vii; m. Ruyschii; tunica Ruyschiana. 3 Vasa vorticosa; venae vorticosae; v. tortuosae. 4 Stellulae vasculosa? Winslowii. 5 Stratum pigmenti; pigmentum ni- grum ; membrana Dcellingeriana. THE ORGANS OF SPECIAL SENSE. 607 tape'tum.1 In this the black pigmentary matter is replaced by colorless granules, which reflect the rays of light falling upon them, and thus give rise to that shining of the eyes of animals in the dark, which has proved to be so fertile a source of terror to the superstitious. THE IRIS. The Iris2 is a flat disk with a central aperture, and regulates the amount of light received by the retina from its being endowed with the power of contracting or dilating. It is inserted into the anterior border of the ciliary muscle, is vertical in position, and is bathed in the aqueous humor. The anterior surface is divided into two zones,3 of which the outer one is the broader. It also appears striated from the circumference Fig. 363. Arteries of the iris. l,long ciliary arteries; 2, 3, their principal divisions; 4, small branches to the ciliary muscle ; 5, 6, anterior ciliary arteries; 7, the pupil. toward the pupil, and in different individuals presents various shades of gray, blue, or brown passing into black. The posterior surface is intensely black, arising from the presence of a layer of pigment cells like those of the choroidea. The central aperture of the iris, named the pupil,4 is circular, and in 1 Membrana versicolor. * Pupila; pupula; fenestra nigrum; 2 Tunica coerulea; uvea. foramen oculi; prunella ; sight of the 3 Annuli irridis ; annulus major et mi- eye. nor iridis; a. externus et internus; a. ciliaris et pupillaris. 608 THE ORGANS OF SPECIAL SENSE. the living eye appears as a black spot. Under the influence of light it decreases, and with the diminution of that agency it enlarges. The iris is a highly vascular fibro-muscular structure, with its surfaces covered by an epithelium. The posterior layer1 of the latter consists of black pigment cells; the anterior layer is composed of colorless pave- ment cells. The muscular fibres of the iris are unstriated; form a circu- lar layer2 around the pupil, and radiate3 toward the circumference of the iris. The blood of the iris is derived from the long and anterior ciliary arteries. The former pierce the back of the sclerotica, one on each side, and advance on the outer surface of the choroidea to the ciliary muscle, when they bifurcate and form together an arterial circle, from which nu- merous branches proceed to the iris. The anterior ciliary arteries, about half a dozen in number, pierce the sclerotica in the vicinity of the cor- nea, and, after anastomosing with the branches of the long ciliary arteries, end in the capillary vessels of the iris. The veins of the latter join the circular sinus,4 situated at the conjunction of the cornea, sclerotica, and ciliary muscle ; and the veins from the sinus pursue the same course as the anterior ciliary arteries to terminate in the ophthalmic vein. The nerves of the iris are numerous, and are derived from the ciliary nerves which enter the eyeball by piercing the back part of the sclerotica. Advancing on the exterior of the choroidea, they reach the ciliary muscle and there form a plexus from which the iris is supplied. Prior to the eighth month of foetal life the pupil is closed by a delicate pu'pillary membrane,5 which appears to be a continuous vascular struc- ture with the iris. At birth it is completely obliterated. THE RETINA. The Ret'ina6 is a soft, delicate, nearly transparent and colorless mem- brane, which extends from the optic nerve on the inner surface of the choroidea to the ciliary body, where it terminates in a waving margin.7 After death it loses much of its transparency, and assumes the appear- ance of ground glass. 1 Uvea; pigmentum nigrum; membra- na pigmenti. 2 Sphincter pupilla?: occlusor muscle of the pupil; fibrae circulares. 3 Dilator pupilla?; fibrae radiatae; f. longitudinales iridis. 4 Canal of Fontana, or of Schlemm ; canalis Fontana?; c. Schlemmii. 5 Membrana pupillaris ; m. Wachen- dorfiana; pupilla? velum. 6 Tunica retina ; t. reticularis or reti- formis; t. nervea; t. arachnoidea; t. in- tima oculi. 7 Ora serrata; margo dentatus; m. undulato-dentatus. THE ORGANS OF SPECIAL SENSE. QQQ The surfaces of the retina are simply in contact with the contiguous structures, and in the living or perfectly fresh state are smooth. Shortly after death a small fold1 appears on the inner surface, extending a little distance outwardly from the entrance of the optic nerve. Upon the summit of this fold, in the axis of the eyeball, there is a yellow spot,2 Fig. 364. The eyeball, with the sclerotica, cornea, cho- roidea, and iris removed. 1, optic nerve; 2, 3, retina; 4, central retinal artery entering the eye- ball through the optic nerve and distributed to the retina; 5, 6, ciliary zone, at which the ciliary folds of the choroidea impress the vitreous humor; 7, Bpace of the hyaloid tunic at the circumference of the crystalline lens, 8, artificially inflated, and as- suming; the form of a beaded canal. Fig. 305. Retina, seen on its posterior inner surface. 1, sclerotica; 2, choroidea; 3, retina; 4, white spot indicating the entrance of the optic nerve; 5, cen- tral retinal artery; 6, a slight fold of the retina, upon which is situated, in the axis of the eye, the yellow spot, 7; 8, its minute central aperture. with an apparent central aperture3 depending on a thinning of the retina. The entrance of the optic nerve is seen as an opaque, white spot,4 from the centre of which diverge the branches of the central retinal artery. The structure of the retina is exceedingly complex, and consists of a series of elements, enumerated from without inwardly, as follows : 1, a layer composed of narrow, vertical, columnar cells;5 2, a granular layer;" 3,- a layer of nerve cells with caudate appendages;7 4, nerve fibres derived from the expansion of the optic nerve ;8 5, a structureless, limit- ary membrane.9 The blood-vessels derived from the central retinal artery form a cap- 1 Plica centralis retina?; p. transversa retinae. 2 Macula lutea ; m. flava centralis re- tinae ; limbus luteus foraminis centralis. 3 Foramen centrale Scemmerringii; fo- vea centralis retinae. 4 Papilla, or colliculus nervi optici. 5 Tunica Jacobi; Jacob's membrane; basillar layer; stratum bassillorum; basilli et coni; rods and cones ; prisma- ta praeacuta et coni gemini; layer of rods and cones. 6 Stratum granulosum. 7 The layer of cineritious cerebral substance of Kolliker; layer of gray nerve substance; stratum globulosum. 8 Expansion of the optic nerve; stra- tum fibrillosum; s. vasculoso-nerveum; stratum medullare. 9 Membrana limitans. 39 610 THE ORGANS OF SPECIAL SENSE illary net-work in the nervous layers of the retina -,1 and the veins return in the course of the corresponding arteries. The retina is the sensitive membrane of the eyeball — that which re- ceives the impression of light, the form and color of exterior objects. THE AQUEOUS HUMOR. The A'queous humor2 is a transparent, colorless, albuminoid liquid, which fills the space between the cornea and crystalline lens. The space it occupies is divided by the iris into two parts, named the anterior and posterior chambers of the eye,3 of which the former is the larger. The iris is freely suspended in the aqueous humor, both of its surfaces being bathed in it, which is likewise the case with the ciliary processes. Lining the interior of the cornea, and continuous with the anterior layer of the iris, is the so-called membrane of the aqueous humor.4 It is an elastic membrane, consisting of a structureless basement layer and a pavement epithelium. Its border is resolved into a fine net-work of fibres,5 which are reflected upon, and become continuous with, the ante- rior surface of the iris. THE CRYSTALLINE LENS. The Crys'talline lens6 succeeds the aqueous humor from behind, and is the most consistent of the humors of the eye. It is a double convex lens, of which the poste- FlG- 366- rior surface is the more 1234 5 convex, and is received into a depression7 of the ritreous humor ; while its anterior surface is bathed The crystalline lens. 1, lens of a foetus of seven months; 2, ky the aqueOUS humor. lens of a foetus of nine months; 3, lens of a child of ten years of It is retained in position age; 4, lens of an adult viewed in profile; 5, the same seen on its . , hvaloid tunic of anterior surface. J •* . the vitreous humor, which is reflected from its border to its anterior and posterior surfaces. 1 Lamina vasculosa retinae. 2 Humor aquosus; h. oviformis; h. ovatus; h. oodes; h. hydatodes; albu- gineous humor. 3 Camerae oculi. * Membrane of Descemet. See page 603. 5 Ligamentum pectinatum iridis; pro- cessus peripherici; pillars of the iris. 6 Lens crystallina; corpus crystalli- num; crystalline humor or body; the crystallinus; corpus discoides or pha- coides; phacus; gemma oculi. 7 Fossa lenticularis ; f. patellaris. THE ORGANS OF SPECIAL SENSE. 611 From foetal life to the adult period the lens gradually diminishes in its degree of convexity, and increases in breadth; and in the advance of life it continues to decline in convexity. It is perfectly transparent and colorless, though in old age it is apt to assume a yellowish hue. Boil- ing water or alcohol coagulate it and render it hard and opaque white. The lens is provided with a transparent membranous capsule,1 which is structureless, and is thickest anteriorly. The substance2 of the lens is composed of concentric laminae, which increase in density toward the centre. The laminae are composed of hexahedral fibres, with corrugated sides closely adapted to one another. In fishes this corrugated character is much exaggerated, and the fibres indigitate by serrated processes. Fig. 367. Fig. 368. Crystalline lens, breaking up into segments. Segment of the crystalline lens, exhibiting the concentric arrangement of the laminae. Not unfrequently, in dissections, the lens is observed with a disposi- tion to separate into segments from its axis, and this appears to indicate the arrangement of structure. The segments are composed of the con- centric laminae above described, and these consist of the hexahedral fibres, which pursue a direction from the bases of the segments to their summits and lateral edges. The intervals of the segments are occupied with a mingled amorphous and finely granular matter. Between the front of the lens and its capsule there exists a layer of delicate epithelial cells,3 which, after death, become detached and mingled with some liquid4 exuding from the contiguous structures. In foetal life, a vessel from the central retinal artery traverses the axis of the vitreous humor, and is distributed to the capsule of the lens; but it is obliterated before birth. THE VITREOUS HUMOR. The Vit'reous humor,5 less consistent than the crystalline lens, but more so than the aqueous humor, is equally transparent and colorless. 1 Capsula lentis; tunica crystalioidea; * Liquor or aqua Morgagni. t. arachnoidea. 5 Corpus vitreum; c. hyaloideum; hu- 2 Humor crystallinus ; h. glacialis. mor vitreus; h. hyalinus ; h. glacialis. 3 Globuli lentis. 612 THE ORGANS OF SPECIAL SENSE. It occupies all the space included within the expanse of the retina and the ciliary body, and consists of a viscid albuminoid liquid1 contained in the meshes of a delicate membranous structure, named the hy'aloid tunic.2 This is homogeneous, and, besides forming partitions3 through the mass of the vitreous humor, affords it an exterior investment. In advance of the retina the hyaloid tunic is thicker than elsewhere, and forms the ciliary zone.4 This is in contact externally with the ciliary body, and is impressed by its processes, which, being received into corresponding grooves of the zone, contribute to maintain the position of the vitreous humor. In front, the tunic separates into two laminae, which diverge upon the border of the crystalline lens, and become confluent with the anterior and pos- terior surfaces of its capsule. The angle of separation5 of the two laminae is partially interrupted at short distances, so that when inflated it assumes the appearance of a beaded canal" at the circumference of the lens. THE EAR. The Ear or organ of hearing is exceedingly complicated in its struc- ture, and is for the most part concealed from view within the petrous portion of the temporal bone. It is divisible into the external, middle, and internal ear THE EXTERNAL EAR. The External ear consists of the auricle and the external auditory meatus. The Auricle,7 or ear of common language, joins the external auditory meatus between the articulation of the lower jaw and the mastoid proc- ess. It resembles the expanded mouth of a trumpet crushed inwardly, and mainly derives its peculiar form from a fibro-cartilage. The wind- ing ridges and hollows of its outer surface correspond with reverse char- acters on the inner surface or back of the ear. Its lower pendant portion, named the lobe,8 is a pouch of skin filled with connective tissue and fat. 1 Vitrina ocularis. 2 Tunica hyaloidea; t. vitrea; mem- brana arachnoidea. 3 Hyaloidea interna; pars cellularis hyaloideae; cellularis corporis vitrei; tunica arachnoidea. 4 Zona ciliaris; pars ciliaris hyaloi- dea? ; corpus ciliare hyaloideae; zonula Zinni; zonula, or zone of Zinn; lamina ciliaris; membranula corona? ciliaris; corona ciliaris; orbiculus capsulo-cilia- ris; ligamentum suspensorium lentis. 5 Canal of Petit; canalis Petitianus; circulus Petiti; camera tcrtia aquosa. 6 Bullular canal of Petit. 7 Auricula; pavilion; pinna; ala; otium. 8 Lobulus auriculae. THE ORGANS OF SPECIAL SENSE. 613 Fig. 369. The inflected border of the auricle, curving from above the audit- ory meatus upward, backward, and downward, is the helix.1 Separated from this by a groove2 is the ridge named the antihelix, which bifur- cates above,3 and includes a trian- gular fossa.* In front of the audit- ory meatus is a conical eminence, the tragus ;5 and separated from this by a rounded notch, and situ- ated below the antihelix, is an- other eminence, the antitragus. The deep concavity within the po- sition of the antihelix, and present- ing a semispiral course toward the entrance of the auditory meatus, is the concha. The auricle, excepting its lobe, consists of a plate of fibro-cartilage, invested with a perichondrium, to which the skin tightly adheres. Several fissures or intervals exist in the fibro-cartilage, occupied by con- nective tissue. Thus the fibro-car- tilage is deficient between the tragus and the commencement of the he- lix, and between the lower end of the latter and the antitragus. Short fissures also exist on the tragus and the fore part of the helix. In the last-mentioned position there is a small conical eminence, named the process of the helix. The fibro-cartilage of the auricle is thin, and rather brittle, but is ren- dered more tenacious by its perichondrium. The skin is thin, and, as elsewhere generally, is furnished with minute hairs and sebaceous glands. The latter are well developed in the fossae of the auricle, more especially in the concha. Besides the connection of the skin, the auricle is attached to the side of the head by ligamentous bands. The anterior ligament, broad and strong, extends from the process of the helix to the root of the zygo- The auricle. 1, helix; 2, fossa of the helix; 3, antihelix; 4, fossa of the antihelix; 5, concha sub- divided by the commencement of the helix; 6, tra- gus; 7, antitragus; 8, entrance of the external auditory meatus; 9, the lobe. The large dots in the concha and fossa of the antihelix are the ori- fices of sebaceous glands. 1 Capreolus. 2 Fossa navicularis, scaphoides, or in- nominata; fossa of the helix. 3 Crura furcata. * Fossa of the antihelix; fossa trian- gularis, or ovalis. 5 Hircus. 614 THE ORGANS OF SPECIAL SENSE. matic process. The posterior ligament attaches the convexity of the concha to the root of the mastoid process. The auricle possesses five small muscles situated between the fibro- cartilage and the skin, and three larger ones which connect it with the side of the head. They are all composed of striated fibres, and while the function of the former is very obscure, the latter are generally quite inactive. The smaller muscle of the helix1 is a short fasciculus situated on the commencement of the latter. The greater muscle of the helix2 is a narrow band situated on the fore part of the auricle, above the process of the helix. The muscle of the tragus3 is a short plane of fibres situated on the outer surface of the tragus. The muscle of the antitragus4 is a band extended from the antitragus to the lower extremity of the helix. The transverse muscle,5 larger than the preceding, is situated on the back of the auricle, and consists of a plane of fibres extending from the concha to the ridge bounding the groove of the antihelix. The superior auric'ular muscle6 is a broad, thin, and pale fan-like plane of fibres, arising from the border of the occipito-frontal aponeu- rosis, and descending to be inserted back of the fossa of the antihelix. In action, it will draw the auricle upward. The anterior auric'ular muscle,7 generally less distinct than the pre- ceding, is a thin, transverse fasciculus arising from the temporal fascia, and inserted into the helix and concha. In action it would draw the auricle forward. The posterior auric'ular muscle,8 stronger and less pale than the others, consists of two or three fasciculi arising from the mastoid proc- ess, and inserted into the back of the concha. In action it draws the auricle backward. The auricle is abundantly supplied with blood-vessels and nerves. Its 1 M. helicis minor. 2 M. helicis major. 3 M. tragicus. 4 M. antitragicus. 5 M. transversus auriculae; m. t. and obliquus auris. 6 M. auricularis superior; m. attollens auricula?, or aurem; m. levator, or su- perior auris; m. temporo-auricularis. 7 M. auricularis anterior; m. attra- hens auriculae; m. anterior auris; m. zygomato-auricularis. 8 M. auricularis posterior; m. retra- hens, or retrahentes auriculae; m. pos- terior auris: m. mastoido-auricularis; m. deprimens auriculae; m. bicaudalis, triceps, or tricaudalis auris; m. pro- prius auris externae; m. secundus pro- priorum auriculae. THE ORGANS OF SPECIAL SENSE. g15 arteries form a conspicuous net-work upon the fibro-cartilage, and are derived from the anterior and posterior auricular branches of the tem- poral and external carotid arteries. Its veins terminate in the temporal vein. The nerves are derived from the great auricular branch of the cervical plexus, the posterior auricular branch of the facial nerve, and the auriculo-temporal branch of the inferior maxillary nerve. The External aud'itory mea'tus1 is a canal extending from the concha to the tympanum, and serves to conduct sounds to the latter which Fig. 370. General view of the ear, right side, laid open from the front. 1, auricle; 2, concha; 3, 4, exter- nal auditory meatus; 5, ceruminous glands; 6, tympanic membrane; 7, anvil; 8, mallet; 9, its handle iuserted into the tympanic membrane; 10, tensor muscle of the latter; 11, cavity of the tympanum; 12, Eustachian tube; 13,14,15, the three semicircular canals; 16, cochlea; 17, the internal auditory meatus; IS, facial nerve occupying a groove of the auditory nerve, 20, 21. are collected by the auricle. It is about an inch in length, is directed inward and forward, and curves in its course upward and downward. Its commencement is vertically oval, its middle is the narrowest part, and its bottom is closed by the tympanic membrane. The meatus consists of an outer shorter portion, which is a prolonga- tion of the auricle, and an inner portion composed of the osseous audit- ory meatus lined with an extension of the skin. The outer portion of the meatus, independently of the skin, is com- 1 Meatus auditorius externus; external auditory canal; auricular canal; alve- arium; scapha. 616 THE ORGANS OF SPECIAL SENSE. posed of a scroll of fibro-cartilage, open above, and continuous by a nar- row slip with that of the auricle. The interval of the scroll is occupied with fibrous membrane, thus producing a complete tube. The fissures intervening between the outer part of the latter and the concha are like- wise occupied with fibrous membrane, and its inner extremity is con- nected by an annular ligament with the orifice of the osseous meatus. The skin of the outer portion of the auditory meatus is comparatively thick, and is furnished with numerous hairs and sebaceous glands. Its surface presents a punctated appearance, from the many orifices of the ceru'minous glands,1 which secrete the ceru'men or ear-wax.2 These glands are small, rounded bodies, of a brownish-yellow color, im- bedded in the subcutaneous tissue. They consist of a narrow tube con- voluted upon itself into a rounded mass, the terminal portion of the tube penetrating the skin as the duct of the gland. The inner portion of the auditory meatus corresponds with the passage of the same name in the macerated bone, and is narrower and longer than the outer portion. The skin lining it is very thin, is unprovided with hairs or glands, and becomes continuous with the structure of the tympanic membrane which closes the bottom of the meatus. The blood-vessels and nerves of the external auditory meatus have the same derivation as those of the auricle. THE MIDDLE EAR. The Middle ear consists of the tympanum, together with its inclosed bones, their ligaments and muscles, and the mastoid sinuses and Eusta- chian tube. The Tym'panum, or drum of the ear,3 is an irregular cavity in the in- terior of the petrous portion of the temporal bone. It is about half an inch in height and breadth, and one to two lines from without inward. Its roof is a plate of bone separating it from the cranial cavity; its floor is a groove between the outer and inner walls. Into its upper back part open the mastoid sinuses; and in front it narrows into the Eusta- chian tube. The outer wall is formed by the tympanic membrane, and its inner wall bounds the labyrinth. The tym'panic membrane, or membrane of the tym'panum,4 is a cir- 1 Glandulae, or folliculac ceruminosae. 2 Cerea; sordes, sordicula?, or mar- morata aurium; ceruminous humor; cypsele, or cypselis; fugile. 3 Cavum, or cavitas tympani; cavity of the tympanum, or drum; barrel of the ear; antrum, or cavitas antrosa auris. * Membrana tympani; membrane of the drum; diaphragma, mediastinum, or tegumentum auris; myringa; myrinx. THE ORGANS OF SPECIAL SENSE. Q-tf cular partition separating the cavity of the tympanum from the external auditory meatus, from which it receives transmitted sounds. It is not flat, but slightly funnel shaped, and is situated obliquely, so that its outer, depressed surface1 is directed downward and forward. The greater part of its circumference is inserted into a fine groove, which in the new- born child is included by an osseous ring, subsequently developed, by f ? > prolongation outwardly, into the osseous auditory meatus. Into its upper part, descending as far as the centre, the handle of the mallet is inserted, so that vibrations of the tympanic membrane are communicated to the latter. The tympanic membrane is thin and translucent, and is composed of a layer of fibrous tissue invested externally with a continuation of the epi- dermis of the meatus, and internally with an extension of the lining mu- cous membrane of the tympanum. Its fibrous layer consists of fibres radiating from the centre, with some concentric fibres at its circumference. Fig. 371. Cavitt of the tympanum and mastoid sinuses, right side. The auditory meatus, tympanic mem- brane, small bones, and outer wall of the mastoid sinuses removed. 1, promontory; 2, pyramid; 3, ridge within which descends the Fallopian canal; 4, round window; 5, oval window; 6, osseous portion of the Eustachian tube; 7. surface of attachment of the cartilage of the latter; 8, canal above the tube which lodges the tensor muscle of the tympanum; 9, Fallopian canal laid open; 10, canal occupied by the gi'eater petrous nerve; 11, mastoid sinuses; 12, communication of the latter with the tympanum; 13, orifice through which the tympanic branch of the facial nerve enters the tympanum. The inner wall of the tympanum presents a convex eminence, the prom'ontory,2 produced by the projection of the cochlea. Above the 1 Umbo. 2 Promontorium; tuber, or tuberositas tympani. 618 THE ORGANS OF SPECIAL SENSE. back of the promontory is an orifice, the oval window,1 which communi- cates with the vestibule, but is closed by the application of the base of the stirrup. Above the oval window and promontory is a ridge, pass- ing from before backward, produced by the course of the Fallopian canal, which transmits the facial nerve. Behind the lower part of the promontory is a pit, at the bottom of which is an aperture named the round window.2 This communicates with the cochlea, but is closed by the secondary tym'panic membrane,3 which consists of a fibrous layer, invested externally with the lining membrane of the tympanum, inter- nally with that of the cochlea. At the back part of the tympanum a descending ridge indicates the continuation of the Fallopian canal to the stylo-mastoid foramen. From the ridge there projects forward a hollow, conical eminence, named the pyramid.4 The small bones5 occupy the upper part Fig. 372. Small bones of the ear. 1. Mallet seen on its inner surface. a, head; 6, articular surface for the anvil; c, handle; d, the long process. 2. Mallet seen on its outer surface, a. head; 6, articu- lar surface; c, handle; d, long process; e, short process. 3. Mal- let seen from behind, a, head and articular facet; 6, short proc- ess; c, long process. 4. Anvil seen on its inner surface, a, body; 6, articular facet for the mallet;-c, short process: d, long process; e, orbicular process. 5. Anvil seen on its outer surface. a, body; 6, articular facet; c, d, short and long processes. 6. Or- bicular process, at birth a distinct bone. 7. Stirrup, a, head; 6, c, crura; d, base. 8. Base of the stirrup, which is applied to the oval window. 9. Stirrup cut so as to exhibit the groove on the inner side of its crura a. the fibrous layer of the tympanic membrane of the tympanum, and are named, from their resem- blance, the mallet, anvil, and stirrup. Articulating movably with one an- other in the order given, the mallet is attached to the tympanic membrane, and the stirrup communi- cates with the oval win- dow, so that the vibra- tions of the former are continued through the se- ries of bones to the latter. The Mallet8 is situated vertically, with its head lodged in the upper part of the tympanum, and its handle descending into as far as its centre. The 1 Fenestra ovalis, or vestibularis; fora- men ovale. 2 Fenestra rotunda, triquetra, or coch- learis; foramen rotundum. 3 Membrana tympani secundaria; m. fenestra? rotunda?; tympanum minus, or secundarium. *Pyramis; eminentia pyramidalis tympani. 5 Ossiculi auditus; o. auris. 6 Malleus, malleolus; ossiculum mal- leolo-assimilatum; the hammer. THE ORGANS OF SPECIAL SENSE. gjg head is rounded, and at its back part has an oval facet invested with cartilage, for articulation with the anvil. The handle1 is a tapering process, slightly twisted and compressed. The neck is slightly con- stricted, and gives off two processes. The long process2 is a slender spine projecting nearly at a right angle from the neck, and enters the glenoid fissure ; the short process3 is a conical eminence at the root of the neck. The Anvil4 is situated behind the mallet, near the entrance to the mas- toid sinuses. Its body is irregularly square, and at its fore part has an oval articular surface for the head of the mallet. Behind, it has a pair of diverging processes, of which the lower is the longer. The short process5 projects backward, and is connected by a ligamentous band to the posterior part of the tympanum. The long process6 is curved and tapering, and descends nearly parallel to the handle of the mallet. Its end internally supports an orbicular process,7 which articulates with the head of the stirrup. At birth the latter process is a distinct bone, but it soon becomes co-ossified with the anvil. The Stirrup8 is directed horizontally inward from the anvil to the oval window. Its head is flattened, and at the summit has a concave artic- ular facet, invested with cartilage, for the orbicular process of the anvil. From the head a pair of crura curve inwardly to join the base, which is applied to the oval window. The three bones just described have movable articulations, surrounded by a capsular ligament and lined with synovial membrane. The articu- lation between the mallet and anvil is hinge like; that between the latter bone and the stirrup is a ball-and-socket joint. The suspensory ligament9 of the mallet is a slender band of fibres, extending from the head of the bone to the roof of the tympanum. The suspensory ligament10 of the anvil extends from its short process to the back part of the tympanum. The annular ligament11 of the stirrup connects the margin of the base with the border of the oval window. 1 Manubrium. 2 Processus, or apophysis longus, gra- cilis, Folii, or Rauii. 3 P. brevis; p. obtusus. * Incus; acmon; os incude simile; os- siculum incudi, or molari denti compa- ratum. 5 Ramus horizontalis. 6 Ramus verticalis. 7 Os, or ossiculum orbiculare, lenticu- lare, squamosum, cochleare, or quartum; processus lenticularis; ossiculum orbicu- lare or lenticulare Sylvii; globulus sta- pedis; epiphysis cruris longioris incudis. 8 Stapes ; stapha; staffa. 9 Ligamentum superiores, or teres. 10 Posterior ligament. 11 L. annulare, or orbiculare baseos stapedis. 620 THE ORGANS OF SPECIAL SENSE. Three minute muscles, composed of striated fibre, are connected with the bones of the ear, to regulate their movements. Others1 have been described, but their existence is not usually acknowledged. The tensor muscle2 arises from the end of the cartilage of the Eusta- chian tube and the contiguous surfaces of the sphenoid and temporal bone. Passing through an osseous canal of the latter, above the Eusta- chian tube, it ends in a tendon which enters the tympanum and turns outwardly to be inserted into the neck of the mallet. Its contraction increases the tensity of the tympanic membrane. The laxa'tor muscle3 arises from the spinous process of the sphenoid bone, passes upward and outward, and enters the glenoid fissure, to be inserted into the long process of the mallet. In action it relaxes the tympanic membrane. The stape'dius muscle4 arises within the hollow of the pyramid, and is inserted into the head of the stirrup. It regulates the pressure of the base of the latter against the oval window. The cavity of the tympanum is everywhere lined with a delicate mu- cous membrane, which likewise invests the small bones, stretching across the aperture of the stirrup,5 and covering the muscles and ligaments. It is pink in color from its vascularity, and is provided with a pavement- like epithelium. The arteries of the tympanum, though small, are nu- merous. They are derived from the tympanic branch of the internal maxillary artery, the stylo-mastoid artery, the great meningeal and de- scending palatine arteries, and from the internal carotid artery as it passes through the carotid canal. The veins communicate with the great meningeal and pharyngeal veins, and through a plexus, near the glenoid articulation, with the internal jugular vein. The nerves are derived from the tympanic branch of the glosso-pharyngeal, and the carotid plexus of the sympathetic nerve. The Mastoid sinuses6 consist of numerous irregular cavities in the interior of the mastoid portion of the temporal bone, communicating by a large orifice7 with the upper back part of the tympanum. They are 1 Laxator tympani minor. 2 M. tensor tympani; m. internus mallei; m. tensor auris internus; m. salpingo-mallei. 3 M. laxator tympani; m. 1. t. major; anterior ligament of the malleus; m. mallei externus, or anterior; m. obliquus, or externus auris; m. laxator auris in- ternus; m. Eustachii; m. spheni-salpin- go-mallei. * M. stapedius, or pyramo-stapedius. 5 Membrana obturatoria, or propria stapedis. 0 Mastoid cells; cellulae mastoidea?; antrum mastoideum. 7 Petro-mastoid canal. THE ORGANS OF SPECIAL SENSE. 621 lined throughout with a delicate mucous membrane, provided with a pave- ment epithelium. The Eusta'chian tube1 is a trumpet-shaped canal, rather over an inch and a half long, extending from the fore part of the tympanum obliquely inward, forward, and downward to the pharynx. Its upper section is formed by an osseous canal in the petrous portion of the temporal bone, which communicates at its outer end with the tympanum, and narrows to its union with the other section in the angle between the squamous and petrous portions of the temporal bone. The lower and longer section of the Eustachian tube proceeds from the angle mentioned along the posterior border of the sphenoid bone to the inner side of the internal pterygoid process. Gradually expanding in its course, it terminates by an oval orifice, with a prominent border, at the side of the pharynx, on a level with the turbinated bone, just back of the posterior nasal orifice. It is composed of a triangular plate of cartilage, bent into a gutter, open at its outer part, but converted into a complete tube by fibrous membrane. The Eustachian tube is lined with mucous membrane, provided with a ciliated epithelium, and is continuous with that of the pharynx and tym- panum. THE INTERNAL EAR. The Internal ear includes the labyrinth and the internal auditory meatus. The Lab'yrinth,2 named from its highly complex character, is the most important portion of the organ of hearing, as it contains the entire dis- tribution of the auditory nerve. It is imbedded in the petrous portion of the temporal bone, and consists of three parts, named the vestibule, the semicircular canals, and the cochlea. Though these may be des- cribed as cavities, it should be understood that the labyrinth has os- seous walls independent of the bony structure embracing it. At birth it may be readily excavated from the looser surrounding osseous sub- stance ; but at a later period this substance becomes condensed and confounded with the exterior surface of the labyrinth. The Ves'tibule3 is an irregularly oval cavity, situated between the tympanum and the bottom of the internal auditory meatus, and joining 1 Tuba Eustachiana, or Aristotelica; canalis gutteralis; meatus caecus: iter a palato ad aurem; ductus auris palati- nus; syrinx; syringa. 2 Labyrinthus; 1. auris intima?; laby- rinthic cavity; pars intima organi audi- tus; antrum buccinosum. 3 Vestibulum labyrinthi. G22 THE ORGANS OF SPECIAL SENSE. Fig .173 the semicircular canals postero-externally, the cochlea antero-intemally. Through its outer wall it communicates with the tympanum by the oval window. A slight semicircular ridge or crest1 springs from the floor of the vestibule, ascends on its inner wall to the roof, and terminates in a small pyram'idal eminence.2 The latter presents a group of minute foramina commu- nicating with the internal auditory meatus, and named the superior crib'riform spot.3 The crest separates two recesses, called, from their shape, the hemispherical* and hemielliptical fossa.5 The former is the smaller, and occu- pies the antero-internal portion of the vesti- bule ; the latter occupies the postero-external portion. Just below the centre of the hemi- spherical fossa is a second group of minute foramina communicating with the internal auditory meatus, and named the middle crib'- riform spot.6 Immediately in advance of the of the vestibular scala of the cochlea communicates Into the hemielliptical fossa open the orifices of the The internal ear, consisting of the labyrinth and internal aud- itory MEATUS, LAID open. The lower part of the figure exhibits the three osseous semicircular canals con- taining the membranous semicir- cular canals. 1, 2, two semicircu- lar canals, ending in a common tube, 3; I. simple extremity of one of the canals ; 5, 6, 7, dilated ex- tremeties or ampulla? of the canals; 8, elliptical, and 9, hemispherical saccules contained in the vestibule. Above the latter is the cochlea; and to its left the internal auditory meatus. fossa, the orifice7 with the vestibule semicircular canals and the aperture8 of a small vascular canal9 which communicates with the posterior surface of the petrous portion of the temporal bone, and transmits the vestibular vein to the inferior petrosal sinus. The Semicircular canals,10 three in number, are situated postero-ex- ternally to the vestibule and above the inner back part of the tympanum. From their position they are named superior,11 posterior,12 and infe- rior;13 the former two being vertical, the last horizontal. They are so 1 Crista vestibuli. 2 Eminentia pyramidalis; pyramis vestibuli. 3 Macula cribrosa superius. 4 Fossa, or fovea hemispherica; re- cessus hemisphericus; sinus rotundus. 5 Fossa, or fovea hemielliptica, semi- elliptica, or elliptica; recessus hemiel- lipticus; sinus ovatus. 6 Macula cribrosa media. 7 Apertura scalae vestibuli. 8 Recessus, or fovea sulciformis. 9 Aqueduct of the vestibule; aqute- ductus vestibuli, orCotunnii; canal of Cotunnius. 10 Canales, or ductus semicirculares, circulares, or tubaeformes; semicirculari ossei; funes, or canaliculi semicirculares labyrinthi. 11 Also vertical, or superior vertical. 12 Also posterior vertical, or oblique. 13 Also external, or horizontal. THE ORGANS OF SPECIAL SENSE. 623 related with one another as to correspond with the inner, back, and lower faces of a cube. Each canal is rather more than half a circle, and forms at one extremity a bottle-like dilatation, named the ampul'la, which communicates with the vestibule. Of the undilated extremities, two conjoin, and, with the re- maining extremity, likewise open into the vestibule ; and thus the three canals communicate with the latter by five orifices. Within the ampulla of the posterior semicircular canal there is a third group of minute foramina communicating with the internal auditory meatus, and named the inferior crib'riform spot.1 The interior of the vestibule and the semicircular canals is lined with a delicate membrane, resembling a serous membrane. It consists of a fibrous layer adhering to the osseous surface as a periosteum, a structure- less basement layer, and a tessellated epithelium. Within this mem- brane the cavity is occupied by a serous liquid, named the perilymph,2 from its surrounding a secondary structure, known as the membranous lab'yrinth. This consists of a pair of communicating pouches,3 con- tained in the vestibule, and three semicircular canals, of the same form as the osseous canals which contain them. The smaller pouch occupies the hemispherical fossa, and is named the spherical saccule ;4 while the other pouch, occupying the hemielliptical fossa, is named the elliptical saccule,5 and is joined by three membranous semicircular canals. The membranous labyrinth consists of an outer fibrous structure, lined internally with a tessellated epithelium, and filled with a serous liquid, named the endolymph.6 The vestibular branch of the internal auditory nerve is distributed to the membranous labyrinth, and maintains its floating position in the perilymph. This nerve divides at the bottom of the internal aud- itory meatus into three branches, of which one enters the vestibule at the superior cribriform spot, to be distributed to the elliptical sac- cule and the ampulla? of the superior and inferior semicircular canals; a second enters at the middle cribriform spot, and is distributed to the 1 Macula cribrosa inferius. 2 Liquor, or aquula Cotunnii; aqua, or aquula acustica, or auditoria; aquula. 3 Sacculus vestibuli. * Sacculus sphaericus; sacculus; sac- cule. 5 Sacculus ellipticus; s. vestibuli; utriculus, sinus, or alveus communis; utricle; sinus, or alveus utriculosus; median sinus. 6 Endolympha; vitrina auditiva; aqu- ula vitrea auditiva; aqua labyrinthi membranacei; humor vitreus auris; liquor of Scarpa. 024 THE ORGANS OF SPECIAL SENSE. hemispherical saccule; and the third enters at the inferior cribriform spot, and is distributed to the ampulla of the posterior semicircular canal. Fig. 374.—Internal ear laid open. 1, vestibular branch of the auditory nerve; •£, branch to the spherical saccule; 3, branch to the elliptical saccule; i, 5,6, branches to the ampulla: of the membranous semicircular canals; 7, cochlear branch of the auditory nerve; 8, cochlea. Fig. 375.—Nerves of the vestibule and semicircular canals, magnified three diameters. 1, vestibular branch of the auditory nerve; 2, branch to the spherical saccule; 3, branch to the elliptical saccule; i, 5, 6, branches to the ampullae of the semicircular canals; 7, cochlear nerve. Adhering to the inner surface of the two saccules of the vestibule, at the point of entrance of the nervous filaments from the cribriform spots, are two white discoidal masses, consisting of minute crystalline particles, called o'tolites.1 These cohere, and appear to be in contact with the nervous filaments distributed to the saccules. They are composed of carbonate of lime, and are an important element of structure to the organ of hearing, as they are found in the ear of most animals. The arteries of the vestibule and semicircular canals are derived from the vestibular branches of the auditory artery accompanying the branches of the vestibular nerve. The veins partly terminate in the venous sinus of the cochlea, and partly in the vestibular vein, which communicates with the inferior petrosal sinus. The Coch'lea2 is the inner portion of the labyrinth, and is named from its resemblance to a snail-shell. Its base is applied to the bottom of the internal auditory meatus, and its apex is directed forward and slightly outward. It consists of an osseous tube, about an inch and a half long, wound nearly three times around a central axis, with each turn suc- cessively rising. The commencement of the tube is connected with the fore part of the vestibule, and produces the promontory of the 1 Otolithi; otoliths; otoconia; otoconites. 2 Concha auris interna; c. labyrinthi; cavitas cochleata, orbuccinata; trochlea labyrinthi; antrum buccinosum. THE ORGANS OF SPECIAL SENSE. ■ist 625 tympanum. Turning from right to left in the right ear; and the reverse direction in the left ear, it ends in a closed extremity, named the cupola, which nearly reaches the front surface of the petrous portion of the tem- poral bone above the ascending part of the carotid canal. Fig. 377. The cochlea, laid open, its summit turned up- ward, magnified three diameters. 1, 2. 3, the tym- panic scala; 4, 5, G, the vestibular scala; 7, 8, os- seous spiral lamina; 9, membranous spiral lamina; 10, orifice of communication of the two scalae at the summit of the cochlea; 11, 12, termination of the osseous and membranous spiral laminae. The cochlea, laid open, and viewed from its summit toward the base. 1, cut edges of the os- seous wall of the cochlea; 2, osseous spiral lamina, seen within the vestibular scala; 3, end of the lamina; 4, 5, its outer border; 6, membranous spiral lamina; 7, its end; 8, foramen of communi- cation with the tympanic scala. The axis of the coch'lea1 is conical, its base forming the spiral tract at the bottom of the internal auditory meatus, and its summit becoming continuous with the inner wall of the last turn of the canal of the cochlea.2 It is traversed by numerous fine canals, continuous with the foramina of the spiral tract and transmitting the filaments of the coch- lear nerve, together with the cochlear branches of the auditory artery. A central canal,3 larger than the others, extends the entire length of the axis, and transmits a branch of the latter vessel. An osseous spiral lamina4 commences just below the hemispherical fossa of the vestibule, winds around the axis of the cochlea, extending about half way across its canal, and terminates in a pointed process5 at the summit of the latter. The lamina is traversed by a multitude of fine anastomosing canals, which are continuous with those of the axis of the cochlea, and open into a groove at the free margin of the lamina. 1 Column of the cochlea: axis, colu- mella, or pyramis cochleae; modiolus. 2 The last turn of the inner wall of the cochlea upon its axis forms the infun- dibulum, or scyphus Vieussenii, or au- ditorius. 3 Canalis centralis modioli. 4 Lamina spiralis ossea; septum scalae, or cochlae auditoria?; zona ossea. 5 Hamulus. 40 626 THE ORGANS OF SPECIAL SENSE. The interior of the cochlea is lined by a delicate membrane continu- ous with, and like that of the vestibule. After investing the two sur- faces of the osseous spiral lamina, it is extended in a double layer from the free border of the latter across the canal of the cochlea to the outer wall, where it is firmly attached. This extension of the membrane, which is named the membranous spiral lamina,1 together with the osseous spiral lamina, divides the canal of the cochlea into two distinct pas- sages, which communicate with each other only at the summit of the cochlea.2 At the lower extremity of the latter, one of the passages terminates at the round window of the tympanum, and is thence named the tym'panic sca'la,3 while the other opens into the vestibule, and is called the vestib'ular sca'la.4 Both scalae5of the cochlea are filled with a limpid serous liquid, which communicates with the perilymph of the vestibule, but is prevented from escaping at the round window by the secondary tympanic membrane. The axis of the cochlea within the tympanic scala is pierced with a series of foramina, transmitting veins from the lining membrane of the cochlea to a spiral sinus6 within the axis. At the lower extremity of the same scala is the orifice of a canal7 which ends in a triangular pit iu ad- vance of the jugular foramen, and transmits a vein from the spiral sinus just mentioned to the inferior petrosal sinus. The cochlear branch of the internal auditory nerve is resolved into a multitude of filaments, which, together with branches of the correspond- ing artery, enter the foramina of the spiral tract at the bottom of the internal auditory meatus. Ascending the canals of the axis of the cochlea, they are reflected outwardly to the osseous spiral lamina, within which they form an intricate plexus, and become associated near its free border with a series of nerve cells. From these the nerve fibres emerge, and enter the membranous spiral lamina, where, with pe- 1 Lamina spiralis membranacea; zona membranacea, or mollis; zona choriacea and pars membranacea; z. cartilaginea and membranacea; z. media and mem- branacea; z. nervea and cartilaginea; z. denticulata and pectinata; habenula in- terna, or sulcata, and h. externa, den- ticulata, or perforata, are subdivisions of the zona denticulata. 2 The communication is named the Helicotrema. 3 Scala tympani, posterior, interna, or superior; incorrectly inferior. 4 Scala vestibuli, anterior, externa, or inferior; incorrectly superior. 5 Gyri; ductus spirales; canales. 6 The canal containing the sinus is the canalis Rosenthalianus, or c. spiralis modioli. 7 Aqueduct of the cochlea; aquaeductus cochleae. THE ORGANS OF SPECIAL SENSE. 627 culiar nerve cells, they form a complex arrangement, the character of which has not yet been conclusively determined.1 Fig. 378. niSTRiBUTiON of the cochlear nerve. 1, trunk cf the cochlear nerve; 2, membranous spiral lamina : 3, terminal filaments of the cochlear nerve emerging from the osseous spiral lamina to spread themselves in the membranous lamina; 4, orifice of communication of the tympanic and vestibular scalse. The arteries of the cochlea are mainly derived from the cochlear branches of the auditory artery, and, as previously indicated, they follow the course of the cochlear branch of the auditory nerve They term- inate in a capillary net of the lining membrane and spiral lamina of the cochlea, from which veins originate and join the spiral venous sinus within the axis of the cochlea. The spiral sinus communicates by means of a vein with the inferior petrosal sinus. The Internal aud'itory mea'tus2 is a cylindroid canal about three- fourths of an inch in length, leading from the posterior surface of the petrous portion of the temporal bone, obliquely downward, forward, and outward to the position of the labyrinth. Its bottom is unequally di- vided by a prominent, transverse, crescentic crest into two compartments, of which the lower is the larger. The upper compartment is subdivided by a vertical ridge into two pits, of which the inner one is the com- mencement of the Fallopian canal for the transmission of the facial nerve, and the outer one corresponds with the superior cribriform spot of the vestibule for the transmission of the superior division of the ves- 1 For a more intimate description of this structure see the admirable researches of Corti and Kolliker. 2 Meatus auditorius internus; foramen, porus, or sinus acusticus. 628 THE ORGANS OF SPECIAL SENSE. tibular nerve to the elliptical saccule. The lower compartment inter- nally is occupied by a spiral tract,1 pierced with a multitude of minute foramina, for the transmission of the cochlear nerve; externally is a fossa corresponding with the middle cribriform spot for the transmission of the inferior division of the vestibular nerve to the hemispherical sac- cule and ampullae of the superior and inferior semicircular canals. In the posterior wall of the meatus there is a small canal, transmitting the posterior division of the vestibular nerve to the inferior cribriform spot of the ampulla of the posterior semicircular canal. The auditory meatus transmits the auditory and facial nerves, and the auditory artery. The facial nerve enters the Fallopian canal, and pursues its course to emerge at the stylo-mastoid foramen. The auditory nerve divides into two branches, the coch'lear and vestib'ular nerves. The former resolves itself into numerous filaments, which enter the foramina of the spiral tract to be distributed in the manner indicated. The vestibular nerve divides into three branches, which resolve them- selves into many filaments transmitted through the foramina of the three cribriform spots as above mentioned. The auditory artery, a branch of the basilar, divides into cochlear and vestibular branches, which accompany the corresponding nerves. THE ORGAN OF TASTE. (For an account of the organ of taste, the student is referred to the description of the tongue, page 280.) THE SKIN AND ITS APPENDAGES. The Skin2 is the organ of touch,3 and in the healthy condition of the body is among the most sensitive to the impression of pain, through which quality we are led to avoid agencies injurious or destructive to life. By its peculiar constitution it prevents evaporation of the liquids of the body, and yet holds a correlation with other organs in getting rid of an excess of those liquids. In general it is thickest on the most ex- posed parts—on the back of the trunk, outer part of the limbs, palms of the hands and soles of the feet. It is thinnest on the eyelids, lips, inner surface of the prepuce, and glans penis. It is flexible, moderately ex- tensible, slightly elastic, semitransparent, and varies in color in different races and individuals. On the palms and soles it is closely covered with 1 Tractus spiralis foraminulosus. 2 Cutis; derma; deris; corium; pellis; integumentum commune. 3 Organon tactus. THE ORGANS OF SPECIAL SENSE. 629 fine parallel ridges, mostly arranged in curving lines, and with peculiar regularity. In other positions it presents fine reticular furrows, and pits from which hairs project. In parts exposed to frequent doubling or flexion it becomes more or less coarsely furrowed or wrinkled, as around many of the joints, and on the forehead. The skin is composed of two* principal layers, the dermis and epider- mis; is provided with two kinds of glands, the sweat and sebaceous glands; and is furnished with two varieties of appendages, the hairs and nails. THE DERMIS. The Dermis1 constitutes the deeper layer of the skin, and is thickest where the entire skin presents that condition. It is about one-sixth of a line thick on the eyelids, from one-fourth to one-half a line on the front of the body, and from one-half a line to one and a half lines on the back of the body and the heels. It is thinner in the female than the male; in children, is about half as thick as it is in adult age, and it becomes thinner in old age. It is of a pinkish cream color, and varies in the depth of pinkish hue in different positions according to its degree of vascularity. The dermis is mainly composed of a dense intertexture of bundles of fibrous tissue, which cross one another at acute angles, in different direc- tions. ' It is mingled with some elastic tissue, which is most abundant on the front of the body and about the joints. It also contains unstri- ated muscular fibres, which descend from the more superficial part of the dermis to the bottom of the hair follicles. When excited to con- traction, through the impression of cold, the emotion of fear, or the influence of electricity, these muscular fibres elevate the hairs and pro- duce the phenomenon of "goose flesh."2 The dermis is densest approaching its exterior surface, which is de- fined by a more homogeneous layer or basement membrane. Its in- terior surface is continuous with the connective tissue of the adipose layer of the superficial fascia, or in positions in which the adipose layer is absent it adheres to the deeper layer of the superficial fascia, or other subjacent structure, by more or less long and loose connective tissue, which allows the skin to be moved backward and forward. The interior surface, when freed from its connections, presents the appearance of a coarsely-corded net, with the meshes occupied by small, round masses of adipose tissue. The outer surface of the dermis is provided with a multitude of mi- 1 Derma; derm; cutis; cutis vera; coriura; true skin. 2 Cutis anserina. 630 THE ORGANS OF SPECIAL SENSE. Fig. 379. nute processes, which, from their function, have been named the tactile papillae.1 They vary in number and degree of development in different parts of the body. They are most numerous and longest on the palms and soles, where they are arranged in double rows supported on linear ridges of the dermis, corresponding with those seen on the surface of the skin. They are also numerous on the prepuce, glans penis, nym- phae, clitoris, and nipple. In other positions they are more widely set apart, less well developed, and on the face are nearly obsolete. The largest or best developed papillae are conical, and either sim- ple or compound—the latter con- sisting of two, three, or even more, springing from a common base. The less well developed pa- pillae are mammillary or wart like, and degenerate into feeble ridges of the surface. In the palms and soles they measure from the one- thirtieth to the one-tenth of a line long, and in other positions descend from the one-thirtieth to one-eight- ieth of a line. They are composed of a continuation of the fibrous structure of the dermis, defined by structureless basement mem- brane, and receive terminal filaments of the cutaneous nerves, and each a looped capillary blood-vessel. Some of the papillae of the palm and sole contain peculiar bodies, which have already been described as tactile corpuscles on page 511. The dermis is richly supplied with blood-vessels, lymphatics, and nerves. The arteries of the skin penetrate from beneath, and end in a capillary net-work, which becomes more close the nearer it approaches the exterior surface of the dermis, and from this net-work single loops enter the tactile papilla?. The veins emerging from the skin are more Vertical section of the skin of the fore- finger across two of the ridges of the sur- face, highly magnified. 1, dermis composed of an intertexture of bundles of fibrous tissue; 2, epi- dermis; 3, its cuticle; 4, its soft layer; 5, subcu- taneous connective and adipose tissue: 6, tactile papillae; 7, sweat glands; 8, duct; 9, spiral pas- sage from the latter through the epidermis; 10, termination of the passage on the summit of ridge. 1 Papillae tactus; papillae of touch; papillary layer of the derm; corpus papillare. THE ORGANS OF SPECIAL SENSE. 631 numerous and much larger than the arteries, and end in the superficial venous trunks beneath. The lymphatics also form an intricate net-work in the dermis, and are most numerous on the fore and inner part of the body and limbs, especially in the palms and soles. The nerves are abundant, and are derived from the various cutaneous branches described in the account of the nervous system. .They extend to the exterior sur- face of the dermis, and into the tactile papillae; but their mode of term- ination has not been accurately ascertained. By boiling, the dermis is resolved into gelatin, and indeed the main source of glue used in the arts is obtained from fragments of the skin of animals. By tanning, the dermis is converted into leather; deprived of fatty and other matters, and properly thinned, it forms parchment. The cut edge and rough surface of a piece of leather illustrates the arrangement of the fibrous structure of the dermis, and its smooth outer surface frequently exhibits the mouths of the hair follicles, papilla?, and other marks. THE EPIDERMIS. The Epider'mis1 constitutes the superficial layer of the skin, and holds the same relation to the dermis that the epithelium does to the deeper layer of the mucous membranes. It is thickest in the palms and soles, where it measures from the one-tenth to one line or more, and in other positions forms a thin layer ranging from about 51a to T^ of a line. The thickness is however in some measure dependent on the pres- sure or friction to which the skin is subjected, and thus it becomes thicker in the palm of the laborer and the sole of the plowman than in most other persons. Corns are much-thickened portions of the epider- mis in particular spots, which are exposed to excessive pressure or friction. They are not necessarily confined to the feet, but are produced on the knee of the shoemaker from frequent hammering, or in front of the clavicle of the soldier from the pressure of his musket. The pain so frequently induced by their presence is due to their exciting inflammation in the sensitive dermis upon which they press, just as a pebble does under the same circumstances. The epidermis is entirely non-vascular, but derives its nutritive liquid by imbibition from the vessels of the dermis. It is without nerves, and therefore completely insensible; but it transmits impressions through pressure to the exquisitely sensitive dermis, the soft and delicate struc- 1 Cuticula; cuticle; epiderma; epichorium; cutis extima; pellis summa; lamina prima cutis; scarf skin. 632 THE ORGANS OF SPECIAL SENSE. ture of which it protects from laceration or drying. If removed, the contact of the atmosphere is sufficient to produce inflammation of the dermis, and after death the latter speedily dries. The epidermis consists of two layers, quite different in many respects; one being named the cuticle, the other the soft epidermic layer. The Cu'ticle1 is a nearly dry, yellowish, translucent, horn-like mem- brane, well illustrated by the slice of a corn. Its deeper surface is con- tinuous with the soft epidermic layer from which it is incessantly renewed, while from its free surface it is constantly worn away, or is shed in small flakes, constituting the so-called scurf and dandruff. In many lower animals, as for instance serpents, it exfoliates from time to time in an Fig. 380. Fig. 381. Scurf from the leg. 1, a fragment of scurf, consisting of dried, flattened, non-nucleated cells or scales; 2, a few cells with a nucleus; 3, a cell more highly magnified, to exhibit its polyhedral form. tion of dandruff, consisting of non-nucleated cells; 2. several fragments, consisting of nucleated cells; 3, isolated cells, some with and without nuclei; 4, a cell more highly magnified, exhibiting granular contents and a nucleus. entire state. It consists of numerous laminae, according to its degree of thickness, of minute scales, which are completely flattened and nearly dried organic cells. These have a small quantity of granular contents, but usually no nucleus, though frequently the remains of one, especially in the deeper part of the cuticle, may be detected. By treatment with a solution of potash, the scales of the cuticle sep- arate from one another, and swell into spheroidal vesicles. Hence it is that alkaline solutions remove the epidermis. A blister or burn pro- duces inflammation of the dermis and effusion of liquid, which breaks up the soft epidermic layer, and elevates the cuticle. By maceration of the skin after death, the cuticle becomes detached from the dermis through disorganization of the soft epidermic layer. When the cuticle is sufficiently thick and strong to sustain itself, it may be removed in large pieces, and thus from the hand it may be stripped off like a glove. 1 Cuticula. THE ORGANS OF SPECIAL SENSE. 633 The Soft epidermic layer1 consists of many laminae of delicate poly- hedral cells with soft granular contents and a nucleus. The upper laminae of cells are successively more and more flattened, and are inces- santly transformed into the comparatively dry scales of the cuticle, while they are as constantly reproduced from the surface of the dermis. In the white race the soft epidermic layer is colorless, and, like the cuticle, translucent, and hence it allows the color and vascularity of the dermis to be seen. In the negro, its cells, especially the deeper ones, are filled with brown or black pigmentary matter, which produces the char- acteristic color of the race. Smaller quantities of the same material give rise to the various shades of complexion of other races, of different individuals, and even different parts of the skin of the same person. The sun-burnt complexion is due to the development or increase of the same coloring matter; and in freckles it is accumulated in spots. As the soft epidermic layer is transformed into the cuticle, the pigmentary matter disappears from its cells. THE SWEAT GLANDS. The Sweat or perspi'ratory glands2 exist almost everywhere in the skin, and number a million or more. They are yellowish-red, spheroidal bodies, averaging about one-sixth of a line in diameter, and are lodged in interspaces of the deep part of the dermis, usually surrounded by adipose tissue. Each gland consists of a tube convoluted into a ball, and afterwards ascending, as the sweat duct, in a slightly tortuous man- ner, to the exterior surface of the dermis. The tube is composed of an exterior fibrous layer, succeeded by one of basement membrane; and is lined with a pavement epithelium, consisting of polyhedral cells contain- ing a nucleus, and granular contents mingled with some yellowish pig- ment particles. From the sweat duct opening on the surface of the dermis a passage way conducts to the exterior of the epidermis. When the latter is thin, the passage is straight; but when thick, as in the palms and soles, it pursues a spiral course, and terminates in a funnel-shaped orifice. The apertures of the ducts are distinctly visible with a common pocket lens, in 1 Rete mucosum; r. Malpighi; cor- pus, or stratum Malpighi; corpus mu- cosum ; c. reticulare; reticulum cuta- neum ; r. mucosum; mesodermum ; mu- cous web; tunica albida superficialis et profunda, et gemmula, et bourgeons sanguins. 2 Glandulae sudoriparae ; g. miliarias; g. hydrophorae ; organa sudoripara; su- doriparous glands; diapnogenous appa- ratus; perspiratory organs; fontes su- doris. 634 THE ORGANS OF SPECIAL SENSE. a single row on the summits of the ridges of the palms and soles ; but in other positions are not so readily distinguished. A modification of the sweat glands constitutes the ceruminous glands, described in the account of the ear, and the odoriferous glands of the axilla.1 These form a patch, an inch and a half or more in diameter, situated in the subcutaneous connective and adipose tissue of the hairy part of the armpit. They are largest near the centre of the patch, and gradually diminish toward the circumference, where they merge into the ordinary sweat glands. They are usually much better developed in the negro, in whom the largest reach the size of a small pea. They are of a dusky, yellowish-red color, and, like the sweat glands, are composed of a tube coiled into a ball, from which the tube continues as the duct to open on the exterior surface of the skin. The tube of the gland con- tains unstriated muscular fibres in its wall; and its cavity is filled with a finely granular matter mingled with brown or yellow pigment and fat particles. Besides an abundance of sweat, these glands yield a strongly odorous substance, which is somewhat peculiar in the different races. Sweat2 is a clear, watery liquid, with an acid reaction and a saline taste. It contains formic, butyric, and acetic acids, and a number of salts, of which the most abundant is chloride of sodium. THE SEBACEOUS GLANDS. The Seba'ceous glands3 of the skin are very numerous, and exist almost everywhere, except in the palms and soles. They are mostly associated with the hair follicles, being situated around them in groups from two to eight for each follicle, imbedded in the more superficial part of the dermis. Generally the largest glands are found with the small- est hair follicles, so that these appear of secondary importance, while the smallest glands exist in pairs in connection with the hairs of the scalp. The largest sebaceous glands are those of the nose, concha of the ear, skin of the penis, the scrotum, labia, and areola surrounding the female nipple. The groups of glands connected with each hair follicle appear as rounded whitish bodies imbedded in the semitransparent skin, and measure from one-tenth to one-half a line or more in diameter. 1 Glandulae odoriferae of Horner. 2 Sudor; perspiration ; perspiratory fluid. 3 Glandulae sebaceae ; g. sebiparae ; g. sebiferaj'; cryptae sebaceae; folliculi se- baceae; sebiparous, or sebiferous glands; sebaceous follicles, or crypts; miliary glands; oil glands. THE ORGANS OF SPECIAL SENSE. 535 The sebaceous glands are simple or compound, being composed of one or more purse-shaped pouches, the ducts of which open into the Fig. 383. SEBACEOUS GLANDS OPENING INTO THE MOUTH OF A hair follicle, much magnified. mouths of the hair follicles, or in the case of the largest glands, together with the latter they open on the sur- face of the skin. In structure the glands possess a delicate wall of fibrous tissue, defined by a base- ment membrane, and are lined with an epithelium consisting of polyhe- dral, nucleated cells with granular contents. The cavity of the glands is filled with sebaceous matter,1 consisting of cells and oil globules. Of the cells, some contain finely granular matter mingled with oil drops, while others are distended with oil. The sebaceous matter anoints the hairs with oil in their progress of growth from the skin, and also imbues the cuticle, by which it is rendered repellant of water. The greasiness of the surface of the skin, occa- sioned by this material, permits the ready adhesion of dust and dirt, and renders the employment of soaps necessary for easy removal of its excess. The too free use of alkaline washes, by depriving the cuticle of its oil, produces a dry and harsh feeling in the skin. The sebaceous matter often becomes inspissated and distends the glands, most frequently in the face, and especially on the nose; and at the mouths of the ducts it A large sebaceous gland from the nose, viewed by transmitted light, and highly magnified, a, epithelium of the gland; b, the same continuous with the epidermis; c, the sebaceous matter; d, subdivisions of the gland; e, a hair follicle; /, a hair. Sebum, or smegma cutaneum. 636 THE ORGANS OF SPECIAL SENSE. becomes incorporated with dirt. By pressure it is squeezed out, and from its assuming the form of the duct, is vulgarly taken for a worm, of Fig. .184. Fig. 38.") i/-:,.\;:AT..v •fy,f Fig. 384.—Sebaceous matter, from one of the sebaceous glands of the nose, magnified. 1, cells filled with granular matter; 2, one of the cells more highly magnified; 3, oil drops mingled with the cells. Fig. 385.—Structure of the sebaceous glands. A. a simple sebaceous gland, or one of the divisions of a compound gland, highly magnified, a, epithelial cells; b, sebaceous matter. B, sebaceous cells, much more highly magnified, a, small cells from the epithelial layer; 6, larger cells abounding in fat; c, cell in which the fat has accumulated in large drops; d, cell distended with fat; e,f, cells from which the fat has partially escaped. which the dirt at the end is supposed to be the head. The sebaceous matter, nevertheless, even in most healthy individuals, contains a curious parasitic animal, the pimple mite.1 THE HAIRS. The Hairs2 are solid, thread-like appendages of the skin, projecting from almost every part of its surface except the palms and soles. They are flexible, elastic, and shining, but vary in degree of development, fineness, color, form, and arrangement in different races, sexes, individ- uals, and parts of the body. From the long hairs of the head3 they exist of every gradation of size to such4 as are hardly visible. The portion of a hair projecting from the skin is its shaft or stem3 terminated by the point or end; the portion inserted into the skin is the root,6 which begins in a club-like expansion, named the bulb.7 The hairs generally project obliquely from the skin, singly, or in groups of two, three, or more. They are regularly arranged in the dif- ferent parts of the body, mostly in curving lines or whorls from particu- lar points. 1 Acarus folliculorum; Demodex folliculorum. 2 Pili; the hair; crinis; pile; thrix. 3 Capilli. 4 Lanugo; down. 5 Scapus. 6 Radix pili. 7 Bulbus pili; button. THE ORGANS OF SPECIAL SENSE. 637 The fine silken hair of the head of the white race is cylindrical; the crisp, curling hair of the beard, other parts of the body, and the head of the negro, is more or less flattened cylindrical. In structure the hairs consist of an exterior cuticle, a cortical sub- stance, and an interior medullary substance. Fig. 386. Fig. 387. A. Portion of the shaft of a light hair, mag- nified. The longitudinal lines are produced by the cortical substance; the transverse, undulating lines, by the cuticle. B. Isolated scales of the cuticle. The cuticle of the hair consists of a single layer of thin, colorless, quadrilateral scales or completely flattened cells, which overlap like the shingles of a roof. The projecting edges of these scales are directed upward and outward along the shaft; and in a hair examined be- neath the microscope are seen as irregularly undulating and intersecting transverse lines. As feebly as their edges appear to project, they nevertheless present an obstacle to the hair being moved in any other direction than with its root forward, when rubbed between two surfaces. It is upon a similar condition that the felting of the hair and wool of various animals depends. The cortical substance1 makes the chief bulk of the hair, and is that upon which the color mainly depends in different races and individuals. When sufficiently translucent, as in white or light-colored hairs, beneath the microscope it presents a longitudinally striated appearance. It is composed of layers of flexible fibres, into which it is not unfrequently found more or less split at the ends of hairs, as the result of dry- ing and friction. The fibres consist of much elongated, fusiform cells containing a linear nucleus. The coloring matter is usually dif- Portion of a hair from the outer part of the thigh, magni- fied. 1, shaft of the hair covered with transverse markings indicat- ing the projecting edges of the cu- ticular scales; 2, cortical substance at the end of the hair broken up into coarse fibre.-* as the result of friction of the clothing. 1 Cortex. 638 THE ORGANS OF SPECIAL SENSE. fused through the cortical substance, though it is also often accumulated in streaks or spots. With the loss of the coloring matter, generally occurring in the advance of age, the cortical substance becomes white. The medullary substance1 is frequently absent, especially in dark- colored hairs of the head, and in fine down-like hairs of the body. It occupies the axis of the hair, and by transmitted light appears as a dark, coarsely granular streak, usually of uniform diameter, but often con- tracted, and sometimes completely interrupted in its course. By re- flected light it appears white, though modified by the color of the cortical substance through which it is seen. It consists of somewhat cuboidal cells, with granular contents and an indistinct nucleus. The medullary substance is generally mingled with more or less air, in small bubbles, which penetrates from the ends of the hairs, and gives to these when white the characteristic silvery lustre. The root of the hair is lodged in a flask-shaped receptacle of the skin called the hair follicle,2 at the bottom of which is a papilla from which the hair grows. The hair follicles are imbedded in the dermis, or, in the case of the large hairs, extend into the subcutaneous connective and adipose tissue. They may be viewed as inflections of the skin, and the hair papilla at their bottom as a modified tactile papilla. The wall of the hair follicle is composed of a fibrous layer defined by a basement membrane, and lined with an inflection3 of the epidermis. The cuticular portion4 of this inflection is remarkably modified from the corresponding layer on the free surface of the skin. It forms a com- paratively thick, transparent, elastic membrane, composed of somewhat elongated non-nucleated cells, adhering to one another in such a manner as to assume the appearance of fenestrated membrane. The elastic cuticular layer merges into the softer epidermic layer beneath, and tightly clasps the root of the hair. It perhaps acts upon the latter as it is projected in its growth from the papilla, as a wire is acted upon when it is protruded through a draw-plate. The hair papilla5 is ovoid, of soft consistence, and supplied with both capillary vessels and nerves. The hair bulb caps or incloses the papilla, 1 Medulla. * Inner root sheath of the hair. The 2 Folliculus pili. softer cells beneath constitute the outer 3 Root sheath of the hair; vagina pili. root sheath. 5 Papilla pili; pulpa, or blastema pili. THE ORGANS OF SPECIAL SENSE. 539 and in the extraction of a hair it is traction on the latter which gives rise to the pain. The root of the hair is softer and thicker than the shaft, the character of which it assumes in its growth. The hair bulb is soft, translucent, and is continuous at the bottom of the hair papilla with the epidermic layer of the hair follicle. It is com- posed of soft, polyhedral nucleated cells, which exhibit a gradual and successive transition into the cu- ticle, cortical and medullary sub- stances of the root above. By the Fig. 388. Root of a hair lodged within its follicle, magnified, a, shaft of the hair; b, root; c, bulb ; d, cuticle of the hair; e,f, epidermic lining of the follicle; g, basement membrane; h, fibrous layer of the wall of the hair follicle; i, hair papilla; k, mouths of two sebaceous glands; I, dermis; m, soft layer of the epidermis; n, cuticle of the epidermis. Fig. 389. Diagram of structure of the root of a hair within its follicle. 1, hair papilla; 2, capil- lary vessel; 3, nerve fibres; 4, fibrous wall of the hair follicle; 5, basement membrane; 6, soft epider- mic lining of the follicle; 7, its elastic cuticular layer; 8, cuticle of the hair; 9, cortical substance; 10, medullary substance; 11, bulb of the hair composed of soft polyhedral cells; 12, transition of the lat- ter into the cortical substance, medullary substance, and cuticle of the hair. transformation of the cells into the elements just mentioned, and the pro- duction of new cells from the papilla, the hair constantly grows in length. Like the epidermis the hairs receive nutriment by imbibition—the liquids being transmitted from one cell element to another in gradually diminishing quantity throughout the length of the hair. 640 THE ORGANS OF SPECIAL SENSE. The hairs are not only renewed by constant growth, but in many in- stances, even in the healthy condition, but especially after diseases, they are cast off or shed, and new ones are produced. In such instances, likewise when the hairs are violently extracted, the new hairs are pro- duced from the same hair follicles, but sometimes at least from new pa- pillae. Permanent baldness, so often occurring in the advance of age, arises from atrophy of the hair papillae. The apparent growth of the beard after death arises from the shrink- ing of the skin, which protrudes the remaining roots of the hairs the eighth of an inch or more. THE NAILS. The Nails1 are corneous appendages of the skin, and correspond with the claws and hoofs of other animals. They are thin, flexible, translu- Fig. 300. Fig. 391. Fig. 392. Fig. 390. Matrix of the nail. 1, fold of the skin which covers the root of the nail; 2, the fold par- tially turned up to show the depth of the groove beneath; 3, 4, posterior and anterior portions of the matrix, the former the less vascular, and giving rise to the appearance called the lunula. The longitudi- nal lines indicate the ridges bordered with papilla?. Fig. -391. Under surface of the nail. 1, root; 2, part corresponding with the lunula; 3, grooved sur- face adapted to the ridges of the matrix; 4, free border. Fig. 392. Vertical section of the end of a finger. 1, epidermis on the back of the finger; 2, point at which it is reflected to become continuous with the nail; 3, the nail; 4, epidermis at the end of the fin- ger; 5, 6, 7, 8, surface of the dermis corresponding with the position of the soft epidermic layer; 9,10, 11,12, dermis; 13, last phalanx; 14, flexor tendon. cent, quadrilateral plates continuous with the epidermis, and resting on a depressed surface of the dermis, called the matrix or bed. The exposed portion of the nail, named its body, is terminated ante- riorly by the free border. The posterior third or fourth of the nail, named its root, is lodged in a deep groove2 of the matrix, and the lateral borders are received into shallow grooves. From the body of the nail the root gradually thins away to a sharp edge, and the lateral borders more abruptly thin out. 1 Ungues. 2 Vallecula unguis; nail follicle. THE ORGANS OF SPECIAL SENSE. 641 The translucency of the nail permits the redness of the matrix to be seen, which color is due to vascularity of the part. The less degree of vascularity of the matrix at the root, defined by a semicircular line, gives rise to the whitish spot called the lu'nula.1 The free surface of the body of the nail is shining and faintly striated longitudinally; its under sur- face is finely grooved in the same direction. The matrix of the nail, constituted by a highly vascular portion of the dermis, is covered with fine longitudinal ridges beset with a multitude of minute papillae. The ridges and papillae fit into the grooves of the under surface of the nail, and correspond with the tactile papillae in other positions. By maceration the nails become detached continuously with the epi- dermis from the dermis. They consist of a thick horny layer attached by a delicate soft layer to the dermis. The horny layer answers to the cuticle of the epidermis, and is com- posed of numerous intimately associated laminae of flattened nucleated cells or scales, which can only be distinguished microscopically after treatment with certain chemical reagents, as the alkalies. The soft layer2 of the nails corresponds with that of the epidermis, and like it is composed of delicate, polyhedral nucleated cells. These ' are incessantly transformed into the scales of the horny layer, and are renewed from the surface of the dermis. By the constant addition of cells at the root, the nail grows in length; by addition beneath, they grow in thickness. 1 Semilunula; arcus; albedo unguium. 2 Stratum Malpighi; soft mucous layer; stratum mucosum. 41 INDEX. ........ 211 595 211 . 213, 220 Ankle.......................... ] 52, 153 938 153 163 ....... 219 ........ 211 613 613 ........ 47 ........ 257 318 internal sphincter of.. 319 ........ 237 319 258 ........ 236 619 351 Accessory flexor of the foot.. ........ 256 383 parotid gland............... ........ 279 381 ........ 124 222 ........ 29 445 ........ 29 180 ........ 28 598 ........ 29 594 ........ 29 610 ........ 457 539 ........ 132 351 ........ 47 378 ........ 257 404 ........ 237 380 ........ 236 ..... 88, 89 ........ 250 276 long............................ 249 ........ 250 531 604 . 193, 440 500 ....... 176 170 ........ 429 223 ...... 452 132 Alar folds......................... ....... 162 »n ....... 26 .... 332 351 Albuminose....................... ...... 26 371 ....... 470 400 ....... 273 .... 382, 453 ........ 273 403 ....... 463 368 77 84 390 ....... 77 digital of superficial palmar ........ 29 381 ........ 623 of plantar arch ... 404 396 ........ 333 478 387 (643) 644 INDEX. Arteries, inferior articular............ 400 intercostal........................... 382 anterior branches of......... 383 dorsal branches of........... 383 interosseous, of palmar arch... 378 jejunal................................ 387 lateral sacral........................ 392 lumbar................................ 389 anterior branches of......... 389 posterior branches of...... 389 spinal branches of........... 389 mediastinal................... 371, 382 oesophageal.......................... 382 ovarian................................ 390 pancreatic........................... 386 perforating, of internal mam- mary................................ 371 of plantar arch............... 404 of profound femoral......... 397 pericardiac........................... 382 phrenic............................... 389 renal.................................. 390 short gastric....................... 386 spermatic............................ 390 splenic branches of splenic..... 386 superior articular.................. 400 supra-renal.......................... 390 tarsal................................. 401 vesical................................ 393 Artery, angular.......................... 358 acromial thoracic.................. 373 anastomotic.................. 376, 398 anterior auricular.................. 360 carpal ................... 377, 380 cerebral......................... 366 ciliary.......................... 365 circumflex..................... 374 communicating............... 366 dental, of infra-orbital...... 362 ethmoidal...................... 365 interosseous................... 379 nasal............................ 366 spinal........................... 368 temporal....................... 360 tibial......................400, 401 ascending cervical................. 371 axillary.............................. 372 basilar................................ 368 brachial........................ 374, 376 bulbo-urethral...................... 394 cavernous........................... 394 central retinal....................... 365 choroid.............................. 366 ciliary arteries..................... 365 long.............................. 365 Bhort............................. 365 circumflex iliac..................... 396 colic, left............................ 388 middle.......................... 387 right............................ 387 common carotid, left.............. 354 right............................. 354 Artery, interosseous..................... 379 communicating..................... 380 coronary............................. 384 left............................... 353 right............................. 353 cystic................................. 385 deferent....................... 393, 4~.) dental, of inferior maxillary ... 362 descending palatine.............. 363 cervical......................... 359 dorsal lingual....................... 356 dorsal, of clitoris.................. 395 of great toe.................... 402 of penis......................... 395 pedal............................ 401 scapular........................ 374 duodenal............................. 387 epigastric............................ 396 external carotid..................... 355 iliac............................. 395 malleolar...................... 401 plantar......................... 404 facial........................... 357, 358 femoral............................... 396 frontal ............................... 366 gastro-epiploic, right............. 385 duodenal....................... 385 gluteal................................ 393 great meningeal.................... 361 haemorrhoidal, inferior........... 394 middle.......................... 394 superior........................ 388 hepatic............................... 385 left.............................. 386 right............................. 385 hyoid branch of superior t hyroid 356 ilio-colic............................. 387 ilio-lumbar......................... 392 inferior coronary................... 358 maxillary...................... 361 mesenteric..................... 388 palatine........................ 358 profound....................... 375 thyroid.......................... 370 vesical......................... 393 infra-orbital......................... 302 innominate......................... 353 ischiatic.............................. 395 internal auditory.................. 369 carotid......................... 363 circumflex..................... 398 iliac........................... 391 malleolar....................... 401 mammary...................... 371 maxillary................ 361, 362 plantar......................... 403 pudic............................ 393 interosseous recurrent............ 380 lachrymal............................ 365 laryngeal............................ 356 lateral nasal........................ 358 lingual......................... ...... 356 INDEX. 645 Artery, long thoracic............. ?7? Artery, sub-maxillary branches of medullary..................... 376 358 403 358 meningeal..................... 308 374 branches of anterior eth- 397 366 397 branches of occipital.. 359 369 378 370 402 358 middle articular of popliteal.... 400 372 366 372 389 362 360 386 muscular branches of superior 371 356 375 372 373 366 355 392 393 359 359 364 365 365 385 370 366 360 parotid branches of external 358 359 360 394 394 403 361 403 8V9 356 395 399 400 «9h 359 368 378 380 377 369 34 374 174 366 34 34 lary................... 362 34 365 Articulation, carpo-metacarpal..... 147 380 443 370 44'^ 360 14b principal, of the thumb... 40'' 403 163 378 147 37" 145 397 146 453 I4'' 405 141 405 145 385 . 163 376 377 377 378 356 401 388 361 . 86 46 119 118 46 164 . 147 . 363 . 166 368 368 . 386 branches of vertebra ,... 111 111 367 . 125 367 356 . 158 111 646 INDEX. Articulations of the ribs........ ...... 118 of the sternum..................... 118 upper extremities............ 141 vertebral column............. 107 Arytenoid cartilages.................... 441 Auditory meatus, external............. 63 internal......................... 63 process...........................63, 64 Axis......................................... 101 cerebro-spinal................ 503, 513 coeliac................................. 384 fibre................................... 505 of the pelvis......................... 127 Aryteno-epiglottic folds................ 445 Astragalus................................. 153 Asperous ridge........................... 148 Atlas........................................ 100 Auricle of the ear................ ...... 612 of the heart......................... 343 left............................... 344 right............................. 343 Auricular appendage............ 343, 344 Auriculo-ventricular orifice, left,344, 347 right........................... 344, 345 Axilla....................................... 223 Basilar process......................... 51 Base of the skull........................ 90 Basement membrane.................... 262 Band, semicircular..................... 524 Back................................. 200, 203 of hand.............................. 223 Ball of the thumb........................ 222 Band-like ligaments..................... 48 Belly....................................... 211 cavity of.............................. 298 muscles of........................... 178 Bile ducts................................. 324 Biliary duct, common................... 328 Biliverdin.................................. 29 Bladder, ligaments of................... 463 urinary......................... 300, 462 Blood....................................... 338 corpuscles................. ......... 339 colorless........................ 340 red.............................. 339 liquor................................. 340 Bodies, geniculate....................... 524 nerve capsular...................... 510 olivary................................ 530 Pacchionian ........................ 536 pyramidal........................... 530 quadrigeminal..................... 525 restiform............................. 531 striated............................... 523 supra-renal.......................... 465 Body, ciliary.............................. 605 dentated....................... 528, 531 of bone................................ 34 of teeth.............................. 285 quadrigeminal...................... 525 pituitary............................. 518 [ Body, striated............................ 523 thymus................................ 156 thyroid................................ 455 Bone, occipital........................... 50 arm.................................... 132 canaliculi of......................... 41 capitate............................. 138 collar................................. 129 cuboid................................ 154 cuneiform............................ 137 ethmoid............................. 56 frontal................................ 58 hip.................................... 121 hyoid................................. 96 inferior maxillary.................. 83 innominate........................... 121 lachrymal............................ 80 lacunse of............................ 41 lunar................................... 137 malar................................. 83 nasal.................................. 81 palate................................. 78 parietal............................... 60 pisiform.............................. 137 scaphoid, of carpus............... 137 scaphoid, of tarsus................ 154 shin.................................... 150 sphenoid.............................. 52 superior maxillary................. 76 temporal.............................. 61 thigh.................................. 148 trapezial.............................. 137 trapezoid............................. 137 turbinated............................ 81 unciform............................. 138 vascular canals of................. 40 Bones, articular extremities of....... 34 articular process of.............. 34 body of................................ 34 borders of............................ 34 canal of.............................. 34 canaliculi of......................... 41 carpal................................. 136 compact substance of............. 36 condyles of.......................... 34 crest of............................... 34 cuneiform, of tarsus............... 155 diaphysis of.......................... 42 distal extremity of................. 34 endosteum of........................ 39 epiphyses of......................... 42 foramen of........................... 34 fossa of............................... 34 head of............................... 34 irregular........;................... 34 lacunae of............................ 41 line of................................. 34 long.................................. 34 marrow of........................... 36 meatus of............................ 34 medulla of........................... 36 medullary cavity of............... 36 index. 647 Bones, metacarpal....................... 138 metatarsal........................... 156 neck of................................ 34 periosteum of....................... 39 process of............................ 34 proximal extremity of............ 34 ridge of.............................. 34 sesamoid....................... 140, 157 shaft of............................... 34 short................................... 34 sinus of.............................. 34 spinous process of................. 34 spongy substance of............... 36 surface of............................ 34 tabular................................ 34 tubercle of........................... 34 tuberosity of........................ 34 vascular canals of.................. 40 Brain.......................... 503, 513, 514 gray substance of........... 503, 505 white substance of.......... 503, 504 ventricles of........... 521, 523, 531 Breasts...................................... 499 Bromine.................................... 21 Bronchi.................................... 448 Bronchial arteries........................ 453 tubes.................................. 453 veins................................... 453 Bronchus, left............................. 449 right................................... 448 Brunner's glands........................ 312 Bulb, olfactory........................... 540 Bundles of muscles...................... 178 Bursae, synovial................... 183, 265 Buttocks.................................... 238 Butyrin.................................... 27 Cjecum...................................... 315 Calcaneum................................. 154 Calcium............................... 21, 25 Calyces.................................... 461 Canal, alimentary....................... 273 anterior dental..................... 77 carotid................................ 65 infra-orbital......................... 77 inguinal.............................. 219 lachrymal............................ 599 naso-palatine....................... 78 posterior dental.................... 77 posterior palatine.................. 79 pterygoid............................ 56 pterygo-palatine.............. 56, 80 sacral................................. 105 semicircular......................... 623 spinal............:.................... 114 Canals, semicircular.............. 622, 623 vascular of bone.................... 40 Canine teeth.............................. 287 Capillaries................................. 337 Capitate papillae......................... 282 Capsular ligaments...................... 48 Capsule of the lens..................... 611 Carbon................................ 21, 25 Carbonate of lime........................ 28 of magnesia.......................... 28 of soda .............................. 28 Carbonic acid............................. 29 Cardiac orifice of stomach............. 305 Carneous columns........................ 345 Carotid canal.............................. 65 Carpal bones.............................. 136 Carpus.............................. 136, 223 Cartilage................................. 171 articular......................... 48, 174 ensiform.............................. 117 Cartilages, costal.................. 114, 116 of the larynx........................ 440 of the nose........................... 589 palpebral............................. 596 permanent........................... 172 temporary......................... 172 Cartilaginous rings of bronchi....... 449 Caruncle, lachrymal..................... 598 Caruncles, myrtiform................... 490 Casein....................................... 26 Cava, inferior............................. 420 superior.............................. 406 Cavernous bodies........................ 476 of clitoris............................ 493 of penis............................... 476 Cavities, nasal............................ 591 Cavity of the uterus..................... 482 Cell, hepatic.............................. 326 organic................................ 22 Cells, spermatic........................... 472 Cellular layer of membranes.......... 259 Cement of teeth................... 289, 291 Centres of ossification.................. 42 Cerebellar falx........................... 538 Cerebellum................................ 526 cortical substance of.............. 527 medullary substance of........... 527 Cerebral falx............................. 538 Cerebro-spinal axis............... 503, 513 liquid................................. 539 Cerebrum.................................. 515 convolutions of............... 515, 516 cortical substance of............... 516 crura of.............................. 516 hemispheres of..................... 515 lobes of. ............................. 515 medullary substance of........... 516 Cerumen.................................... 616 Cervical vertebrae........................ 99 triangles.............................. 199 Chambers of the eye.................... 610 Cheek bone................................ 83 Cheeks...................................... 275 Chest................................. 119, 200 Chlorine.............................. 21, 25 Chloride of sodium..................... 28 of potassium........................ 28 Chloro-hydric acid....................... 28 Cholesterine............................... 29 648 INDEX. 26 ' ...... 502 604 ...... 430 536 604 ....... 267 ....... 339 Chyle....................................... 430 ....... 510 431 ....... 320 605 611, 630 261 Cortical layer of the supra- renal 605 ...... 466 605 substance of cerebellum .. ...... 527 612 ....... 516 Circle of Willis........................... 369 ...... 637 47 ...... 159 282 ...... 116 Clavicle..................................... 129 53 ....... 67 ....... 68 492 ....... 68 Clot of blood.............................. 340 ...... 67 340 333 ....... 69 ....... 502 336 105 ....... 29 ....... 29 624 625 ....... 34 ....... 56 384 ....... 59 26 ....... 52 129 ....... 54 Colon...................................... 315 ....... 479 502 241, 243 502 ....... 57 113 ....... 623 Commissure............................... 514 518 ....... 622 ....... 622 Commissures of brain and spina 519 ....... 441 ....... 52 514 274 ....... 184 ....... 285 526 ....... 222 492 ....... 222 335 ....... 528 613 34 ....... 516 Condyles.................................. .. 222 51 ....... 521 149 ....... 27 133 ....... 610 of inferior maxillary bone...... 85 ....... 632 51 ....... 637 134 ....... 328 409 282 ....... 468 215 ...... 486 597 ....... 77 170 349 292, 293 Convolutions of the cerebrum.. 515, 516 ....... 286 130 pulp............................ 291, 292 130 sacs............................ ....... 292 130 603 ....... 522 ....... 528 519 ....... 290 487 523 ....... 289 ....... 629 INDEX. 649 Descriptive anatomy.................... 17 Diaphragm................................. 221 Diaphysis of bones...................... 42 Dilatation of heart...................... 349 Disks, intervertebral.................... 107 Dorsal vertebrae.......................... 102 Drum of the ear.......................... 616 Duct, common biliary................... 328 cystic................................. 328 hepatic........................ 324, 328 lachrymo-nasal............... 91, 600 lactiferous............................ 501 of glands............................. 269 of Muller............................ 489 pancreatic........................... 320 parotid................................ 279 right lymphatic.............. 430, 432 spermatic............................. 472 submaxillary........................ 279 thoracic........................ 430, 431 Ducts, ejaculatory........................ 474 Duodenal glands.......................... 312 Duodenum.................................. 309 Dura mater................................ 537 Eae.......................................... 612 external.............................. 612 internal.............................. 621 ligaments of.................. 613, 619 middle................................ 616 muscles of..................... 614, 620 small bones of............... 618, 619 wax.................................... 616 Efferent lymphatic vessels............. 429 Egg.......................................... 486 Ejaculatory ducts......................... 474 Elastic tissue.............................. 175 Elbow joint................................ 144 Eminence, nasal.......................... 58 parietal............................... 60 pyramidal.......................... 622 Eminences, mammillary............... 518 Enamel.........................285, 289, 290 organ................................. 293 Endocardium.............................. 347 Endolymph................................ 623 Endosteum................................. 39 Ependyma.................................. 537 Epidermis........................... 259, 631 Epigastric fold........................... 220 region................................ 299 Epiglottis.................................. 441 Epiphyses of bones..................... 42 Epiploic appendages.................... 317 Epithelium................................. 259 ciliated................................ 261 columnar............................. 260 irregular.............................. 260 pavement............................. 260 polyhedral........................... 260 spheroidal........................... 260 squamous............................. 260 Erectile tissue............................ 476 Ergot....................................... 523 Eruption of temporary teeth......... 293 permanent teeth.................... 294 Ethmoidal crest......................... 56 fissure................................. 59 gutters............................... 57 sinuses................................ 57 wings................................. 56 Ethmoid bone............................. 56 Eustachian tube.................. 65, 621 valve.................................. 344 Excretion................................... 267 Extremities, lower....................... 238 upper................................. 223 Eye.......................................... 594 Eyeball.............................. 594, 600 Eyebrow................................... 595 Eyelashes.................................. 597 Eyelids...................................... 595 Eye teeth................................... 287 Face........................................ 87 Facial angle............................... 88 Falciform process................. 240, 243 Fallopian canal.......................... 63 tube................................... 488 False vocal cords........................ 447 Falx, cerebellar.......................... 538 cerebral.............................. 538 Fang of tooth............................ 285 Fascia....................................... 182 cervical............................... 194 cribriform.................... 239, 241 crural........................ 239, 241 deep............................ 224, 239 perineal....................... 497 temporal........................ 185 femoral.............................. 239 ischio-rectal......................... 497 lata.................................... 239 lumbar..................... ......... 218 of the foot........................... 239 palmar................................ 225 pectineal...................... 240, 243 pelvic................................. 496 plantar.............................. 242 recto-vesical........................ 497 sartorial....................... 240, 243 spermatic............................ 469 superficial.............. 212,224, 238 superficial perineal................ 497 superficial temporal............... 185 transverse..................... 216, 218 Fasciculi of muscular fibres ......... 178 Fat tissue..................... ............ 176 Fauces..................................... 276 Femoral arch...................... 214, 243 hernia......................... 243, 244 ring.................................. 243 Femur..................................... 148 Fenestrated membranes................ 334 650 INDEX. Fibre, muscular.......................... 178 Fibres, striated muscular.............. 181 unstriated muscular.............. 271 Fibrils, muscular........................ 181 Fibro-cartilage........................... 173 interarticular................. 86, 142 semilunar............................ 160 Fibro-serous membranes............... 264 Fibrous (issue............................ 167 Fibula...................................... 152 Filaments, homogeneous............... 30 Fimbriated extremity of Fallopian tube................................ 488 body................................... 522 Fingers..................................... 139 Fissure of the anus..................... 238 ethmoidal............................ 59 glenoid.............................. 62 great longitudinal................. 515 longitudinal, of liver.............. 323 oral.................................... 274 transverse, of liver................ 323 of the vulva......................... 492 Flesh........................................ 178 Flexion..................................... 47 Flexure, sigmoid.................. 315, 316 Fluoride of calcium..................... 28 Fluorine.................................... 21 Fold, alar.................................. 162 aryteno-epiglottic.................. 445 axillary.............................. 223 epigastric............................ 220 glosso-epiglottic.................... 445 recto-uterine................. 304, 484 recto-vesical................. 304, 463 semilunar............................ 598 utero-vesical........................ 463 vesico-uterine...........304, 463, 484 Follicular glands........................ 269 Fontanel, anterior...................... 74 lateral................................ 75 posterior............................. 75 Fontanels.................................. 74 Foot.................................. 148, 157 arch of................................ 157 hollow of............................. 157 sole of................................. 157 Foramen, of bone........................ 34 anterior ethmoidal................. 92 anterior palatine............. 78, 90 condyloid............................ 51 coracoid.............................. 130 infra-orbital........................ 77 jugular............................... 69 lacerated............................. 68 obturator............................. 124 of Winslow.......................... 302 optic.................................. ;>5 oval, of sphenoid bone........... 56 of heart........................ 344 posterior ethmoidal............... 92 posterior palatine.................. 90 Foramen, quadrate...................... 223 rotund................................ 56 sphenoidal........................... 55 spheno-palatine.................... 80 spheno-maxillary..........,....... 89 spinous............................... 56 spinal................................. 98 stylo-mastoid...................... 64 supra-orbital........................ 58 Foramina, inter-vertebral............. 98 great sciatic......................... 126 sacral................................. 105 small sciatic........................ 126 Forearm.................................... 223 Fornix...................................... 521 Fossa of bone............................. 34 glenoid............................... 62 hemielliptical....................... 622 hemispherical...................... 622 infra-clavicular.................... 200 infra-spinous....................... 130 intercondy loid...................... 149 ischio-rectal........................ 497 jugular................... 64, 193, 199 navicular............................ 479 pterygo-maxillary................. 89 spheno-maxillary.................. 89 submaxillary....................... 199 subscapular......................... 130 supra-clavicular............ 193, 199 supra-spinous...................... 130 temp oral............................. 88 trochanteric......................... 148 Fossae, cranial, anterior................ 67 middle.......................... 68 posterior....................... 68 inguinal, internal........... 220, 304 external................. 220, 304 nasal.................................. 92 Fourchette................................. 492 Fraena, glosso-epiglottic............... 280 Fraenum, inferior labial............... 275 lingual ............................... 280 preputial............................. 475 superior labial..................... 275 Fringes, synovial.....................49, 265 Frontal bone.............................. 58 Front teeth................................ 286 Fundus, of gall-bladder............... 328 of urinary bladder................ 463 of uterus............................. 482 Furrow, naso-labial..................... 184 Gall-bladder........................... 328 Ganglia..................................... 512 Gangliated cord.......................... 582 Gangliform enlargement of the fa- cial nerve......................... 552 Gangliform plexus....................... 555 Ganglion, inferior cervical............ 584 jugular............................... 555 middle cervical..................... 584 INDEX. 651 Ganglion, ophthalmic................... 544 otic..................................... 550 petrous............................... 554 semilunar, of solar plexus...... semilunar, of trifacial............ spheno-palatine..................... submaxillary........................ superior cervical.................... Ganglionic system of nerves......... Gastric juice.............................. General anatomy........................ Germinal eminence..................... spot.................................... vesicle................................. Gimbernat's ligament............ 215, Glabella.................................... Gland....................................... mammary............................ parotid................................ pineal................................. prostate............................... sublingual........................... submaxillary........................ Glands, agminated............... 312, Bart holine' s......................... bronchial............................. Br unner' s............................ ceruminous.......................... cceliac.......................... ...... convoluted........................... Cowper's............................4 deep inguinal....................... duodenal............................. follicular............................ gastric................................ iliac, external....................... internal........................ intercostal........................... lachrymal........................... lin gual__'............................ lumbar................................ lymphatic..................... 428, mediastinal, anterior............. posterior........................ mesenteric........................... mesocolic............................. odoriferous.......................... palatine.............................. 275 palpebral............................. 596 perspiratory........................ (533 Peyer's............................... 313 popliteal.............................. 437 preputial............................. 476 pulmonary........................... 436 racemose............................. 270 sebaceous............................ 634 • simple follicular.................... 276 solitary.................. 312, 313, 318 suburethral.................. 481, 494 superficial inguinal............... 437 sweat................................. 633 tubular.................. 269, 312, 318 543 546 550 583 512 309 17 486 487 487 243 183 267 500 278 526 480 279 279 313 494 436 312 616 439 270 481 437 312 269 308 437 437 436 598 283 438 429 436 436 438 438 634 Glans of the penis....................... 475 of the clitoris...................... 493 Glenoid cavity............................ 131 fissure................................. 62 fossa.................................. 62 tubercle.............................. 62 Globulin.................................... 27 Glomerule, renal........................ 460 Glosso-epiglottic fraena................. 280 folds................................. 445 Glottis....................................... 447 Glucose.................................... 28 Glycogen................................... 27 Grape sugar.............................. 28 Gray substance.......................... 505 Grinders.................................... 288 Gristle...................................... 171 Groin................................ 212, 238 Groove, bicipital......................... 133 dental.......................... 292, 293 digastric............................. 62 labial................................. 184 labio-mental........................ 184 Gubernaculum of testicle............. 469 Gullet....................................... 297 Gums....................................... 273 Gutters, ethmoidal....................... 57 Guttural region........................... 90 Hairs....................................... 636 Ham......................................... 251 strings................................ 251 Hand........................................ 140 Handle of sternum...................... 117 Hard palate................................ 275 Head........................................ 183 of bone.............................. 34 of muscle............................ 179 Heart........................................ 341 Heel......................................... 238 Helicine arteries......................... 478 Helix....................................... 613 Hemispheres of the cerebellum...... 527 of the cerebrum.................... 515 Hepatic cells.............................. 326 duct........................... 324, 328 substance............................. 324 Hernia...................................... 220 femoral........................ 243, 244 inguinal, direct..................... 221 oblique......................... 220 Hernial sac ................... 220, 244 Hilus of kidneys........................ 458 of spleen............................. 329 of supra-renal bodies............ 466 Hip.......................................... 212 bones................................ 121 joint................................... 159 Hippocampus............................. 522 Hollow of the foot....................... 157 of the knee.......................... 238 Homogeneous filaments.......... 18, 30 052 INDEX. 18 '»9 19-' 18 29 275 19, 30 Labyrinth, of ear................ 621 Horns of the lateral ventricles. 522 623 17 68 132 598 610 80 611 598 600 595 599 612 papillre....................... 595 599 21 599 Hypochondriac regions.......... 490 96 ..80 91 299 438 299 Lamina, membranous spiral.. 626 625 Ileum................................. 310 316 527 Ileo-colic valve.................... 440 Iliac regions....................... 299 445 121 cartilages of................. 44(1 Ilio-pectineal line................ 126 muscles of................... 444 445 124 445 286 Layer, cellular, of membranes...... 259 518 219 202 Ligament, anterior annular... . 138, 225 220 159 internal................ 220, 304 annular, anterior, of the wrist.. 225 hernia, direct............. 221 145 220 241 242 212 616 121 619 28 posterior, of the wri -t...... 225 157 218 Intermuscular partitions........ 182 164 524, 535 107 capsular, between radius and 165 98 107 145 163 98 of astragalus and sc iphoid 313 bone................. 164 309 of calcaneum and cuboid 315 165 309 144 21 159 607 161 21 26 of scapulo- clavicul ir ar- 34 142 121 124 of shoulder joint.... of sterno-clavicular artic- 143 289 141 of tempero-maxilla ry ar- 83 87 310 46 69 199 coraco-acromial............ 146 143 51 193 14'' 143 130 458 costo-clavicular............ 14-' 150 238 costo-transverse, anterior....... 119 160 140 middle and posterioi 119 119 INDEX. 653 Ligament, cotyloid...................... 159 dental................................. 286 denticulate........................... 537 external calcaneo-scaphoid...... 165 lateral, of ankle joint....... 164 of the jaw............... 87 of elbow joint........... 145 of knee joint............ 162 of wrist joint........... 146 glenoid................................ 143 great sacro-sciatic................. 126 ilio-lumbar.......................... 126 inferior calcaneo-cuboid.......... 165 calcaneo-scaphoid............ 165 inter-articular, of rib............. 118 inter-clavicular..................... 142 internal lateral, of ankle joint.. 164 of elbow joint.......... 145 of knee joint............ 162 of wrist joint............ 146 interosseous, of tarsal bones... 164 left lateral, of liver......... 302, 321 long plantar......................... 166 nuchal................................ Ill of the patella................. 161, 249 ovarian............................... 485 palmar, of fingers................. 147 pterygo-maxillary................. 190 radiating............................. 118 round, of hip joint............... 159 of ulna and radius........... 145 of uterus....................... 484 right lateral, of liver...... 302, 321 small sacro-sciatic................. 126 spheno-maxillary.................. 195 stylo-hyoid..................... 64, 96 stylo-maxillary..................... 194 superior calcaneo-cuboid......... 165 supra-spinous........................ Ill sub-pubic............................ 125 suspensory, of the anvil......... 619 of the clitoris................. 493 of the liver............. 302, 321 of the mallet..................- 619 of the penis................... 476 of the spleen........... 302, 329 thyro-epiglottic..................... 443 t ra nsverse........................... 112 triangular........................... 497 vertebral, anterior................. 109 posterior...................... 110 Ligaments, acromio-clavicular....... 142 anterior of the bladder........... 463 arcuate............................... 221 atlo-axoid, anterior............... 112 posterior....................... 112 band-like............................. 48 broad, of the uterus.............. 304 capsular.............................. 48 of the costal cartilages..... 119 of the ribs.............. IIS, 119 costo-sternal........................ 119 Ligaments, crucial....................... 161 dorsal.......................... 147, 165 interosseous......................... 147 of metatarsus................. 165 of tarsus....................... 165 interspinous........................ Ill intervertebral....................... 107 lateral, of the bladder............ 463 lateral, of phalanges.............. 147 occipito-atloid, anterior......... Ill posterior........................ Ill odontoid.............................. 113 of the ear..................... 613, 619 of the liver............ 301, 302, 321 of the metatarso-phalangial ar- ticulations ........................ 166 of the phalangial articulations.. 166 of the tibio-fibular articula- tions............................... 163 of the uterus........................ 484 of the urinary bladder........... 463 of the larynx....................... 442 palmar................................ 147 palpebral............................. 596 sacro-iliac........................... 126 sterno-clavicular.................. 142 thyro-hyoid.......................... 442 vaginal, of fingers................. 226 of the toes..................... 242 yellow.......•.......................... 109 Linea aspera.............................. 148 alba.................................... 217 Line, median, of abdomen............ 217 semilunar, of abdomen........... 217 Lines, transverse, of abdomen...... 217 Lime, phosphate of...................... 28 carbonate of......................... 28 oxalate of............................ 29 Lingual frsenum.......................... 280 Lips.......................................... 274 of the uterus........................ 4S2 Liquid, cerebro-spinal.................. 539 Liquor sanguinis......................... 340 Liver................................. 300, 321 Lobes of a gland........................ 270 of the cerebrum.................... 515 of the liver................... 322, 323 of the lungs......................... 451 of the prostate gland............ 480 Lobules of glands........................ 270 of the liver................... 271, 325 of lungs, primary................. 452 secondary....................... 452 Loins....................................... 211 Lower jaw bone......................... 83 Lumbar regions................... 211, 299 vertebrae............................. 103 Lungs....................................... 450 Lunula...................................... 641 Lymph...................................... 430 corpuscles........................... 430 Lymphatic system....................... 428 654 INDEX. Lymphatic glands................ 428, 429 anterior auricular.......... 434 axillary......................... 435 bronchial....................... 436 cceliac........................... 439 deep cervical.................. 434 deep inguinal................. 437 external iliac.................. 437 intercostal..................... 436 internal iliac................... 437 internal maxillary.......... 434 lumbar.......................... 438 mediastinal, anterior ...... 436 posterior.................. 436 mesenteric................... 438 mesocolic....................... 438 occipital........................ 433 popliteal........................ 437 posterior auricular.......... 433 pulmonary..................... 436 submaxillary................. 434 superficial cervical.......... 434 inguinal.................. 437 trunk, broncho-mediastinal..... 436 intestinal....................... 439 vessels................................ 428 anterior mediastinal........ 436 deep cervical.................. 434 deep facial..................... 434 intercostal....:................ 435 lingual.......................... 434 occipital........................ 433 of the exterior of the tho- rax ........................... 435 of the large intestines...... 438 of the liver.................... 438 of the lower extremities... 437 of the stomach............... 438 of the upper extremities.... 435 pulmonary.................... 436 superficial cervical.......... 434 facial...................... 434 temporal........................ 433 Magnesia, phosphate of............... 28 Magnesium........................... 21, 26 Malar bone................................ 83 Malleolus, internal...................... 152 external.............................. 153 Mallet....................................... 618 Malpighian corpuscles................. 460 Mammae.................. ................. 499 Mammillary eminences................ 518 Manganese................................. 21 Margarin................................... 27 Marrow.............................. 36, 39 Mastoid portion of temporal bone... 62 process................................ 62 sinuses.......................... 62, 620 Matrix of nails........................... 640 Maxillary bone, inferior............... 83 superior........................ 76 Maxiliary sinus. ........................ 76 Meatus...................................... 34 external auditory............ 03, 615 inferior, of the nose............... 94 internal auditory............. 63, 627 middle, of the nose.......... 57, 93 superior, of the nose........ 57, 93 Mediastinal cavities..................... 151 Mediastinum of the testis............. 470 M ediastinum.............................. 451 Medulla............................... 36, 39 oblongata............................ 530 Medullary cavity........................ 36 sheath................................. 505 substance of kidney.............. 459 of supra-renal bodies...... 466 Melanin..................................... 27 Membrane, arachnoid.................. 539 basement............................. 262 fenestrated.......................... 334 mucous................................ 200 of the aqueous humor..... 603, 610 of the tympanum.................. 016 perforated........................... 334 pupillary............................. 608 serous................................. 263 synovial........................ 48, 265 thyro-hyoid.......................... 442 tympanic............................. 616 vocal.................................. 443 Membranous labyrinth................. 623 portion of urethra................. 479 semicircular canals............... 623 Mesentery........................... 301, 303 Mesocolon, ascending........... 301, 303 descending................... 301, 303 transverse..................... 301, 303 Mesorectum........................ 301, 304 Metacarpal bones........................ 138 Metacarpus................................ 138 Metatarsal bones.....'................... 156 Metatarsus................................ 156 Milk......................................... 502 ■globules............................. 502 plasma............................... 502 Mineral bodies............................ 18 Mitral valve............................... 347 Molars..................................... 288 Mons veneris.............................. 491 Motion, ciliary.......................... 261 Mouth...................................... 273 floor of the.......................... 278 roof of the........................... 275 Mucus....................................... 267 Mucous corpuscles...................... 267 membrane........................... 266 gastro-pulmonary............ 266 genito-urinary................ 266 mammary...................... 266 nasal........................... 593 Muscle, accessory flexor............... 256 adductor, great..................... 250 INDEX. 655 Muscle, adductor, long................. 249 of the great toe............... 257 of the little finger............ 237 of the little toe............... 258 of the thumb.................. 236 short............................ 250 anal elevator........................ 499 sphincter....................... 499 anconeous........................... 229 arytenoid............................ 445 biceps flexor........................ 228 biceps flexor of thigh............. 250 brachial.............................. 229 buccinator........................... 190 bulbo-urethral...................... 498 ciliary......................... 187, 605 coccygeal............................ 499 complex............................^. 208 constrictor of the pharynx, in- ferior......................... 296 middle.......................... 296 superior........................ 295 coraco brachial..................... 228 cremaster.........-................... 469 crico-arytenoid, lateral.......... 444 posterior....................... 444 crico-thyroid........................ 444 cruralis .............................. 249 deltoid................................ 227 depressor of the lower lip....... 189 of the oral angle............. 190 digastric............................. 196 dorsal extensor..................... 206 elevator of the lower lip......... 190 of the oral angle............. 189 of the palate.................. 277 of the scapular angle ...... 205 of the upper lip.............. 189 \ extensor, common, of the fin- gers .......................... 233 metacarpal, of thumb....... 235 of the great toe............... 253 of the index finger........... 235 of the little finger............ 235 of the toes, long............. 252 of the toes, short............. 253 phalangial, of thumb, first. 235 phalangial, of thumb, sec- ond ........................... 235 radio-carpal, longer......... 233 radio-carpal, shorter........ 233 ulno-carpal.................... 234 external pterygoid................ 191 flexor, deep, of fingers........... 232 long, of great toe............ 256 of little finger......... 237 of the thumb............ 232 of the toes............... 255 metacarpal, of thumb...... 236 of the little toe............... 258 short, of great toe........... 257 of the thumb........... 236 Muscle, flexor, snort, of the toes..... 256 superficial, of fingers............. 231 gastrocnemius...................... 254 geminous............................. 246 genio-glossal........................ 284 genio-hyoid......................... 197 gluteal, great........................ 244 middle.......................... 245 small............................ 245 gracilis............................... 248 great serrated...................... 202 pectoral........................ 201 hyo-glossal.......................... 284 iliac................................... 247 inferior oblique..................... 209 serrated........................ 206 infra-spinous........................ 226 internal pterygoid................. 191 interosseous of the foot.......... 258 ischio-cavernous................... 498 labio-nasal depressor............ 189 elevator....................... 188 larger straight anterior ......... 198 posterior....................... 209 larger zygomatic................... 189 lateral straight..................... 209 latissimus........................... 294 laxator............................... 620 lingual................................ 284 long cervica]........................ 198 lumbrical..................... 232, 256 masseter.............................. 191 multifid spinal...................... 208 mylo-hyoid........................... 197 nasal compressor.................. 188 dilator........................... 188 pyramidal..................... 186 oblique, external.................. 213 inferior ....................... 602 internal...........,........... 215 superior ....................... 601 obturator, external ............... 246 internal........................ 246 occipito-frontal.................... 185 omo-hyoid........................... 196 oral orbicular.. .................... 188 palato-glossal....................... 278 pharyngeal................... 295 palmar, long........................ 230 short............................ 236 palpebral elevator................. 187 orbicular....................... 187 pectineal.................... ........ 249 peroneal, anterior.................. 252 long............................. 253 short............................ 253 plantar............................... 255 popliteal............................ 255 posterior tibial..................... 256 psoas.................................. 247 small ....................... 247 pyramidal........................... 217 656 INDEX. Muscle, pyriform........................ 246 quadrate femoral................. 246 lumbar......................... 218 pronator........................ 230 quadriceps extensor............... 249 radio-carpal flexor................ 230 rectus................................. 249 rhomboid............................ 205 sacro-lumbar........................ 207 sartorius........................... 248 scalene, anterior................... 197 middle.......................... 197 posterior....................... 198 semi-membranous.................. 251 semispinal........................... 208 semi-tendinous..................... 250 smaller straight anterior......... 198 straight posterior............ 209 small pectoral...................... 202 zygomatic...................... 189 soleus.................................. 254 splenius.............................. 207 stapedius............................. 620 sterno-costal........................ 210 sterno-hyoid........................ 195 sterno-mastoid..................... 195 sterno-thyroid...................... 196 straight, of abdomen............. 216 stylo-glossal......................... 284 stylo-hy oid........................... 196 stylo-pharyngeal................. 295 subclavian.......................... 202 subcutaneous cervical............ 193 subscapular.......................... 226 superciliary.......................... 187 superior oblique.................... 209 serrated......................... 205 supinator, long..................... 233 short............................ 235 supra-spinous...................... 226 tarsal tensor........................ 187 temporal............................. 192 tensor of the ear................... 620 of the femoral fascia........ 248 of the palate.................. 278 terete, greater.................... 227 lesser........................... 226 pronator....................... 230 thyro-arytenoid.................... 444 thyro-hyoid......................... 196 tibial, anterior..................... 252 trachelo-mastoid................... 208 transverse.......................... 215 of foot.......................... 258 transverse perineal................ 499 trapezius............................ 203 triceps extensor.................... 229 sural............................ 254 ulno-carpal flexor................. 230 uvular.............................. 278 vaginal constrictor................. 498 vastus, external.................... 249 Muscle, vastus, internal.............. 249 Muscles.................................... ITS ciliary. .............................. 605 costal elevator...................... 210 form of............................... 179 head of............................... 179 insertion of.......................... 179 intercostal............................ 210 interosseous of the hand......... 23,7 inter-spinal.......................... 209 inter-transverse.................... 209 of eyeball........................... 601 of the larynx....................... 443 origin of.............................. 179 pectinate ............................ 344 straight............................... 601 Muscular fibres........................... 178 striated......................... IS] unstriated...................... 271 fibrils................................. 181 Myolemma................................. 181 Myrtiform caruncles.................. 490 Nails....................................... 640 Nares........................... 92, 184, 588 Nasal bone................................. 81 cavities.......................... 92, 591 fossae.................................. 92 meatuses........................ 93, 591 notch.................................. 77 orifices................................ 92 partition............................. 591 plate.................................. 79 process................................ 77 septum..........................'..... 92 spine................................. 77 Nates........................................ 238 Navel....................................... 212 Navicular fossa........................... 479 Neck........................................ 193 Nerve, auriculo-temporal ............. 548 capsular bodies..................... 510 cells.................................... 505 circumflex......................... 568 crural................................. 574 cutaneous, external............... 566 internal........................ 566 small........................... 566 deep auricular...................... 552 dorsal of penis..................... 578 clitoris........................ 578 external cutaneous, of lumbar plexus............................. 574 fibres........................... 504, 508 frontal................................. 544 genito-crural........................ 573 great auricular..................... 563 sciatic........................... 578 ilio-hypogastric..................... 573 ilio-inguinal......................... 573 inferior dental...................... 549 haemorrhoidal................ 577 INDEX. 657 Nerve, inferior maxillary........543, 548 infra-orbital......................... 552 intercosto humeral................. 572 internal cutaneous of crural.... 576 lachrymal............................ 544 lingual................................ 548 long saphenous..................... 576 median................................ 568 middle cutaneous.................. 575 musculo-cutaneous................ 579 musculo-spiral...................... 570 nasal............................ 544, 547 obturator............................. 574 perineal.............................. 578 peroneal communicating......... 581 phrenic............................. 563 popliteal, external................. 579 internal........................ 579 posterior interosseal............... 570 pterygoid............................. 547 pudendal........................... 578 pudic.................................. 577 radial................................. 570 short saphenous.................... 580 small occipital..................... 563 petrosal........................ 550 sciatic.......................... 578 splanchnic, great........... ...... 585 small............................ 585 third............................ 585 superficial cervical................ 563 superior gluteal..................... 577 maxillary...................... 545 temporal............................. 552 temporo-malar...................... 546 tibial, anterior..................... 579 posterior........................ 581 trifacial.............................. 542 tympanic...................... 552, 554 ulnar................................. 568 zygomatic........................... 552 Nerves...................................... 503 abducent............................. 550 accessory........................... 558 apparent origin of................. 510 auditory.............................. 553 cochlear branch of.......... 626 vestibular branch of........ 623 cardiac.............................. 557 inferior......................... 584 middle.......................... 584 superior....................... 583 cerebral...................... 514, 540 cerebro-spinal.............. 507, 514 cervical.............................. 661 coccygeal............................ 576 ciliary............................... 644 cochlear.............................. 628 deep origin of....................... 510 dental................................. 546 digital............................... 581 facial.................................. 651 Nerves, fibres of......................... ganglionic system of............. glosso-pharyngeal................. hypoglossal......................... inferior gluteal..................... infra-orbital........................ intercostal........................... laryngeal............................ lumbar................................ oculo-motor......................... olfactory............................. ophthalmic.......................... optic.................................. origin of.............................. palatine.............................. pathetic.............................. pharyngeal .................. 557, plantar............................... plexuses of.......................... pneumogastric...................... pulmonary........................... real origin of........................ sacral................................. spheno-palatine..................... spinal......................... 514, subscapular......................... superficial origin of............... supra-clavicular.................... termination of....................... thoracic ...................... 565, vestibular........................... Nervous system........................... Neurilemma.............................. Nipple...................................... Nitrogen...............................21, Nose........................................ back of................................ bridge of............................ cartilages of.................. 590, column of............................ meatuses of.......................... root of....... ...................... sinuses of............................. wings of.............................. Nostrils.................................... Notch, coracoid........................... great sciatic......................... lesser sciatic........................ nasal ................................. semilunar............................ Nucleolus................................... Nucleus.................................... lenticular............................. Nymphae................................... 508 512 553 559 578 546 571 557 572 541 540 543 541 509 547 542 583 581 508 555 557 510 576 546 559 566 510 563 509 570 628 503 505 500 25 588 184 184 591 184 591 184 591 591 184 130 122 123 77 85 23 23 523 493 Obturator foramen................... 124 membrane........................... 125 Occipital angle........................... 52 bone................................... 50 cross................................... 52 protuberances....................... 52 region................................ 9] 658 INDEX. Odontoid ligaments..................... 113 process............................... 101 Oesophageal orifice....................... 222 Oesophagus................................ 297 Olecranon.................................. 135 Olein........................................ 27 Olfactory region.......................... 593 Olivary bodies............................ 530 Omentum, gastro-colic................. 303 gastro-hepatic............... 301, 302 gastro-splenic................ 303, 329 great............................301, 303 Optic commissure.................. 518, 541 tract................................... 541 Orbital entrance......................... 91 plate.................................. 77 Orbits....................................... 91 Organic cells.............................. 22 Organized bodies........................ 18 Orifice, aortic............................. 222 auriculo-ventricular............... 344 oesophageal.......................... 222 urethral.............................. 480 Orifices of the ureters.................. 464 Origin of nerves.......................... 510 Osseous tissue............................. 40 Ossification................................ 42 centres of............................. 42 Otolites .................................... 624 Oval foramen, of heart................. 344 sphenoid bone....................... 56 Oval window.............................. 618 Ovarian ligament........................ 485 Ovaries.................................... 485 Oviduct ..................................... 488 Ovisacs..................................... 486 Ovum....................................... 486 Oxalate of lime........................... 29 Oxygen................................ 21, 25 Pacinian corpuscles.................. 510 Palate....................................... 275 half arches of...................... 276 bone................................... 78 Palatine region........................... 90 Palm.................................. 140, 223 Pancreas........................... 300, 320 Pancreatic juice......................... 321 Pancreatin............................ 27, 326 Papillae of taste.......................... 282 tactile................................. 630 Papillary muscles........................ 345 Parietal bone........................... . 60 Parotid gland............................. 278 Parovarium................................ 487 Partitions, intermuscular........ 182, 239 Patella...................................... 150 Pavilion.................................... 488 Pectinate muscles........................ 344 Pectineal line.............................. 123 Pedicle, olfactory........................ 540 Peduncles of cerebellum......... 528, 529 Peduncles of pineal gland............. 526 Pellucid septum...............'........... 521 Pelvis....................................... 126 cavity of.............................. 494 of kidney............................ 461 Penis ....................................... 475 Pepsin................................. 27, 309 Pericardium............................... 319 Perilymph.................................. 623 Perineum .................................. 496 Periosteum................................. 39 Peritoneum............................... 300 Permanent teeth.......................... 280 Petrous portion of temporal bone... 63 Peyer's glands............................ 313 Phalanges of foot...................... 157 of hand.........................139, 14(1 Phalanx.................................... 139 Pharynx.................................... 294 Phosphorus................................ 21 Pia mater of brain...................... 535 of spinal cord...................... 536 Pimple mite............................... 636 Pineal gland.............................. 526 Pit of the stomacli ............... 200, 212 Pituitary body............................ 518 fossa................................... 53 Plane of the ischiur.i.................... 124 Plate, nasal............................... 79 of malar bone....................... 83 orbital...................... 57, 59, 77 palate............................ 78, 79 Pleura..................................... 454 Plexus, aortic............................. 586 brachial .............................. 563 cardiac................................ 584 carotid............................... 583 cavernous.......................... 583 cervical............................... 562 choroid......................... 523, 536 coronary ............................. 586 dorsi-spinal.......................... 423 gangliform............................ 555 haamorrhoidal................ 319, 424 hepatic................................ 586 hypogastric ........................ 587 intra-spinal ......................... 423 lumbar................................ 573 mesenteric, inferior.............. 586 superior......................... 586 oesophageal.......................... 558 pampiniform........................ 473 pharyngeal ......................... 583 phrenic.............................. 586 prostatic............................. 424 pulmonary........................... 557 renal.................................. 586 reteform............................. 471 sacral ................................ 577 solar................................. 585 spermatic............................ 586 splenic................................ 586 INDEX. 659 Plexus, supra-renal..................... 586 uterine............................... 587 uterovaginal....................... 424 vesical................................ 425 vesico-prostatic................... 587 vesico vaginal...................... 587 Plexuses, nervous....................... 508 venous................................ 336 Pons......................................., 529 Popliteal region................... 238, 251 Potassa, carbonated................... 28 phosphate of........................ 28 urate of.............................. 29 Potassium................................. 25 chloride of.......................... 28 Poupart's ligament...................... 242 Premolars................................. 287 Preperitoneal cavity.................... 217 Prepuce of clitoris...................... 493 of penis.............................. 475 Process, angular, external............ 58 internal........................ 58 articular, of temporal bone.. .. 64 auditory............................. 63 basilar............................... 51 ciliary................................. 605 clinoid, anterior.................... 53 posterior....................... 53 coracoid.............................. 132 coronoid........................ 85, 135 falciform. ........................... 243 frontal................................ 83 lateral, of calcaneum............. 154 long, of the mallet................. 619 malar................................. 78 mastoid............................... 62 nasal.................................. 77 odontoid............................. 101 of bone............................... 34 olivary............................... 53 orbicular............................ 619 orbital.................. ........... 80 pterygoid, external............... 55 internal........................ 55 pyramidal............................ 80 short, of the mallet.............. 619 sphenoidal......................... 80 spinous.............................. 34 of ilium, anterioi ....*........ 122 posterior.................. 122 superior ................ 122 of radius....................... 136 of sphenoid bone............ 55 of temporal bone............ 63 of the tibia................... 151 of vertebrae.............. 98 styloid, of ulna............... 135 transverse, of occipital bone... 51 transverse, of vertebrae........... 98 turbinated, inferior................ 57 superior........................ 57 vaginal................................ 63 Process, vermiform...................... 527 Promontory............................... 617 of the pelvis......................... 126 Prostate gland............................ 480 Prostatic portion of urethra........... 478 Protuberance, occipital, external.... 52 internal...,.......................... 52 mental............................... 84 zygomatic...................... 62, 83 Ptyalin..................................... 27 Pubio symphysis......................... 125 arch................................... 127 Pubis................................. 121, 123 Pulp of cavity............................ 286 of teeth............................... 286 of the spleen........................ 330 Pulsation................................... 350 Pulse....................................... 350 Pupil........................................ 607 Pulmonary circulation.................. 350 Pyloric extremity of stomach......... 305 orifice................................. 305 sphincter............................ 306 valve ................................. 307 Pyramidal bodies........................ 530 Pyramid of the tympanum............ 618 Pyramids, decussation of.............. 531 posterior. ........................... 531 renal.................................. 459 Quadrate foramen.................... 223 Radius..................................... 135 Rami of pubis............................ 123 Ramus of ischium....................... 123 Raphe" of perineum.................... 496 of scrotum........................... 468 of tongue............................. 280 Receptacle of chyle.................... 431 Rectum .................................... 318 Region, guttural......................... 90 occipital.............................. 91 oral.................................... 90 palatine................. ............ 90 Regions of the abdomen............... 299 Renal glomerule ...................... 460 papillae.............................. 459 pyramids............................ 459 Restiform bodies ........................ 531 Reteform plexus.......................... 471 Retina....................................... 608 Ribs ....................................... 114 Ridge, asperous......................... 148 inter-trochanteric.................. 148 molar................................ 84 of bone............................... 34 superciliary........................ 58 temporal........................ 61, 88 Ring, external abdominal...... 213, 219 internal............................. 219 Root of lungs............................ 450 of hairs .............................. 636 660 INDEX. Rostrum.................................... 54 Rotation.................................... 48 Rotund foramen......................... 56 Round window........................... 618 Sac, lachrymal......................... 599 Saccule, spherical ...................... 623 elliptical............................ 623 Sacrum.................................... 104 Saliva....................................... 280 Saphenous opening..................... 240 Scala, tympanic ......................... 626 vestibular............................ 626 Scalp........................................ 184 Scapula.................................. 130 Sclerotica ................................. 602 Sclerotic coat.............................. 602 Scrotum.................................... 468 Sebaceous glands........................ 634 matter................................. 635 Secondary tympanic membrane...... 618 Secretion................................... 267 Semen....................................... 474 Semi-bulbs of the clitoris.............. 493 Semicircular band....................... 524 canals................................ 622 membranous.................. 623 Semilunar fibro-cartilages............. 160 folds................................... 598 valves.......................... 346, 347 Seminal liquid..................... 474, 472 vesicles............................... 473 Seminiferous tubules............ 471, 472 Septal fibres ............................. 531 Septula of testicles...................... 470 Septum, osseous nasal.................. 92 pellucid.............................. 521 Serum....................................... 340 Sexual differences of the pelvis...... 128 Shaft of bone............................. 34 Shin......................................... 151 Shin bone.................................. 150 Shoulder blade........................... 130 Sigmoid flexure of the colon.......... 315 Sinews...................................... 180 Sinus, anterior occipital............... 411 cavernous............................ 411 circular............................. 418 circular, of the iris................ 601 frontal................................ 60 inferior longitudinal............... 410 petrosal......................... 411 lateral................................ 409 maxillary........................... 76 of bone............................... 34 posterior occipital................. 412 straight............................... 410 superior longitudinal............. 410 petrosal....................... 411 Sinuses, sphenoidal..................... 54 ethmoidal........................... 57 lactiferous........................... 501 Sinuses, mastoid................... 62, 620 of dura mater............... 409, 538 venous................................ 336 Soda, carbonate of...................... 28 phosphate of......................... 28 taurocholate of..................... 29 urate of............................... 29 Sodium................................ 21, 25 chloride of........................... 28 Skeleton................................... 33 Skin......................................... 628 Skull................................... 85, 87 Smegma.................................... 476 Soft epidermic layer.................... 633 Soft palate................................. 275 Solar plexus.............................. 585 Sole.......................................... 157 Space, anterior, perforated............ 519 posterior " ............ 518 Special anatomy......................... 17 Sperm cells............................. 472 Spermatic cones.......................... 471 cord.................................... 469 duct............................ 471, 472 liquid................................. 472 Spermatozoids .................... 474, 472 Sphenoid bone...........................-. 52 Sphenoidal foramen..................... 55 Spinal cord....................... 513, 633 columns of........................... 534 commissures of.................... 533 fissures of. .......................... 533 gelatinoid substance of............ 535 gray substance of.................. 505 horns of ............................. 534 white substance of ............... 504 Spine, nasal.............................. 77 of scapula........................... 131 palate................................. 79 Sphincter of the anus.................. 319 of the bladder..................... 464 Spinous foramen......................... 56 Spiral lamina, osseous................. 625 membranous........................ 626 tract.................................. 628 Spleen...................................... 329 Splenic corpuscles...................... 330 Spongy body, of clitoris............... 493 of penis.............................. 477 portion of urethra................. 479 Squamous portion of temporal bone. 61 Sternum..................................... 117 Stirrup.................................... 019 Stomach ................................... 305 pit of. ............................... 211 position of........................... 299 Strait, inferior, of pelvis....... 127, 494 superior " ....... 127,494 Striated body............................. 523 Stroma of the ovary......... ............ 485 Sub-arachnoid space.................... 539 Sub-arachnoid tissue................... 264 INDEX. 661 Submaxillary gland..................... 279 Sub-mucous tissue...................... 266 Sub-serous tissue ...................... 264 Substance of bone...................... 36 Superciliary ridge........................ 58 Suprarenal bodies...................... 465 Sutures................................ 46, 66 dentated............................. 46 of the cranium..................... 66 of the face..................... 86, 90 serrated.............................' 46 squamous............................. 46 Sweat........................................ 034 duct.................................... 633 glands................................ 633 Sylvian fissure........................... 515 Sympathetic system of nerves........ 581 Symphysis................................. 46 of inferior maxillary bone...... 84 pubic.................................. 125 sacro-iliac........................... 125 Synovia............................... 49, 265 Synovial bursae................... 183, 265 fringes.......................... 49, 265 membranes..................... 48, 265 Systemic circulation..................... 351 Tactile corpuscles............. 511, 630 papillae................................ 630 Tapetum.................................... 607 Tarsal bones.............................. 153 Tarsus....................................... 153 Teeth....................................... 285 bicuspid.............................. 287 canine................................. 287 eruption of........................... 293 eye.................................... 287 front.................................... 286 jaw.................................... 288 milk................................... 288 permanent.................... 285, 286 stomach.............................. 287 temporary..................... 285, 288 Temple...................................... 183 Temporal bone........................... 61 fossa................................... 88 regions................................ 183 Tendinous cords.......................... 346 Tendon of Achilles...................... 254 Tendons....................... 178, 180, 182 Tentorium................................. 538 Testicles.................................... 468 Thalami.................................... 524 Thalamus............... .................. 524 Thoracic aorta............................ 381 duct..................................... 431 Thorax...................................... 119 Throat................................ 193, 294 Thymus body............................. 456 Thyroid body............................. 455 cartilage ............................. 440 Tibia........................................ 150 Tissue, adipose........................... 176 areolar.............................. 170 connective ........................... 170 elastic................................. 175 fat...................................... 176 fibrous................................ 167 sub-archnoid........................ 264 sub-serous........................ 264 Toes......................................... 157 Tongue...................................... 280 Tonsils..................................... 276 Tonsils of the cerebellum............. 528 Topographical anatomy................ 17 Trabeculae of penis ..................... 476 of spleen............................. 330 Trachea.................................... 447 Tract, spiral.............................. 628 Tricuspid valve........................... 345 Trochanters................................ 148 Trunk of skeleton....................... 96 Tubercle................................... 34 mental................................ 84 Tuberosity................................. 34 Tunics of the eye........................ 600 Turbinated bone ........................ 81 Tympanic membrane.................... 616 secondary......................... 618 Tympanum................................ 616 Ulna........................................ 134 Umbilical region......................... 299 Umbilicus ................................. 212 Urachus.................................... 463 Urea.................................... 29, 462 Ureter..................................... 461 Ureters...................................... 458 Urethra.............................. 465, 478 Urinary bladder......................... 462 Urine....................................... 462 Uriniferous tubules ..................... 460 Uroerythrin............................... 29 Uterus...................................... 481 Utricle.............'......................... 474 Uvula....................................... 275 of the cerebellum.................. 528 vesicle................................ 464 Vagina........................ ............ 489 Valley...................................... 527 Valve, ileo-colic.......................... 316 mitral................................. 347 of the brain......................... 529 pyloric................................ 307 tricuspid............................. 345 Valves of veins........................... 336 semilunar..................... 346, 347 Valvulae conniventes.............. 266, 310 Vas deferens.............................. 472 Vein, angular ............................ 414 axillary .............................. 417 azygos................................. 419 basilic................................ 418 662 INDEX. ......... 406 41'! ............ 406 41? ........... 418 412 41" .......... 422 41" ........... 116 ........... 425 .......... 425 of penis............. 4"3 ........... 414 423 ........... 426 424 ........... 414 419 .......... 425 121 ........... 424 414 ........... 406 406 ........... 406 120 ........... 415 right........................... 119 .......... 413 ........... 413 107 423 .... 408, 409 408 mastoid................... ........... 413 114 ........... 416 I "3 .......... 419 423 cephalic............. ........... 419 421 .......... 422 414 superior............. ......... 422 419 ........... 420 413 .......... 416 414 .......... 413 419 .......... 414 421 .......... 416 415 .......... 426 421 ... 405, 421 424 .......... 415 453 .......... 125 421 .......... 418 421 ........... 416 414 .......... 419 superficial, of lower extremity. 426 ........... 422 417 .......... 426 414 .......... 426 416 490 supra-renal......................... 421 .......... 417 ulnar cutaneous................... 415 .......... 414 425 ........... 414 utero-vaginal plexus of.......... 124 .......... 413 336 .......... 415 425 ........... 414 535 ......... 414 336 , . .415 .......... 414 336 521 .......... 407 531 .......... 413 .......... 415 521 ......... 407 343 ... 335, 405 of the larynx...................... 445 .......... 415 Vermiform appendix.................... 315 ......... 415 527 .......... 417 97 .......... 453 99 .......... 414 102 ......... 406 103 .......... 412 103 INDEX. 663 Vertebrae, true........................... 97 Vertebral column.................. 97, 113 Vertex...................................... 184 Vesical sphincter........................ 464 triangle.............................. 464 uvula................................. 464 Vesicles, seminal........................ 473 Vesico-uterine pouches..... ........... 304 folds.................................. 304 Vessels afferent.......................... 429 efferent............................... 429 lymphatic............................ 428 Vestibule.................................. 494 of the ear............................ 621 of the labyrinth.................... 621 Villi......................................... 311 Vitelline membrane..................... 487 Vitreous humor.......................... 611 table of bone........................ 65 Vocal cords..........................443, 446 false............................. 447 membrane........................... 443 Vomer...................................... 82 Vulva...................................... 491 White substance....................... 505 of the eye..................... 598, 602 Windpipe.................................. 447 Window, oval............................. 618 round............................ ... 618 Wings of the sphenoid bone.......... 54 ethmoidal............................ 56 Womb...................................... 481 Wrist........................................ 136 joint.................................. 146 Yelk....................................... 487 Yellow ligaments....................... 109 spot................................... 609 Zone, ciliary.............................. 612 Zygoma................................... 62 Zygomatic arch..................... 88, 89 •^"