'.■%'•':;«■?•, SKfi i Jftifc j.->i < 3$ fit* ?•/«' *V;..-. •: w ». ■; *•... ,- >b;n^ ! tot''-' ■ •: -."»>*' • i'-/ * ':*, .." .' uttr .■.m< ' .\ . •• >•■••■ v. ■• V.V.' ■.' : ~ .1. / (I 9 0 GfYV\ vOl^- WILSON'S HUMAN ANATOMY. A SYSTEM 0 F HUMAN ANATOMY, GENERAL AND SPECIAL. BY ERASMUS WILSON, F.R.S., AUTHOR OF "THE DISSECTOR'S MANUAL," "A TREATISE ON DI8EASES OF THE SKIN," ETC. ETC. A NEW AND IMPROVED AMERICAN, FROM AN ENLARGED LONDON EDITION. EDITED BY WILLIAM II. GOBRECIIT, M.D., PROFESSOR OF ANATOMY IN THE PHILADELPHIA COLLEGE OF MEDICINE, FELLOW OF THE COLLEGE OF PHYSICIANS OF PHILADELPHIA, ETC. WITH THREE HUNDRED AND NINETY-SEVEN ILLUSTRATIONS ON V/003 PHILADELPHIA: BLANCIIARD AND LEA. 1858. Entered, according to the Act of Congress, in the year 1858, by BLANCHARD AND LEA, in the Clerk's Office of the District Court of the United States for the Eastern District of Pennsylvania. collin's, printer. \rV74 7 B~ / B S3 c;/ NATIONAL LIBRARY OF MEDICINE BETHESDA 14, MD, - AMERICAN PUBLISHERS' ADVERTISEMENT. In presenting a new edition of "Wilson's Human Anatomy," the publishers have only to express the hope that it will be found to merit a continuance of the very distinguished favor with which it has been hitherto received. The extensive additions made by the hand of the author, in successive revisions, are indicated by the fact that it contains fully one-fourth more matter than the previous American edition, rendering a smaller type, and an enlarged page, necessary to keep the volume within a convenient size. The engagements of the former editor, Dr. Goddard, being such as to prevent his taking charge of the work, it has been placed in the hands of Dr. Gobrecht, who has made such additions as his experience of the wants of students has suggested as desirable, including an Introductory Chapter of a general character, containing such preliminary information as appeared necessary to facilitate the progress of those commencing the study of anatomy. The num- ber of woodcuts has also been largely increased by the addition of about one hundred and thirty illustrations, selected from various authorities, which, it is hoped, may assist the student to an easy comprehension of the text. These, and such notes as are intro- duced, are distinguished by inclosure in brackets [ ]. The utmost care has been employed throughout to render the text correct, and to verify all the references to the illustrations; and some few errors, which had escaped the attention of the author, or of his assistants, have thus been removed. Although the English edition is still known by the name of "The Anatomist's Vade Mecum," the publishers find, in the increased size of the work, an additional motive for retaining the title of "A System of Human Anatomy," by which it has been so long and so favorably known to the American profession. Philadelphia, September, 1858. ( vii ) AUTHOR'S NOTE TO THE SEVENTH EDITION. The present Edition has been carefully revised and corrected; many parts, especially those relating to Histological Anatomy, have been rewritten, and a considerable addition has been made to the number of the Woodcuts. The Author, therefore, feels some confidence and satisfaction in presenting this Edition to his Readers; and trusts that the Anatomist's Vade Mecum may con- tinue to deserve the favor which it has hitherto received at the hands of the Student of Medicine. 17 Henrietta Street, Cavendish Square, 1857. (he) PEEFACE. In presenting for the Sixth time a new Edition of the Anato- mist's Vade Mecum to my brethren of the profession of medicine, it gives me great and heartfelt satisfaction to have the opportunity of announcing, that, in the preparation of the present Edition, I have received the valuable aid of a distinguished Professor of Medicine of northern Europe, Andreas Retzius, M. D., F. R. Acad. S., Master of Surgery, Dean, and Professor of Anatomy in the Royal Caroline Institute of Stockholm — a man justly renowned in the science of our art. The assistance of Professor Retzius is the more gratifying to me, as being the spontaneous offering of a great and distinguished man of science to a humble but zealous fellow-laborer; and his appro- bation has served as a stimulus to me to make the present Edition not unworthy of the praise which he has kindly bestowed upon it. "I use your Anatomist's Vade Mecum," he observes, "for my stu- dents in the dissecting-room. It has become my favorite manual for young students; for I find that, by it, they get a clearer and quicker insight into the study of Anatomy, than by any other book. These are my reasons for interesting myself in its success, and for contributing my remarks for its emendation." In pursuance of these observations, Dr. Retzius had conveyed to me an interleaved copy of the work containing many notes for its improvement; and, furthermore, took the trouble of sending to me, from across the seas, a preparation of the ligaments of the foot, showing the ligament to which he has given the name of liga- Ui) xii preface. mentum fundiforme (page 280). More deeply cherished is the pro- mise conveyed in the following passage : " If the Almighty God will continue to bless me with health and life for some years longer, I will assist you in revising every new Edition, and introducing all those new discoveries in anatomy which may be of use to the Stu- dent of Medicine." While thus acknowledging the assistance given to me by the great Scandinavian Professor, it may not be out of place to put on record an act of liberality, in connexion with this book, from another foreign source, namely, from the well-known medical pub- lishers of Philadelphia, Messrs. Blanchard and Lea. The following extract from a letter addressed to me by them, and bearing date April 4, 1854, will explain the incident to which I refer. "You may perhaps be acquainted with the name of our house as having published in this country your works on Anatomy and Dis- eases of the Skin. When English works which we issue are suc- cessful, it always affords us pleasure to make the author an acknowledgment more substantial, if not more gratifying, than the transatlantic reputation thus obtained; and we accordingly take pleasure in handing you the annexed draft, which we trust you will do us the favor to accept." With the above encouraging passages in the annals of the Ana- tomist's Vade Mecum, I now conclude, trusting that my reader, and those for whom the book was specially written, may find no reason to utter a judgment less favorable than the foreign reputation and wide circulation of the volume would seem to justify. 17 Henrietta Street, Cavendish Square, 1854. CONTEXTS. CHxiPTER I. INTRODUCTORY. PAGE Classification of natural objects . . 27 Definition of anatomy......27 Divisions of anatomy......27 Stcechiology........28 Simple chemical elements ... 28 Immediate principles.....28 Tabular classification .... 29 PAGE Histology.........32 Simple structural elements ... 32 The tissues........35 Tabular classification .... 36 Properties........38 Groups of organs.......39 CHAPTER II. OSTEOLOGY. Definition.........41 Chemical composition of bone ... 41 Division of bones into classes ... 41 Structure of bone.......42 Development of bone......44 Periods of ossification.....47 The skeleton........48 Vkrtkbral column......48 Cervical vertebrae......49 Dorsal vertebras.......51 J Lumbar vertebras......51 General considerations .... 52 Development........53 Attachment of muscles .... 54 Sacrum.........55 Coccyx..........57 The skull.........57 Bones of the cranium ..... 57 Occipital bone ...... 57 Parietal bone.......CO (xiii ) XIV CONTENTS. Frontal bone....... Temporal bone...... Sphenoid bone ...... Ethmoid bone....... Bones of the face...... Nasal......... Superior maxillary..... Lachrymal bone...... Malar bone....... Palate bone....... Inferior turbinated bone . Vomer......... Inferior maxillary..... Table of developments, articulations, &c.......... Sutures......... Regions of the skull..... Superior region...... Lateral regions...... Base of the skull...... Face.......... Orbits.......... Nasal fossae........ Teeth......... Structure........ Development....... Growth......... Eruption........ Succession......., 61 G3 67 70 73 75 76 79 80 82 82 80 83 83 85 90 91 92 94 96 98 98 Os hyoides.........98 Thorax and upper extremity . . ''-J Sternum.........99 Ribs..........100 Costal cartilages......102 Clavicle.........102 Scapula.........103 Humerus.........105 Ulna..........107 Radius..........108 Carpal bones........109 Metacarpal bones......112 Phalanges.........113 Pelvis and lower extremity . . .113 Os innominatum.......113 Ilium.........114 Ischium.........115 Os pubis........115 Pelvis as a whole......117 Axes..........117 Diameters........117 Femur..........119 Patella..........121 Tibia..........121 Fibula..........122 Tarsal bones...... . .124 Metatarsal bones......127 Phalanges.........128 Sesamoid bones........129 CHAPTER III. THE LIGAMENTS. Forms of articulation......129 Synarthrosis........129 Amphi-arthrosis.......130 Diarthrosis........130 Movements of joints......131 Gliding..........131 Angular movement . . . . . .131 Circumduction.......131 Rotation.........131 General anatomy of articular struc- tures ..........131 Cartilage.........132 True cartilage......132 Reticular cartilage.....133 Fibrous cartilage......133 Fibrous tissue.......134 CONTENTS. XV White fibrous tissue.....134 Ligament.......134 Tendon........134 Yellow fibrous tissue . . . .135 Adipose tissue.......135 Synovial membrane.....136 Ligaments of the trunk . . . .137 Articulation of vertebral column . 137 of Atlas with occipital bone . .139 " Axis with occipital bone . . 140 " Atlas with axis.....141 " Lower jaw.......142 " Ribs with vertebrae .... 144 " Ribs with sternum, and to- gether .......145 " Sternum.......147 " Vertebral column with pelvis . 147 " Pelvis........147 Ligaments of the upper extremity 150 Sterno-clavicular articulation . . 150 Scapuloclavicular articulation . .151 Ligaments of the scapula . . . . 152 Shoulder joint.......152 Elbow joint........153 Radio-ulDar articulation .... 154 Wrist joint........155 Articulations of the carpal bones . 156 Carpo-metacarpal articulations . . 157 Metacarpo-phalangeal articulation 158 Articulation of the phalanges . . 158 Ligaments of the lower extremity 158 Hip joint.........159 Knee joint........160 Articulation of tibia and fibula . .163 Ankle joint........164 Articulation of the tarsal bones . 165 Tarso-metatarsal articulation . .167 Metatarso-phalangeal articulation . 167 Articulation of the phalanges . .167 CHAPTER IV. THE MUSCLES General anatomy of muscle .... 168 Nomenclature.......168 Structure.........169 Muscles of the head and neck . . 172 Muscles of the head and face . . 172 Cranial group.......173 Orbital group.......174 Ocular group.......176 Nasal group.......179 Superior labial group . . . .181 Inferior labial group . . . . 182 Maxillary group......183 Auricular group......185 Muscles of the neck.....186 Superficial group.....186 Depressors, os hyoides and larynx 188 Elevators of the os hyoides . . 189 Muscles of the tongue .... 191 Muscles of the pharynx . . . 193 Muscles of the soft palate . . .195 Praevertebral muscles . . . .196 Laryngeal group......198 Muscles of the trunk.....198 Muscles of the back.....198 First layer........199 Second layer.......201 Third layer.......202 Fourth layer.......203 Fifth layer........206 Sixth layer.......207 Table of origins and insertions . 210 Muscles of the thorax.....212 Muscles of the abdomen .... 213 Table of actions of muscles . . . 221 CONTENTS. Muscles of the perineum . . 222 Male perineum . . . 222 225 Muscles of the upper extremity 227 Anterior thoracic region . . . 228 Lateral thoracic region . . . 229 Posterior scapular region . . 230 232 Anterior humeral region . . . 232 Posterior humeral region . . . 234 Anterior brachial region . . . 235 Posterior brachial region . . . 238 ?A?, Table of actions of muscles . • • 24o Muscles of the lower extremity . 247 Gluteal region.......-48 Anterior femoral region .... 251 Internal femoral region .... 253 Posterior femoral region .... 255 Anterior tibial region.....257 Posterior tibial region.....258 Fibular region.......261 Foot..........262 Dorsal region.......262 Plantar region......262 Table of actions of muscles . . . 266 CHAPTER V. THE FASCIiE. General anatomy.......268 Fascle of the head and neck . . 269 Temporal fascia.......269 Cervical fasciae.......269 Fasciae of the trunk.....270 Thoracic fascia.......270 Fascia transversalis.....271 Oblique inguinal hernia. . . . 271 Congenital hernia......272 Encysted hernia......273 Direct inguinal hernia .... 273 Fascia iliaca........273 Fascia pelvica.......273 Obturator fascia.......275 Perineal fasciae.......275 fasciie of the upper extremity . . 276 Fasciae of the lower extremity . . 277 Fascia lata........277 Femoral hernia......280 Plantar fascia.......281 CHAPTER VI THE ARTERIES. General anatomy of arteries .... 281 Inosculations........282 Structure.........283 Capillaries........285 Aorta...........286 Table of branches......288 Coronary arteries.......288 Arteria innominata......289 Common carotid arteries.....289 External carotid artery.....290 Table of branches......291 Superior thyroid artery .... 292 Lingual artery.......292 Facial artery........292 CONTENTS, Sterno-mastoid artery.....294 Occipital artery.......294 Posterior auricular artery . . . 294 Ascending pharyngeal urtery . . 294 Parotidean arteries......294 Temporal artery.......295 Internal maxillary artery .... 295 Internal carotid artery.....298 Ophthalmic artery......299 Anterior cerebral artery .... 300 Middle cerebral artery . . . .301 Subclavian artery.......301 Table of branches......303 Vertebral artery......303 Basilar artery.......303 Circle of Willis......304 Internal mammary artery . . . 305 Inferior thyroid artery .... 306 Supra-scapular artery.....306 Transversa colli artery .... 306 Superior intercostal artery . . 307 Axillary artery........307 Table of branches......308 Brachial artery........310 R-adial artery........311 Ulnar artery.........313 Thoracic aorta ; branches .... 316 Abdominal aorta; branches . . . 317 Phrenic arteries.......317 Coeliac axis........317 Gastric artery.......317 Hepatic artery.......317 Splenic artery.......319 Superior mesenteric artery . . . 820 Spermatic arteries......321 Inferior mesenteric artery . . . 321 Renal arteries.......323 Common iliac arteries......323 Internal iliac artery......324 Ischiatic.........325 Internal pudic artery.....326 External iliac artery......328 Femoral artery........329 Popliteal artery.......333 Anterior tibial artery......334 Dorsalis pedis artery......335 Posterior tibial artery.....337 Peroneal artery.......337 Plantar arteries........338 Pulmonary artery.......340 CHAPTER VII THE VEINS. General anatomy.......341 Valves of veins.......343 Veins of the head and neck . . . 343 Veins of the exterior of the head . 344 Veins of the diploe......345 Cerebral and cerebellar veins . . 340 Sinuses of the dura mater . . . 346 Veins of the neck......348 Veins of the upper extremity . . 349 Veins of the lower extremity . . 351 2 Veins of the trunk......352 Vena? innominatee......353 Superior vena cava......354 Iliac veins.........354 Inferior vena cava......354 Azygos veins........355 Vertebral and spinal veins . . . 356 Csirdiac veins.......356 Portal vein........357 Pulmonary veins......358 X V 111 CONTENTS. CHAPTER VIII. THE LYMPHATICS General anatomy.......359 Lymphatics of head and neck . . . 362 Lymphatics of upper extremity . . 363 Lymphatics of lower extremity . . . 363 Lymphatics of the trunk.....364 Lymphatics of the viscera Lacteals..... Thoracic duct .... Ductus lymphaticus dexter 365 366 367 368 CHAPTER IX. THE NERVOUS SYSTEM. General anatomy.......368 The brain . .■.......383 Membranes of the encephalon . . 383 Dura mater.......383 Arachnoid membrane .... 386 Pia mater........387 Cerebrum.........387 Lateral ventricles.....389 Fifth ventricle......392 Third ventricle......393 Fourth ventricle......395 Lining membrane of ventricles . 396 Cerebellum........396 Base of the brain......398 Medulla oblongata......401 Spinal cord........402 Cranial nerves.......405 Spinal nerves........425 Cervical nerves.......426 Cervical plexus .....426 Brachial plexus......429 Dorsal nerves.......436 Lumbar nerves.......438 Lumbar plexus......438 Sacral nerves.......443 Sacral plexus.......444 Sympathetic system......449 Cranial ganglia.......440 Cervical ganglia.......453 Thoracic ganglia......456 Lumbar ganglia.......457 Sacral ganglia.......458 CHAPTER X. ORGANS OF SENSE Organ of smell.......458 Nose..........459 Nasal fosste........460 Organ of vision.......4qo Eyeball.........4^0 Sclerotic coat and cornea . . . 4G2 CONTENTS. XIX Choroid coat .... Ciliary ligament ; iris . Retina; zonula ciliaris . Humors...... Physiological observations Appendages of the eye Lachrymal apparatus . Organ of hearing . . . External ear..... Pinna...... Meatus auditorius . . Middle ear or tympanum . Ossicula auditus . . . Muscles of the tympanum 464 465 466 467 469 469 471 473 473 473 475 475 475 477 Internal ear or labyrinth .... 479 Vestibule........479 Semicircular canals.....480 Cochlea.........481 Membranous labyrinth .... 483 Organ of taste.......484 Tongue.........484 Organ of touch.......486 Skin..........486 Appendages of the skin .... 489 Nails..........489 ■ Hair..........489 Sebiparous glands.....490 Sudoriparous glands .... 491 CHAPTER XI. THE VISCERA. Thorax..........492 Heart..........492 Structure of the heart .... 500 Organs of respiration and voice . . 503 Larynx.........503 Trachea and bronchi .... 509 Thyroid gland.......510 Lungs.........511 Pleurae.........514 Mediastinum.......514 Abdomen.........515 Peritoneum........517 Alimentary canal......520 Cheeks.........521 Gums.........521 Palate.........521 Tonsils.........522 Fauces.........522 Mucous glands......522 Salivary glands......524 Pharynx........526 Stomach........527 Small intestine......528 Large intestine......529 Structure of the intestinal canal . 531 Liver..........543 Gall-bladder........552 Pancreas......... 553 Spleen..........554 Supra-renal capsules.....556 Kidneys.........558 Pelvis..........562 Male pelvis........562 Bladder.........562 Prostate gland ...... 565 Vesiculos seminales.....566 Male organs of generation . . . 567 Penis.........567 Urethra........569 Testes........572 Female pelvis.......575 Bladder.........576 Urethra........576 Internal organs of generation . 577 Vagina........ 577 Uterus........578. Fallopian tubes.....580 Ovaries ........582 External organs of generation . 584 Mammary glands.......580 XX CONTENTS. CHAPTER XII. ANATOMY OF THE FffiTUS. Osseous system........588 Ligamentous system......589 Muscular system.......589 Vascular system.......589 Foetal circulation......589 Nervous system.......590 Organs of sense.......591 Eye.......... 591 Ear..........591 Nose.........591 Thyroid gland........591 Thymus gland........591 Foetal lungs.........594 Fcetal heart.........595 Viscera of the abdomen.....595 Omphalo-meseuteric vessels . . . 595 Alimentary canal......595 Spleen..........595 Liver..........596 Kidneys.........596 Supra-renal capsules.....596 Viscera of the pelvis......596 Testes..........597 Descent.........597 LIST OF ILLUSTRATIONS. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. PAGE Vegetable nucleated cells ... S3 Formation of animal nucleated cells.........33 Cells..........33 Endogenous cell development . . 34 Multiplication of cells by division, 34 Cytoid corpuscles......35 Development of red blood-corpus- cles .........35 Development of striated muscular fibre.........36 Epithelial plates......37 Pigment-cells.......37 Development of cartilage ... 37 Id. advanced stage ... 37 Id. more advanced stage . 37 Ligneous cells.......37 Formation of fibres.....38 Haversian canals......42 Intimate structure of bone ... 42 Section of femur......43 Lacunae of osseous tissue ... 44 Periosteum........44 Development of bone .... 45 Id. advanced stage ... 46 Id. more advanced stage . 46 Young femur.......47 Cervical vertebra......49 Atlas..........49 27. Axis........ 28. Dorsal vertebra . . . 29. Lumbar vertebra .... 30. Section of spinal column 31. Development of vertebrae 32. Development of vertebral epiph y 33. Sacrum: anterior face . , 34. Sacrum: posterior face . 35. Coccyx....... 36. Occipital bone : external face 37. Occipital bone: internal face 38. Development of occipital bone 39. Parietal bone: external face 40. Parietal bone: internal face 41. Frontal bone: external face 42. Frontal bone: internal face 43. Development of frontal bone 44. Temporal bone : external face 45. Meatus auditorius . . . 46. Temporal bone: internal face 47. Meatus auditorius internus 48. Tympanic bone .... 49. Sphenoid bone: superior face 50. Sphenoid bone : anterior face 51. Ethmoid bone..... 52. Nasal bone: internal surface 53. Nasal bone: external surface 54. Superior maxillary bone: exter nal surface...... (xxi) 73 XXll • LIST OF ILLUSTRATIONS. 56. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71, 72. 73. 74. PAGE Superior maxillary bone: inter- nal surface.......74 Lachrymal bone......76 Malar bone.......76 Palate bone : internal surface . 77 Palate bone: external surface . 78 Inferior turbinated bone: inter- nal view........79 Inferior turbinated bone: exter- nal view........79 Vomer . . ......80 Inferior maxillary bone ... 81 Skull: anterior view .... 84 Base of the skull: interior . . 85 Base of the skull: exterior . . 87 Section of cranium and face . . 88 Nasal fossa; turbinated bones . 90 Permanent teeth.....91 Temporary teeth.....92 Section of molar tooth ... 93 Development of teeth: at four- teenth week.....94 Id. the various stages . . 96 Id. Pulp cavity and enamel sac........96 Id. tooth-sacs of an eight months' foetus.....97 Gubernaculum dentis .... 98 Os hyoides.......99 Sternum :.......99 Thorax.........101 Rib..........101 First rib........102 Clavicle........103 Scapula: anterior face. . . . 104 Scapula: axillary border . . . 104 Scapula: posterior face . . . 105 Humerus........106 Ulna and radius......107 Bones of the carpus, dorsum . 109 Hand: anterior view . . . .111 Os innominatum......114 Development of os innomina- tum .........116 Female pelvis: anterior view. . 117 FIG. FACE 93. Male and female pelves . . .118 94. Femur: anterior view . . . .119 95. Femur: posterior view . . . 120 96. Patella: anterior view. . . . 121 97. Patella: postorior view . . . 121 98. Tibia and fibula: anterior view . 122 99. Tibia and fibula: posterior view 123 100. Foot: dorsal surface .... 124 101. Foot: plantar surface .... 127 102. Articular cartilage: its cells near the bone.......132 103. Articular cartilage: its cells fur- ther from the bone .... 132 104. Articular cartilage: its cells near the free surface.....132 105. Reticular cartilage.....133 106. Fibrous cartilage '.....133 107. White fibrous tissue .... 134 108. Yellow fibrous tissue . . . .135 109. Fat vesicles.......136 110. Serous epithelium.....136 111. Ligaments of vertebrae and ribs.........137 112. Posterior common ligament . . 138 113. Intervertebral substance . . .138 114. Intervertebral substance . . .138 115. Ligamenta subflava . . . .139 116. Ligaments of atlas, axis, and oc- cipital bone......140 117. Id. posterior view . . .140 118. Id. internal view . . .141 119. Id. internal view . . . 141 120. Ligaments of the lower jaw . .142 121. Id. internal view . . . 143 122. Id. section.....143 123. Ligaments of vertebrae and ribs . 144 124. Ligaments of vertebral column and ribs.......144 125. Middle costo-transverse ligament 145 126. Costo-sternal articulations: ante- rior view.......146 127. Costo-sternal articulations: pos- terior view.......146 128. Costo-sternal articulations: in section........146 LIST OF ILLUSTRATIONS. XX111 FIG. PAGE FIG. 129. Ligaments of pelvis and hip . . 148 172. 130. Ligaments of pelvis and hip . 149 173. 131. Ligaments of clavicle and costal 174. 150 175. 132. Ligaments of scapula and shouldei 176. 151 177. 133. Scapuloclavicular ligaments . . 152 178. 134. Ligaments of elbow: internal . 153 179. 135. Id. external view . . . 153 180. 136. 154 181. 137. Inferior radio-ulnar articulation 155 182. 138. Ligaments of wrist and hand 155 183. 139. Synovial membranes of wrist 157 184. 140. Knee joint: anterior view. . . 160 141. Knee joint: posterior view . . 161 185. 142. Knee joint: internal view . . . 162 143. Knee joint: synovial membrane 163 186. 144. Ankle joint: posterior view . . 164 187. 145. Ankle joint: internal view . 164 146. Ankle joint: external view . . 165 188. 147. Ligaments, sole of foot . . . 166 148. 169 189. 149. Id., transverse section 169 190. 150. Id., animal fibre 169 191. 151. Id., transverse splitting 170 192. 152. Id., foetal .... 170 153. Id., ultimate fibril . 171 193. 154. Id., organic fibre . . 172 194. 155. Muscles of the face . . . . 174 195. 156. Tensor tarsi muscle . . . 175 196. 157. Muscles of the orbit . . . . 177 158. Ocular fascia and muscles 179 197. 159. Muscles of the nose . . . . 180 160. 184 198. 161. Muscles of the neck . . . . 187 199. 162. Muscles of the tongue . . . . 191 163. Muscles of the pharynx . . . 193 200. 164. Muscles of the soft palate . . 195 201. 165. Muscles: praevertebral region . 197 202. 166. Muscles of the back . . . . 200 203. 167. Muscles of the back: deep . . 203 168. Muscles of the back: deep . . 204 204. 169. Muscles of trunk: anterior . . 215 205. 170. Muscles of trunk: lateral. . . 217 206. 171. Diaphragm....... 219 JPAGE Muscles of the male perineum . 224 Muscles of the female perineum 226 Posterior scapular mus-cles . . 231 Muscles of the humerus . . . 233 Triceps extensor cubiti . . . 234 Muscles of the forearm . . . 235 Tendons of the fingers . . . 2:10 Muscles of forearm: deep layer. 237 Muscles of forearm : posterior . 238 Extensor tendons of a finger . 239 Muscles of forearm : deep layer 241 Muscles of the hand .... 242 Palmar interosseous muscles of the hand.......244 Dorsal interosseous muscles of the hand.......244 Muscles of gluteal region . . 249 Muscles of anterior and internal femoral region.....252 Muscles of gluteal and posterior femoral region.....255 Muscles, anterior tibial . . . 257 Id., posterior tibial . . . 258 Id., deep layer . 260 Dorsal interosseous muscles of the foot.......262 Muscles of sole of foot . . . 263 Id. deep......264 Id. second layer . . . . 264 Plantar interosseous muscles of the foot........265 Section of neck, showing deep cervical fascia.....269 Anatomy of the spermatic canal, 272 Transverse section of pelvis, show- ing fasciae.......274 Pelvic fasciae.......274 Perineal fasciae......276 Saphenous opening in fascia lata, 278 Distribution of fasciae at the fem- oral arch.......279 Smooth muscular fibre cells . . 283 Coarse network of elastic tissue 284 Fenestrated membrane of elastic tissue........284 LIST OF ILLUSTRATIONS. FIG. PAGE FIG. 55. Superior maxillary bone: inter- 93. nal surface....... 74 94. 56. Lachrymal bone...... 76 95. 57. 76 96. 58. Palate bone : internal surface . 77 97. 59. Palate bone: external surface . 78 98. 60. Inferior turbinated bone: inter- 99. 79 100. 61. Inferior turbinated bone: exter- 101. 79 102. 62. Vomer . . ...... 80 63. Inferior maxillary bone 81 103. 64. Skull: anterior view .... 84 65. Base of the skull: interior . . 85 104. 66. Base of the skull: exterior . 87 67. Section of cranium and face . 88 105. 68. Nasal fossa; turbinated bones . 90 100. 69. 91 107. 70. 92 108 71. Section of molar tooth . . . 93 109 72. Development of teeth: at four- 110. 94 111. 73. Id. the various stages . 96 74. Id. Pulp cavity and enamel 112. 96 113. 75. Id. tooth-sacs of an eight 114. 97 115. 76. Gubernaculum dentis . . . . 98 116. 77. 99 78. 99 117. 79. 101 118. 80. Rib.......... 101 119. 81. 102 120. 82. 103 121. 83. Scapula: anterior face .... 104 122. 84. Scapula: axillary border . . . 104 123. 85. Scapula: posterior face . 105 124. 86. 106 87. 107 125. 88. Bones of the carpus, dorsum 109 126. 89. Hand : anterior view .... 111 90. 114 127 91. Development of os innomina- 116 128 92. Female pelvis: anterior view. . 117 PAGE 118 119 120 121 121 Male and female pelves Femur: anterior view . Femur: posterior view Patella: anterior view . Patella: postorior view Tibia and fibula: anterior view . 122 Tibia and fibula: posterior view 123 Foot: dorsal surface . . . .124 Foot: plantar surface .... 127 Articular cartilage: its cells near the bone.......132 Articular cartilage: its cells fur- ther from the bone .... 132 Articular cartilage: its cells near the free surface.....132 Reticular cartilage.....133 Fibrous cartilage ".....133 White fibrous tissue .... 134 Yellow fibrous tissue . . . .135 Fat vesicles.......136 Serous epithelium.....136 Ligaments of vertebrae and ribs.........137 Posterior common ligament . . 138 Intervertebral substance . . .138 Intervertebral substance . . . 138 Ligamenta subflava . . . .139 Ligaments of atlas, axis, and oc- cipital bone......140 Id. posterior view . . .140 Id. internal view . . . 141 Id. internal view . . . 141 Ligaments of the lower jaw . . 142 Id. internal view . . . 143 Id. section.....143 Ligaments of vertebrae and ribs . 144 Ligaments of vertebral column * and ribs.......144 Middle costo-transverse ligament 145 Costo-sternal articulations: ante- rior view.......146 Costo-sternal articulations: pos- terior view.......146 Costo-sternal articulations: in section........146 LIST OF ILLUSTRATIONS. XX111 FIG. PAGE 129. Ligaments of pelvis and hip . . 148 130. Ligaments of pelvis and hip . . 149 131. Ligaments of clavicle and costal cartilages.......150 132. Ligaments of scapula and shoulder joint........151 133. Scapuloclavicular ligaments . . 152 134. Ligaments of elbow: internal . 153 135. Id. external view . . . 153 136. Orbicular ligament.....154 137. Inferior radio-ulnar articulation 155 138. Ligaments of wrist and hand . 155 139. Synovial membranes of wrist . 157 140. Knee joint: anterior view. . . 160 141. Knee joint: postei'ior view . . 161 142. Knee joint: internal view. . . 162 143. Knee joint: synovial membrane 163 144. Ankle joint: posterior view . . 164 145. Ankle joint: internal view . . 164 146. Ankle joint: external view . . 165 147. Ligaments, sole of foot . . . 166 148. Muscular fibre......169 149. Id., transverse section 169 150. Id., animal fibre . . 169 151. Id., transverse splitting 170 152. Id., foetal.....170 153. Id., ultimate fibril . .171 154. Id., organic fibre . .172 155. Muscles of the face . . . .174 156. Tensor tarsi muscle .... 175 157. Muscles of the orbit . . . .177 158. Ocular fascia and muscles . .179 159. Muscles of the nose .... 180 160. Pterygoid muscles.....184 161. Muscles of the neck . . . .187 162. Muscles of the tongue .... 191 163. Muscles of the pharynx . . .193 164. Muscles of the soft palate . .195 165. Muscles: praevertebral region . 197 166. Muscles of the back . . . . 200 167. Muscles of the back: deep . . 203 168. Muscles of the back: deep . . 204 169. Muscles of trunk: anterior . . 215 170. Muscles of trunk: lateral. . . 217 171. Diaphragm.......219 fAGE 224 226 231 "33 234 235 236 239 FIG. 172. Muscles of the male perineum 173. Muscles of the female perineum 174. Posterior scapular mus«les 175. Muscles of the humerus . 176. Triceps extensor cubiti 177. Muscles of the forearm 178. Tendons of the fingers 179. Muscles of forearm: deep lay 180. Muscles of forearm: posterior 181. Extensor tendons of a finger 182. Muscles of forearm : deep layer 241 183. Muscles of the hand .... 242 184. Palmar interosseous muscles of the hand.......244 185. Dorsal interosseous muscles of the hand.......244 186. Muscles of gluteal region . . 249 187. Muscles of anterior and internal femoral region.....252 188. Muscles of gluteal and posterior femoral region.....255 189. Muscles, anterior tibial . . . 257 190. Id., posterior tibial . . . 258 191. Id., deep layer . 260 192. Dorsal interosseous muscles of the foot.......262 193. Muscles of sole of foot . . .263 194. Id. deep......264 195. Id. second layer . . . . 264 196. Plantar interosseous muscles of the foot........265 197. Section of neck, showing deep cervical fascia.....269 198. Anatomy of the spermatic canal, 272 199. Transverse section of pelvis, show- ing fasciae.......274 200. Pelvic fascia?.......274 201. Perineal fasciae......276 202. Saphenous opening in fascia lata, 278 203. Distribution of fasciae at the fem- oral arch.......279 204. Smooth muscular fibre cells . . 283 205. Coarse network of elastic tissue 284 206. Fenestrated membrane of elastic tissue........284 XXIV LIST OF ILL USTRATIONS. FIG.* 207. 208. 209. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 042. 243. 244. 245. 246. Epithelial cells of bloodvessels . Structure of capillary vessels Great vessels of the chest . . Branches of external carotid Internal maxillary artery . . . Circle of Willis...... Branches of subclavian . . . Axillary and brachial arteries . Radial and ulnar arteries . . . Branches of abdominal aorta Cceliac axis, with branches . . Superior mesenteric artery . . Inferior mesenteric artery . . Internal iliac artery .... Arteries of the perineum . . . Femoral artery...... Anterior tibial artery. .... Posterior tibial artery .... Arteries of sole of the foot . . Valves of veins...... Veins of the head, face and neck Sinuses of the dura mater . . Sinuses of base of skull Veins at bend of elbow Internal saphenous vein Veins of trunk and neck Portal vein . . . . Lymphatic vessels . . Lymphatic glands and vessels . Thoracic duct...... Minute structure of nerve . . Multi-nucleated nerve-cells from the spinal cord..... Nerve-cells from the substantia gelatinosa....... Large multipolar nerve-cells . . Cortical substance of the cere- bellum ........ Cortical substance of the cere- brum ......... Ganglion of spinal nerve . . . Pacinian corpuscles, on a nerve . Pacinian corpuscle: its structure A ganglion of the sympathetic nerve ........ PAGE FIG. 284 247 285 248 287 249 291 250 296 251 304 306 252. 308 253. 312 254 318 255. 319 321 256. 322 324 257. 326 258. 330 259. 335 260. 338 261. 339 262. 343 263. 344 264. 346 265. 348 266. 350 267. 352 268. 353 269. 357 270. 359 271. 360 272. 369 273. 372 274. 372 373 275. 276. 375 277. 377 278. 379 279. 380 280. 380 281. 282. 381 283 PAGE Dura mater.......385 Centrum ovale majus . . . .^288 Lateral ventricles.....3! 0 Hippocampus major .... 391 Longitudinal section of the brain........393 Third and fourth ventricle . . 394 Cerebellum.......397 Base of brain......399 Section of the medulla oblon- gata .........401 Distribution of the fibres of the brain........402 Section of spinal cord .... 404 Olfactory nerve......406 Optic tracts and chiasm . . . 407 Origin of optic nerve .... 408 Cerebral nerves......409 Trifacial or fifth nerve . . .411 Nerves of the orbit.....412 Distribution of the fifth nerve . 414 Facial and cervical nerves . .418 Portio mollis.......419 Eighth pair of nerves .... 422 Hypoglossal nerve.....424 Origins of the spinal nerves . . 425 Axillary plexus and nerves . . 429 Diagram of axillary plexus and its branches.......432 Nerves of the forearm: ante- rior .........433 Nerves of the forearm: poste- rior .........435 Cutaneous nerves of chest and abdomen.......437 Intercostal nerves.....437 Lumbar and sacral plexuses . . 439 Diagram of lumbar and sacral plexuses and branches . . . 440 Anterior crural nerve .... 442 Branches of sacral plexus . . 444 Internal popliteal nerve . . . 446 Posterior tibial nerve .... 446 Plantar nerves......447 Nerves of leg: anterior . . . 448 LIST OF ILL US TR ATION S. XXV FIG. PAGE 284. Cranial ganglia of the sympa- thetic ........450 285. Sympathetic nerve.....454 286. Thoracic ganglia of the sympa- thetic ........456 287. Fibro-cartilages of nose: front view.......460 288. Id. lateral view . . 460 289. Nasal septum......461 290. Outer wall of nasal fossa . . .461 291. Section of globe of eye . . . 463 292. Ciliary nerves......464 293. Choroid coat of eyeball . . .464 294. Section of globe of eye . . . 465 295. Another transverse section . . 466 296. Crystalline lens: interior planes 468 297. Id. course of fibres . . 468 298. Appendages of the eye . . . 469 299. Id. lachrymal apparatus 470 300. Meibomian glands.....470 301. Lachrymal apparatus and nasal duct.........472 302. External ear.......473 303. Muscles of the pinna .... 474 304. Id. from behind . . . .474 305. Diagram of the ear.....476 306. Tympanum of left ear .... 478 307. Osseous labyrinth of the left ear 480 308. Anatomy of the cochlea . . .481 . 309. Labyrinth........482 310. Tongue, with papillae .... 485 311. Anatomy of the skin .... 487 312. Development of epidermis . . 487 313. Anatomy of the skin .... 490 314. Heart.........493 315. Right chambers of heart . . . 495 316. Left chambers of heart . . .498 317. Valves of the heart.....499 318. Epithelium of endocardium . . 502 319. Anastomosing muscular fibres . 503 320. Ligaments of larynx .... 505 321. Muscles of larynx: posterior view 507 322. Id. lateral view .... 507 323. Ciliated epithelium, from the trachea........510 FIG. PAGE 324. Anatomy of lungs and heart . . 511 325. Bronchial tubes and intercellular passages.......513 326. Transverse section of the chest . 515 327. Regions of the abdomen . . .516 328. Viscera of the abdomen . . .516 329. Peritoneum.......517 330. Section of nose, mouth, pharynx, etc..........522 331. Follicular gland: structure . . 523 332. Racemose mucous gland . . . 524 333. Racemose gland: structure . . 524 334. Pharynx........526 335. Stomach and duodenum . . . 527 336. Ciecum.........529 337. Rectal pouches......532 338. Epithelial scales.....533 339. Columnar epithelium .... 534 340. Id. separate columns . . 534 341. Id. bases of columns . . 534 342. Spheroidal epithelium .... 534 343. Ciliated columnar epithelium . 535 344. Id. bases of columns. . . 535 345. Alveoli of stomach.....535 346. Alveoli of colon......535 347. Villi, follicles......536 348. Lamellated villi......536 349. Section of stomach : structure . 537 350. Tubular gastric gland .... 537 351. Solitary gland from the colon: section.......538 352. Id. superficial view . . . 538 353. Peyer's gland......539 354. Peyer's gland: section.... 539 355. Muciparous glands.....540 356. Mucous membrane : circulation . 541 357. Rectal columns . . . . . . 542 358. Liver: upper surface .... 544 359. Liver: under surface .... 546 360. Lobules of the liver.....517 361. Lobules of the liver.....547 362. Hepatic corpuscles.....548 363. Hepatic corpuscles: network . 548 864. Lobules of liver: section . . . 550 365. Lobules of liver: section . . • 550 XXVI LIST OF ILLUSTRATIONS. ™- PAGE 366. Splenic corpuscles.....655 367. Splenic corpuscle: structure . 555 368. Section of supra-renal capsule . 556 369. Bloodvessels of supra-renal cap- sule .........557 370. Section of the kidney . . . .559 371. Structure of kidney.....560 372. Plan of renal circulation . . . 561 373. Viscera of the male pelvis. . . 563 374. Bladder and vesiculae seminales 566 375. Erectile tissue of corpus caver- nosum . 376. Anatomy of urethra . . . 570 377. Anatomy of urethra . . . 571 378. Transverse section of testis •. 573 379. Anatomy of testis . . . 380. Glandular structure of testis . 575 381. Viscera of the female pelvis . 576 382. Uterus, with appendages . . 578 FIG. PAGE 383. Section of virgin uterus . . . 578 384. Muscular fibres of uterus: ex- ternal........579 385. Id. internal.....579 386. Mucous membrane of the ute- rus .........580 387. Section of ovary......582 388. Graafian follicle......582 389. Female external organs of gene- ration ........584 390. Erectile structures of female or- . 585 391. Section of mammary gland . . 580 392. , 587 393, . 589 394. Section of thymus gland . . . 592 395. Duct of thymus gland . . . . 593 396. Descent of testis in the foetus . 597 397. . 597 A SYSTEM OF HUMAN ANATOMY. CHAPTER I. INTRODUCTORY. BY THE EDITOR. All natural objects are divided into two great kingdoms, the organic and inorganic. A mineral, inorganic or unorganized object undergoes no change except through the agency of mechanical or chemical forces; any augmentation of its bulk being caused by the addition of similar particles to its exterior; it therc- fore# increases not by growth but by accretion. An organized body or organism is possessed of such an internal cellular or cellulo-vascular structure as admits of the reception of fluid matters into its inte- rior which it may alter or assimilate and add to itself. The acts by which these results are produced being inexplicable on any known mechanical or chemical prin- ciples, are called " vital acts," and during their continuance the object lives, and is a living being. Animals and vegetables are both included in this kingdom, forming its two grand divisions, between which and inorganic bodies there is a wide distinction • the former being composed of dissimilar parts or organs, which have a mutual relation to and dependence upon each other, whilst the latter are homogeneous in their structure. The science which has for its object the structure of living beings is Anatomy. The word is derived from the Greek, ava, up, -rsfivu,, I cut, since it is by dis- sections principally that we are enabled to separate and study the different organs. In accordance with the division of living beings, therefore, we must have an animal and a vegetable anatomy; with the latter the botanist is more particu- larly concerned. When anatomy considers the entire series of animals, comparing the same organs in the different species, it is called zoological or comparative. When anatomy is restricted to the examination of one species only, it i3 denominated special, as the anatomy of man, etc. Physiological anatomy regards the organs in their healthy state. Pathological anatomy, regards them as influenced by disease. Descriptive anatomy gives us all the knowledge of an organ which may be learned without division of its substance; thus its name, situation, size, color, weight, etc. Regional, topographical or surgical anatomy is that branch of descriptive anatomy which teaches us the order of superposition and relations of all the parts in a given region, and embraces the practical application of our anatomical knowledge to both medicine and surgery. General anatomy, anatomy of textures or histology, separates the elementary textures of a part or organ, thus determining its particular construction; it is of essential service to the physician and physiologist. An animal body is composed of solids and fluids, the former differing in den- sity from being permeated to a greater or less extent by the latter, of which (2 7) 28 ST(ECHIOLOGY. water is the chief constituent. In the completely developed human body about two-thirds the entire weight is water. In a minute examination of the human body we' shall find that it is composed of simple chemical elements, which, uniting in various manners, constitute cer- tain compounds, which are called immediate principles, from which are deve- loped the simple structural elements, and from these the tissues, properly so called, are formed; these latter by their combinations constituting the organs. The consideration of the simple chemical elements and immediate principles which compose the tissues and fluids of the body is denominated stoechiology, from atot%elov, an element, and %6yos, a discourse. The description of the tissues and the simple structural elements from which they are formed, and of those which are found in the fluids, is called histology, from lotos, a web, and a.6yo$, a discourse. S T CE C H 10 L 0 G Y. The consideration of the simple chemical elements and immediate principles. SIMPLE CHEMICAL ELEMENTS. Fifteen simple chemical elements are recognized as occurring naturally in the human body. These are — Oxygen, hydrogen, carbon and nitrogen, found in all the tissues and most of the fluids, except fat; the latter is devoid of nitrogen. Sulphur, in the albuminous group of immediate principles and the tissues which they form, and in the brain, hair, and nails; and as sulphuric acid in the urine. Phosphorus, in the albuminous group of immediate principles and their tis- sues ; in the brain; as phosphoric acid in the urine, and in the bones, combined with lime and magnesia. Calcium and magnesium, found only in combination with oxygen as lime and magnesia, and these with acids forming salts; they are found in the bones, milk, and other fluids. Sodium, with chlorine as a chloride, to form common salt, found in every part of the body; and with oxygen forming soda, which forms salts by its com- bination with acids, and is found in various tissues and fluids. Potassium occurs, as a chloride, in the muscular tissue; and as an oxide in combination with acids. Chlorine forms hydrochloric acid when combined with hydrogen, and is thus found in the gastric juice; it also forms the chlorides of sodium and potassium, as before stated. Fluorine is found combined with calcium, in the bones. Sdicum is found combined with oxygen, as silica, in the hair and urine. Iron is found in the blood, hair, muscle, milk, and pigment-cells. Manganese is found as the oxide in bones, coloring-matter of the hair, and in the bile. Besides these fifteen elements, others, as arsenic, capper and lead, have been stated to exist in small proportions in the human body as normal constituents, but they are no doubt merely accidental. IMMEDIATE PRINCIPLES. The immediate principles of the tissues are " the last bodies constituting the organism to which the tissues can be reduced by mere anatomical analysis; and which admit of no further subdivision without chemical decomposition." STCECHIOLOGY. 29 Water, albumen, fat, etc., are immediate principles; the oxygen, hydrogen, carbon, etc., into which these may be decomposed by chemical agencies, are the simple chemical elements. Oxygen, nitrogen, and hydrogen are, however, also under certain conditions immediate principles, that is, when existing in a free state in solution. The exact number of immediate principles in the human body is not determined. The subjoined table of 84, being Robin and Verdeil's modi- fied by Peaslee, presents them in a classified form.1 Tabular Classification of the Immediate Principles. Group /.—PRINCIPLES CRYSTALLIZABLE OR VOLATILE, INDEPENDENTLY OF DECOMPOSITION. First Class.—Principles of Mineral Origin (24). First Division. Gaseous and not Saline (5). Oxygen, Carbonic acid, Hydrogen, Water. Nitrogen, Second Division. Salts (19). Chloride of Sodium, Sulphate of Soda, " Potassium, " Lime, Fluoride of Calcium, Basic Phosphate of Lime (Bones), Hydrochlorate of Ammonia, Acid Phosphate " Carbonate of Lime, Phosphate of Magnesia, " Magnesia, Neutral Phosphate of Soda, " Potassa, Acid " " " Soda, Phosphate of Potassa, Bicarbonate " Ammonio-Magnesian Phosphate. Sulphate of Potassa, Second Class. — Principles of Organic Origin formed within the Body by Dis-assimilation (42). First Division. Acid or Saline Principles (23). Lactic Acid, Hippuric Acid, Lactate of Soda, Hippurate of Lime, " Potassa, " Soda, " Lime, u Potassa, Oxalate of Lime, Inosate of Potassa, Uric Acid, Pneumic Acid, Neutral Urate of Soda, Pneumate of Soda, Acid " " Taurocholate " Urate of Potassa, Hyocholinate " " Magnesia, Glycocholate " " Lime, Lithofellic Acid. " Ammonia, Second Division. Neutral Nitrogenized Compounds (5). (Nitrogenized Alkaloids.) Creatine, Urea (and Chloro-sodate of Urea — Creatinine, Urea with marine salt), Cystine. 1 For more detailed information concerning these subjects the student is referred to Professor Peaslee's "Human Histology," an excellent compendium of the present state of Histological science, and the only American work of this character with which we are acquainted. BO STCECHIOLOGY. Third Division. Neutral Non-nitrogenized Compound. Sugars (2). Sugar from the Liver, Sugar of Milk. Fourth Division. Fatty and Saponaceous Compounds (13). Cholesterin, Caproate of Potass., Soda, &c Oleic Acid, Olein, Margaric Acid, Margarin, Stearic " Stearin, Oleate of Soda, Elaterin, Margarate " Stearerin. Stearate " Group II.— PRINCIPLES NON-CRYSTALLIZABLE OR NON-VOLATILi,, INDEPEN- DENTLY OF DECOMPOSITION. Third Class. — Organic Substances, or Coagulable Principles (18). First Division. Those naturally Liquid (7). Fibrin, Pancreatin, Albumen, Mucosin, Albuminose, Ptyalin. Casein, Second Division. The Solid an* Demi-solid (7). G-lobulin, Cartilagein, Crystallin, Ostein, Musculin, Keratin. Elasticin, Third Division. Pigmentary Substances (4). Hsematin, or Hsematosin, Melanin. Biliverdin, Urrosacin. Besides these, there are other substances known to exist, but which being doubtful, or not well determined as immediate principles, it is unnecessary here to enumerate. The organic substances or coagulable immediate principles constituting the third class, compose the greatest part of the body, the principles of the first class being in much smaller proportions; whilst those of the second, except the fatty principles, being formed by dis-assimilation or waste, to be quickly thrown off, must be regarded as merely accessory to, and not as original components of the organism. The first and third classes (including fat) then are alone assimilable. Of the First Class. Oxygen (0) is an immediate principle when it exists in a free state; it is thus dissolved in the blood, and acts as a vital stimulus — its combination with the tissues and elements producing heat. Hydrogen (H) exists free in the stomach and large intestine, though none has as yet been found in the blood. Nitrogen (N) is found dissolved in the blood. Carbonic Acid (Co2) resulting from the combination of oxygen with the carbon of the tissues, etc., is found dissolved in all the fluids. It is removed princi- pally by the lungs. Water (Protoxide of Hydrogen, HO) is one of the most important imme- diate principles, forming as it does a part of every tissue or fluid in the organ- ism; and is essential to their existence; nearly every tissue is more than half STCECHIOLOGY. 31 water. It exists in a solid, demi-solid, liquid, and gaseous state. Thus in muscle it is in such chemical combination with the tissue that it is solid; in other substances not being in sufficient quantity to effect solution, it is rendered demi-solid; in fluids it is fluid ; in the halitus of the lungs it is gaseous. It is taken into the body in food and drink, and is also supposed to be formed in the system. Without its presence in the body, chemical and vital acts would be impossible. The Salts are found in every tissue and fluid, dissolved in their water, and thus serve as solvents for certain other immediate principles; and some of them by combining in the state of solution with certain organic immediate principles compose tissues. Common Salt (Chloride of Sodium, NaCl) is found in every portion of the body, both solid and fluid, except enamel; and exists in greater quantity than any other immediate principle of inorganic origin. It always freely exists in fluids where cells are developing. Its existence in the blood is necessary to endosmosis of dissolved alimentary substances from the digestive tract. It is necessary for the performance of assimilation and dis-assimilation. Chloride of Potassium (KG.) is always dissolved in water, like common salt, and is found in the milk, muscles, liver, blood, etc. Carbonate of Lime (CaO, C02) is found in all cases combined with the phos- \ phates of lime. Carbonate of Soda (NaO, Co2) is found in the blood, etc., and is always dis- solved in water; it is combined with and dissolves the albumen of the blood. Sub-phosphate or Basic Phosphate of Lime (8CaO, 3P05) is found in the bones, teeth, nails and hair, in a solid state, and in a liquid form in the blood and all the other fluids. Of the Second Class.—The immediate principles of organic origin formed within the body by dis-assimilation or waste contain but nine of the simple chemi- cal elements, viz., sodium, potassium, calcium, magnesium, sulphur, carbon, oxygen, hydrogen, and nitrogen, as may be observed by reference to the table. These compounds, although so numerous, constitute by far the smallest part of the body; about two-thirds of them are found in the blood—they are also found in the urine and bile, by which they are for the most part removed from the system. It is not necessary for our purpose to enter into a detailed description of these immediate principles, or do more than state that it.is not so certain that all the fatty principles (which are non-nitrogenized) included in this category are the results of " waste " or dis-assimilation; in a normal condition they all exist in the body in a fluid state, either inclosed in cells forming adipose tissue, in chemical combination with other elements, or as oil-globules, without any envelop, existing in nearly every tissue. Most of these fatty principles are taken into the body already formed in the food, and may also be, to some extent, formed in the body; thus cholesterin is probably a result of " waste " of the liver itself. The uses of the fatty principles are manifold—they serve to nourish the tissues which contain fat, and to be consumed by uniting with oxygen, and thus maintain vital heat. The presence of fat seems to be indispensable to the original devel- • opment of the tissues, for the nuclei of all primary cells contain fat-granules. Of the Third Class of immediate principles, which constitute the greater part of the body, all are composed of the four elements, carbon, hydrogen, oxy- gen and nitrogen, and are called nitrogenized compounds; they are prone to rapid decomposition. The two first divisions form the albuminous compounds, which are found, as is shown in the table, either in a liquid or in a solid or demi- solid condition; water, however, being an essential part of their chemical con- stitution, since, if they are completely dessicated, their vital properties are com- pletely lost. 32 histology. Albumen, fibrin and casein have been called protein compounds; since they may be supposed to be formed by the combination of small proportions of either sulphur or phosphorus, or both, with a compound radical, called protein (jtpotsva, I am first) by Mulder. Protein, however, does not exist in nature, and is only obtained by the destructive decomposition of the substances which it is supposed to aid in forming. The formula of Mulder for protein is, C36H25N4OI0+2HO, which represents, according to him, perfectly non-sulphurous protein. Albumen (Pr10-(-PS2) is found in the serum of the blood, chyle, and lymph; like all other of these organic immediate principles, its chemical composition is not definite. Sulphur and phosphorus are always found aiding to form it. It is the essential pabulum of the tissues, for from it they are all developed and nourished. It is itself probably formed from Albuminose, which is formed in the alimentary canal by the digestion of albuminous compounds. Fibrin (PrI0+PS) is found in the blood, chyle and lymph. It is probably not a simple substance as has been supposed, but is formed from albumen, fat, and some saline materials. It has the property of spontaneous coagulability or fibril- lation, which is readily witnessed a few minutes after venesection ; and by this property exercised within the body affords a matrix for new growth, but is not the only plastic element which is called into requisition. Fibrin maybe formed directly from albuminose, or from the albumen in the blood. Casein (Pr10-f S) is found in the milk, both as the investing membrane of the milk-globules and in solution; its properties generally resemble albumen. Pancreatin is found in the pancreatic juice. Ptyalin is found in the saliva. Mucosin is found in mucus, and varies according to its source. Globulin constitutes the principal part of the red corpuscles of the blood, and is no doubt developed from albumen by their cell-membranes. Crystallin exists in the crystalline lens, and is similar to globulin. Musculin exists in the striated and non-striated muscular tissue, and is its main constituent; it is probably formed from albumen; that which has been called fibrin in the muscles is musculin. Ostein exists in bone and white-fibrous tissue; in bone it is chemically com- bined with phosphate of lime. Gartitagein is found in cartilage and fibro-cartilage. Elasticin is found in yellow-fibrous tissue. Keratin is peculiar to nails, hair, and epidermis. Hcematin, Billverdin, Melanin, and Urrosacin are the coloring matters of the blood, bile, pigment-cells and urine. HISTOLOGY. This is the description of the simple structural elements, and the tissues which are formed from them. THE SIMPLE STRUCTURAL ELEMENTS. The simple structural elements, of which the proper tissues are formed, are — 1. Homogeneous substance, 2. Simple membrane, 3. Simple fibre, 4. Cells. 1. Homogeneous substance, homogeneous matrix or hyaline substance, is a structureless material, varying in density, found in several tissues, often filling up the spaces between fibres and cells, and sometimes constituting a great part of their bulk; sometimes it is granular. It is developed from albumen, which histology. 33 has thereby assumed a higher stage, and with it a low grade of vital properties. It is used to connect other structural elements, and is found in bone and cartilage. 2. Simple membrane is a thin structureless layer of coagulated albumen, occasionally being granular; it is not traversed by either vessels or nerves, but receives its nourishment from neighboring capillaries; it forms limitary mem- brane and the walls of every variety of cell. 3. Simple fibre consists of threads of coagulated fibrin, and it is supposed a rete or net thus formed furnishes a matrix for the development of tissues, and the nidus for repair of solutions of continuity, being absorbed after the higher struc- tural elements are developed. 4. Cells. The cell is the most important of the simple structural elements; for from cells almost all the tissues proper are formed — the three just described structural elements being inferior in grade, and of course not derived from them. Vegetable tissues are likewise formed from cells. Fig. 1. Fio, 2. • © 0 NUCLEATED CELLS FROM A BULBOUS root ; magnified 290 diameters. (Schwann.) Plan representing the formation, FROM BLASTEMA, OF a nucleus, and of a cell on the nucleus, according to Schlei- den's view. Fig. 3. A cell is a vesicle, which may be from y^- to goVo °f an ^ncn m diameter, formed from a plasma, blastema, or cytoblastema, which is the liquor sanguinis : a granule first appears in the clear plasma, and is called the nucleus or cytoblast (xvto$, cell, QXaattn, to produce), this increases in size and becomes vesicular, and there is then perceived in its interior other granules, one of which being larger than the others is called the nucleo lus; from the nucleus is developed the cell- wall, and the space between the nucleus and the cell-wall is filled with a fluid containing granules, which constitute the cell-contents. The cell-wall is simple membrane, formed from albumen, and possessing great endosmotic proper- ties. The contained fluid varies in composition according to the character of the cell, that is, it differs in epithelial, epidermic, or fat cells, etc.; the granules contained, which are very numer- ous or may be altogether absent, may be fat- globules devoid of investment, or pigment-gran- ules, etc. The nucleus is generally attached to some part of the wall of the cell, and contains a fluid, and, as stated, the nucleolus, supposed to be formed of fat with an albuminous envelop, and which may itself become vesicular; sometimes several nucleoli are found in one nucleus. CELL-MEM- GRANULES. Cells showing the brane, the contained the nucleus, and the nucleolus, 1 and 2. The typical spherical form. The rest as changed by pressure. Cells are developed in several ways : 1st. Directly from the plasma (by virtue of the vital force communicated by 3 34 histology. its contact with living tissues), in the manner already described, which is called free cell-development. 2dly. In the interior of other cells, which is the endogenous method. By this method the nucleus of the primary cell, after enlarging, and becoming pos- sessed of two nucleoli, becomes constricted in the middle, and finally divides into two distinct portions, each of which becomes the nucleus of a new cell. Fia. 4. Endogenous cell-development, a, b, c, d. Early stages of the process, showing dupli- cation of cells (ovum of Ascaris dentata). e, f, g, h. More advanced stages (ovum of Cucullamu elegant). The original cell may now burst, and set free the secondary cells, or enlarge until several generations have been formed in the same manner within it; the nucleoli becoming the nuclei of the new cells, and developing new nucleoli within themselves. 3dly. Cells may multiply by division. Here the original cell elongates, and Fia. 5. Multiplication of cartilage-cells by division: a, original .cell; b, the same be- ginning to divide; c, the same showing complete division of the nucleus; d, the same with the halves of the nucleus separated, and the cavity of the cell subdivided; e, continua- tion of the same process, with cleavage in contrary direction, to form a cluster of four cells; f, g, h, production of a longitudinal series of cells, by continuation of cleavage in the tame direction. HISTOLOGY. 35 the nucleus divides into two. The cell then, after being constricted, divides into two distinct nucleated cells, and this process may be continued. Different cells have different functions, thus some are Formative, producing the solids of the body, by absorbing from the surrounding blastema their pabu- lum, which they alter by a vital process. Others are Secreting, and may receive their pabulum without altering it, or but slightly, where they are intended simply to separate formed materials from the blood, or they may produce substances in their interior from the pabulum furnished, as in the bile-cells. Fig. 6. A peculiar structural element, called the Cytoid corpuscle (xvtos, *i5oj, cell resembling), is found in some of the fluids of the body, viz., in the lymph, chyle, blood, etc., and has been called the lymph-, chyle-, and colorless blood-corpuscle, etc.; from this element the red blood-corpuscle is formed, pro- bably by being converted into a non-nucleated cell by alteration and solidification of the cell-contents, and change of color, and the assumption of a bi-concave dis- coid form; the colorless blood-corpuscles originating by free cell-formation in the lymph and chyle, and perhaps in the liquor sanguinis itself. These cytoid corpuscles also exist in mucus, pus, and exudations. In exudations they form the basis of new tissues, but in mucus and pus never arrive at a higher organization. Fig. 7. Cytoid corpuscles of blood. 1. Natural ap- pearance. 2 and 3. Changed by dilute acetic acid. Development of the red from the colorless corpusclf.s of the blood, a. Cy- toid corpuscle, b. Same, being converted into a red corpuscle, c. Cytoid corpuscle with its membrane raised by the action of water, d. Same, having lost most of its granules. e. Same, acquiring color; a single granule remaining like a nucleus, f. Perfect red cor- puscle. THE TISSUES. The tissues are formed from the simple structural or histological elements, and of these the cells are of chief importance. In some tissues the cellular structure is retained as a permanent characteristic, as in the adipose; whilst in others the cells are converted into other forms, as in the striped muscular tissue. The following table, from Todd and Bowman, will present a general view of the various tissues which enter into the construction of the organs of which the body is composed. 36 HISTOLOGY Tabular View of the Tissues of the Human Body. Examples.—Posterior layer of the Cornea.—Capsule of the lens. Sarcolemma of muscle, &c. White and yellow fibrous tissues.— Areolar tissue. Mucous membrane.— Skin.— True or secreting glands.—Serous and synovial membranes. Adipose tissue.— Cartilage.— Gray nervous matter. Bone.—Teeth. Muscle.—Nerve. Fibro-cartilage. Fig. 8. 1. Simple membrane, homogeneous, or nearly so, employed alone, or in the formation of com- pound membranes. 2. Filamentous tissues, the elements of which are real or apparent filaments. 3. Compound membranes, composed of simple membrane, and a layer of cells, of various forms (epithelium or epidermis), or of areo- lar tissue and epithelium. 4. Tissues which, retain the primitive cellular structure as their permanent character. 5. Sclerous or hard tissue. 6. Compound tissues. a. Composed of tubes of homogeneous mem- brane, containing a peculiar substance. 6. Composed of white fibrous tissues and cartilage. Simple membrane has been before described, but is here referred to as form- ing part of the tissues. The Filamentous tissues are employed to connect different parts, and for asso- ciating the elements of other tissues : thus, the ligaments which bind together the bones forming joints, and the areolar or proper con- nective tissue, composed of yellow and white fibrous tissues, which surrounds the fibres of muscles and nerves, etc., are filamentous tissues. The Compound membranes are formed of the simple membrane lying upon vessels, nerves and areolar tissue, and covered by epithelium. The skin and mucous membrane, and glands which open upon their surfaces, are formed in this manner, as are also the serous and synovial membranes. The tissues which retain their Primitive cellular form, are very dissimilar as regards their vital endow- ments, as also in the relative cohesion of their cells. In adipose tissue the intervals between the cells con- taining the fat are filled with areolar tissue and capilla- ries; in the gray nervous matter, capillaries and nerve tubes exist between the cells; and in cartilage there is a firm intercellular substance. The Sclerous tissue (axXr^o^, hard) owes its hardness to the amount of inorganic matter combined with its animal matter, as in bone and teeth. The Compound tissues are those, the elementary parts of which are made up of two distinct tissues. In the muscular fibre, a tube composed of simple mem- brane incloses the sarcous element in which the vital properties of the tissue reside. In nerves similar tubes Fibro-cartilage is also properly a compound tissue, being First stages of the development of striated muscular fibre. 1. Ar- rangement of the primitive cells in a linear series, after Schwann. 2. The cells united: the nuclei sepa- rated and some broken up, longitudinal series becom- ing apparent — from a foe- tal calf three inches long. contain the neurine. formed of cartilage and white fibrous tissue. The transformation of cells into tissues is effected in several ways. At the earliest period of embryonic life textures are as yet unformed, but the embryo consists of primordial cells, from which others are developed by the endogenous method, or from the intercellular granular blastema. In these cells changes take place for the production of the elementary parts of the tissues. 1. Cells may lose their fluid contents; and their walls collapsing until they come in contact and adhere, they form simple, membranous and transparent HISTOLOGY. 37 Fio. 9. Epithelial plates of the oral cavity, a. Large. 6. Middle-sized. nuclei.—Magnified 350 diameters. (Kb'lliker.) c. Same, with two discs, as in some kinds of epithelium, epidermis, etc. Some physiologists sup- pose that simple homogeneous membrane is formed by the flattening of cells and the fusion of their walls. 2. In the tissueswhich are composed Fig. 10. of tubes of homogeneous membrane, containing a peculiar substance, as muscle and nerve, neighboring cells adhere by their ends, and the par- titions between them being removed their cavities communicate, and thus a tube or sheath is formed, contain- ing the proper muscular or nervous substance. Capillary bloodvessels are formed in the same manner. Curious forms are produced by modi- fications of the same method, as in pigment-cells. 3. Solid deposits may be formed within the cell, obliterating its cavity. 4. The intercellular substance may become thickened, and solid deposit, or a new arrangement of particles, occur. Cartilage is a good example of the last two methods. Pigment-cells from the tail of a tadpole, magnified about two hundred and twenty-five dia- meters. (Schwann.) Fig. 11. Fio. 12. Fio. 13. Fig. 14. Cross section of Development of cartilage. Cartilage of the branchial ray of ligneous cells con- a fish (Cyprimts erythrophtfaalmua) in different stages of advance- taining stratified de- ment; magnified 450 diameters. (Schwann.) posit. A similar method is seen in the deposits in the interior of vegetable cells. A curious modification of development occurs in the feathers of birds, where 38 HISTOLOGY. Cells from the cortex of a growing Feather, showing their division into fibres. a nucleated cell elongates, and becomes filled with fibres, the cell-wall is rubbed off, and the fibres are exposed. In fact the nucleated Fig. 15. cell is the agent of most of the organic processes, both in animals and vegetables, from their earlier stages to their full development, in the formation of their tissues, and the production of their secretions. Properties of the Tissues. The fully-developed tissues are possessed of proper- ties which differ among themselves. These are physi- cal and vital. Physical properties.—These are the results of the peculiar arrangement of their component particles, and their chemical constitution, and can be perceived both in dead and living textures. Elasticity is the property by which a tissue returns to its original condition after being stretched or com- pressed. The ligamenta flava and the middle coat of arteries exhibit this property in a remarkable degree. Extensibility. This property allows a tissue to be stretched, but in the healthy state only after a long-continued effort. Porosity is a property possessed by the various tissues, and seems to play a most important part in the maintenance of the functions of life. It admits of the transudation of the solids by the fluids, and this process was called by Dutro- chet, who first described it, Endosmose and Exosmose. All the tissues contain water, some of them more than four-fifths their weight; to this is due their pliancy and other physical properties, besides which it allows nutritious mate- rials to be conveyed into, and the products of dis-assimilation out of, their sub- stance. A tissue saturated with water, and placed in contact with another tissue or fluid having a greater affinity for water than it has, will part with its superabun- dance, and if not supplied from behind will even part with a portion of that which is essential to its natural condition. If, however, it is supplied from the other side, it will continue to supply the imbibing fluid, and receive more from behind. Thus a current will be established from the water on one side of the tissue to the fluid having a high affinity for it on the other (Endosmose). But this is not all, for the fluid, in turn, transudes the tissue to mix with the water on the other side, and thus a counter-current (Exosmose) is set up in an opposite direction, which is, however, slower than the first, and this will continue until the two liquids are equally saturated by each other. That this process is purely physical is proved by the fact that it will take place through porous inorganic bodies, as well as through organic membranes. It is supposed to be employed in the processes of secretion and absorption. Vital properties.—The most prominent vital property possessed by the tissues is the power of assimilation, or of appropriating to themselves such of the organizable substances presented to them as may suit their purposes. This power is supposed to be partly due to chemical affinity, and partly to vital affi- nity. It is most probable, however, that future researches will prove that the power of assimilating is subject to the ordinary chemical laws, but under modi- fying circumstances, which can only exist in a living body or tissue. To this may be added the power of reproducing, in its appropriate place, a new portion of a tissue, when injured or destroyed. Another property which is essentially vital is contractility — a phenomenon which is made manifest by the visible shrinking or contraction of a living tissue GROUPS OF ORGANS. 39 when irritated, either by mechanical or chemical stimuli. This property is characteristic of muscle, and probably exists in no other animal texture. A third vital property is sensibility, which, however, requires that the tissues shall be united so as to form a continuous line from the part manifesting it to the brain. This property is enjoyed in very different degrees by the different tissues, and constitutes an important distinction between them, depending upon the presence and number of nerve-fibres mixed with the tissue. The tissues, the manner of whose formation, and properties we have just described, are variously combined to constitute the organs of the body, all of which differ in their structure and use, but are combined for a double purpose, viz.: 1. The preservation of the individual; and 2. The continuance of the species. To effect these objects the organs are arranged in groups, each of which has a definite purpose or function to fulfil. Each group of organs is called an apparatus. The general distribution of organs is shown in the following table: A. For the Preservation of the Individual. 1. Apparatus of Relation. k /. C Organs of Sense, a. Appara us of \ ^ Sensation, (Bram and Spinal Cord. {Muscles . Active Organs. Bones, ") Articulations, > Passive " Aponeuroses, J 2. Apparatus of Nutrition. a. Apparatus of Digestion, Alimentary canal, < ' Mouth, Pharynx, (Esophagus, Stomach, f Duodenum, Small intestine, < Jejunum, (_ Ileum. ( Caecum, Large intestine, -j Colon, (_ Rectum. f Salivary Glands, Annexed organs, 1 a , ' ° ' j Spleen, [Pancreas, etc. {Heart, Arteries, Veins, Lymphatics. c. Apparatus of ( ^J ] Voice. Respiration, ; j „ 40 GROUPS OF ORGANS. {Kidneys, BlalS, Urethra. B. For the Continuance of the Species. Apparatus of Generation. In the Male, Testicles — vasa deferentia, Vesiculae seminales — ejaculatory ducts, Prostate gland, Penis. In the Female, Ovaries, Fallopian tubes, Uterus, Vagina, Mammary glands. The succeeding pages are descriptive of the various organs, an outline of whose classification we have just presented. classes of bones. 41 CHAPTER II. osteology. The bones are the organs of support of the animal frame; they give firmness and strength to the entire fabric, afford points of connection to the numerous muscles, and bestow individual character on the body. In the limbs they are hollow cylinders, admirably calculated, by their conformation and structure, to resist violence and support weight. In the trunk and head, they are flattened and arched, to protect cavities and provide an extensive surface for attachment. In some situations they present projections af variable length, which serve as levers; and in others are grooved into smooth surfaces, which act as pulleys for the passage of tendons. Moreover, besides supplying strength and solidity, they are equally adapted, by their numerous divisions and mutual apposition, to fulfil every movement which may tend to the preservation of the creature, or be con- ducive to his welfare. According to the latest analysis by Berzelius, bone is composed of about one- third of animal substance, which is almost completely reducible to gelatine by boiling, and two-thirds of earthy and alkaline salts. The special constituents of bone are present in the following proportions: — Cartilage...............32-17 parts. Bloodvessels .............1*13 Phosphate of lime............51*04 Carbonate of lime............11*30 Fluate of linie.............2*00 Phosphate of magnesia..........1*16 Soda, chloride of sodium..........1*20 100-00 [That bony tissue is composed essentially of two distinct elements, one organic and the other inorganic, can be readily shown, on the one hand, by calcination, when the whole of the organic matter is destroyed, emitting the odor of burned horn during the process, the residuary inorganic matter, which is light and porous, preserving the shape and size of the original bone, and being exceedingly friable, crumbles on the slightest pressure: whilst, on the other hand, if the bone be treated with dilute hydrochloric acid, the saline components are removed, and the remaining organic mass, which also preserves the original size and form of the bone, is tough and flexible, and much diminished in weight.] Bones are divisible into three classes : — Long, flat, and irregxdar. The Long bones are found principally in the limbs, and consist of a shaft and two extremities. The shaft is cylindrical or prismoid in form, dense and hard in texture, and hollowed in the interior into a medullary canal. The extremities are broad and expanded, to articulate with adjoining bones; and, in internal structure, are cellular or cancellous. Upon the exterior of the bone are processes and rough surfaces for the attachment of muscles, and foramina for the transmis- sion of vessels and nerves. The character of long bones is, therefore, their general type of structure and their divisibility into a central portion and extremities, and not so much their length; for there are certain long bones, as the second pha- langes of the toes, which are less than a quarter of an inch in length, and which, in some instances, exceed in breadth their longitudinal axis. The long bones are, the clavicle, humerus, radius and ulna, femur, tibia and fibula, metacarpal bones, metatarsal, phalanges, and ribs. Flat bones are composed of two layers of dense bone with an intermediate cel- lular structure, and are divisible into surfaces, borders, angles, and processes. 42 structure of bone. They are adapted to inclose cavities; have processes upon their, surface for the attachment of muscles; and are perforated by foramina, for the passage of nu- trient vessels to their cells, and for the transmission of vessels and nerves. They articulate with long bones by means of smooth surfaces plated with cartilage, and with each other, either by fibro-cartilaginous tissue, as at the symphysis pubis, or by suture, as in the bones of the skull. The two condensed layers of the bones of the skull are named tables; and the intermediate cellular structure, diplbe. The flat bones are the occipital, parietal, frontal, nasal, lachrymal, vomer, ster- num, scapulae, and ossa innominata. The Irregular bones include all that remain after the long and the flat bones have been selected. They" are essentially irregular in their form, in some parts flat, in others short and thick; and are constructed on the same general princi- ple as other bones: they have an exterior dense, and an interior more or less cel- lular. The bones of this class are the temporal, sphenoid, ethmoid, superior maxillary, inferior maxillary, palate, inferior turbinated, hyoid, vertebrae, sacrum, coccyx, carpal, tarsal, and sesamoid bones, the latter including the patellae. [The symmetry or want of symmetry of bones is also a basis for the determi- nation of their figure. Thus, some bones being divisible into two halves, exactly resembling each other, are called symmetrical or azygos bones, and as these always occupy the mesial line, they are also denominated median; whilst the remainder, which cannot be divided into two similar parts, are called asymme- trical, and as they always occur in pairs, and are situated on opposite sides of the mesial line, they are also denominated corresponding or lateral bones.] Structure of Bone—Bone is a dense, compact, and homogeneous substance (basis substance) filled with minute cells [lacunae] (corpuscles of PurkiDje), Fig. 17. [Fig. 16. Haversian Canals, seen on a longitudinal section of the com- pact tissue of the shaft of one of the long bones. 1. Arterial canal. 2. Venous canal. 3. Dilatation of another venous canal.] Minute structure of bone, drawn with the micro- scope from nature, by Bagg. Magnified 300 diameters. 1. One of the Haversian canals surrounded by its con- centric lamellae. The corpuscles are seen between the lamellae; but the calcigerous tubuli are omitted. 2. An Haversian canal with its concentric lamellae, Purkinjean corpuscles, and tubuli. 3. The area of one of the canals. 4, 4. Direction of the lamellae of the great medullary canal. Between the lamellae, at the upper part of the figure, several very long corpuscles with their tubuli are seen. In the lower part of the figure, the outlines of two other canals are given, to show their form and mode of arrangement in the entire bone. STRUCTURE OF BONE. 43 which are scattered numerously through its structure. The basis substance of bone is subfibrous and obscurely lamellated, the lamellae being concentric in long, and parallel in flat bones: it is traversed in all directions, but especially in the longitudinal axis, by branching and inosculating canals (Haversian1 canals), which give passage to vessels and nerves, and in certain situations the lamellae separate from each other, and leave between them areolar spaces (cancelli) of various magnitude. The lamellae have an average diameter of go'cu °f an incn> and, besides constituting the general structure of the basis substance, are collected concentrically around the Haversian canals, and form boundaries to those canals of about ^q of an inch in thickness. The number of lamellae surrounding each Haversian canal is commonly ten or fifteen, and the diameter of the canals has a medium average of g^ of an inch. The cancelli of bone, like its compact sub- stance, have walls which are composed of lamellae: and, such is the similarity in structure of the parts of a bone, that the entire bone may be compared to an Haversian canal, of which the medullary cavity is the magnified channel; and the Haversian canals may be likened to elongated and ramified cancelli. The Haver- sian canals are smallest near the surface of a bone, and largest near its centre, where they gradually merge into cancelli; by the frequent communications of their branches they form a coarse network in the basis substance. [Fig. 18. Transverse section of a human femur, about its middle, exhibiting the erratic course of the Haversian canals, and their relations to each other, and at the same the general lami- nated condition of a long bone. This laminated condition is well shown by polarized light, which causes the corpuscles to disappear, and the laminae to come out boldly.] The corpuscles of Purltinje, are thickly disseminated through the basis sub- stance ; they are irregular in size and form, give off numerous minute branching tubuli [canaliculi], which radiate from all parts of their circumference, and, in the dried state of the bone, contain merely the remains of membranous cells and some calcareous salts.2 In the living bone, the corpuscles and their tubuli are probably filled with a nutritive fluid holding calcareous salts in solution. The form of the cells is oval or round, and more or less flattened; their long diameter 1 [After their discoverer, Clopton Havers, an English physician and writer of the 17th century.] 1 Miiller and Henle conceived that the bone cells and tubuli were the principal seat of the calcareous matter. Hence they were called calcigerous cells and tubuli. 44 DEVELOPMENT OF BONE. corresponds with the long axis of the bone, and their tubuli cross the direction of the lamellae, and constitute a delicate network in the basis substance by com- municating with each other and with the tubuli of neighboring cells. The tubuli of the cells nearest the Haversian canals terminate on the internal surface of [Fig. 19. [Fig. 20. Two lacunae of osseous tissue, seen on their surfaces, showing the disposition of their pores. The granular aspect of the tissue, both on their walls and around them, is well repre- sented. Magnified 1200 diameters. Drawn from a preparation of the cancelli of the Femur made by Mr. Tomes.] those passages. The size of the cells varies in extreme measurement from -g^Q to g^ of an inch in long diameter, an ordinary average being yo'oo> ^e Dread'th of the oval cells is about one-half or one-third their length, and their thickness one-half their breadth. They are situated between the lamellae, to which cir- cumstance they owe their compressed form. In the fresh state, bones are invested by a dense fibrous mem- brane, the periosteum, which covers every part of their surface with the exception of the articular extremities, the latter being coated by a thin layer of cartilage. The periosteum of the bones of the skull is termed pericranium ; and the analogous mem- brane of external cartilages, perichondrium. Lining the interior of the medullary canal of long bones, the Haversian canals, the cancelli, and the cancelli of the flat and irregular bones, is the medullary membrane, which acts as an internal periosteum. It is through the medium of the vessels ramifying in these mem- branes that the changes required by nutrition occur in bones, and the secretion of medulla into their interior is effected. The medullary canal, Haversian canals and cancelli of long bones, and the cancelli of other bones, are filled with a yellowish, oily substance, the medulla, which is contained in a loose, cellular tissue formed by the medullary membrane. Development of Bone.—To explain the development of bone, it is necessary to inform the student that all organized bodies, whether belonging to the vegetable or animal kingdom, are deve- loped primordially from minute vesicles. These vesicles, or, as they are .properly termed, .cells, are composed of a thin mem- brane, containing a fluid or granular matter, and a small rounded mass, the nucleus, around which the cell was originally formed. Moreover, the nucleus generally contains one or more small round granules, the nucleolus, or nucleoli. From cells having this structure all the tissues of the body are elaborated; the ovum itself origi- nally presented this simple form, and the embryo at an early period is wholly composed of such nucleated cells. In their relation to each other, cells may be The Perios- teum laid open and turned off from a young hu- merus.] DEVELOPMENT OF BONE. 45 isolated and independent, as is exemplified in the corpuscles of the blood, chyle, and lymph; secondly, they may cohere by their surfaces and borders, as in the epidermis and epithelium; thirdly, they may be connected by an intermediate substance, which is then termed intercellular, as in cartilage and bone; and, fourthly, they may unite with each other in rows, and upon the removal, by liquefaction, of their adherent surfaces, be converted into hollow tubuli. In the latter mode capillary vessels are formed, as also are the tubuli of nerves. One of the properties of cells may also be adverted to in this place; it is that of reproducing similar cells in their interior. In this case, the nucleoli become the nuclei of the secondary cells, and, as the latter increase in size, the membrane of the primary or parent cell is lost. Bone, in its earliest stage, is composed of an assemblage of these minute cells, which are soft and transparent, and are disposed within the embryo in the site of the future skeleton. From the resemblance which the soft bone-tissue bears to jelly, this has been termed the gelatinous stage of osteo-genesis. As development advances, the cells, heretofore loosely connected together, become separated by the interposition of a transparent intercellular substance, which, at first fluid, gradually becomes hard and condensed. The cartilaginous stage of osteo-genesis is now established, and cartilage is shown to consist of a transparent basis-sub- stance, having minute cells disseminated through it at pretty equal distances. Coincident with the formation of cartilage is the development of vascular canals in its substance, the canals being formed by the union of the cells in rows, and the subsequent liquefaction of their adhering surfaces. The change which next en- sues is the concentration of the vascular canals towards some one point; for exam- ple, the centre of the shaft in a long, or the mid-point of a flat bone, and here the punctum ossificationis, or centre of ossification, is esta- blished. What determines the vascular concentration now alluded to, is a question not easily solved, but that it takes place is certain, and the vascular punctum is the most easily demon- strable of all the phenomena of ossification. During the formation of the punctum ossificationis, changes begin to be apparent in the cartilage cells. Originally they are simple nucleated cells (soVo" to 20V0 °f an *ncn m diameter), having a rounded form. As growth proceeds, they become elongated, and it is then perceived that each cell contains two and often three nucleoli, around which smaller cells are in progress of forma- tion. If we examine them nearer the punctum ossificationis, we find that the young or secondary cells have each attained the size of the parent cell (30W °^ an inch), the membrane of the parent cell has disappeared, and the young cells are separated to a short distance by freshly effused intercellular substance. Nearer still to the punctum ossificationis a more remarkable change has ensued, the energy of cellule reproduction has augmented with proximity to the ossifying point, and each cell, in place of producing two, gives birth to four, five, or six young cells, which rapidly destroy the parent membrane and attain a greater size (jjgs of an inch) than the parent cell, each cell being, as in the previous Fig. 21. B ^' * J \%® Figures illustrative of the development of bone ; magnified 155 times, and drawn with the camera lucida. A. A portion of cartilage the furthest removed from the seat of ossi- fication, showing simple nucleated cells, having an ordinary size of ojj'gjj of an inch, long diameter. B. The same carti- lage,nearer the seat of ossification j each simple cell has pro- duced two, a little larger than the cells in figure a. 46 DEVELOPMENT OF BONE. $ 09 case, separated to a slight extent from its neighbor by intercellular substance. By one other repetition of the same process, each cell producing four, five, or six young cells, a cluster is formed, containing from thirty to fifty cells. These clusters lie in immediate relation with the punctum ossificationis; they are oval in figure (about 2^ of an inch in length by ^g in breadth), and elongated in the direction of the long axis of the bone. The cells com- posing the cluster lie trans- versely with regard to its axis. In the first instance they are closely compressed, but by degrees are parted by a thin layer of intercellular substance, and each cluster is separated from neighboring clusters by a broader layer (33*^0 of an inch) of intercellular substance. Such are the changes which occur in cartilage preparatory to the formation of bone. Fig. 23. Fig. 22. The same cartilage, still nearer the seat of ossi- fication: each single cell of b has given birth to four, five, or six cells, which form clusters. The clusters become larger towards the right of their figure, and their cells more numerous and larger, t^ud °f an inch, long diameter. The same cartilage at the seat of ossification : the clusters of cells are arranged in columns; the intercellular spaces between the columns being 5^55 of an inch in breadth. To the right of the figure osseous fibres are seen occupying the intercellular spaces, at first bounding the clusters laterally, then splitting them longitudinally, and encircling each sepa- rate cell. The greater opacity of the right-hand border is due to a threefold cause, namely, increase of osseous fibres, opacity of the contents of the cells, and multiplication of oil- globules. In the lower part of the figure some attempt has been made to show the texture of the cells. Ossification is accomplished by the formation of very fine and delicate fibres ■ within the intercellular substance: this process commences at the punctum ossi- ficationis, and extends from that point through every part of the bone, in a longi- tudinal direction in long, and in a radiated direction in flat bones. Starting from the punctum ossificationis, the fibres embrace each cluster of cells, and then send branches between the individual cells of each group. In this manner the net- work, characteristic of bone, is formed, while the cells by their conjunction con- stitute the permanent areolae and Haversian canals. With a high magnifying power, the delicate ossific fibres here alluded to are seen themselves to be com- posed of minute cells having an elliptical form and central nuclei. These cells attract into their interior the calcareous salts of the blood, and their nuclei become developed, as I believe, into the future corpuscles of Purkinje. It is possible also that some of the cartilage cells become corpuscles of Purkinje in the fully developed bone. PERIODS OF OSSIFICATION. 47 During the progress of the phenomena above described, the contents of the cells undergo certain changes. At first, they are transparent, then they become granular, and still later opaque, from the presence of amorphous matter mingled with nuclei, nucleoli, and the remains of secondary cells. In the latter state the cells contain an abundance of minute oil globules, which increase in size as the ossific changes advance, and in the newly-formed osseous areolae, have attained the ordinary size of adipose cells. Cartilaginification is complete in the human embryo at about [Fig. 24. the sixth week; and the first point of ossification is observed in the clavicle at about the fifth week. Ossification commences at the centre, and thence proceeds towards the surface; in flat bones the osseous tissue radiates between two membranes from a central point towards the periphery, in short bones from a centre towards the circumference, and in long bones from a central portion, diaphysis, towards a secondary centre, epiphy- sis, situated at each extremity. Large processes, as the tro- chanters, are provided with a distinct centre of development, which is named apophysis. The growth of bone in length takes place at the extremity of the diaphysis, and in bulk by fresh deposition on the sur- face ; while the medullary canal is formed and increased by absorption from within. The period of ossification is different in different bones; the order of succession may be thus arranged : — During the fifth week, ossification commences in the clavi- cle, lower jaw, and upper jaw. During the sixth week, in the femur, humerus, tibia, radius, and ulna. During the seventh and eighth weeks, in the fibula, frontal, occipital, sphenoid, ribs, parietal, temporal, nasal, vomer, A you palate, vertebrae, first three pieces of sacrum, malar, metacar- i; 5 The epjphy- pus, metatarsus, third phalanges of the hands and feet, and Ses. 4. The dia- ilium. physis. 2, 3. Apo- During the third month, in the first and second phalanges physes.] of the hands and feet, lachrymal bone, and ischium. During the fifth month, in the mastoid portion of the temporal, ethmoid, infe- rior turbinated, sternum, os pubis, and last two pieces of sacrum. During the sixth month, in the body and odontoid process of the axis, and in the os calcis. During the seventh month, in the astragalus. During the tenth month, in the cuboid bone and os hyoides. During the first year, in the coracoid process of the scapula; first piece of the coccyx, inferior turbinated bone, last piece of the sternum, anterior arch of the atlas, os magnum, os unciforme, and external cuneiform bone. During the third year, in the cuneiform of the carpus, internal cuneiform of the tarsus, and patella. During the fourth year, in the middle cuneiform and scaphoid of the tarsus. During the fifth year, in the trapezium and os semilunare. During the seventh year, in the second piece of the coccyx. During the eighth year, in the scaphoid of the carpus. During the ninth year, in the os trapezoides. During the twelfth year, in the os pisiforme and third piece of the coccyx. During the eighteenth year, in the fourth piece of the coccyx. The ossicula auditus are the only bones completely ossified at birth; the ver- tebrae are not completed until the five-and-twentieth year. The entire osseous framework of the body constitutes the skeleton, which, in 48 VERTEBRAL COLUMN. the adult man, is composed of two hundred and forty-six distinct bones. They may be thus arranged : — Head.................8 Ossicula auditus..............6 Face..................14 Teeth.................32 Vertebral column, including sacrum and coccyx .... 26 Os hyoides, sternum, and ribs..........26 Upper extremities.............64 Lower extremities.............62 Sesamoid bones..............8 246 [When the bones which constitute the skeleton, as presented for study, are connected with each other by their own ligaments, it is called a natural skeleton ; when, however, they are connected by wires, or other artificial media, it is called an artificial skeleton^ The skeleton is divisible into: 1. The vertebral column, or central axis. 2. The head and face, or superior development of the central axis. 3. The hyoid arch. 4. The thoracic arch and upper extremities. 5. The pelvic arch and lower extremities. VERTEBRAL COLUMN. The vertebral column is the first and only rudiment of internal skeleton in the lower Vertebrata, and constitutes the type of that great division of the animal kingdom. It is also the first developed portion of the skeleton in man, and the centre around which all the other parts are produced. In its earliest formation it is a simple cartilaginous cylinder, surrounding and protecting the primitive trace of the nervous system; but, as it advances in growth and organization, it becomes divided into distinct pieces, which constitute vertebrae. The vertebrae admit of a division into true and false. The true vertebrae are twenty-four in number, and are classed, according to the three regions of the trunk which they occupy, into cervical, dorsal, and lumbar. The false vertebrae consist of nine pieces united into two bones, the sacrum and coccyx. The arrangement of the vertebrae may be better comprehended by means of the accompanying table : — f 7 Cervical, ( p, q True vertebrae, 24 \ 12 Dorsal, False vertebrae, 9 \ ? £acrutn* ( 5 Lumbar. 14 Coccyx. Characters of a Vertebra.—A vertebra consists of a body, two laminae, a spinous process, two transverse processes, and four articular processes. The body is the solid part of the vertebra; and, by its articulation with adjoining vertebrae, gives strength and support to the trunk. It is flattened above and below, con- vex in front, and slightly concave behind. Its anterior surface is constricted around the middle, and pierced by numerous small openings, which give passage to nutritious vessels. On its posterior surface is a single irregular opening, or several, for the exit of the venae basis vertebrae. The laminae commence upon the sides of the posterior part of the body of the vertebra by two pedicles ; they then expand; and, arching backwards, inclose a foramen, which serves for the protection of the spinal cord. The upper and lower borders of the laminae are rough for the attachment of the ligamenta sub- flava. The concavities above and below the pedicles are the intervertebral notches. The spinous process stands backwards from the angle of union of the laminae. It is the succession of these projecting processes along the middle line of the back, that has given rise to the common designation of the vertebral CERVICAL VERTEBRAE—ATLAS. 49 column, the spine. The use of the spinous process is for the attachment of mus- cles. The transverse processes project, one at each side, from the laminae of the vertebra; they also are intended for the attachment of muscles. The articular processes, four in number, stand upwards and downwards from the laminae, to articulate with the vertebra above and below. Cervical Vertebrae.—In a cervical vertebra the body is smaller than in the other regions; it is thicker before than behind, broad from side to side, concave on the upper surface, and convex below; so that, when articulated, the vertebrae lock the one into the other. The lamino? are narrow and long, and the included spinal foramen large and triangular. The superior intervertebral notches are slightly deeper than the inferior; the inferior being the broadest. The spinous process is short and bifid at the extremity, increasing in length from the fourth to the seventh. The transverse processes are also short and bifid, and deeply grooved along the upper surface for the cervical nerves. Piercing the base of the transverse process is the vertebral foramen,' which gives passage to the ver- tebral artery and vein, and vertebral plexus of nerves. The transverse processes in this region are formed by two small developments, which proceed, the one from the side of the body, the other from the pedicle of the lamina, and unite near their extremities to inclose the circular area of the vertebral foramen. The anterior of these developments is the rudiment of a cervical rib; the posterior, the analogue of the transverse processes in the dorsal region. The extremities of these developments are the anterior and posterior tubercles of the transverse process. The articular processes are oblique; the superior looking upwards and backwards; the inferior, downwards and forwards. Fig. 25. Fig. 26. A central cervical vertebra, seen upon its upper surface. 1. The body, concave in the middle, and rising on each side into a sharp ridge. 2. The lamina. 3. The pedicle, rendered concave by the supe- rior intervertebral notch. 4. The bifid spi- nous process. 5. The bifid transverse process. The figure is placed in the concavity between the anterior and posterior tubercle, between the two processes which correspond with the rudimentary rib and the true transverse pro- cess. 6. The vertebral foramen. 7. The supe- rior articular process, looking backwards and upwards. 8. The inferior articular process. There are three peculiar vertebrae in the cervical region: — The first, or atlas; the second, or axis; and the seventh, or vertebra prominens. The Atlas (named from supporting the head) is a simple ring of bone, without body, and composed of arches and processes. The anterior arch has a tubercle on its anterior surface, for the attachment of the longus colli muscle; and on ita 1 Sometimes, as in a vertebra now before me, a small additional opening exists by the Bide of the vertebral foramen, in which case it is traversed by a second vein. 4 The upper surface of the atlas. 1. The anterior tubercle projecting from the anterior arch. 2. The articular surface for the odontoid process on the posterior surface of the anterior arch. 3. The posterior arch, with its rudimentary spinous process. 4. The intervertebral notch. 5. The transverse pro- cess. 6. The vertebral foramen. 7. Superior articular surface. 8. Tubercle for the attach- ment of the transverse ligament. The tuber- cle referred to is just above the head of the figure; the convexity below it is the margin of the inferior articulating process. 50 AXIS — VERTEBRA PROMINENS. posterior aspect is a smooth surface, for articulation with the odontoid process of the axis. The posterior arch is longer and more slender than the anterior, and flattened from above downwards; at its middle is a rudimentary spinous process; and upon its upper surface, near the articular processes, a shallow groove1 at each side, which represents a superior intervertebral notch, and supports the vertebral artery (just before it perforates the dura mater) and the first cervical nerve. The intervertebral notches are peculiar, from being situated behind the articular pro- cesses, instead of before them as in the other vertebrae. The transverse processes are remarkably large and long, and pierced by the foramen for the vertebral artery. The articular processes are situated on the most bulky and strongest part of the atlas. The superior are oval and concave, and look inwards, so as to form a kind of cup for the condyles of the occipital bone, and are adapted to the nodding movements of the head; the inferior are circular, and nearly horizontal, to permit of the rotatory movements. Upon the inner face of the lateral mass which supports the articular processes, is a small tubercle at each side, to which the extremities of the transverse ligament are attached, a ligament which divides the ring of the atlas into two unequal segments; the smaller and anterior, for receiving the odontoid process of the axis; the larger and posterior, to give pas- sage to the spinal cord and its membranes. The Axis (vertebra dentata) is so named from having a process, shaped like a tooth, upon which the head turns as on a pivot. The body is of large size, and supports a strong process, the odontoid, which rises perpendicularly from its upper surface. The odontoid process presents two articulating surfaces; one on its anterior face, to articulate with the anterior arch of the atlas; tho other on its posterior face, for the transverse liga- ment; the latter surface constricts the base of the process, which has given rise to the term neck ap- plied to this pant. Upon each side of its apex is a rough depression, for the attachment of the alar ligaments; and running down from its base, on the anterior surface of the body of the vertebra, a vertical ridge, with a depression at each side for the attachment of the longus colli muscle. The laminae are large and strong, and unite posteriorly to form a long and bifid spinous process, which is concave beneath. The transverse processes are rudimentary, not bifid, and project only so far as to inclose the vertebral foramen, which is directed obliquely outwards instead of perpendicularly as in the other vertebrae. The superior articulating processes are situated on the body of the vertebra, at each side of the odontoid process. They are circular and nearly horizontal, having a slight in- clination outwards. The inferior articulating processes look downwards and forwards, as do the same processes in the other cervical vertebrae. The superior intervertebral notch is remarkably shallow, and lies behind the articular process as in the atlas. The lower surface of the body is con- vex, and is received into the concavity upon the upper surface of the third vertebra. The Vertebra prominens, or seventh cervical, approaches in character the upper dorsal vertebrae. It has received its designation from having a very long 1 This groove is sometimes converted into a foramen. Fig. 27. A lateral view of the axis. 1. The body ; the figure is placed on the depression which gives attach- ment to the longus colli. 2. The odontoid process. 3. The smooth facet on the anterior surface of the odontoid process which articulates with the anterior arch of the atlas ; the facet for the transverse ligament is beneath No. 2, where the con- striction called the neck of the odontoid process is seen ; the bulk of the process between 2, 3, would represent its head. 4. The lamina. 5. The spinous process. 6. The transverse process, pierced ob- liquely by the vertebral foramen. 7. The superior articular surface. 8. The inferior articular process. DORSAL VERTEBRAE—LUMBAR VERTEBRAE. 51 spinous process, which is single and terminated by a tubercle, and forms a pro- jection on the back part of the neck; to the extremity of this process the liga- mentum nuchae is attached. The transverse processes are but slightly grooved along the upper surface, have each a small foramen for the transmission of the vertebral vein, and present only a rudimentary bifurcation at their extremity. Sometimes the anterior tubercle represents a small but distinct rib. Dorsal Vertebrae.—The body of a dorsal vertebra is as long from before back- wards as from side to side, particularly in the middle of the dorsal region; it is thicker behind than before, and marked on each side by two half articulating sur- faces for the heads of two ribs. The pedicles are strong, and the laminae broad and thick; the spinal foramen small and round, and the inferior intervertebral notch of large size, the superior can scarcely be said to exist. The spinous pro- cess is long, prismoid, directed very obliquely downwards, and terminated by a tubercle. The transverse processes are large and strong, and directed obliquely backwards. Upon the anterior and superior aspect of their summits is a small facet for the articulation of the tubercle of a rib. The articular processes are vertical, the superior facing directly backwards, the inferior directly forwards. The peculiar vertebrae in the dorsal region are, the first, ninth, tenth, eleventh, and twelfth. The first dorsal vertebra approaches very closely in character, the last cervical. The body is broad from side to side, and concave above. The superior articular processes are oblique, and the spinous process horizontal. It has an entire articular surface for the [head of the] first rib, and a half surface for the second. The ninth dorsal vertebra has only one half articular surface at each side. The tenth has a single entire articular surface at each side. The eleventh and twelfth have each a single entire articular surface at each side; they approach in character, the lumbar vertebrae: their transverse processes are very short, trifid at their summits, and have no articulation with the corresponding ribs. The transverse processes of the twelfth dorsal vertebra are rudimentary, and its inferior articular processes look outwards. Fig. 29. Lateral view of a dorsal verte- bra. 1. The body. 2, 2. Articular facets for the heads of ribs. 3. The pedicle. 4. The superior intervertebral notch. 5. The inferior intervertebral notch. 6. The spi- nous process. 7. The extremity of the transverse process, marked by an articu- lar surface for the tubercle of a rib. 8. The two superior articular processes, look- ing backwards. 9. The two inferior articu- lar processes, looking forwards. Lateral view of a lumbar vertebra. 1. The body. 2. The pedicle. 3. The su- perior intervertebral notch. 4. The infe- rior intervertebral notch. 5. The spinous process. 6. The transverse process. 7. The superior articular processes. 8. The infe- rior articular processes. 9. The posterior transverse process. Lumbar Vertebrae.—These are the largest pieces of the vertebral column. The body is broad and large, and thicker before than behind. The pedicles very strong; the laminae short, thick, and broad; the inferior intervertebral notches 52 VERTEBRAL COLUMN. [Fig. 30. A lateral view of the spinal column, showing its curvatures and internal structure. 1. at- las. 2. Dentata. 3. Seventh cer- vical vertebra. 4. Twelfth dorsal vertebra. 5. Fifth lumbar vertebra. 6. First piece of sacrum. 7. Last piece of sacrum. 8. Coccyx. 9. A spinous process. 10,10,10. Inter- vertebral foramina.] very large, and the spinal foramen large and oval. The spinous process is thick and broad. The trans- verse processes (costiform processes) are slender, pointed, and directed very slightly backwards. The superior articular processes are concave, and look backwards and inwards; the inferior convex, look forwards and outwards. Projecting back- wards and upwards from the superior articular process is a short and flattened tubercle or poste- terior transverse process, and in a strongly marked vertebra there is not unfrequently at the base of this a smaller tubercle which has a direction downwards. The last lumbar vertebra differs from the rest in having the body very much bevelled posteriorly, so as to be thick in front and thin be- hind, and the transverse processes thick and large. General Considerations.—Viewed as a whole, the vertebral column represents two pyramids ap- plied base to base, the superior being formed by all the vertebrae from the second cervical to the last lumbar, the inferior by the sacrum and coccyx. Examined more attentively, it will be seen to be composed of four irregular pyramids, applied to each other by their smaller extremities and by their bases. The smaller extremity of the upper- most pyramid is formed by the axis, or second cervical vertebra; and its base, by the first dorsal. The second pyramid is inverted; having its base at the first dorsal, and the smaller end at the fourth. The third pyramid commences at the fourth dorsal, and gradually enlarges to the fifth lumbar. The fourth pyramid is formed by the sacrum and coccyx. The bodies of the vertebrae are broad in the cervical region; narrowed almost to an angle in 9 the middle of the dorsal, and again broad in the lumbar region. The arches are broad and imbri- cated in the cervical and dorsal regions/the infe- rior border of each overlapping the supWior of the next; in the lumbar region an interval is left be- tween them. A considerable interval exists be- tween the cranium and atlas, and another between the last lumbar vertebra and sacrum. The spinous processes are horizontal in the cer- vical, and become gradually oblique in the upper part of the dorsal region. In the middle of the dorsal region they are nearly vertical, and imbri- cated, and towards its lower part assume the direc- tion of the lumbar spines, which are quite hori- zontal. The transverse processes developed in their most rudimentary form in the axis, gradually in- crease in length to the first dorsal vertebra. In the dorsal region they project obliquely back- wards, and diminish suddenly in length in the eleventh and twelfth vertebrae, where they are DEVELOPMENT OF VERTEBRiE, 53 very small. In the lumbar region they increase in length to the middle verte- bra, and again subside to the last. The transverse processes consist essentially of two parts, the anterior of which in the dorsal region is the rib, while the posterior retains the name of transverse process. In the cervical region these two elements are quite apparent, both by their different points of attachment to the vertebra, and by the vertebral foramen which divides them at their base. In the lumbar region the so-called transverse processes are in reality lumbar ribs, while the transverse processes will be found behind them in a rudimentary state, developed like the true transverse processes in the cervical region, from the superior articular processes. When the anterior and posterior transverse processes are examined in relation with each other, they will be observed to converge; if they were prolonged they would unite as in the cervical region and inclose a foramen, or they would rest in contact as in the dor- sal region, or become consolidated as in the formation of the sacrum. Moreover, the posterior transverse processes are directed upwards, and if they were pro- longed, they would come into contact with a small tubercle which is found at the base of the posterior transverse process (in strongly marked vertebrae) in the ver- tebra above. This junction would form a posterior intervertebral foramen, as actually occurs in the sacrum. In brief, the lumbar vertebrae exhibit those tran- sitional changes which are calculated, by an easy gradation, tp convert separate vertebrae into a solid bone. The transverse processes of the eleventh and twelfth dorsal vertebrae are interesting in a transcendental point of view, as exhibiting a tendency, which exists obscurely in all the rest, to trifurcate. Now, supposing these three branches to be lengthened in order to fulfil their purposes, the ante- rior would constitute the articulation or union with a rib, while the superior and inferior would join similar branches in the vertebra above and below, and form a posterior intervertebral foramen. The intervertebral foramina formed by the juxtaposition of the intervertebral notches are smallest in the cervical region, and gradually increase to the last lumbar. On either side of the spinous processes, and extending the whole length of the column, is the vertebral groove, which is shallow and broad in the cervical, and deeper and narrower in the dorsal and lumbar regions. It lodges the prin- cipal muscles of the back. Viewed from the side, the vertebral column presents several curves, the prin- cipal of which is situated in the dorsal region, the concavity looking forwards. In the cervical and lumbar regions the column is convex in front; and in the pelvis an anterior concave curve is formed by the sacrum and coccyx. Besides the antero-posterior curves, a slight lateral curve exists in the dorsal region, having its convexity towards the right side. Development.—The vertebrae are developed by three primary and five secondary centres or epiphyses. The primary centres are, one for each lamella, and one for the body; the epiphyses, one for the apex of the spinous process, one for that of each transverse process, one for the upper and one for the under surface of the body. Exceptions to this mode of development are met with in the atlas, axis, vertebra promineus, and lumbar vertebrae. The atlas has four centres : one for each lateral mass, one (sometimes two) for the anterior arch, and one for the centre of the posterior arch. The axis has five : one (sometimes two) for the body, two for the odontoid process, appearing side by side in its base, and one for each lamella. The vertebra prominens has two additional centres for the anterior or costal segments of the transverse processes, and the lumbar vertebras two for the posterior segments of the transverse processes. The primary centres of the vertebrae make their appearance during the seventh or eighth week of embryonic existence, the lamella being somewhat in advance of the body. From the lamella are produced the spinous, transverse, and articular processes, and the sides of the body; they unite, to complete the arch, one year after birth, and with the body during the fifth year. The epiphyses for the extre- 54 DEVELOPMENT OF VERTEBRA. mities of the spinous and transverse processes make their appearance at fifteen or sixteen, and become united between twenty and twenty-five. The epiphyses of the body are somewhat later in appearance, and are consolidated between the periods of twenty five and thirty years of age. [Fig. 32. [Fig. 31. Development of vertebrae. A. The three principal pieces of the vertebrae are seen to be distinct. b. The lateral pieces have joined behind. The spinous and transverse processes remain cartilaginous at their ends. The arch is still separable from the middle anterior piece, and the carti- lage having been removed from the body, the surface of this is rounded, rough, and fissured. 1, 2. The lateral pieces. 3. The an- terior part for the body. * Line of sepa- ration between the lateral pieces and the anterior.] Development of vehtebral epiphyses. C. Dorsal vertebra. The epiphyses of the pro- cesses are drawn slightly away from the rest of the bone. d. The arch and processes of a lumbar verte- bra, with the epiphyses. These are somewhat elongated, but are apparently reduced in the drawing by being viewed from above. e. A front view of the body of a vertebra, to exhibit the thin epiphyses which belong to its upper and lower surfaces. 4, 5. The ends of the transverse processes. 6. Spinous process. 7, 8. The two epiphyses of the body ; the flat surface of one is seen in figure c; the edges of both are marked in figure e. 9, 10. Epiphyses of the articular tubercles of a lumbar vertebra.] The ossific centres, for the lateral masses, of the atlas, appear at the same time as those of the other vertebrae; they unite posteriorly at the end of the second year, by the intervention of the centre for the posterior arch. The one or two centres of the anterior arch appear during the first year, and become con- solidated with the lateral pieces during the fifth or sixth year. The axis deve- lops its lateral pieces at the same time as the other vertebrae: they join poste- riorly soon after birth, and with the body during the fourth or fifth year. The centres for the body and odontoid process appear during the sixth month, and are consolidated during the third year. The body of the axis is more largely developed at birth than that of the other vertebrae. The costal segments of the vertebra prominens appear during the second month, and become united to the body at the fifth or sixth year; they sometimes remain permanently separate, and constitute cervical ribs. The transverse process of the first lumbar vertebra has sometimes a distinct centre, which may remain permanently separate, in that case forming a lumbar rib. The ossification of the arches of the vertebrae commences from above, and pro- ceeds gradually downwards; hence arrest of development gives rise to spina bifida, generally in the loins. Ossification of the bodies, on the contrary, com- mences at the centre, and proceeds from that point towards the extremities of the column; hence imperfection of the bodies occurs either in the upper or lower vertebrae. Attachment of Muscles.—To the atlas are attached nine pairs of muscles * the lon- gus colli, rectus anticus minor, rectus lateralis, rectus posticus minor, obliquus supe- rior and inferior, splenius colli, levator anguli scapulae, and first intertransversales. SACRUM. 55 To the axis are attached eleven pairs, viz.: longus colli, intertransversales, ob- liquus inferior, rectus posticus major, interspinales, semi-spinalis colli, multifidus spinae, levator anguli scapulae, splenius colli, transversalis cervicis, and scalenus medius. To the remaining vertebrae collectively, thirty-one pairs and one single muscle, viz.: posteriorly, trapezius, latissimus dorsi, levator anguli scapulae, rhomboideua minor and major, serratus posticus superior and inferior, splenius, sacro-lumbalis, longissimus dorsi, spinalis dorsi, cervicalis ascendens, transversalis cervicis, tra- chelo-mastoideus, complexus, semispinalis dorsi and colli, multifidus spinae, inter- spinales, intertransversales, levatores costarum : anteriorly, rectus anticus major, longus colli, scalenus anticus, medius, and posticus, psoas magnus, psoas parvus, quadratus lumborum, diaphragm, obliquus internus and transversalis. The Sacrum is a triangular bone, situated at the lower extremity of the ver- tebral column, and formed by the consolidation of five false vertebrae. It is divisible into an anterior and a posterior suface, two lateral and a superior bor- der, and an inferior extremity. The anterior surface is concave, and marked by four transverse lines, which indicate its original constitution of five separate pieces. At the extremities of these lines, on each side, are the four anterior sacral foramina, which diminish in size from above downwards, and transmit the anterior sacral nerves. The projec- tion of the superior piece is the sacro-vertebral angle or promontory. Fig. 33. Fig. 34. The sacrum seen upon its anterior surface. 1,1,1, 1. Transverse lines mark- ing the original constitution of the bone of four pieces. 2, 2, 2, 2. Anterior sacral fora- mina. 3. Promontory of the sacrum. 4. Ear- shaped surface to articulate with the ilium. 5. The sharp edge to which the sacro-ischi- atic ligaments are attached. 6. The verte- bral articular surface. 7. The broad trian- gular surface which supports the psoas muscle and lumbo-sacral nerve. 8. Articu- lar process of the right side. 9. Inferior extremity, or apex of the sacrum. 10. One of the sacral cornua. 11. The notch which is converted into a foramen by the coccyx. Posterior view of the sacrum.— 1,1, 1,1. The four rudimentary spinous pro- cesses. 2, 2. The sacral canal. 3, 3, 3, 3, 3. Rudimentary articular processes. The low- est of these processes, with the correspond- ing process of the opposite side, 4, are the sacral cornua. 5,5, 5, 5. The four posterior sacral foramina. 6, 6, 6, 6, 6. Posterior trans- verse tubercles. 7. The auricular surface. 8. Sharp edge for the attachment of the sa- cro-ischiatic ligaments. 9. Surface for ar- ticulation with the body of the last lumbar vertebra. 10, 10. Articulating facets of the articular processes. 11. Apex of the sacrum by which it articulates with the coccyx. 12. Rough surface for the attach- ment of the posterior sacro-iliac ligaments. The posterior surface is narrower than the anterior, and convex. On the middle line is a rough crest formed by the rudiments of four spinous processes, the fifth remaining undeveloped, and exposing the lower termination of the sacral 56 SACRUM. canal. Immediately external to and parallel with the median crest, is. a range of five small tubercles which represent the articular processes of the true verte- brae; beyond these is a shallow groove in which the four posterior sacral fora- mina open, and further outwards, a range of five tubercles corresponding with the posterior transverse processes of the lumbar vertebrae. The lowest pair of articular tubercles bound on each side the termination of the sacral canal, and send each a process downwards to articulate with the coccyx. The two descending pro- cesses are the sacral cornua. The posterior sacral foramina are smaller than the anterior, and transmit the posterior sacral nerves. Of the posterior trans- verse tubercles the first corresponds with the angle of the superior border of the bone; the second is small, and enters into the formation of the sacro-iliac articu- lation ; the third is large, and gives attachment to the oblique sacro-iliac liga- ment; the fourth and fifth are smaller, and serve for the attachment of the sacro- ischiatic ligaments. The lateral border of the sacrum presents superiorly a broad and ear-shaped (auricular) surface to articulate with the ilium; and inferiorly a sharp edge, to which the greater and lesser sacro-ischiatic ligaments are attached. On the superior border, in the middle line, is an oval articular surface, corre- sponding with the under part of the body of the last lumbar vertebra; and on each side a broad triangular surface, which supports the lumbo-sacral nerve and psoas magnus muscle. Immediately behind the vertebral articular surface is the triangular entrance of the sacral canal; and, on each side of this opening, an articular process, which looks backwards and inwards, like the superior articular processes of the lumbar vertebrae. In front of each articular process is an inter- vertebral notch. The inferior extremity of the bone presents a small oval surface which articu- lates with the coccyx; and on each side a notch, which, with a corresponding notch in the upper border of the coccyx, forms the foramen for the transmission of the fifth sacral nerve. The sacrum presents some variety in respect of curvature, and of the number of pieces which enter into its structure. The curve is often very slight, and situated only near the lower part of the bone; while in other subjects it is con- siderable, and occurs at the middle of the sacrum. The sexual differences in the sacrum relate to its greater breadth, and the greater angle which it forms with the rest of the vertebral column in the female, rather than to any peculiarity in shape. It is sometimes composed of six pieces, more rarely of four, and, occa- sionally, the first and second pieces remain permanently separate. Development. — By twenty-one points of ossification; five for each of the first three pieces, viz., one for the body, one for each lateral portion, and one for each lamina; and three for each of the last two, namely, one for the body and one for each lateral portion. In the progress of growth, and after puberty, fourteen epi- physal centres are added, namely, two for the surfaces of each body, one for each auricular surface, and one for the thin edge of each lateral border. Ossification begins in the bodies of the sacral pieces somewhat later than in those of the true vertebrae; the first three appearing during the eighth and ninth week, and the last two at about the middle of intra-uterine existence. Ossification of the lamellae takes place during the interval between the sixth and ninth month. The epiphyses for the upper and under surface of the bodies are developed during the interval between the fifteenth and eighteenth year; and for the auricular and marginal piece, after twenty. The two lower vertebral pieces, although the last to appear, are the first to be completed (between the fourth and fifth year), and unite by their bodies. The union of the bodies takes place from below upwards, and finishes, between the twenty-fifth and thirtieth year, with the first two pieces. Articulation. — With four bones; the last lumbar vertebra, ossa innominata, and coccyx. COCCYX — OCCIPITAL BONE. 57 Attachment of Muscles.—To seven pairs; in front, pyriformis ; on the-side, coccygeus; and behind, gluteus maximus, latissimus dorsi, longissimus dorsi, sacro-lumbalis, and multifidus spinae. The Coccyx (x6xxv%, cuckoo, resembling a cuckoo's beak) is composed of four small pieces, which form the caudal termination of the vertebral column. The superior piece is broad, and ex- pands laterally into two transverse processes; it is sur- mounted by an oval articular surface and two cornua, the former to articulate with the apex of the sacrum, the latter with the sacral cornua. The lateral wings sometimes be- come connected with the sacrum, and convert the notches for the fifth pair of sacral nerves into foramina. The re- maining three pieces diminish in size from above down- wards. Development.—By four centres, one for each piece. Ossification commences in the first piece soon after birth; fROnt view of the in the second, between five and ten years; in the third, coccyx, l, 2, 3,4. The between ten and fifteen ; and in the fourth, between fifteen four pieces of the bone. and twenty. The pieces unite at an earlier period than 5,5- The transverse pro- the bodies of the sacrum, the first two pieces first, then the cesses of tbe first Piece- third and fourth, and lastly the second and third. Be- 6" Articulil|- surface for tween forty and sixty years, the coccyx becomes consoli- e ex ""I,1 y ° dated with the sacrum ; this event taking place later in the whic^ art'iculate with the female than in the male. sacral cornua. Articulations. — With the sacrum. Attachment of Muscles. — To three pairs, and one single muscle; gluteus maxi- mus, coccygeus, posterior fibres of the levator ani, and sphincter ani. OF THE S KULL. The skull, or superior expansion of the vertebral column, is divisible into two parts, the cranium and the face; the former being adapted, by its form, struc- ture, and strength, to contain and protect the brain; the latter, the chief organs of sense. The Cranium is composed of eight separate bones; viz., the Occipital, Two Temporal, Two Parietal, Sphenoid, Frontal, Ethmoid. Occipital bone.— This bone is situated at the posterior part and base of the cranium. It is trapezoid in figure, and divisible into two surfaces, four borders, and four angles. External Surface. — Crossing the middle of the bone transversely, from one lateral angle to the other, is a prominent ridge, the superior curved line. In the middle of the ridge is a projection, called the external occipital protuberance ; and descending from it a small vertical ridge, the spine. Above and below the supe- rior curved line the surface is rough, for the attachment of muscles; and on either side of the spine is a convexity, the receptaculum cerebelli. About three-quar- ters of an inch below the superior curved line is another transverse ridge, the inferior curved line, and beneath the latter the foramen magnum. On each side of the foramen magnum, nearer its anterior than its posterior segment, and encroaching somewhat upon the opening, is an oblong articular surface, the con- dyle, for articulation with the atlas The condyles approach towards each other anteriorly, their articular surfaces looking downwards and outwards. Directly 58 OCCIPITAL BONE. behind each condyle is an irregular fossa, and a small opening, the posterior condyloid foramen, for the transmission of a vein to the lateral sinus. In front of the condyle is the anterior condyloid foramen, for the hypoglossal nerve; on the outer side of each condyle, a projecting ridge, the transverse process, exca- vated in front by a notch which forms part of the jugular foramen ; and directly behind the ridge, and forming its posterior boundary, a prominent process, the jugular tubercle.1 In front of the foramen magnum is a thick square mass, the basilar process, and in the centre of the basilar process a small tubercle for the attachment of the superior and middle constrictor muscles of the pharynx. Fig. 36. Fig. 37. M§i flit*' External surface of the occipital bone. 1. Superior curved line. 2. Ex- ternal occipital protuberance. 3. Spine. 4. Inferior curved line. The convexity of the bone in this situation on either side of the spine is the reeeptaculum cerebelli. 5. Foramen magnum. 6. Condyle of the right side. 7. Posterior condyloid fossa, in which the posterior condyloid foramen is found. 8. Anterior condyloid foramen, concealed by the margin of the condyle. 9. Transverse process; this process on the internal surface of the bone forms the jugu- lar eminence. 10. The notch in front of the jugular eminence, forming part of the jugular foramen. 11. Basilar process. 12. Rough projections into which the odontoid ligaments are inserted. 13. Su- perior border. 14. Inferior border. Internal surface of the occipital bone. 1. Left cerebral fossa. 2. Left cere- bellar fossa. 3. Groove for the posterior part of the superior longitudinal sinus. 4. Spine for the falx cerebelli, and groove for the occipital sinuses. 5. Groove for the left lateral sinus. 6. Internal occipital protuberance, the groove on which lodges the torcular Herophili. 7. Foramen mag- num. 8. Basilar process, grooved for the medulla oblongata. 9. Termination of the groove for the lateral sinus, bounded exter- nally by the jugular eminence. 10. Jugu- lar fossa; this fossa is completed by the petrous portion of the temporal bone. 11. Superior border. 12. Inferior border. 13. Border which articulates with the petrous portion of the temporal bone, grooved by the inferior petrosal sinus. 14. Anterior condyloid foramen. Internal Surface. — On the internal surface is a crucial ridge, which divides the bone into four fossae; the two superior or cerebral fossae lodging the poste- rior lobes of the cerebrum ; the two inferior or cerebellar, the lateral lobes of the cerebellum. The superior arm of the crucial ridge is grooved for the superior longitudinal sinus, and gives attachment to the falx cerebri; the inferior arm is sharp and prominent for the attachment of the falx cerebelli, and slightly grooved for the two occipital sinuses. The transverse ridge gives attachment to the ten- torium cerebelli, and is deeply grooved for the lateral sinuses. At the point of 1 Retzius remarks that the jugular tubercle is very long in certain mammalia. OCCIPITAL BONE 59 meeting of the four arms is a projection, the internal occipital protuberance, which corresponds with the similar process situated on the external surface of the bone. The convergence of the four grooves forms a slightly depressed fossa, upon which rests the torcular Herophili. In the centre of the basilar portion of the bone is the foramen magnum, oblong in form, and larger behind than before, transmitting the spinal cord [with its envelops], spinal accessory nerves, and vertebral arteries. Upon the lateral margins of the foramen magnum are two rough eminences, which give attachment to the odontoid ligaments, and immediately above these, the openings of the anterior condyloid foramina. In front of the foramen magnum is the basilar process, grooved on its surface for supporting the medulla oblongata, and along each lateral border for the inferior petrosal sinus. On each side of the foramen magnum is a groove, for the termi- nation of the lateral sinus; a smooth surface, which forms part of the jugular fossa; and a projecting process, which divides the two, and is called the jugular eminence. Into the jugular fossa will be seen opening the posterior condyloid foramen. The superior borders are strongly serrated, and assist in forming the lamb- doidal suture; the inferior are rough, not serrated, and articulate with the mas- toid portion of the temporal bone by means of the additamentum suturae lamb- doidalis. The jugular eminence and side of the basilar process articulate with the petrous portion of the temporal bone, and the intervening space, which is irregularly notched, forms the posterior boundary of the jugular foramen, or foramen lacerum posterius. The angles of the occipital bone are, the superior, inferior, and two lateral. The superior angle is received in the interval formed by the union of the poste- rior and superior angles of the parietal bones, and corresponds with that portion of the foetal head which is called the posterior fontanel. The inferior angle is the articular extremity of the basilar process. The lateral angles, at each side, project into the interval formed by the articulation of the poste- terior and inferior angle of the parietal with the mastoid portion of the temporal bone. Development. — By seven cen- tres ; four for the four parts of the expanded portion divided by the crucial ridge, one for each condyle, and one for the basilar process. Ossification commences in the expanded portion of the bone at a period anterior to the vertebrae; at birth the bone con- sists of four distinct pieces ; which are united at about the fifth or sixth year. After twenty the basilar process unites with the body of the sphenoid. Articulations. — With six bones; two parietal, two tempo- ral, sphenoid, and atlas. Attachment of Muscles.—To thirteen pairs; to the rough sur- face above the superior curved line, the occipito-frontalis; to the superior curved line, the trapezius and sterno-mastoid; to the rough space between the curved lines, complexus, and splenius capitis; to the space between [Fig. 38. The occipital bone at different periods of its growth. a. At about the tenth week, a, the expanded por- tion of the bone. 1, 2. Its four nuclei, b, the nuclei for the condyloid pieces. The basilar nucleus is not yet apparent. b. At the ordinary period of birth, composed of four pieces, a, posterior or proper occipital, b, b, condy- loid pieces, c, basilar portion.] 60 PARIETAL BONE. the inferior curved line and the foramen magnum, the rectus posticus major and minor, and obliquus superior; to the transverse process, the rectus lateralis; and to the basilar process, the rectus anticus major and minor, and superior and middle constrictor muscles. Parietal Bone. — The parietal bone is situated at the side and vertex of the skull; it is quadrilateral in form, and divisible into an external and internal sur- face, four borders and four angles. The superior border is straight, to articulate with its fellow of the opposite side. The inferior border is arched and thin, to articulate with the temporal bone. The anterior border is concave, and the pos- terior somewhat convex. External Surface. — Crossing the bone in a longitudinal direction from the anterior to the posterior border, is an arched line, the temporal ridge, to which the temporal fascia is attached. In the middle of this line, and nearly in the centre of the bone, is the projection called the parietal eminence, which marks the centre of ossification. Above the temporal ridge the surface is rough, and covered by the aponeurosis of the occipito-frontalis; below the ridge the bone is smooth (planum semicirculare), for the attachment of the fleshy fibres of the temporal muscle. Near the superior border of the bone, and at about one-third from its posterior extremity, is the parietal foramen, which transmits a vein to the superior longitudinal sinus. This foramen is often absent. Fig. 40. Fig. 39. Internal surface of the left parie- tal bone. 1. Superior, or sagittal border. 2. Inferior, or squamous border. 3. Ante- rior, or coronal border. 4. Posterior, or lambdoidal border. 5. Part of the groove for the superior longitudinal sinus. 6. In- ternal termination of the parietal foramen. 7. Anterior inferior angle of the bone, on which is seen the groove for the trunk of the arteria meningea media. 8. Posterior infe- rior angle, on which is seen a portion of the groove for the lateral sinus. Internal Surface. —The internal table is smooth; it is marked by numerous furrows, which lodge the ramifications of the arteria meningea media, and by digital fossae which correspond with the convolutions of the brain. Along the upper border is part of a shallow groove, completed by the opposite parietal bone, which serves to contain the superior longitudinal sinus. Some slight pits are also observable near this groove, which lodge the glandulae Pacchioni. The anterior inferior angle is thin and lengthened, and articulates with the External surface of the left parie- tal bone 1. Superior, or sagittal border. 2. Inferior, or squamous border. 3. Ante- rior or coronal border. 4. Posterior, or lambdoidal border. 5. Temporal ridge ; the figure is situated immediately in front of the parietal eminence. 6. The parietal foramen, unusually large in the bone from which this figure was drawn. 7. Anterior inferior angle. 8. Posterior inferior angle. FRONTAL BONE. 61 Fig. 41. greater wing of the sphenoid bone. Its inner surface is deeply grooved for the trunk of the arteria meningea media; the groove being frequently converted into a closed canal. The posterior inferior angle is thick, and presents a broad and shallow groove for the lateral sinus. Development. — By a single centre. Ossification commences in the parietal eminence at the same time as in the bodies of the vertebrae. Articulations. —With/we bones; with the opposite parietal, occipital, frontal, temporal, and sphenoid. Attachment of Muscles. — To one only, the temporal. The aponeurosis of the occipito-frontalis glides over its upper surface. Frontal Bone. — The frontal bone bears some resemblance in form to the under valve of a scallop-shell. It is situated at the anterior part of the cranium, forming the forehead, and assisting in the construction of the roof of the orbits and nose. Hence it is divisible into a superior or frontal portion, and an infe- rior or orbito-nasal portion. Each of these portions presents for examination an external and internal surface, borders, and processes. External Surface. — At about the middle of each lateral half of the frontal portion is a projection, the frontal eminence. Below these points are the super- ciliary ridges, large towards their inner termination, and becoming gradually smaller as they arch outwards: they support the eyebrows. Beneath the superciliary ridges are the sharp and prominent arches which form the upper margin of the orbits, the supraorbital ridges. Externally the supraorbital ridge terminates in the external angular process, internally in the internal angu- lar process; at the inner third of this ridge is a notch, sometimes converted into a foramen, the supraorbital notch, which gives passage to the supraorbital artery, veins, and nerve. Between the two superciliary ridges is a rough projec- tion, the nasal tuberosity [glabella]; this portion of the bone denotes by its prominence the situation of the frontal sinuses. Extending upwards and back- wards from the external angular process is a sharp ridge, the commencement of the temporal ridge, and beneath the ridge a depressed surface, forming part of the temporal fossa. The orbito-nasal portion of the bone consists of two thin processes, the orbital plates, which form the roof of the orbits, and an intervening notch which lodges the ethmoid bone, and is called the eth- moidal fissure. The edges of the eth- moidal fissure are hollowed into cavities, which, by their union with the ethmoid bone, complete the ethmoidal cells; and, crossing these edges transversely, are two small grooves, sometimes canals, which open into the orbit by the anterior and posterior ethmoidal foramina. At the anterior termination of these edges are the irregular openings which lead into the frontal sinuses; and between the External surface of the frontal bone. 1. Situation of the frontal eminence of the right side. 2. Superciliary ridge. 3. Supra- orbital ridge. 4. External angular process. 5. Internal angular process. 6. Supraorbital notch, for the transmission of the supraorbital nerve and artery: in the figure it is partly converted into a foramen by a spiculum of bone. 7. Nasal tuberosity; the swelling around this point denotes the situation of the frontal sinuses. 8. Temporal ridge, com- mencing from the external angular process (4). The depression in which the figure 8 is situated is part of the temporal fossa. 9. Na- sal spine. 62 FRONTAL bone. two internal angular processes is a rough excavation which receives the nasal bones, and a projecting process, the nasal spine. On each orbital plate, imme- diately beneath the external angular process, is a shallow depression which lodges the lachrymal gland; and beneath the internal angular process a small pit, some- times a tubercle, to which the cartilaginous pulley of the superior oblique muscle is attached. Internal Surface.—Along the middle line of this surface is a grooved ridge, the edges of the ridge giving attachment to the falx cerebri, the groove lodging the superior longitudinal sinus. At the commencement of the ridge is an open- ing, sometimes completed by the ethmoid bone, the foramen caecum. This opening lodges a process of the dura mater, and occasionally gives passage to a small vein which communicates with the nasal veins. On each side of the ver- tical ridge are some slight depressions which lodge the glandulae Pacchioni, and on the orbital plates a number of irregular pits called digital fossae, which corre- spond with the convolutions of the anterior lobes of the cerebrum. The superior border is thick and strongly serrated, bevelled at the expense of the internal table in the middle, where it rests on the junction of the two parietal, Fig. 42. Internal surface of the frontal bone; the bone is raised to show the orbito-nasal portion. 1. Grooved ridge for the lodgment of the superior longitudinal sinus and attach- ment of the falx. 2. Foramen caecum. 3. Superior, or coronal border of the bone ; the figure is situated near that part which is bevelled at the expense of the internal table. 4. Inferior border of the bone. 5. Orbital plate of the left side. 6. Cellular border of the ethmoidal fissure. The foramen caecum (2) is seen through the ethmoidal fissure. 7. Anterior and pos- terior ethmoidal foramina ; the anterior is seen leading into its canal. 8. Nasal spine. 9. The depression within the external angular process (12) for the lachrymal gland. 10. Depression for the pulley of the superior oblique muscle of the eye; immediately to the left of this num- ber is the supraorbital notch, and to its right the internal angular process. 11. Opening lead- ing into the frontal sinuses; the leading line crosses the internal angular process. 12. Ex- ternal angular process. The correspo ding parts are seen on the other side of the figure. [in young subjects this obtuse angle, which is received into the retiring angle formed by the two parietal bones, is wanting; in its situation the anterior angle of the anterior fontanel is found,] and at the expense of the external table on each side where it receives the lateral pressure of those bones. The infe- rior border is thin, irregular, and squamous, and articulates with the sphenoid bone. Development. —By two centres, one for each lateral half. Ossification begins in the orbital arches, somewhat before the vertebrae. The two pieces are sepa- rate at birth, and unite by suture during the first year, the suture sometimes TEMPORAL BONE. 63 remaining permanent through life, frontal suture. The frontal sinuses make their appearance during the first year, and increase in size until old age. [Fig. 43. Frontal bone of a f