.#\ 
5
*
 
A TREATISE
ON
ANATOMY  AND PHYSIOLOGY,
W. P. ESREY, M. D.
      i « ^
WITH THIRTY ILLUSTRATIONS.
             PHILADELPHIA:
PUBLISHED bt RADEMACIIER & SHEEK, No. 239 ARCH STREET.
         NEW YORK: WM. RADDE, 322 BROADWAY.
      ST. LOUIS: J. G. WESSELHCEFT, 64 NORTH FOURTH ST.
          BOSTON: OTIS CLAPP, 23 SCHOOL ST.

                 18 5 1. 
/^w v\-e.xf
Entered, according to Act of Congress, in the Year 1851, by Rademacher & Sheek,
         in the Clerk's Office of the Eastern District of Pennsylvania. 
PREFACE.
   The  following Treatise was prepared to accompany a
work on Domestic Medicine, and without any design of
publishing it in  a separate form.  The Publishers, how-
ever, have thought  proper to issue it separately, believ-
ing that the multiplication of books of the kind, especially
w.en presented in a cheap and  condensed form, cannot
be other than productive of good results, as a greater
uu.nber of persons will thereby be induced to read and
study them.  Some  knowledge of the  structure and
functions of our organization is  almost indispensable, in
order to the proper preservation  and enjoyment of health,
without which life itself frequently becomes burdensome,
and with which  contentment  may be found in the hum-
blest cottage.
   To insure accuracy, the latest and best works on the
subjects have  been  carefully consulted, and the views of
the most  distinguished Anatomists  and Physiologists
given, as far as the  limits  allowed would admit of it. 
 
Anatomy and Physiology.
   The  growing  interest manifested in all classes to become
acquainted with the structure and formation of the human organ-
ism is sufficient excuse, if any be needed, for the introduction of
some general  remarks  on anatomy  and physiology into a work
of this  kind.   It is  indeed  important that  those  laymen who
occasionally prescribe for disease should have some acquaintance
with these subjects, to enable them  to discriminate with greater
accuracy between different morbid conditions, and to distinguish
really dangerous symptoms from those of but little consequence.
   No pretension is made to originality of matter in the prepa-
ration of this treatise, but the best  standard  text-books on the
subjects have  been freely consulted; and the chief aim has been
to condense into a small compass as  much useful matter as pos-
sible, though from the very limited  space  to  be occupied,  and
the wide field to go over, the information on many points must
necessarily be brief and imperfect.
   The  subjects being  very  intimately allied—Anatomy being
the science which investigates the structure and organization of
living beings, Physiology the science which treats of the actions
or functions peculiar  to living organized beings while in health
—it has been thought best to consider them together, rather than
under  separate heads,  as is  done  in all  the more  systematic
treatises.
   Comparative Anatomy treats of  the structure  of the lower
orders of animals.
   Comparative Physiology considers the functions of the inferior
animals.
   Vegetable Physiology treats exclusively of plants.   It is to
Human Anatomy and Physiology that this treatise will be prin-
cipally devoted.
   The substances in nature are divisible into two chief classes :
—the organized, or those which possess separate parts or organs 
8
ANATOMY AND PHYSIOLOGY.
 suited for the performance of certain actions or functions,  and
 the inorganic, or  such as are  without this arrangement.   The
 former  includes animals and vegetables,  the  latter the earths,
 metals,  &c.  All organized bodies have their origin from parents;
 they must spring from beings like themselves, and they are  con-
 trolled by vitality, or the principle of life. The several separate
 organs have a mutual dependence on each other, and to preserve
 the harmony of the whole,  the integrity of each part must be
 preserved.
   Organized bodies have likewise a definite shape and size,  and
 an allotted time to  live; and after death they are  decomposed,
 and pass into the simple combination  of the inorganic elements.
   Inorganic bodies, on the contrary, do not spring from parents;
 they  are  not  born;  but they  have  their origin  in,  and are
 governed by certain fixed and invariable natural laws.  The  par-
 ticles of which they consist are in a  state of aggregation only.
 And their growth, or increase of size, or change of  shape, takes
 place  by the accretion of matter to their surfaces.  The parts of
 which an inorganic body is composed  are  all alike  in structure
 and properties, and may exist as well in  detached portions, or
 when broken in pieces, as in large masses. And each body consists
 wholly of matter, either in the solid, liquid, or gaseous form.
   Organized bodies, on  the other hand,  are  always composed
of a combination  of solids and  fluids; they differ  in character
and properties, and  are  arranged into organs, so as to form of
 the whole a single  system.
   They also increase in size by  a process called nutrition, which
consists  in imbibing substances from without, and changing them,
by means  of internal organs, to  their own  nature.
   In respect to the chemical character of  inorganic and organic
bodies,  great difference exists.   All  the substances considered
elementary, amounting to about sixty, are  found in  the mineral
kingdom.   In the organized, only a few of these elements  are
met with—about seventeen—and of these but four are considered
essential,  viz. carbon, hydrogen, oxygen, and nitrogen; two of
which, at  least, will be found in every organic compound.  The 
ANATOMY AND PHYSIOLOGY.
9
other simple elements exist  in smaller quantities, and may  be
considered non-essential: they are, sulphur, phosphorus, chlorine,
sodium, calcium, potassium,  magnesium, silicon, aluminum, iron,
manganese, iodine, and bromium. The last two are found princi-
pally in marine plants and  animals.  The composition of inor-
ganic bodies is more simple, some consisting of but one element;
and when composed of more the combination rarely exceeds three.
Organized bodies, on the contrary,  in most instances consist of
three or four elements;  the simplest  vegetable  consists  of a
union of oxygen, carbon, and hydrogen; and the simplest animal
of oxygen, hydrogen, carbon,  and nitrogen.
   As both animal and vegetables are included  under the head
of organized bodies, it is necessary to point out some of the dis-
tinctive characters between  these kingdoms.   Nutrition, or the
capacity of assimilating foreign matters to  their own substance for
purposes of development and growth, and reproduction, or the
power of producing a living being similar to  themselves,  are
properties common to each.   Besides these  there are other pro-
perties peculiar to animals, and hence called animal properties
or functions.  These are  sensation and voluntary motion.
   Though plants are not destitute of motion—their roots seeking
the most nutritious soil; the leaves and branches  turning spon-
taneously to the light; the  internal circulation  of the sap;  and
some, as the sensitive plant, even seem to  perform  movements
almost indicative of sensibility—yet these  are quite different from
the motions of animals,  not being the  result of consciousness.
They result  from  physical changes produced  directly in  the
part of the  plant touched,  and  strictly organic;  and are indi-
cations  of irritability, but not of sensibility.  A distinction is to
be made between these qualities. In the lower orders of animals,
indeed, the distinction is more difficult; naturalists having been
for a long time undecided whether the zoophites—sponge, coral,
&c.—should be considered  as animals or  vegetables.   They  are
as firmly attached to the soil  as the latter, and like them receive
their nourishment from  without. Some species of plants, on  the
other hand, as the  Fucus natans, or gulf weed, lives and fruc- 
10          ELEMENTARY  COMPOSITION OF MAN.
titles on the water, and are constantly borne about by the waves.
This motion, however, is very different from  that  of  animals;
it is entirely passive.
  Animals likewise differ from vegetables very materially with
respect to nutrition.  In  the  former a stomach is necessary, in
order  to receive the food, which is generally crude and unfitted
for  absorption, and prepare it for the nutrition of the individual
by a process termed digestion.   The nourishment  of  plants is
derived from inorganic substances,  from  the excretions  of ani-
mals,  and from decaying organic matter, while animals can only
be nourished by organized substances, either animal or vegetable.
The absorption of nutritive matters  by the latter is from with-
out, by means of the roots; that of  the former from within, by
vessels situated in the lining membrane of the alimentary canal.
  Differences also exist in the functions of reproduction; in the
animal, volition is required in almost every stage of the process;
in vegetables, on the contrary, the whole is effected without the
exercise of volition or consciousness.
  The proportion of fluids to solids is,  likewise, much greater in
animals than  in  vegetables, which  accounts for decomposition
taking place much sooner  in the former than in the latter.
  All organized bodies are composed chiefly of carbon, oxygen,
hydrogen,  and nitrogen,  with alkaline and earthy salts.  Vege-
tables mostly consist  of the three first of these  elements, and
nitrogen is combined with them in the animal only.   Or,  when
this latter element is found in vegetables, it is in limited quan-
tity, and generally confined to one part.  It is this difference of
composition which gives to animal substances the peculiar smell
when burning by which they are readily distinguished from vege-
tables.
             Elementary Composition of Man.

   The human body is composed of fluids  and solids; the blood,
chyle, lymph, and the various secretions  constitute the former;
and the various textures, as the bones, muscles, viscera, &c, the
latter.  Water is one of the most  important  constituents of the 
ELEMENTARY  COMPOSITION OP  MAN.
11
human body; it is in large proportion in all the fluids, and also
in the solids, and gives to the latter softness and flexibility.
   The proportion of fluids is far  greater than that of the solids,
being in the proportion of six or nine to one,  according  to  the
estimate of  different observers, it  being exceedingly difficult to
arrive at an exact estimate. Chaussier found a dead body which
weighed one hundred and twenty pounds; after being dried in
an oven, it weighed only twelve.  And a perfectly dry mummy in
the possession of Blumenbach, which contained all  the  viscera,
weighed but seven pounds and a half.
   There exists in  organic structures a class of compounds, called
proximate principles,  or organic elements, which consist of  two
or more of the elementary substances, combined in definite pro-
portions.
   The chief of these are : albumen, caseine, fibrine, gelatine, chon-
drine, elaine, stearine, margarine, haematosine, and  globuline.
   Albumen.—Is  found in two  forms, fluid and concrete;  the
former, which is met with in the white  of egg, is colorless  and
transparent, without smell or taste, and is  coagulable by heat,
acids, and corrosive sublimate; it is found in the blood,  lymph,
and chyle.  The latter, concrete or  solid albumen, is  white, taste-
less and  elastic;  it is  insoluble in water,  alcohol,  or  oil,  but
readily soluble in alkalies; it is found in the brain, spinal cord,
and nerves, and  in the mucous membranes.  Hair, nails  and
horn, also, consist principally of albumen. It is one of the most
common of the organic constituents.
   Caseine.—Exists abundantly in milk,  and  is the  basis of
cheese.  It may be obtained by allowing milk to remain at  rest
till it is coagulated, taking off the  cream, then washing the  clot
in water and drying it.  It is readily coagulated by the action of
rennet; this is  owing  to the pepsin contained in the latter.
Caseine is white, insipid, and inodorous, insoluble in water,  but
readily soluble in the  alkalies, ammonia especially.   It  contains
sulphur.  It has many properties analogous  with albumen.
   Fibrine.—This principle exists in the chyle, lymph, and blood,
in solution; it also forms the basis of the  muscles, where  it is 
12          ELEMENTARY COMPOSITION OP MAN.
found in the solid form, and is one of the most abundant of the
animal substances.   It may be obtained by beating blood with
a stick as it is flowing from a vein, or by washing a clot repeat-
edly in clean water so as to dissolve  out the coloring matter.
   Fibrine  is solid, white, flexible, and slightly elastic, insipid,
inodorous,  and heavier than water; it is insoluble in water, alco-
hol, and acids, but soluble in caustic potassa. Chemically speak-
ing, it does not differ essentially from albumen;  the chief varia-
tion is physiologically, in  the spontaneous coagulation of the
fibrine ; in coagulating, the fibres assume a definite arrangement,
crossing each other in  all directions.   It constitutes the buffy
coat of the blood.  In the reparation of injured parts it is thrown
out from the blood vessels as a secretion, and becomes organized.
It is often  called coagulable lymph under such circumstances.
   Gelatine.—Is the chief ingredient of the cellular tissue, skin,
tendons,  cartilages,  and  ligaments; it also enters largely  into
the composition of bones. It may be obtained by boiling any of
these substances for some time  in water; clarifying the concen-
trated solution; allowing it to cool, and then drying  the  sub-
stance obtained  in the air. When dry and hard, it is called glue ;
in a liquid form jelly.  Gelatine is soluble in hot water, in acids
and  alkalies.  It is insoluble  in  cold water, alcohol and ether,
and  has a  strong  affinity for  tannin.   The process of tanning
leather results  from  the combination of tannin with gelatine.
The air-bags of fishes  consist  of pure gelatine, known as isin-
glass.  The  article known as  portable  soup consists of dried
gelatine seasoned with spices.  Under the form of glue and size,
gelatine is extensively used in the arts,  its  adhesive properties
rendering it valuable.
   Chondrine.—Kesembles  gelatine,  but does  not unite with
tannin, and is precipitated by acetic acid, acetate  of lead, alum,
and  protosulphate of  iron.  It is  obtained by boiling the carti-
lages, and allowing the solution to cool.
  Elaine, stearine, and margarine, are the proximate principles
of fat. The first is  fluid at ordinary temperatures; the second is
fluid, and is the chief ingredient of vegetable and animal suet, 
ELEMENTARY  COMPOSITION OP MAN.
13
and of fat and butter; it is but sparingly present in human fat.
The third is of medium consistency.
  Hscmatosine—Is the red  coloring matter of the blood, con-
tained in a capsule which is composed of globuline.
  There are other organic elements, called  secondary organic
compounds,  as urea, cholestrine, pepsine, sugar of milk, &c,
which are excretions of particular organs.  They will be treated
of under the head  of secretions.
  Of the inorganic, ultimate, or chemical elements it has been
already remarked  that oxygen, hydrogen, carbon, and nitrogen,
are the  most essential. Besides these there are phosphorus, lime,
sulphur, iron,  manganese, silicum,  chlorine, sodium, magne-
sium, &c.
   Oxygen—Is distributed throughout nearly all the  solids and
fluids.  It is  indispensable to life, and a supply is constantly
furnished from the atmosphere.   It is  mostly found  combined
with other bodies,  often with carbon in the form of carbonic acid.
  Hydrogen —This gas is found universally distributed through-
out the animal kingdom.  It  is contained in all the  fluids and in
most of the solids, and is generally in combination with carbon.
It has been found pure in  the intestines, as well  as combined
with carbon and sulphur.
  In  the form of sulphuretted hydrogen gas, it has an offensive
smell. The flatulence emitted from the intestines mostly consists
of this combination.
  Carbon.—Is met with  in  both fluids  and solids in various
forms.  Generally  it exists  under the form of carbonic acid.  It
is emitted by  all animals in the act of expiration.  In animal
bodies it mostly  exists in combination with alkalies, or earths,
though  it has  been found uncombined.
  Nitrogen.—Exists extensively in animal substances.  Its pre-
valence is  so  general that it  frequently serves as a test  to dis-
tinguish them from vegetables.  It is this principle  that gives
to animal substances their  peculiar smell when burning.
  Phosphorus—Occurs in combination with oxygen—phosphoric
acid—in many animal substances, both solids and fluids.  Com- 
 14          ELEMENTARY COMPOSITION  OP MAN.

 bined with earthy matters this acid forms  one of the chief ingre-
 dients  of bones.  It is likewise combined in  other parts with
 potassa, soda, ammonia, and  magnesia.
   Calcium  or lime,  is  found in the state of oxide of lime only
 in animals.   It is generally in  the form of phosphate or car-
 bonate.  This earth  constitutes  the hard parts  of animals, as
 bone, &c.
   Sulphur—Is sparingly met with  in animal  fluids and solids,
 and is always combined with oxygen, and united to lime,  soda,
 or potash.   In the lower part of  the intestines, and also as an
 exhalation from fetid ulcers, it is met with in the form of sul-
 phuretted hydrogen gas.
   Iron—Is found in  the blood; in bile and in  milk.  It is the
 coloring matter of the red globules of blood.
   Manganese.—This substance has been found along with iron
 in the ashes of the hair in a  state of oxide.
   Silicum.^-Exists in the hair and  urine.
   Chlorine.—Is contained in most of  the  animal fluids;  it is
 generally combined with hydrogen, forming muriatic acid which
 is united with soda.  Muriatic acid  in a free state also exists in
 the stomach.
   Sodium.—As an  oxide soda  is  found in all of the fluids.
 It is likewise united to albumen.   Most frequently, however, it
 is combined with the  phosphoric and muriatic acids; sometimes
 also with the lactic, sulphuric, and carbonic acid.
   Potassium—Is  likewise  found in animal fluids  united  with
 acids.  It is, however, more abundant in vegetables.
   Magnesium—Exists in the form of an oxide, magnesia, spar-
 ingly in the bones, and in some other parts.  It is always com-
 bined with phosphoric acid.
   Out of the proximate principles described, the  various tissues
 of the human  body are formed.   The different solid parts are
 arranged in a  variety  of ways: and of these the principal are in
 filaments, or elementary fibres, tissues, organs, apparatuses, and
systems. 
ELEMENTARY  COMPOSITION OP MAN.          15
  By a filament is understood the elementary solid, consisting
of minute particles  of matter arranged in a row.
  A fibre consists of a number of filaments united together and
enclosed in a sheath.
  By the term tissue is generally meant a particular arrangement
of fibres.
   Organs are formed by the union of tissues—the  liver, stom-
ach, &c,  are examples.
   An apparatus consists of the union of several different organs
to accomplish one end—as the biliary apparatus, consisting of
the liver, gall bladder, &c, all of  which aid in the secretion of
food.
   A system is composed of a  number of similar organs, united
for one end—as the muscular or nervous system.

   Anatomists define a solid to be, a body the particles of which
adhere to each other, so that they will not separate by their own
weight, but require the application of some external force  to
effect disunion.   And they likewise divide  the various solids of
which the human body is  composed,  into the following varieties,
viz. bone, cartilage, muscle,  ligament, vessel, nerve, ganglion,
follicle, gland, membrane, cellular membrane, and viscus.
   Bone.—This is the hardest of the solids,  and forms the ske-
 leton, serving as a protection to  various important  organs and
 for attachments to muscles.
    Cartilage.—Ranks next to bone in hardness; it  is white and
 elastic, covers the  articulating extremities of bone  to  facilitate
 their movements; it serves also in some cases, as in the ribs, to
 prolong  the  bones; in the  foetus it is a substitute for bone
 There  are several varieties of cartilage.
    Muscles.—What is called flesh in  animals consists of muscles.
 They are the agents of all  movements,  and are  composed of
 bundles of red and contractile fibres, extending from one bone
 to another.
    Ligaments.—Are cords  or bands,  exceedingly tough  and
 difficult to tear.  They serve  to  connect different parts to each 
 16          ELEMENTARY COMPOSITION OF  MAN.

 other, as the bones and muscles. By some they are divided into
 two varieties—those which connect  the joints, and those attached
 to the muscles,—the tendons and aponeuroses.
   lessees.—These are in the form  of canals or tubes, and serve
 to carry on the  circulation of the various fluids.  And are called
 sanguineous, chyliferous, lymphatic, &c, according to the nature
 of the fluid they carry.
   JYerves.—The nerves are solid cords  consisting of numerous
 fasciculi or bundles.  They are connected with the brain, spinal
 marrow,  or great sympathetic,  and their function is to convey
 impressions to the nervous centres; and  to endow each part with
 vitality.   There are two  chief divisions  of nerves—those of  the
 brain and spinal marrow, and the organic or great sympathetic.
   Ganglions.—A ganglion is a knot situated in the course of a
 nerve and formed apparently by an interlacing of filaments. The
 term is  likewise applied to a similar interlacing of lymphatic
 vessels.
   Follicles or crypts.—Are small  membranous vesicles seated
 in the substance of the skin or mucous membrane.
   Their  office is to secrete a fluid to lubricate these parts.  It is
 the secretion from these follicles chiefly that keeps the skin soft,
 and  gives to it its oily character.
   Glands.—Are likewise secretory organs, but differ from the
 follicle—their organization being more complicated.   The liver,
 for instance, is a gland, and its office the secretion of bile.  The
 glands of the human body are numerous and diversified in  their
 character.
   Membrane.—The membrane is formed by the cellular tissue,
 and is one of the most important and  extensive substances of
 the body.  It is spread out like  a web, and serves to  form, sup-
port, and envelope all  the organs, to line the cavities and reser-
voirs. It  is divided into simple and compound.  The simple beino-
again subdivided into  three varieties, viz. the serous, mucous
and fibrous.  The first of these,  the serous, form all the sacs or
closed cavities of the body—as those of the chest and abdomen.
The compound membranes are formed by the  union of the  sim- 
            ELEMENTARY COMPOSITION  OP MAN.          17

pie, and are divided  into fibro-serous, sero-mucous,  and fibro.
mucous.  The pericardium is an example of the first of these;
the gall-bladder of the second;  and the ureter of the third.
   Cellular  or laminated  tissue.—This is a kind of  spongy or
areolar  structure, which encloses all the solids, fills up  the spaces
between them, serving  at  the same  time as  a bond of union
and a medium of  separation.  It will be more fully described
presently.
   Viscus.—The name viscus is  given to those solids which are
the most complicated,  both as  regards texture and  use.  The
brain, lungs, liver, &c, are examples.

   The  tissues have been  variously classified :  the classification
of Holler, which reduces them  to  three primary ones, has been
very generally adopted by anatomists and physiologists. These
are the cellular or areolar, the  muscular, and the nervous,  out
of which all the organs are formed, either from the  first alone,
or by the union of the last two.
   1. The cellular or areolar tissue.—This tissue is the most
simple  and  abundant of  the solids; it exists  in all organized
beings, and is an  element in every solid, with the exception per-
haps of the enamel of the  teeth,  where it has not  as yet been
detected.  It is formed by the interlacing and crossing of nu-
merous fibres or  bands, of  a  delicate whitish color, so as to
leave numerous interstices, or  areola, which communicate with
each other.  A proof of this is furnished in anasarca or general
dropsy, where the excess of fluid passes readily from  one part
to another;  and by pressing with  the finger,  the fluid is forced
into adjoining parts of the membrane, and a pit is formed which
gradually disappears again on removing the pressure.  They may
also be filled with air, as occurs occasionally in the disease called
emphysema; and it is a knowledge  of this fact that enables
butchers to inflate or blow their meat, to give to it a fat appear-
ance.   This membrane possesses elasticity and extensibility, but
not much vitality; it is composed chiefly of gelatine. During
life the interstices are filled with a dilute serous or watery fluid,
                                                     4 
18          ELEMENTARY COMPOSITION  OF MAN.
which passes  from  the  blood-vessels.   It is the excess of this
fluid  caused by disease  that constitutes anasarca  or  general
dropsy.
   2.  Muscular  tissue—Consists  of an arrangement of exceed-
ingly minute fibres or filaments of  a peculiar substance.  These
fibres are arranged in parallel layers in all the voluntary muscles
and a few others; in the involuntary, including those  of  the
alimentary canal, bladder, uterus, &c, they interlace. They are
soft, of a grayish or reddish color,  and possessed of contractibil-
ity or irritability, that is, they move responsive to chemical and
mechanical irritants.  They are composed principally of fibrine.
   Nervous tissues.—This tissue or fibre is of a pulpy consistence;
it is composed essentially of  albumen  united to a  fatty matter,
and is  the  organ of sensibility, or for receiving and conveying
impressions to the mind.  The brain, nerves, &c, are composed
of it, and it is not near so generally distributed as the preceding.
The ultimate nervous fibre or filament is  said to be ten or twelve
times larger than that of muscle.
   These three varieties of  tissues or fibres, by uniting in dif-
ferent proportion, from the first order of solids; and these again
by union constitute compound tissues, out of which the various
organs, glands,  bones,  &c, are formed.   Thus, for instance, a
bone  is composed of several  tissues, the body being osseous, the
interior nervous, the extremities cartilaginous, and  the  exterior
fibrous.
   The primary form taken by organic matter,  as it passes from
the state of a proximate principle to that of an organized struc-
ture,  appears  to  be a cell;  this cell contains another within it
called nucleus, which again  contains a granular  body, called
nucleolus.  Almost all  the  organic tissues, however unlike  arc
in the embryo composed of cells which are afterwards developed
by a vital process into the various structures  that make up the
perfect  being.  Cells in great numbers are found floating in the
blood, chyle and lymph,  and their development goes on during
the life of the organism.
   Physical and vital properties of the tissues.—The tissues pre- 
ELEMENTARY COMPOSITION  OF MAN.          19
sent striking differences, as well in their properties, as in their
anatomical arrangement.  These properties are divided into phy-
sical and vital.  The physical  belong as well to the dead as to
the living tissue, and are dependent altogether on the particular
arrangement or mode of cohesion  of their constituent particles
and their chemical composition.  The vital  properties are those
which belong exclusively  to the living organism, and  which
terminate with organic life.
   The most marked  of the physical properties are : elasticity,
flexibility, extensibility, and porosity.
   Plasticity is that  power by which  a tissue reacts after the
withdrawal of an extending or compressing force. It is manifested
in the yellow ligament, in  the  middle coat of the  arteries, and
in the cartilages of the ribs, and the articular faces of the  bones.
   Extensibility. — Tissues may  be  extensible without  being
elastic;  those which  are so yield only to long continued pres-
sure ; an example of this is furnished in the  resistance of fibrous
membranes to the growth of a tumour.
   Flexibility, or the capability of being bent, is witnessed  in the
white  fibrous tissues, which are flexible, and not elastic nor ex-
tensible.  The tendons are examples.
   Porosity.—The tissues even  after death  are porous, that is,
they  are permeable  by  watery fluids.   This  property is also
termed imbibition. The softness of tissues is owing to  the watery
fluids which fill their pores.
   The vital properties of tissues.—These properties which belong
only to organic life, manifest themselves by  a change of their
molecules or elementary constituents, from the application of a
stimulus.  This change may take place directly, with a visible
alteration of the tissue impressed, or indirectly through the inter-
vention of some other organ or tissue with which the impressed
tissue may be in connection.
   There are two  tissues which have these   properties, viz. the
muscular and the nervous.  In  nerves  it is  manifested in three
ways : 1) by causing contraction in the muscle supplied by it;
2) by inducing contraction in muscles not supplied by it, through 
20
OF THE BONES.
a change in the nervous centres with which it is connected;
3) by exciting sensation.
  When seated in muscle it is called contractility, and is charac-
teristic of that tissue.  Hence there are two vital  properties,—
sensibility and contractility—the first, seated in the nervous tis-
sue, the second in the muscular. Vegetables having no nervous
system cannot be sensible, as this property requires a brain, a
particular part of the nervous system,  for its exercise. The only
vital property, therefore, which belongs both to animals and vege-
tables is  better expressed by  the term excitability or irritability.
Plants are not sensible;  being without consciousness, they are
irritable.  Muscles, when  removed from  the  body, are likewise
irritable, and not sensible. Physiologists have variously termed
this  one  vital property,  irritability, excitability,  contractility,
or incitability.

                       Of the  Bones.
  Anatomists generally reckon  two hundred and  eleven  bones
in the human skeleton, though  the number varies, they being
more numerous in youth than in old age; some bones which in
the young consist of several pieces, as life advances become united
by the ossification of the intervening cartilages.  Bones are of a
dull white color, hard, and  inflexible;  by boiling and  proper
preparation they may be made of an ivory whiteness; when held
together  by their natural connection of ligaments and cartilages
they form a natural skeleton;  when joined by wires, or other
means, an artificial skeleton.
  The regional division of the skeleton is into the head, trunk,
the superior, and the inferior  extremities.  Twenty-two  bones
belong to the head, fifty-six to the trunk, sixty-nine to the supe-
rior, and sixty-four to the inferior extremities.
  The bones are classified as long, thick and flat bones, and are
either  symmetrical, that  is,  they consist of two lateral portions
exactly alike; or  else are in pairs, which have a perfect corre-
spondence with each other.
  The symmetrical bones are, the frontal, occipital, sphenoidal 
OF THE BONES.
21
ethmoidal, vomer, inferior maxillary, hyoid, the spinal, and the
sternal;  all of these  are  placed  in  the middle verticle line of
the body. The pairs are situated on both sides of the middle line.
   The long  bones are generally cylindrical or prismatic; the
shaft of a long bone is called dyaphysis;  its extremities, which
are generally enlarged for the purposes of articulating with other
bones, epiphyses.
   The eminences and projections on the surfaces of bones are
called apophyses;  they are numerous, and serve for the origin
and insertion of muscles,  and for articular faces.
   The small foramina, or holes, on the surfaces of  bones serve
for the transmission of blood-vessels; the largest is mostly about
the middle.
   Structure of bones.—The  density of bones, though  always
considerable, and greatly exceeding that of any other part of the
body, is  variable;  being different in different bones, and also in
the same bone.  This has  led  to the division of their substance
into  compact and  cellular, the former being external, the latter
internal.  The cellular structure  grows from the  inner surface
of the compact, and is composed of filaments and small lamina,
or plates, radiating in every direction.  The cells resulting from
this  arrangement communicate with each other, and are filled
with  marrow.  This  structure increases the strength without in-
creasing  the  weight, and also diminishes the effect of concussion,
as a  fall, blow, &c.
   Development of bones.—In the development of bones three
stages of ossification are apparent in the embryo. The first is the
mucous or pulpy stage, which continues for one month; the second
is  the cartilaginous, and the third the osseous which commences
about the third month.  Up  to this period  the vessels convey
lymph only; subsequently they  convey red blood to a central
point (point of ossification), and there is a deposit of calcareous
particles.  Most of the bones  are formed of several pieces, for
each of which there is a distinct  point or centre of  ossification.
These pieces gradually coalesce and form one bone.  Bones  in-
crease in length by continued deposit at their extremities between 
22
OF THE BONES.
the diaphysis and epiphysis, and in thickness by external deposit
and by secretion from the periosteum.  The latter is proved by
the experiment  of feeding a young pig on  food colored  with
madder.  By suspending and  resuming  this mode of feeding,
alternate lamina of white and colored bone will  be produced.
  Composition of bones.—All the bones are composed of the same
elementary constituents; the relative proportion of these  con-
stituents,  however,  is not always the same.   They  consist  of
earthy and animal matters,  united generally in the proportion
of two parts of earthy to one of animal. Or according to minute
chemical analysis they are composed of 32 parts of gelatine, 1 part
of insoluble animal matter, 51 parts of phosphate of lime, 11 of
carbonate  of lime, 2 of fluate of lime,  1  of phosphate of mag-
nesia, and 1 of soda and muriate of soda.
  The earthy matter is most abundant in the bones  of the head;
the animal matter in  the  cellular  structure.  In advanced age,
and in some forms of  disease, the proportion of earthy matter is
also increased.
  The animal matter may be removed  by combustion, and the
bone will  then be quite white and friable; the  original form,
however, will be preserved. Immersing a  bone in dilute acid will
remove  the earthy  matters, owing to  their  strong affinity for
acids; in  this state the animal part remaining is cartilaginous,
flexible, and elastic.
  Periosteum.—The  periosteum is a dense, white, fibrous mem-
brane, which covers the surface  of the bones; it adheres with
less tenacity in infancy than in adult age. In old  age it becomes
ossified;  it is vascular, and possesses but  little sensibility in
health;  its  office is  to  assist in the secretion of  the external
laminas  of bone; to protect it against  suppuration  in the vicin-
ity, restrain the deposit of  bone  within  proper  limits, receive
the insertion of muscles, tendons, &c.
  The delicate vascular membrane, lining the  cells, canals and
cavities  of bone is termed the internal periosteum.  It contains
marrow, a substance  resembling fat, but  of finer consistence.  In
protracted chronic diseases the marrow is absorbed and its place 
BONES OF THE TRUNK.
23
supplied with serum.  It, therefore, would seem to be like fat—
a reservoir of nutriment.
  Bones  are  supplied with  arteries,  veins, lymphatics, and
nerves.
  Formation of callus.—After a bone is fractured, nature sets
to work to repair the injury, and the development of the medium
of union, called  callus, somewhat resembles the primitive forma-
tion of bone.   From  the vessels ruptured about the seat of the
injury blood is at first effused; this is gradually absorbed, and
meanwhile coagulating lymph is effused.   This coagulates and
ossifies in the form of  a ring around the broken bone, the thickest
part being directly over the seat of the fracture; and also in the
form of a pin in the interior of the bone. The extremities of the
broken bone now begin to unite or knit together,  and after this
is effected, the  superfluous bony matter (the ring and pin) being
no  longer of any  service, are absorbed.  They act merely as
splints.  It is  of the utmost importance that the parts be kept
at rest whilst this process is going on, otherwise the  ossification
may be arrested, and  a crooked limb, or even a false joint, result.

                    Bones of the Trunk.
  The trunk is formed by the spine, the thorax and the pelvis.
   The  spine.—The spine extends from the head  to the lower
part of the pelvis at the posterior part of the trunk. It is formed
of 28 or 29 distinct  bones called vertebrae, and contains a bony
canal for  the spinal marrow.  It has several curves; in the neck
it is convex anteriorly, and concave behind; in the thorax con-
cave anteriorly and convex behind; in the loins convex in front
and concave behind; and in the pelvis concave in  front and
convex behind.   Of the 28 or 29 pieces of which it consists, 24
are considered as true vertebrae on account of their mobility, and
the remainder—5—not being movable, are called false vertebrae.
They are divided into 7  for the neck, called  cervical; 12 to
the  thorax, called dorsal; and 5 to the loins, called lumbar;
the false  and the sacrum, and 3 or 4 coccygeal bones, situated at
the  inferior extremity of the column. 
21
BONES OF THE TRUNK.
   A vertebrae consists of a body, 7 processes or extremities, and
a canal or foramen for the reception of the spinal cord.  The
body is in front, and in shape is somewhat ovoid;  it is  convex
anteriorly, and concave behind;  its surfaces  above and  below,
articulate with a contiguous vertebra) by means of a cartilage,
and it is the thickest part.
   The processes, or extremities, are four oblique, which  articu-
late with corresponding ones from the vertebrae above and  below;
two transverse, one projecting on either side from between the
oblique processes, and which serve  for  the  attachment of mus-
cles and ligaments; and one spinous process, which is placed in
the middle  of the bone behind, and which also serves  for  the
attachment of muscles.
   Cervical  vertebrae.—The  first of these is called the atlas, on
account of its supporting the head;  it has no body, but presents
the appearance of a large irregular ring, thickest at the sides.  In
place of a body it is supplied with a bony arch which is occupied
by  the processus dentatus of the  second vertebrse.  The oblique
processes are peculiar, the two above are large, oblong and con-
cave, to suit the condyloid  processes of the occipital bone with
which  they articulate.  The  two  lower  ones are round, flat,  and
horizontal, adapted to the rotary motion of the head.
  The second is called dentata, from its tooth-like  process pro-
jecting from the upper surface  of the body.   The head  rotates
on  this process, which is kept in'its place by the transverse liga-
ment of the neck—an exceedingly strong  ligament extending
across  the atlas and attached to a tubercle  on  each  side of that
bone.  This process is smooth in front where it touches the arch
of the  atlas, and likewise behind where  the transverse ligament
plays.  The  spinous process is long and forked.
   The remainder of the cervical vertebras, except the last, do not
require special description;  their bodies are small,  flattened in
front, and gradually increase in size as they descend.  The spinous
processes are short, thick, horizontal, and bifed or forked.  The
oblique processes are flat, oval, and  short.   The  transverse pro-
cesses  are broad, and have a foramen at their  base  for the  pas- 
BONES OF THE TRUNK.
25
sage of the vertebral artery.   The  foramen for the spinal cord
is very large.
  The spinous process of the sixth vertebrse is long and termin-
ated by a sharp point.  The seventh is the largest and looks like
a dorsal vertebrae; its body is larger than that of the others, and
its spinous process is the longest of all, and  is not bifurcated,
but terminates by a rounded tubercle easily felt under the skin.
The foramen at the base of the transverse processes is too small
to receive the vertebral vessels.
  Dorsal vertebrae.—The dorsal vertebrse situated intermediate
between the neck  and loins, are also inferior in  point  of size.
They are 12 in number.  Their bodies are cylindrical, their trans-
verse diameter decreases from the first to the third,  and then
regularly decreases to the last.  They have articular  marks on
the sides for the  heads of the  ribs.   These marks or pits, except
in the first and the eleventh  and  twelfth,  are each formed by
two  contiguous vertebrae.  The first has a complete pit in its
side for the head of the rib.   The eleventh and twelfth have also
complete fossae or pits for the ribs.  The oblique  processes are
vertical, the two  upper looking backward, and the two lower for-
ward.   The  transverse processes are  long  and terminate in an
enlarged extremity, which has an articular face in front for the
tubercle of the rib. The spinous processes are long, triangular,
and broad at  the base, sharp - pointed, somewhat rough and
swollen at the extremities, and overlap each other.
   Lumbar vertebrse.—These  are five  in number.   Their bodies
are larger than those of the other true vertebrae, oval, and have
the transverse diameter  the longest.  The spinal foramen is tri-
angular, and larger than  in the dorsal vertebras.  The groves for
the nerves to pass  out are likewise large. The oblique processes
are vertical; the superior looking inwards and the inferior look-
ing outwards.  The transverse processes  are very long, and stand
out  at right angles.   The spinous  processes are short, thick,
quadrangular, horizontal, and terminate by an oblong  tubercle.
The lumbar  vertebras increase in  size successively—the first is
the smallest, and the fifth the  largest; the body of the latter is
                                                    a 
26
BONES OF THE TRUNK.
also wedge-shaped.  The third has the longest transverse and
spinous processes.
   Sacrum.—The os  sacrum  is much the largest bone in the
spinal  column.  It  forms the upper  and posterior boundary of
the pelvis; it is triangular  in shape, with  the  base  above, and
originally consist of five bones, bearing  a strong resemblance
to vertebrse;  hence they received  the name of false vertebrae;
The anterior face of this bone is smooth and concave, and has
four holes on  each side, which communicate with the spinal
cavity  and transmit the anterior branches of the sacral nerves.
Its posterior face is  convex and rough, and is equally divided by
its spinous processes.  The marks of the original  separation of
this bone are evident, particularly on its front surface. The base
has an articular mark to receive the last lumbar vertebrse : the
apex is below and has an articular surface for the coccyx.  The
sacral  canal, a continuation  of the  spinal, runs through the
length  of the sacrum.  The portion of the  spinal cord lodged
within it is called the cauda equina, from its fancied resemblance
to a horse's tail.
   Coccyx.—The coccyx, like  the sacrum, is triangular; it has
its base upwards, and is flat.   It consists of three  or four bones
united  in the same curve as that of the sacrum.  These pieces as
life advances  become joined together by bone, and  also joined to
the sacrum;  so that all the false vertebrae, from the base of the
sacrum to the point of the coccyx, are united into a single bone.
The coccyx forms the lower extremity of the spinal column, and
corresponds with the tails of animals.
  The  vertebral column affords a secure lodgment  to  the spinal
marrow, is a line of support to the trunk in every  position, and
is the centre  of all  its  movements.  In  the erect posture  the
spine also supports the head.
  The motions of the spine are, flexion or bending forward ex-
tension or bending backward, lateral bending and circumduction
or that motion in which the trunk  is caused to describe a cone
the base of which is above,  and the  apex below.
   The  first  of these  motions, flexion, is the most  extensive • it 
BONES OF  THE TRUNK.
27
is produced mainly by the action of the abdominal muscles.  In
this position the inter-vertebral, elastic, cartilages are compressed
in front, and thickened behind, the anterior vertebral ligament
is relaxed, and the posterior vertebral ligament correspondingly
tense.
  Extension or backward bending is very limited, owing to the
mechanical obstruction offered by the spinous processes of the
back  and  neck, which are  very near to and overlap each other.
The abdominal muscles  also  strongly resist  it.   The muscles,
arising either from the back of the pelvis  or from the transverse
processes, and going upwards to be inserted either into the ribs,
the transverse or  spinous processes, which produce this motion,
act less  advantageously than do the abdominal muscles  in pro-
ducing flexion; the leverage in the latter case being much more
favorable.
  The  lateral  inclination  of  the  spine  is considerable,  it  is
favored  by the advantageous  position of  the muscles  on the
side of the neck and trunk,  as well as by the mechanical arrange-
ment  of the  parts; the  transverse processes being so far apart
as scarcely to offer any resistance. The principal  obstruction  is
presented by the ribs, which strike against each other when this
motion is carried  too far.
  Circumduction is performed chiefly on the lower dorsal and
the lumbar  vertebrae, and  is  a  succession of the movements
above described.
  The rotation of the spine  is very  limited; it is performed
chiefly on  the lower dorsal and upper lumbar vertebrae, and con-
sists of a series of oblique motions of the body of one vertebrae
upon  another.  In old age, when the inter-vertebral substance
has become  hardened, it is  almost inappreciable.
  The rotation of the  head is effected by the motion of the atlas
upon  the dentata, which is  the only motion allowed to this ver-
tebrse, flexion and rotation being prevented by the confinement
of the transverse  ligament behind, and by the anterior bridge  of
bone in front.  The flatness of the  articular surfaces of the two
bones likewise  prevent any  lateral motion. 
28
BONES OF  THE TRUNK.
  Pelvis.—The bones of the pelvis are the sacrum, the coccyx,
and the two innominata or hip bones; the two first, which form
the posterior boundary, have already been described.
  Innominatum.—The innominatum is a large flat bone, and
is the  hip or haunch bone of common language;  it has  some
resemblance  to the  figure 8.  From having originally consisted
of three pieces, though these  pieces unite in the cavity of the
hip joint (acetabulum), and in the adult leave but a slight trace
of their former  distinction, anatomists divide the  innominatum
into the ilium, ischium, and pubes.
  Ilium.—This is the largest of the three pieces, and forms the
upper rounded part of the innominatum, or the wall of the upper
pelvis. It is the hip bone. Externally its surface is convex and
rough, with a semi-circular ridge crossing it; the glutei muscles
arise from this surface.  Internally it is concave;  the  anterior
portion is smooth and gives origin to the iliacus internus muscle;
the posterior is  rough and articulates with the sacrum, behind
which  arise muscles and ligaments.  The margin, called the crista
or spine of the  ilium, is curved and somewhat resembles the
italic /.  In front of the crista there are two eminences or pro-
jections,  one of  which is called the anterior superior spinous
process, and the other the anterior inferior spinous process; the
former gives origin  to the sartorius and tensor vaginae muscles
and Poupart's ligament;  the latter to  the rectus  muscle; the
cavity  between the two gives origin to the  gluteus medius.   A
large prominence called ilio-pectineal is situated below these pro-
cesses ; in a groove above  this,  the  iliacus internus and  psoas
magnus pass.
  The posterior margin of  the ilium is marked by two projec-
tions  called  posterior  superior, and  posterior inferior spinous
processes.  Just below the latter there is a deep excavation called
sciatic notch, through which  the  pyriform muscle, the  sciatic
nerve, and several blood-vessels pass out.   The crista has  three
lips, the internal of which gives origin to the transversalis muscle,
the middle to  the internal oblique,  and into the external the
external oblique is inserted. 
BONES OF THE TRUNK.
29
   Ischium.—This portion of the innominatum is the most in-
ferior and is the next in size to the ilium;  it consists of a body
and ramus or branch.  The external surface of the body is rough;
the internal surface  is smooth, and  is called the plane of  the
ischium.  On  the posterior margin there is a projection called
the spine, into which the lesser sacro-sciatic ligament is inserted;
beneath the spine there is a groove in which the tendon of the
obturator internus muscle plays.   The inferior portion of  the
body is called the tuberosity of the ischium;  it gives origin to
the  biceps adductor, semi-membranosus and semi - tendinosus
muscles; in front there is a long ridge  into  which the great
sacro-sciatic ligament is inserted. The ramus is short and thick,
and ascends forward and inward to join the ramus of the pubes,
and form a part of the pubic arch; it  is rough externally, and
smooth internally; the crus of the penis arises from the latter face.
   Pubis.—This bone is much the smallest of the three, and con-
stitutes  the anterior boundary of the pelvis.   It consists  of a
body and two branches, one  of which runs downwards to join
the ischium, and the other backwards and upwards to join the
ilium.   The body is joined to its fellow by a flat surface, called
the symphysis;  the  superior portion  of the body is  horizontal
at right angles with  the  symphysis, and is  bounded outwardly
by a projection,  called the spinous process.  From this process
two ridges proceed outwardly; the posterior, is called the crista
of the pubes, or linea pectinea, and to it is attached  a part of
Poupart's ligament.   Between these two ridges is a triangular
space from which the pectineus muscle arises, and over which
the femoral vessels pass.  The extremity of the superior ramus
is triangular, and much enlarged where it contributes to form the
acetabulum, a hemispherical concavity for the articulation of the
femur.   At the bottom of this cavity there is a  rough depres-
sion occupied by a mass of fat generally called a gland of Havers.
The obturator or  thyroid foramen is  the large opening in  the
lower part of the bone.   In shape it is mostly oval;  it  is filled
up, with the exception of a groove in the upper  part to transmit
the obturator vessels and nerve, by a membranous ligament.
       6 
30
BONES OF THE TRUNK.
  As a whole, the  pelvis is  a conoidal  cavity, having its base
above, and  its apex below.   Internally it forms an irregular
floor for the support, in the erect position, of the  abdominal vis-
cera.  Externally its projections furnish favorable points for the
attachment  of muscles.   There  are marked  differences in the
male and female pelvis.   The diameters  of the latter are larger,
and the depth less than in the male.  The,  arch  as it is called,
under the symphysis pubis, is regularly rounded  in females;  in
males, on the contrary, it is merely an acute angle. The sacrum
also, in women is shorter, more concave, and of greater breadth.
                          Thorax.
  The thorax is the upper part  of the trunk, and in  shape  is
conoidal, flattened in front, and concave behind;  it is formed by
the dorsal vertebrae behind, by the sternum in front, and at the
intermediate spaces by the ribs.
  The superior part, or apex, of the cone presents a heart-shaped
opening, and is much smaller than the base;  the latter has a
large notch  in front, into  which the lower end of the sternum
projects.
                Fig. 1.                 Fig. 1. A representation of
                                     the thorax;  1, 2, 3 bones of
                                     the sternum; 4, 5 first and
                                     last dorsal vertebrae; 6,10 an-
                                     gle of ribs j  11 cartilages.
                                       Sternum.—This  bone
                                     is placed  in the middle
                                     and front of the thorax,
                                     and is oblong and slightly
                                     curved;  its direction  is
                                     also  slanting,  the  lower
                                     part  receding  much far-
                                     ther  from the spine than
                                     the upper.  The concavity
                                     is in front.  In the adult
                                     it is usually composed of 3
                                     pieces; an upper, middle,
                                     and lower, which are held
                                     together by cartilages and
                                     ligaments.  Frequently in
 
BONES OF  THE TRUNK.
31
advanced life these pieces  are  fused together and form but one
bone.
   The first or upper bone is the thickest, and has an irregular
square figure;  the upper  margin  projects somewhat, and  is
slightly scooped out.  On  each side are marks for articulating
with the clavicle, and first and second ribs.
   The second or middle bone is longer and narrower than the
first; the lower part  increases somewhat in  breadth, and then
terminates by being rounded off on either  side.   The sides  of
this piece present pits for the articulation of part of the second,
the third, fourth, fifth, sixth, and part of the seventh ribs.
   The third bone of the sternum in young persons is very often
wholly  cartilaginous,  and  is  called  the zyphoid or  ensiform
(sword-shaped)  cartilage.   It is thin, and varies very materially
in shape  in  different  individuals.   The  extremity is mostly
pointed, and inclined slightly forwards; sometimes it is forked,
and sometimes also turned  backwards.
   Ribs.—There are twenty-four ribs in all, twelve on  either
 side; the upper seven, from their cartilages articulating with the
 sternum are called the  sternal or  true  ribs;  the lower five in
 consequence of their  cartilages stopping short of the sternum
 are called false ribs.
   In some rare cases there have been eleven or thirteen ribs on
 a side.
    The ribs  are parallel, and directed obliquely downwards and
 forwards; each having  a parabolic  curve, and gradually increas-
 ing in size to the eighth, and afterwards gradually diminishing.
 The surface of  each rib is  convex externally, and concave inter-
 nally ;  the anterior or sternal extremity is  larger  and flatter than
 the posterior; the vertebral or posterior extremity of the rib is
 its head, and presents two articular surfaces separated by a ridge.
 Surrounding the head the rib is very narrow, and called the neck.
 Near the vertebral extremity  is an oblique ridge caused  by the
 insertion of the sacro-lumbalis muscle; just at this line a curve,
 somewhat abrupt, takes place, which is the angle of the rib.
    The upper margins  of  the ribs are rounded,  and  somewhat 
32
BONES OF  THE TRUNK.
rough for the insertion of the intercostal  muscles; the  inferior
margins have a thin cutting edge, just with and above which is
a groove running two-thirds of their length, which contains the
intercostal vessels and  nerve.   Each  rib is twisted and  bent,
the spinal extremity being directed upwards, and the sternal ex-
tremity downwards.   About an inch from the head of each rib
is a tubercle, or prominence, for articulating with the transverse
processes of the vertebrae; just beyond this is a smaller tubercle
for the insertion of the  external transverse ligament.
   The first rib is small, and more circular than the other;  it is
flat above and below.
   The eleventh and twelfth are not connected with the others,
and are thence called floating ribs; they have no tubercles, and
but one articular surface on the head.
   The thorax performs  two important offices in the human eco-
nomy—first it protects the organs of circulation and respiration,
and second, it assists in the function of respiration.  Its structure
affords a very secure defence to its viscera, from  the effect of
blows on the outside.   Posteriorly the spinal column, and  the
masses of longitudinal muscles  which fill up the gutters on each
side of the spinous processes furnish, ample protection.  In front
the protection  is less secure, in consequence  of the  sternum
being placed immediately under the skin.  The effects of blows,
however, on this part are much diminished by the elasticity oj
the cartilages,  and by the  oblique downward direction of the
ribs themselves; both of which circumstances dispose the  ster-
num to retreat backward, and  to yield to the impelling force.
The arched form of the thorax is likewise a favorable one to
enable it to resist the force  of  blows, &c.
   The thorax aids respiration by expanding and contracting;
the expansion takes place in three directions, vertically, trans-
versely, and antero-posteriorly, or from back to  front.  In the
vertical direction the augmentation is effected by the diaphragm;
it is much more considerable in adults than  in children, owing
to the viscera of the abdomen being comparatively larger in the
latter.   In the other directions the dilatation is accomplished 
BONES OF THE HEAD.
33
chiefly by the action of the intercostal  muscles, which  contract
successively—beginning at the first rib  which serves for a fixed
point—and elevate the ribs.   The obliquity of the ribs and the
attachments of their cartilages to the  sternum, which have to
ascend in order to reach it, allow of this augmentation.   While
the enlargement is going on the sternum is slightly elevated and
projected forwards.
   In expiration all the diameters of the thorax are  diminished,
all its movements being directly  the reverse of those which take
place in inspiration.  The chief cause of  expiration  is atmo-
spheric pressure  upon the external walls of the  thorax, acting
in conjunction with the  natural  elasticity of  the  lungs.  Some
slight aid is also furnished by muscular contraction and the elas-
ticity of the cartilages.

                     Bones of the Head.
   In the head there  are twenty-two bones,  which are divided
into those  of the cranium—eight in number,—and those of the
face—fourteen in number.

                          Cranium.
   The  cranium  is composed of one frontal, two parietal, two
temporal,  one sphenoid, and one ethmoid bone.
   The  frontal bone is  situated  in front of  the  cranium;  the
 occipital bone is at its hind part; the two parietal bones, one on
 each side, form its superior lateral part;  the two temporal also,
 one on each side, its inferior lateral part; the  sphenoid is situated
 at the middle of its base; and the ethmoid also at its  base, and
just in front of the body of the latter  bone.
   Frontal Bone.—This bone forms the forehead of common lan-
 guage ;  it is symmetrical and shell-like, and is  occasionally di-
 vided into two parts by a suture, continuous  with that, dividing
 the parietal bones.   The external surface is convex, and the in-
 ternal concave.  About the middle of the  external surface on
 each side  is a protuberance called the frontal, which is the origi-
 nal centre of ossification.  The  internal surface is concave, and 
34
BONES OF THE HEAD.
marked by numerous depressions, corresponding  with the con-
volutions of the brain.  Near the middle and lower margin of
the external surface is a ridge called  the nasal, or superciliary
protuberance; just below this there is a protuberance called the
nasal spine, which serves for an  abutment  to the  nasal bones.
At the inferior margin of  the bone on either side  are the two
orbital ridges,  which form the anterior boundary of the eye.
These ridges are terminated outwardly by the external angular
processes, and inwardly by the internal angular processes.  The
lachrymal gland is placed in a depression just within the external
angular process.
   The frontal sinuses consist of one or more large  cells placed
beneath the nasal protuberances;  they vary very much in size,
and in some rare instances  in the adult do not exist.
   This bone unites laterally with the parietal and  sphenoid;  and
below with the ethmoid and several of the bones of the face.
   Parietal Bones.'—These, as stated, occur in pairs and form the
middle, superior and lateral portions of the cranium ; they are
quadrangular, convex externally, and concave internally.  About
the middle of the external surface the bone is  raised into the
parietal protuberance—the centre  of ossification.  Immediately
below this is a semi-circular ridge for the attachment of the tem-
poral fascia and muscle.  Internally, the surface of the bone is
marked by the convolutions of  the brain, and contains also a
number of furrows, produced by the middle artery of the dura
mater.  The superior margin is the thickest, and much serrated;
when joined to its fellow it forms a deep groove  for the  accom-
modation of  the longitudinal sinus.  The inferior edge is thinner
and arched.   This bone  articulates with its fellow, with the
frontal, the  sphenoid, the temporal and the occipital bones.
   Occipital Bone.—This bone is placed  at the posterior and in-
ferior part of the head, and is of an oval or trapezoidal shape;
it is convex  externally  and concave internally.   Both surfaces
contain a number of ridges and  processes.   A  large opening,
called the foramen magnum, is found  in its lower  part.   This
hole is oval, the long diameter extending  from before backwards; 
BONES OF THE HEAD.
35
it transmits the medulla oblongata, the vertebral vessels, and the
spinal accessory nerves.  On each side is an oblong convex sur-
face, called condyloid process, for articulating  with  the atlas.
Near the middle of the external surface of the  bone is a pro-
minence, called the external occipital cross, from which, on each
side, there proceeds a semi-circular ridge, which serves for the
origin  and  insertion  of muscles.   About an inch below this
ridge is another, into which the superior oblique muscle is in-
serted.  In front of the foramen magnum  is the basilar process,
the extremity of  which joins the sphenoid bone.  The internal
surface is likewise marked by a cross near its centre, called the
internal occipital cross, which is more prominent  than the ex-
ternal ; from this cross three groves diverge, which contain the
two lateral and the  superior longitudinal sinus;  inferiorly a
ridge proceeds to the foramen magnum to which the falx cere-
belli is attached.   In this way four  concavities  are formed, the
two superior of which contain the posterior  lobes of the cere-
brum, and the two inferior the  hemispheres  of the cerebellum.
   Superiorly the occipital bone joins the  parietal, laterally the
temporal, and in front the sphenoid.
   Temporal Bones.—These bones are placed on either side of
the cranium, below the parietal, and form portions of its inferior
lateral parieties and base.  They are divided  into three portions,
the squamous, the  mastoid, and the petrous.
   The squamous portion is thinner  than the other bones of the
cranium, but is covered by the  temporal muscle, which  affords
sufficient protection to the brain. Externally it is slightly con-
vex, and  has grooves for the deep temporal  artery.  The zygo-
matic process projects from its  lower part, and  forms a part of
the zygomatic arch.  Beneath  the  base of this process, which
is triangular, is the  glenoid  cavity for  the  articulation of the
lower jaw.  Just behind this cavity is another, which contains
a portion of the parotid gland.   Between these cavities is the
Grlasserian  fissure, which transmits  the chorda tympani nerve,
and the levator tympani muscle, to the ear.   The internal sur-
face has a groove for the middle artery of the dura mater. 
36
BONES OF THE HEAD.
   The mastoid portion is behind, and is thick and cellular;  its
upper part is angular, has  serrated edges,  and  is  received be-
tween the parietal and occipital bones.   Below there is a large
conical  projection, called mastoid  process,  which  receives the
insertion of sterno-mastoid  and trachelo-mastoid muscles.  At
the base of this  process  is a  fossa  from which  the digastric
muscle arises. A foramen, called the mastoid, and which trans-
mits a blood-vessel, is  found near the upper  margin of the bone.
   There are  numerous and large cells  in  this portion of the
bone, which  are  called sinuses; they communicate with  the
tympanum by a large  orifice.
   The petrous portion is triangular and pyramidal; it arises by
a broad base  from the inner portions of the  mastoid and squam-
ous portions; its  structure is extremely dense and brittle.  In
the posterior surface of the petrous portion  is a large foramen,
called the meatus auditorius internus, through which the seventh
or auditory, and the facial nerves are transmitted.  The  base
has a large oval opening, between the zygomatic  and  mastoid
processes, which leads to the tympanum, and is called the meatus
auditorius externus; its margin is called the auditory  process,
its lower part is rough for the attachment  of the cartilage  of
the external ear.   In the  angle between  the  squamous and
petrous portions  is the orifice of the  Eustachian tube.   The
styloid process, which  is round, tapering, and about an inch and
a half long, projects from a  ridge on the inferior surface, called
the vaginal process.  Immediately behind the base of the styloid
process  is the stylo-mastoid foramen, through which the  facial
nerve and stylo-mastoid artery pass.  The internal jugular vein,
and the eighth pair of nerves pass through  the posterior fora-
men lacerum, which is formed by the articulation  of this with
the occipital  bone.  Just before the foramen lacerum is the
opening of the carotid canal, which  contains besides  the artery
the ganglion  of Laumonier.
  The temporal bone  articulates with the occipital, the parietal,
the sphenoid, and the malar.
   Sphenoid Bone. — This bone is placed  transversely in the 
BONES OF THE HEAD.
37
middle of the base of the cranium.   In shape  it bears resem-
blance to a bat;  it consists of a body and  four wings, two, a
large and a small one, being placed on each  side.  The body is
in the centre, and is cuboidal in shape. Besides the wings men-
tioned it has a number of angular margins,  and additional pro-
cesses, two of the latter are directed vertically  downwards.   A
deep depression exists on the superior surface of the body, which
is called the  sella turcica, and contains the pituitary gland. On
either side of this depression are two grooves, called sulci caro-
tica, for the carotid arteries;  in front is  a  prominence, called
processes  olivaris, upon which is a groove, indicating the posi-
tion of the chiasm of the optic nerves.   The  posterior clinoid
process projects over the depression behind.   In front of the
body is a ridge, which articulates with the nasal lamella of the
ethmoid bone, on either side  of this are the orifices of the two
sphenoidal cells;  these empty into the posterior ethmoidal cells,
and do not exist  in infancy. The posterior surface of the body
is flat, and rough for articulating with the cuneiform process  of
the occipital bone.  Generally in the adult the bones are anchy-
losed at this point.
   The small wings are in front of the large, and are triangular,
fiat, and narrow.   Their posterior extremities form the anterior
clinoid processes,  and  are perforated by the  optic foramen,
which transmits the optic nerve and ophthalmic artery.   They
articulate with the frontal bone.
   The great  wings are divided from the small, by the sphenoidal
fissure  or foramen, through which pass the third, fourth, first
branch of  the fifth, and the sixth nerves;  it has three surfaces.
One is anterior, and called  orbital, from its  forming a part  of
the  orbit; another is external  and called temporal;  the  third,
towards the brain, is concave, and contains a considerable por-
tion of the middle lobe of  the cerebrum;  its face is marked by
the convolutions  of the brain, and by a furrow for  the passage
of the middle artery of the dura mater to  the  cranium.   The
temporal surface is somewhat concave, and covered by the tem-
poral and external pterygoid muscles. The orbital face is square 
38
BONES OF TnE FACE.
and slightly concave.  The inferior portion of the great wing is
elongated backwards, and called the spinous process.  From the
point of this process the styloid process projects downwards.
  The sphenoid bone  articulates above and in  front with the
vomer, the frontal, ethmoid, malar, and parietal bones; behind
with the occipital, and by its pterygoid processes with the palate
bones;  and laterally with the temporal.
  Ethmoid Bone.—The ethmoid bone, so named from its resem-
blance to a sieve, is placed at the base of the skull and between
the orbitar processes of the frontal.  In shape it is cuboidal, and
in structure extremely cellular and light.  The  superior surface
is called the cribriform plate, and is perforated with holes which
transmit filaments of the olfactory nerve.   From  the middle
line of this surface, a narrow, triangular, hollow process projects
called the crista galli,  to which is attached the falx cerebri.  A
vertical plate of bone, called the  nasal lamella, divides the bone
longitudinally into two halves;  it articulates posteriorly with
the crista sphenoidalis, and  below with the vomer.
  The lateral surfaces of the bone are called ossa plana; they
are extremely thin and form a large portion of the orbits of the
eyes.   Attached to the internal face of the os planum on either
side of  the nasal lamella are two scrolls or shells placed one
above the other, and called superior and middle turbinated bones.
They are separated by a fissure which is the superior meatus of
the nose.   The middle meatus is between  the  middle  and in-
ferior turbinated bones.   The anterior  ethmoidal cells  empty
into the middle  meatus;  the  most anterior of them  is funnel
shaped and receives  the fluid from the frontal sinus.   The pos-
terior ethmoidal cells and the sphenoidal sinus empty  into the
superior meatus.
  The ethmoid articulates with the frontal, sphenoidal, inferior
turbinate, superior maxillary, nasal,  lachrymal, palate bones,
and vomer.
                    Bones of the Face.
  The face is composed of fourteen  bones viz. the  superior
maxillary, the palate bone, malar, nasal, unguiform, inferior tur- 
BONES OF THE FACE.
39
binated, vomer, and inferior maxillary;  all of these except two,
the inferior maxillary and vomer, are in  pairs, there being six
on either side.   The inferior maxillary bone has corresponding
or symmetrical sides.
   Superior Maxillary Bones.—These constitute the upper jaw
and  are the  largest bones  of  the face;  they articulate with
all the others except the lower  jaw.   They  have an irregular
cuboidal body,  and four processes.  The body  is hollow, and
has four surfaces.   The  anterior or facial surface is  bounded
above by the lower margin of the orbit, below which is a fora-
men, the infra  orbitar, which transmits the infra orbitar nerve
and an artery.   The posterior or temporal surface  is round;  it
has a roughened prominent part,  called the tuber, through which
pass by several small foramina, the posterior dental nerve, artery,
and vein to the floor of the antrum.   The superior or orbital
surface is triangular.  The internal or nasal surface has a large
opening of the antrum  highmorianum—the large cavity in the
centre of  the bone.  The walls  of this cavity are grooved by
the passage of the dental nerves.
   The nasal process arises by a  broad and thin  base from the
upper and anterior part of the  bone;  it articulates anteriorly
with the nasal  bone, and superiorly with the  frontal;  the pos-
terior edge forms a canal, by articulating with the os ungus,  to
contain the lachrymal sac.
   The malar process is on the upper and outer  surface of the
bone;  it is rough and articulates with the malar bone.
   The alveolar process, contains the sockets of the teeth, eight
to each side; it is broader behind than in front.  Just behind
the alveolar process, at the junction of the two bones, is the fora-
men incisivum which contains the naso-palatine nerve and  gan-
glion.
   The palate process arises from the internal  face of  the body
of the bone, just within the circle of the alveoli;  it forms the
horizontal roof of the mouth, and floor  of the nose.   The nasal
crista arises at the junction with its fellow  and articulates  with
the vomer.  Behind, this process unites with the horizontal part 
40
BONES OF THE FACE.
 of the palate  bone;  its anterior  extremity forms the anterior
 nasal spine.
   Palate Bones.—These bones,  two in number,  are placed  be-
 tween  the  superior maxillary and the sphenoid  bones.  They
 are irregular in shape, and divided into two portions.
   The horizontal, or palate  plate, is  square, and in  the same
 line with the palate process of the superior maxillary bone, form-
 ing a part  of  the floor of the nostril and  roof  of the  mouth.
 At its suture it forms part of the nasal crista for articulating
 with the vomer.  Behind, it is elongated into the  posterior nasal
 spine.
   The vertical or nasal plate forms  the posterior and outer part of
 the nostril, and is much thinner  than the palate plate; its nasal
 surface articulates by a ridge with  the  inferior turbinated bone;
 externally it articulates by a roughened surface with the maxil-
 lary bone.  Posteriorly it has an elongated triangular process,
 called pterygoid.
   The orbital portion, or plate, is hollow and irregular; it forms
 a  small part of the  orbit between the ethmoid  and  superior
 maxillary bones.
   The palate  bone  articulates with the upper  maxillary,  the
 sphenoid, ethmoid, inferior spongy,  the vomer,  and  with   its
 fellow.
   Nasal Bones.—These are placed between  the nasal processes
 of the superior maxillary bones; they  are oblong in shape, and
 compact in structure, and so placed together, as to form a strong
 arch,  called the bridge of nose.  The upper extremity is thick
 and narrow, and articulates with  the  frontal bone.   The lower
 is  thinner and  broader, and has  the  cartilages of the  nose  at-
 tached.  They  articulate with each other, with the nasal pro-
 cesses of the superior maxillary,  and  with the frontal bone.
   Unguiform Bones.—So called from its resemblance to a finger
nail, likewise called lachrymal. It is  placed at the internal side
of the orbit, between the nasal process  of the upper maxillary,
and the os planum of  the ethmoid,  and is very small and thin.
The external surface forms a part of  the orbit of  the  eye.   It 
BONES OF THE FACE.
41
articulates loosely with the frontal, upper maxillary, os planum,
and the inferior spongy bone.
   Malar Bones.—The malar or cheek bones, two in number, are
quadrangular in shape.  They are situated at the external  part
of  the orbit of the eye, and form the prominence of the  cheek.
The cheek bone has three surfaces;  the external or facial, which
is convex, and forms part of the face;  the internal or orbital,
which is crescentic,  and contributes  to the orbit; and the pos-
terior, which is concave, and forms the anterior boundary of the
zygomatic fossa.  It has four margins, two of which are superior,
and two inferior.  The anterior of the upper is curved to form
the external and part of the inferior margin of  the orbit;  the
posterior upper is irregular, and  has attached to it the temporal
fascia.  The anterior inferior is serrated, and articulates with the
upper maxillary; the posterior inferior serves for the  origin of
a part of the masseter muscle.   The angles of this  bone are
called processes,  the superior or frontal articulates with the an-
gular process  of the frontal bone. The temporal process extends
backwards, and forms part of the zygomatic arch; the  maxillary
articulates with the upper maxillary bone.
   The malar bone articulates with the maxillary, frontal, sphe-
noidal, and temporal bones.
   Inferior turbinated Bones.—These, also, called spongy bones,
are situated  immediately below  the  opening into the antrum
Highmorianum.   They are scroll-like, and extremely  light  and
porous.  The internal surface is convex, and looks towards the
nose; the external surface has a broad hook which rests upon
the lower margin of  the orifice of the antrum and partly closes
it.   Two processes arise from the superior margin of  the bone,
and join the ethmoid.  The  lower  margin  is thicker  than the
upper.
   Vomer.—Called so from its resemblance to a ploughshare.
It is a single bone placed between the nostrils, and forms a large
part of the septum.  It is formed  of two  plates of compact
structure.  It is  flat, has four margins, and is frequently more
inclined to one side than the  other.  The  superior margin is the 
42
BONES OF THE FACE.
 thickest and contains a groove for  the  reception of the azygos
 process of the sphenoid; the inferior margin articulates with the
 nasal crista of the upper maxillary and palate bones; the ante-
 rior margin  is directed obliquely downwards  and forwards, its
 front half joins the cartilaginous septum of the nose, and its
 posterior half unites with the nasal lamella of the ethmoid;  the
 posterior margin is concave,  sharp, and  thin, and  divides  the
 posterior opening of the nose.
   Inferior Maxillary.—This bone, commonly called the lower
jaw, is also single.   It forms the lower boundary of the  face,
 and is the only bone in the head capable of motion.   Its shape
 is that of a parabolic curve. In infancy its halves are separable,
being joined in the middle only by cartilage;  two or three years
after birth, however, they become consolidated, and the cartilage
disappears.   It consist  of a body or region which corresponds
with the teeth, and two rami or branches.
   The body is convex in front, having its upper part formed by
the alveolar cavities for receiving the teeth, and its  lower  part
presenting a thick and  rounded margin,  which is the base of
lower jaw.  At the middle or symphysis is a triangular promi-
nence, called the anterior mental tubercle.  Near to this tubercle,
on either side, there is a large hole, called the anterior  mental
foramen, which conducts the inferior maxillary artery and nerve
to the teeth.
  The internal or posterior face is concave, and has  also a pro-
minence at its symphysis, called the posterior mental tubercle ;
a fossa exists on each side of this tubercle for  the insertion of
the digastric muscle.  Exterior to this on  either side is a larger
fossa for the  sublingual gland.
  The alveolar processes are thin with cutting edges; and con-
tain sockets  for sixteen teeth.   They  come and go with  the
teeth; it is the absorption  of these processes, after the  loss of
the teeth, in aged persons,  and the consequent falling in of the
mouth that gives to the chin its prominent appearance.
  The ramus or extremity  of the lower jaw is square, and  ele-
vated above the body.   In middle age it  is at right angles to 
GENERAL REMARKS ON THE HEAD.
43
the latter, and in youth and old age oblique. The superior mar-
gin has a thin, concave edge, and is bounded  in  front by the
coronoid, and  behind  by the condyloid process.  The first  of
these processes is triangular  and thin, and receives at its  point
the insertion of the temporal muscle; the second articulates with
the glenoid cavity of the temporal bone, and is attached to the
ramus by a narrow neck on the inside of which is a fossa for
the  insertion  of the  external pterygoid muscle.  Externally
the surface of the ramus is rough; internally there is a foramen
for conducting the  inferior  alveolar artery and nerve  to the
teeth.   The junction of the body and ramus is the angle of the
jaw; it is rough  for the attachment  of the  stylo-maxillary
ligament.
   The lower jaw has a greater influence on the form of the face
than any of the other bones.  In some persons it is much smaller
in proportion than in others.   The  inclination of the alveolar
processes externally or internally, frequently cause the chin  to
recede or project  unusually.   At times, also, the  separation  of
its sides, shorten the chin, and give increased width to the lower
part of the face.

              General Remarks on the Head.
   In the adult the bones of the head consist of two tables, one
external, and the other internal.  The external table is hard
and fibrous, the internal  thinner and more brittle, and hence has
received the name of vitreous table.
   These tables are united by a cellular bony substance, called
diplos, which is traversed by channels, filled with veins having
delicate parietes, and provided with valves, and which like all
other veins are intended  to return the blood to the heart.
   They empty at the base of the brain into  the emissaries of
Santorini.
   The bones  of the cranium are united by  seams or sutures
which, except in old age, are very distinctly marked.  They are
formed by the junction of the edges of the bones, which are
serrated or notched, and accurately and firmly fitted  into each 
44
GENERAL  REMARKS  ON THE HEAD.
other.  Indeed, in some of the sutures uniting the flat bones of
the head, a complete dove-tailing is, here and there, met with.
   This kind of union is often  confined to the external table
and to the diploe, whilst in the internal  table the bones are
united by a nearly straight joint.
   The principal sutures of the head  are: the coronal, so named
from its  corresponding in situation with the garlands,  worn by
the ancients, which unites the parietal and  frontal bones;  the
saggital, which unites the two parietal bones in the adult, and
in the child extends through the frontal bone to the root of the
nose;  the occipital, or lambdoidal, uniting  the  parietal and
occipital bones, and also the latter to the temporal  bones—the
latter half is sometimes called the additamentum suturae lamb-
doides;  and the squamous which joins the parietal and temporal
bones  on either side of the head.  One or more small bones are
often met with in the upper part of  the lambdoidal suture, at-
tached to the parietal and occipital bones by serrated margins;
they are  called Ossa Wbrmiana, or  Triquetra.
   Besides  these sutures, which belong exclusively to the head,
there are others uniting the bones of the face.
   Much speculation has been  entered into in regard to the uses
of the  sutures; they appear, however, to be  only a provision for
the growing state, as they cease  when this  terminates.   In the
foetus they are  often serviceable  in facilitating delivery, by per-
mitting the head of the child to  accommodate itself to the pelvis
of the mother.
   The Fontanelles.—These are  membranous spaces peculiar to
the foetus and to  early infancy.  They are owing to a deficiency
of bone at their angles of junction.
   In the bones of the cranium the points of ossification begin-
ning at  the centre, and  going towards the circumference, the
angles, being the longest radii, are  last in ossifying.   Hence
they are  generally incomplete  at birth.   The fontanelles are six
in number, two on the middle line of  the head above, and two
on either side.  The anterior, known in common language  as
the " opening of  the head", is the largest.   It is quadrangular 
GENERAL  REMARKS ON  THE HEAD.           45
 or lozenge shaped, the anterior angle generally being the long-
 est,  and is situated at the fore part of the sagittal suture. The
posterior fontanel is situated at the junction of the lambdoidal
 and sagittal sutures; it is small and triangular, of the two fon-
 tanelles on either side, one is at the angle of junction of the tem-
 poral, occipital, and parietal bones; the other at the junction of
 the parietal and sphenoid bones. They are quite small and often
 indistinct.  All of these fontanelles  ossify speedily after birth,
 and are often entirely closed by the end of the first year.
   Nasal cavities.—These cavities are large and irregular; they
 are divided by the nasal septum.  Each  nostril  or cavity has
 three distinct passages, or meatuses, as they are sometimes called
 —a superior, a middle, and an inferior.   The superior  meatus
 is bounded by the superior and middle  turbinated  bones; the
 posterior ethmoidal and sphenoidal cells, and the spheno-palatine
 foramen open into it.   The middle is between the middle and
 lower turbinated  bones, and has  opening into it, the anterior
 ethmoidal  cells, the  frontal sinus, and  generally the antrum.
 The inferior is bounded above by the inferior turbinated bone,
 and below by the  floor of the nostril; it is the largest, and at
 its upper and anterior part is the nasal duct which communicates
 with the orbit of the eye.   The opening of the nostrils in front
 is called anterior nares; the opening behind posterior nares. The
 mucous membrane lining the nostrils is called  the Schneiderian
 membrane; it extends into the various cavities which empty into
the nostrils, and when in a state of irritation from cold, &c, the
secretions from it  are often copious and exceedingly annoying.
   Orbits of the Eyes.—The orbital cavities are conical,  having
the base outwards, and the apex backwards; they are also some-
what quadrangular.   Seven bones unite  in forming each  orbit
namely, the frontal, malar, superior maxillary, ethmoid, unguis,
sphenoid, and palate bones.
   The roof or superior face of the orbit is formed  by the frontal
and the lesser wing of the sphenoid;  the floor or inferior face
by the upper maxillary, malar, and palate bones; the external
face by the malar and greater wing of  the sphenoid; the interna]
         8 
46
GENERAL  REMARKS ON TnE HEAD.
 face  by the unguis, or  lachrymal, os planum  of the  ethmoid,
 and the body of the sphenoid.
   The apex of  the  orbital cavity contains the optic foramen for
 the transmission of the optic nerve.  Several other foramina for
 the passage of blood-vessels and nerves also  open into the orbits.
   The Facial Angle.—The bones of the face  usually project
 beyond those of the cranium.  In general the races of man that
 are most perfectly developed have this projection less than those
 of inferior conformation.   The facial angle has been instituted
 to denote the differences in this respect.   It is  formed by two
 straight lines,—one drawn from the  lower  part of the frontal
 bone, to the anterior nasal spine, at  the  orifice  of the nose be-
 tween the roots of the middle incisor teeth of the upper jaw,—
 and the other from this latter point through  the external meatus
 of the  ear.   The angle included between  these  lines has been
 found in Caucasian  or European heads to be about eighty de-
 grees ;  in the  heads of the Mongolian or copper-colored races
 about seventy-five degrees;  and in those of the Negro or Ethio-
 pian about  seventy degrees.  The nearer the angle approaches
 to a  right  angle the greater is the degree of intellectual culti-
 vation  manifested.   Even in Europeans, however, this rule  is
 liable  to many exceptions, the facial angle  varying  in its  size
 from causes which have no connection with  the development of
 the brain.
   The internal surface of the cranium is regularly arched above;
 below it presents three deep fossae on each side.  The  anterior
 fossae contains the anterior lobes of the  brain, the middle the
 middle lobes, and the posterior is for the cerebellum.  The entire
 surface  is marked by round superficial depressions made by the
 convolutions of the brain, and is lined by the dura mater.  In
adults the diameters of the cavity of the cranium are, about six
and a half inches  from front to rear,  five inches laterally, and
five vertically. 
HYOID BONE.   UPPER EXTREMITIES.          47
                        Hyoid Bone.
  This is an insulated bone placed in the neck at the root of the
tongue.   In shape it resembles the  letter  u,  and has the con-
vexity in front.  It consists of a body and four cornua or horns;
the body is in the middle, is convex in front, concave behind,
and is the largest part of the bone; its front gives origin  and
insertion  to muscles; two  of the cornua are called the greater,
and two  the lesser, the former are about an inch and a half long,
and mostly united to the body  by cartilage and ligaments; they
are flattened, project backwards, and terminate in a tubercle.
The lesser cornua are small cartilaginous bodies, three or four
lines long, placed at the junction of the body and great cornua.
   They are frequently found ossified; a ligament, the stylo-hyoid,
is attached to each.

                     Upper Extremities,
   This part of the skeleton is  divided on either side into the
shoulder, arm,  fore-arm, and hand.   Two  bones belong to the
shoulder—the scapula and the clavicle.
   Scapula.—This bone, known as  the shoulder-blade, in ordi-
nary language, is placed on the back  part of  the  thorax, and
extends  from the second to the seventh rib.   Its shape is trian-
gular, and it is also  thin and flat, presenting  two surfaces—one
anterior, and one posterior;  three edges or margins—one being
superior, another external, and the  third internal, or posterior,
the latter being parallel with and near to the spinal column;—
and three angles, one of which is superior, another  inferior, and
the third exterior or anterior.
   The posterior surface or dorsum is somewhat concave, and is
divided by the spine into two fossae, of which the lower is much
larger than the upper;  the latter, called  fossa supra spinata, is
occupied by the supra-spinatus muscle, and the former the fossa
infra spinata, by the infra-spinatus muscle.  The spine is a rough
process beginning at the posterior edge of the bone, and running
obliquely across it towards the anterior angle,  and terminating 
48
CLAVICLE.
in the acromion process, which is flat and triangular, overhangs
the shoulder joint, and has a small articular mark in  front for
the clavicle.  The trapezius muscle is inserted into, and the del-
toid arises from, the edge of the spine.
   The internal edge, that parallel to the spine, is the longest, and
into it are inserted the rhomboid and serratus anticus muscle.
   The superior edge is thin and  small, and has  a notch in it,
called the coracoid notch, through which the scapular artery and
nerve pass.
   The external edge is thick, and gives origin to the teres minor,
and the long head of the triceps  muscle.
   The anterior angle is converted into a large shallow cavity,
called glenoid, for articulating with  the head  of the  humerus.
The long head of the biceps arises from a flat surface at its upper
end. Immediately blow the glenoid  cavity the bone  is narrowed
and thickened; this part is termed the neck, or cervix, and from
it a curved  process  projects forwards and outwards called the
coracoid.   This process serves for the attachment  of muscles
and ligaments.

                          Clavicle.
   The clavicle is a long bone  placed transversely at the upper
and anterior part of the chest.  It articulates with the sternum
and the acromion process of the scapula, and in shape is curved
somewhat resembling the italic letter s.   The sternal two-thirds
of the bone is convex, and the outer third  concave anteriorly;
it is cylindrical in the middle, flattened at the  humeral, and tri-
angular at the sternal extremity.  In males it is shorter, thicker,
and more crooked than in females.
   The superior face is smooth, and  marked near the sternum
with a  depression  for the origin of the sterno-cleido mastoid
muscle.   The inferior face is  roughened  near the  sternum for
the costo-clavicular or rhomboid ligament; near the outer extre-
mity is a rough tubercle for the attachment of the coraco-clavi-
cular ligament; between the ends a superficial fossa exists for
the subclavius muscle.   From the  sternal two-thirds of the 
HUMERUS.
49
anterior edge the pectoralis major muscle arises, and from the
humeral third of the same edge the deltoid has its origin.  Near
the middle of the posterior edge one or more foramina are pre-
sented for nutritious vessels.

                          Humerus.

   The humerus, or  arm-bone, is cylindrical, and extends  from
the shoulder to the  elbow.   It consists of a superior extremity,
also called the head, a neck, an inferior extremity, and a body.
  Fig. 2. The humerus.  1 the body;  2 the head;
3 the neck;  10 nutritious foramen;  13  external con-      Fig. 2.
dyle; 14 internal condyle;  11 articulating face for
the radius;  12 articular face for the ulna;  17 lesser
sigmoid cavity.  The remaining figures refer to ridges
marks, &c, for the attachment of muscles.
                                                XWi
   The superior extremity  or head  is hemi-
 spherical,  and articulates with  the glenoid ca-
 vity of the scapula; immediately beneath the
 head, and  separated from it by a groove is the
 neck.   Below this groove  are two  knobs,
 called tuberosities,  one of  which  is external,
 and the other internal; they recrivc the inser-
 tion of muscles, and are separated from each
 other by the  bicipital groove,  in which the
 tendon of the long head of the biceps muscle
 plays.  _
   The inferior extermity is flat and broad, and
 is covered  in  front  by the  brachialis anticus
 muscle, and behind by  the  triceps.   It  pre-
 sents a hemispherical head for  articulating
 with the radius and an irregular cylindrical
 surface for the ulna. Just above the articular
 surface in front is a cavity, called the lesser
 sigmoid which receives  the  coronoid process
 of the  ulna when the fore-arm is much flexed.  Behind is a cor-
 responding though  larger cavity, called the greater sigmoid, for
 the olecranon  process when the fore-arm is extended.  Imme-
 diately above the articular surface for the radius, and continuous
 with a ridge three  or four inches long is the external  condyle,
 from which and the ridge arise the supinator and extensor mus-
 cles.  The internal condyle is just above  the internal margin of 
50
BONES OF THE FORE-ARM.
Fig. 3.
the ulnar articular surface, and  is more prominent than the ex-
ternal.  It may be felt beneath the skin;  from this condyle and
the ridge leading from  it the flexor  muscles of the hand and
fore-arm arise.
                  Bones of the Fore-Arm.

  The fore-arm extends from the elbow to the hand, and contains
two bones, the  ulna, and radius.   The ulna is on the same side
as the  little finger, and is the longer.  Both are straight bones.
                  Ulna.—The ulna is somewhat triangular, and
               its superior or humeral extremity is the larger,
               and has a hook-like process—the olecranon—be-
               hind,  to which is attached the triceps  extensor
               cubiti muscle.  A little below, and in  front of
               the upper extremity is the coronoid process; the
               greater sigmoid cavity for articulating with the
               humerus is between the olecranon  and coronoid
               processes;  and on the outside  of the coronoid
               process is the lesser sigmoid cavity for articulat-
               ing with the radius.   The external edge is the
               sharpest, and to it is  attached the interosseous
               ligament.
                 Fig.  3.  The ulna and radius.  1 body of the  ulna;
               2 greater sigmoid cavity; 3 lesser sigmoid cavity ;  4 ole-
               cranon process ;  5 coronoid process ; 8 lesser extremity ;
               9 styloid process. 14 Body of the radius;  11 rounded
               head;  12 neck; 13 tubercle;  15 inferior extremity; 16
               styloid process.
                 Radius.—This  bone is placed  on the  outer
               side of the ulna, is shorter, and like it extends
               from the humerus to  the wrist.  It  is slightly
           -9   curved, and the inferior extremity is  the larger.
  The upper extremity has a cylindrical head, surrounded by a
smooth rim or border, a part of which plays in the lesser sigmoid
cavity  of the ulna while  the remainder is in  contact with the
annular ligament.   On the upper surface of the head is a fossa
for articulating with the humerus.  Below the head is  the neck
which  is about half an inch in length.  Immediately beneath the
neck is a rough prominence or tubercle for the insertion of the
biceps flexor cubiti.
   The lower extremity is flattened transversely.   It  articulates
 
BONES OF THE HAND.
51
by a concave surface with the scaphoid and lunare bones of the
wrist.  On the internal face of the extremity is a small articular
surface for the ulna.  Externally is the styloid process  for the
attachment of the external lateral ligament.  Upon the back of
this extremity are several grooves, occupied by the tendons of
the muscles which go to the wrist and hand.
   The body of  the bone  is irregularly triangular, and presents
three surfaces and three angles, which are principally occupied
with the origin and insertion of muscles.

                    Bones of the  Hand.
   The hand consists of the carpus or wrist, the metacarpus, and
the phalanges, or digiti, and is made up of twenty-seven bones
exclusive of the sesamoid bones.
    Carpus.—The carpus or wrist is placed next to the fore-arm,
and consists of  eight bones arranged into two rows, called first
and second rows.  The bones in the first  row are the scaphoid,
lunare, cuneiform,  and pisiform; those in the second row are the
trapezium, trapezoides, magnum, and unciform.  They  are dif-
ficult to distinguish from each other.
   The scaphoides,  placed on the radial side of the wrist, is con-
cave above, and convex  below; it articulates above with the
radius, below and in front with the  magnum, trapezium, and
 trapezoides, and on the inside with the lunare.   It  may  be
 known from the others in the row  by its greater length.
    The lunare is at the ulnar side of the latter, and is of a semi-
 lunar shape. Above it is convex,  and below concave.  It arti-
 culates with the radius above, with the magnum below, and with
 the cuneiform on the inside.
    The cuneiform is placed at the ulnar side of the lunare, and
 is somewhat wedge-shaped. It articulates above with  the lunare,
 below with  the unciform, and on the inside with the pisiform.
 *  The pisiform, so named from its resemblance to a pea, is the
 smallest of  the carpal bones.   It has but one articular surface,
 which joins the cuneiform, and may be readily felt at the ulnar
 side of the arist. 
52       METACARPAL BONES.   PHALANGEAL BONES.

  The trapezium is placed at the radial side of the second row,
and is very irregular in shape;  it articulates with the thumb,
scaphoid and trapezoides.
  The trapezoides is at the ulnar side of the trapezium, and the
smallest in the second row;  it is somewhat pyramidal, with the
apex towards the palm, and has four articular faces for the ad-
joining bones.
  The magnum is placed at the ulnar  side  of the last, and  is
the largest bone in  the wrist.  On the upper surface it has a
rounded head to  articulate with the scaphoides and lunare. The
body  is quadrilateral.
  The unciform is  at the ulnar side of the magnum, and nearly
as large;  it may be distinguished by its long crooked process.

                     Metacarpal Bones.
  Of these there are five;  they are placed  between the wrist
and the phalanges  of the fingers and  thumb.   Those for the
finger are parallel with each other;  but the one for the thumb
diverges, and is  so placed that it can be brought in front of the
others during its motions.   Each has a rounded head for articu-
lating with its corresponding phalanx, a cylindrical shaft which is
smaller than the extremities, and a base which articulates with
the carpal bones. The first,  that for the thumbs, is the shortest
and thickest;  the second for the index finger is the longest; the
third, fourth, and fifth gradually diminish in size.

                     Phalangeal Bones.
  Each finger contains three bones, called phalanges; the thumb
has but two.  The  first row, that adjoining the metacarpus, is
called the first phalanx;  the middle row the second;  and the
remaining row the third.
  The bones of  the first phalanx are the largest; they are con-
vex posteriorly,  and flattened anteriorly.  A superficial  cavity
exists in the upper  extremity of each for articulating with the
metacarpal bones.
  The bones of  the second  phalanx are smaller, and  are also 
          REMARKS ON THE UPPER EXTREMITIES.        53

convex behind, and flattened in front.   The upper extremities
of each has  two superficial  cavities for articulating with the
bones of the first phalanx.
   The bones of the third phalanx are the smallest, and differ
materially from the others.   They have but one  articular ex-
tremity the upper, which has two  superficial cavities for the
corresponding faces of the second phalanx.
   The lower extremity is rounded, flattened, thin, and rough.
   The sesamoid bones are two in number; they are small and
hemispherical,  and are placed on the inside of the hand, at the
lower  extremity of the metacarpal bone of the thumb; they
assist the action of the short flexor muscle.  Sometimes they
are  also found at the metacarpal bones of the fingers of  robust
persons.

            Remarks on the Upper Extremities.
   The relative proportion of the upper extremities to the lower
is much greater at birth than at any after period.  This relative
size gradually diminishes up to  the  age of puberty, by which
time it has generally disappeared.  It is probably owing to the
lower extremities, receiving less blood in the foetal state than
the upper.
   At birth, also, the extremities of the clavicles, humeri, bones
 of the fore-arm, carpus, and phalanges—all the long bones—arc
cartilaginous, and larger proportionably than in the adult.  The
 proportion of animal matter is likewise greater, which renders
them less liable to fracture.   They may, however, be bent easily,
and hence too much force should not be applied to them.  Bow-
legs are not unfrequently  caused by permitting young infants to
stand on their feet too long at a time.  Distortion of the spine
may also be induced by the same cause.
   The  clavicle is susceptible of motion in four directions—up-
 wards, downwards, forwards, and  backwards, and also of cir-
 cumduction, which is a rapid succession of these  motions; the
 articulation at the externum is the centre upon which these move-
 ments are performed.  It also assists in supporting the shoulder,
        9 
54        REMARKS ON THE  UPPER EXTREMITIES.
and by keeping it from falling forwards greatly facilitates the
motions of the joint.  In females the clavicles are longer in pro-
portion than in  males, to accommodate the breasts, and in conse-
quence of this increased length, some of the motions of the
shoulder are performed with great awkwardness.
   The scapula, besides, having all the motions ascribed to the
clavicle,  is capable of performing a partial rotation;  it serves as
a movable basis for all the motions of the arm.
   The humerus is susceptible of motion, upwards, downwards,
forwards, and backwards, and also of circumduction and rotation.
The motion of  circumduction is very extensive in the shoulder
joint; it is a regular succession of all the other movements, ex-
cept rotation, by which the arm describes a cone having for its
apex the glenoid cavity.
   Rotation is the turning of the bone upon itself; it is not ex-
tensive,  rarely  exceeding a half circle.
   In the fore-arm there are two kinds of motion;  in one kind
the fore-arm is flexed or extended on the arm, and the ulna is
the principal agent.   In the other,  the radius rotates upon  the
ulna, the latter being almost stationary.   When  the hand, fol-
lowing the forward rotation of the radius, has its palm directed
downwards, it is said to be in a state of supination.  This is the
most common and easiest position of the fore-arm.  In the back-
ward rotation of the radius,  in which the palm is upwards, the
hand is  in a state of supination; in this position  the radius is
parallel  with the ulna; in pronation the middle part of the  ra-
dius crosses that of the ulna.
   The motions of the hand on the fore-arm are, flexion, extension,
lateral inclination, or abduction, and adduction, and circumduc-
tion ;  those which take place between the first and second rows
of the carpus are chiefly flexion and extension.   The metacarpal
bone of the thumb moves freely on the trapezium;  its motions
 are, flexion, extension, abduction, adduction, and  circumduction.
 The latter is the result of the others, and resembles that of the
 shoulder joint.   The motions of the other metacarpal bones are
 much more limited, being confined mostly to a moderate degree 
LOWER  EXTREMITIES.   THIGH BONE,  OR FEMUR.    55
of flexion and extension.  The first phalanges admit of flexion,
extension, lateral motion, and circumduction;  the second and
third are restricted to the two first.  It will thus  be perceived
from the nice mechanism of the upper extremities,  and the num-
ber of  pieces which enter into their structure, what a variety of
movements they are capable of performing.

                    Lower Extremities.

  The bones of the lower extremity are, the femur, os femoris,
or thigh bone, the tibia, fibula, patella; and the  tarsal, meta-
tarsal,  and phalangeal bones belonging to the foot—in all sixty-
four.
                  Thigh Bone,  or  Femur.
  The thigh contains but one bone,  which  is      . Fig. 4.
the longest  in  the  body, reaching from the
pelvis to the knee; it consists of a superior,
and an inferior extremity, and a body.

  Fig. 4.  Thigh hone, or Femur. 1 Body, or shaft;
2 head; 3 neck;  4 trochanter major; 6 trochanter
minor; 7 internal condyle; 8 external condyle.

  The superior extremity  has  a  spherical
head, with a depression upon it for the liga-
mentum teres.   Between the  head and body
at an angle of about thirty degrees with the ,
latter is the neck,  which is about two inches
in length.  At the base  of the neck on either
side are two prominences, called the trochan-
ters major  and minor;  the former,  which is
situated  externally, is much the larger, and
receives the insertion of several muscles com-
ing from the pelvis; the latter is placed in-
ternally, and has the psoas magnus and iliacus
internus muscles inserted into it. Between the
two trochanters behind is a ridge, into which
is inserted the quadratus femoris.  A simi-
lar ridge in  front marks the attachment  of
the capsular ligament.                       ,
  The inferior extremity is much larger than  (
the superior, and is divided by a fossa in front
and a notch behind into two parts, called the 
56
BONES OF  THE  LEG.
all
external and the internal condyle.  Of these
the internal from being placed  the most  ob-
liquely, appears to be the larger.  These con-
dyles have articular faces for the tibia below,
and the patella in front.
  The body of the bone is nearly round, and
is slightly curved anteriorly;  its front surface
is covered by the cruraeus muscle.

  Fig. 5. Posterior view of femur, showing the ridge,
called the linea aspera, and the origin  and insertion
of the muscles along its two lips.

  p insertion of the pectineus;  ab  insertion of the
adductor brevis;  g m  insertion of the  gluteus maxi-
mus; a m insertion of the adductor magnus; g m ori-
gin of the vastus externus; h origin of the short head
of the biceps flexor cruris.

  Posteriorly there is an elevated ridge,  the
linea aspera, which is considerably elevated,
and  serves for  the origin  and insertion  of
muscles.  Near the middle of this ridge is a
large foramen for the  nutritious artery.
                      Bones of the Leg.
  There are two bones to the leg, the  tibia and the fibula, of
which the former is placed internally, and the latter externally;
they extend from the knee to the foot.
   Tibia.—This bone is much longer and larger than the fibula;
next to  the femur it is the largest hone in the body;  its lower
half is commonly called the shin-bone.   The upper extremity,
or head, is large, and  contains  two  superficial cavities, divided
by a ridge, called the spinous process, for articulating with the
condyles of the femur.   At  the base of  the spinous process in
front and behind the crucial ligaments are attached; at its sum-
mit is a depression for the attachment of the posterior extremity
of the external  semilunar cartilage.  Upon each  side  of the 
BONES OF THE LEG.
57
head is an enlargement, called the  internal and external con-
dyles, or tuberosities; on the back part of latter, looking down-
wards, is a small articular mark for the  fibula.  In  front  and
just below the head is a tubercle for the attachment of the liga-
ment of the patella.
   The lower extremity of the tibia is  much smaller  than the
upper, and somewhat quadrilateral; it articulates by a trans-
verse cylindrical concavity with the astragalus;  externally there
is a triangular groove for articulating with the fibula; internally
a large process, called the internal  malleolus; posteriorly a slight
groove for the tendon of the flexor longus pollicis muscle.  The
extensor tendons pass over the anterior surface.
   The body is triangular, and consequently presents three edges
and three surfaces.  The anterior edge,  called the spine, or crest,
is sharp, superficial, and slightly curved;  the external  has at-
tached to  it one edge of the interosseous ligament; the internal
edge is rounded,  and in it  are  inserted several muscles.   The
internal surface is only covered by the  skin;  the external  sur-
face is covered by the muscles of  the leg; the posterior  surface
gives origin to the tibialis anticus  and flexor communis muscles.
      Fig. 6.                                         Fig. 7.
  Fig. 6.  Anterior view of the ti-
bia and fibula.  1 External face of
the body of tibia;  2 internal con-
dyle ; 3 external condyle;  4 spin-
ous process; 5 tubercle; 6  anterior
edge, or spine; 7 lower extremity;
8 internal malleolus;  9 fibula; 10
upper extremity; 11 lower  extrem-
ity, or external malleolus.
  Fig. 7.  Posterior view of the
tibia and fibula  1 External con-
dyle ;  2 internal condyle; 3 fossa
for the insertion of the semi-mem-
branosus muscle; 4 fossa for the
attachment of the posterior crucial
ligament; 5 oblique ridge for the
origin of the soleus muscle;  6 ex-
ternal edge; 7 posterior face of bo-
dy; 8 internal malleolus; 9 groove
for the tendon of the flexor longus
pollicis; 10 fibula; 11 superior ex-
tremity; 13,14  inferior extremity,
or external malleolus.
 
58
BONES OF  THE FOOT.
  Fibula.—The fibula is placed on the outside of the leg, with
its upper part somewhat posteriorly.  It is a long, thin bone,
extending from the head of the tibia to the foot;   it is rather
shorter than the tibia.  The upper extremity or head is enlarged,
and has a concave surface  on its upper part for articulating with
the external condyle of  the tibia;  behind  is a  styloid process
for the insertion of the head of the biceps.  The lower  extrem-
ity is also enlarged, and is called  the external  malleolus;  its
internal  surface is smooth, triangular, and slightly convex  for
articulating with  the astragalus;  its external  surface is  also
triangular and superficial.  The pointed extremity of the exter-
nal malleolus is sometimes called the coronoid process.
  The body is triangular, presenting a twisted appearance, and
has three faces; the external face gives origin to the peroneus
longus and brevis muscles in its upper two-thirds;  the internal
face is towards the tibia, and is divided longitudinally by a ridge
to which is  attached the interosseous  ligament;  the spaces in
front and behind this ridge give origin to muscles;  the posterior
face gives origin to the soleus and flexor longus pollicis muscles.
The  anterior angle is sharp and elevated in the middle.  There
is also a  slight bend, towards the tibia, in this bone.
  Patella.—This  is a flat ovoid bone, situated at the fore part
of the knee joint;  it is commonly  called the knee-pan.  Its  an-
terior face is convex and rough, and covered  by the integuments;
its posterior face is smooth, and unequally divided by a longi-
tudinal ridge.   The external part is the larger,  and articulates
with the trochlea in front of the external condyle of the femur;
the  internal part is the smaller, and articulates with the trochlea
of the internal condyle.  The superior margin is  thick,  and into
it is inserted the tendon of the rectus femoris; the inferior mar-
gin  is thinner and pointed, and  has the tendon  of the patella
attached  to it.

                    Bones of the Foot.
  The foot consist of the tarsus, metatarsus, and  phalanges.  In
the  tarsus, which forms the posterior half of the  foot, are seven 
BONES OF  THE FOOT.
59
bones, the os calcis, astragalus, naviculare, cuboides,  and the
external,  middle, and internal cuneiform.
   Os calcis.—This bone forms the heel, and is much the largest
of the bones of the foot.  In shape it is irregular;  its longest
diameter is lengthwise of the foot, and it is also thicker verti-
cally than transversely.  The superior surface has two  articular
faces at its front part for the astragalus. Between these cavities
is a  deep  groove, the posterior part of which is occupied by the
interosseous ligament. The internal surface is very concave, and
is called  the sinuosity;  over it pass the  tendons, vessels, and
nerves for the  sole of the foot;  the external  surface is  nearly
flat,  and is marked by the passage of tendons of the  peroneus
longus and brevis; the under surface is  slightly concave, and
has  two tuberosities behind, of which the internal is the larger;
they give origin to the muscles of the foot.   This surface has
also  a tuberosity in front.
   The anterior extremity forms the greater apophysis,  and arti-
culates with  the cuboides;  the posterior  extremity is convex,
and  rough to receive the insertion of the tendon Achillis.
   Astragalus.—This is  next in size to the latter, and  is placed
between it and  the bones of the leg.  It consists of a body and
head.  Above,  the body articulates with the tibia, and  on either
side  with the malleoli.  The head is placed anteriorly  and arti-
culates with  the scaphoides.
   Scaphoid.—This is an oval bone situated at the inner side of
the tarsus, between the astragalus and  the  cuneiform bones;
behind is a deep concavity for the astragalus, and in front three
triangular articular surfaces for the three  cuneiform bones;  at
the inner side is a large tuberosity for the insertion of the tendon
of the tibialis posticus.
   Cuboid.—Is  on  the outer side of the tarsus, between  the  os
calcis and the  metatarsal bones, and as its  name indicates, is
somewhat cuboidal in shape.   The internal face is flat, and has
an articular  mark  for the  cuneiform internum; the  posterior
face is triangular, and articulates with the os calcis; the anterior
face articulates with the last two metatarsal bones. 
GO
BONES OF THE METATARSUS.
   Internal cuneiform.—This is the largest of the three cunei-
 form bones, and is  placed between the  scaphoid  and the first
 metatarsal bone.  Anteriorly it joins the first metatarsal bone;
 posteriorly the scaphoid;  internally it is marked by the tendon
 of the tibialis posticus;  externally it joins the second metatarsal
 bone, and middle cuneiform.  As may be infered from the name,
 in its general shape it resembles a wedge.
   Middle cuneiform.—Is  the smallest of the  tarsal bones, and
 is also shaped like a wedge with the base above;  it is placed
 upon the scaphoid, at the outside of the internal cuneiform.
 It articulates with these two  bones and  likewise  with external
 cuneiform.
   External cuneiform.—This is also wedge-shaped, and placed
 upon the scaphoid, between the  second cuneiform and  the  cu-
 boides.   It articulates anteriorly with the third metatarsal bone ;
 posteriorly with the  scaphoid;  internally with the second cunei-
 form, and the second metatarsal bone; externally with  the  cu-
 boides.

                 Bones of the Metatarsus.

   In the metatarsus are five parallel long bones;  they extend
 from the tarsus behind  to the toes  in  front, and are called nu-
 merically, beginning on the inner side of the foot.
   The first is  shorter and thicker than the  others;  its base
 articulates with the internal cuneiform, and its head, which is
 spherical, with the first phalanx of the  great toe.  Below its
 head are the sesamoid bones.
   The second is the longest; its base articulates at the extremity
 with the middle cuneiform, on the inside with the internal cunei-
 form, and on the outside with the external cuneiform and second
 metatarsal.
   The third has a triangular  base which articulates with the
 third cuneiform, and also laterally with the second and fourth
 metatarsal bones.
  The fourth articulates at its base with the cuboid, and  on
either side with  the third and  fifth  metatarsal bone*. 
BONES OF THE TOES.
61
   The fifth is the shortest, and is readily distinguished by a
 large tubercle, which projects outward from its base beyond the
 external margin of the cuboides, into which the tendons of the
 peroneus tertius and  brevis are inserted.  Its base articulates
 with the cuboid and fourth  metatarsal bones; its anterior ex-
 tremity is more rounded than that of the others.

                     Bones of the Toes.
   There are five toes on each foot, which are named numerically,
 beginning at the great toe.   Each toe is formed of three bones,
 called phalanges, except the great toe, which like the thumb, has
 but two.
   The  first row or phalanx bear a  general resemblance to  the
 first row of the fingers, but are smaller; the bases articulate by a
 deep cavity with the metatarsal  bones; the anterior extremities
 have two small condyles for  the second row.
   The  second row  or phalanx, also resemble, the second  row of
 the fingers, though they are  much  shorter, scarcely having  any
 bodies; the bases  have two cavities  for articulating with  the
 first phalanx, and the anterior  extremities two convexities  for
 the third phalanx.
   The  third row articulates with the second, and are very small;
 the fourth and  fifth are generally but imperfectly developed.
   The  phalanges of the  great  toe are much  larger  than  the
 others.   Two sesamoid bones are connected with the  tendon of
 the flexor brevis pollicis of each foot;  they have articular faces
 which join the head of the metatarsal bone of  the great toe.

            Remarks  on the Lower Extremities.
   As before remarked the lower extremities are proportionably
smaller  than the upper at birth,  owing to their receiving  up to
that time a smaller quantity of blood.
   Like  those of the upper extremities, the  bones of  the lower
are but  partly ossified at birth; the ends of all  the long bones
are cartilaginous, as are  also the patella and  tarsal bones with
the exception of parts of the  os calcis and astragalus.  The meta-
        10 
62        REMARKS ON THE  LOWER EXTREMITIES.
tarsal and phalangeal bones are not so much developed  as  the
corresponding bones of the hand.
  At birth also the upper end of the femur is more at a right
angle to the body than it is in the adult; the body of the bone
is but slightly curved, and the  neck short; all of which tend
to make standing and walking difficult in young children.
  The bones of the lower extremities all become ossified about
the fifteenth year, and they have then nearly the same form as in
the adult.  The epiphyses are the only exceptions to this, which
where they join  the body of the bone are  often  cartilaginous,
and until the twentieth or twenty-fifth year may be separated by
boiling.
  The motions of the thigh are the same as those  of the arm,
viz. flexion, extension, abduction, adduction, circumduction,  and
rotation, though they are much less extensive in consequence of
the acetabulum, the basis on which they are performed, being
fixed.
   Flexion, by which the thigh is carried forward, is  performed
with great facility and ease;  extension, the reverse of this, is  also
performed with much freedom, though it is  less extensive than
the former; abduction is that motion  by which the  thighs are
separated, and  adduction the act of bringing them together
again or crossing them;  the muscles concerned in the latter are
called adductors.  Both of these motions are performed to a  con-
siderable extent.   Circumduction—the regular succession  in a
circle of the other motions mentioned—is less extensive than in
the arm.   Rotation or the turning of the femur upon itself, is
effected with much facility, especially rotation outwards, or back-
wards.
   The chief motions of the leg on the thigh are flexion and exten-
sion; rotation is also performed in a slight degree.  Those of the
foot upon the leg are flexion, extension, and some lateral  motion.

                    Of the Articulations.
   The connection of one bone with another is called an articula-
tion, or joint.  Some articulations are movable, and  others im- 
OF THE ARTICULATIONS.
63
movable;  in  the structure of the former cartilage, ligaments,
and synovial  membranes are  necessary.
   Cartilage is a smooth, white, flexible, and  elastic substance,
and ranks next to bone in hardness.  Chemically, it is composed
of gelatine and water with a small portion of phosphate of lime.
It resists the attacks of disease almost as firmly as bone;  it is
not highly organized, being without red blood-vessels, nerves,
and lymphatics, and unless diseased  has no sensibility.  In old
age it is disposed to ossify.  It is invested by a  fibrous  mem-
brane, called perichondrium, which  corresponds with  the  peri-
osteum.
   That portion of cartilage, called articular, which covers the
extremities of bone, is thicker in the middle when it covers con-
vex surfaces, and thicker on  the edges when it lines cavities.
   Cartilages, which  are  movable in  a joint, are called inter-
articular.
   Fibro-cartilage, which consists partly of cartilage, and partly
of ligament, and is much stronger than the former, is  found in
the external  ear, between the vertebra, in the knee-joint, &c.
   Ligaments are composed of fibrous  tissue, and are  inelastic.
Those connecting the joints pass from one extremity of the bone
to the other, mostly exterior to the  synovial membrane.   They
are of  two kinds, white and yellow;  the  tendons and most of
the ligaments are examples of  the former, and the  ligamentum
nuchae of the latter.  "When  ligaments are  cord-like, they are
called funicular, and when open at the  ends like a bag, capsular.
   Synovial  membranes are thin, closed serous sacks, which line
the  movable joints.   They  secrete  a viscous fluid, resembling
the white of  an egg, called synovia, which lubricates  the joints
and prevents friction.
   The different kind of articulations have been divided into
 Synarthrosis, Amphiarthrosis, and Diarthrosis.
   Of the first, which implies immobility, there are several spe-
 cies—that which unites the bones of the skull is termed Sutura;
 that  which unites the bones of the  upper jaw Harmonia; that 
64
OF THE ARTICULATIONS.
by which the vomer joins  the azygos, Schindylesis;  and  that
joining the  teeth with the alveoli,  Gomp)hosis.
   In the second, which  implies partial motion, the bodies of
the vertebrae and symphyses are included.
   In the third, diarthrosis, three species are included; Arthro-
dia, that uniting the tarsal and carpal  bones; Ginglymus, or
hinge-like, as the elbow and wrist;  and  Enarthrodia,  or  ball
and socket joint, as  the hip and shoulder.
   In the articulation of the lower jaw there are: a capsular liga-
ment, an internal and an  external  lateral ligament, a  stylo-
maxillary ligament  extending from  the  styloid process of the
temporal bone  to the angle of the jaw;  an inter-articular carti-
lage—a thin oval plate dividing the joint into two cavities—with
two synovial membranes,  one on either side of the inter-articular
cartilage;  or when  the  cartilage  is  imperfect but one synovial
membrane.
   In the articulation of  the vertebrae  there  are: an  anterior
vertebral ligament, which is placed in front of the  bodies of the
vertebrae, and extends from the second cervical to the first sacral
vertebra, gradually increasing in breadth as it descends; a poste-
rior vertebral ligament, which is placed at the posterior part of the
bodies of the vertebra within the spinal canal,  and  extends from
the occiput  to the coccyx; it is narrow and thick in the thorax,
wider below, and adheres more  closely to the inter-vertebral
substance than to the bodies of the vertebrae, which  gives  it a
serrated appearance.   Between the bodies  of the vertebrae,  and
adhering closely to  their  substances, are twenty - three fibro-
cartilaginous disks;  these  are arranged in concentric  lamina,
compressible, and gradually increase in thickness from  above
downwards.  Owing to this compressibility, the trunk becomes
shortened after the erect position has been maintained for several
hours, but is restored to its original length  again by an interval
of rest in the horizontal posture.
   The oblique processes are  united by a capsular ligament.
   The spinous processes are joined  together by the inter-spinal
ligaments, which fill  up  the spaces between  them.   They are, 
OF THE ARTICULATIONS.
65
however, wanting in the neck, and their place is supplied by the
ligamentum nuchae, which extends from the seventh cervical
vertebrse to the posterior occipital  protuberance, dividing the
muscles of the neck.
  The yellow  ligaments, which are  elastic, are placed between
the bony bridges of the vertebrae; there  are twenty-three  pairs
of them.
  Between the occiput and atlas are: an anterior ligament, which
extends from the back parts of the occipital foramen to the front
of the atlas; a posterior ligament, which  extends from the back
part of the occipital foramen to the corresponding edge of the
atlas;  and a capsular ligament, surrounding the superior oblique
process of  the atlas, and the condoloid process of the  occiput.
   Between the atlas and dentata are:   a transverse  ligament,
which passes across the atlas transversely from one tubercle to
the other;  two moderator ligaments,  extending  from the sides
of the processus dentatus to the inner side of each occipital con-
dyle;  a middle or straight ligament, passing from the processus
dentatus to the anterior edge  of the  occipital foramen;  a loose
capsular ligament surrounding the oblique processes;  and  some
ligamentous bands, called Lacerti ligamentosi, reaching from
the back part of the body of the dentata to the  occiput.
   In the articulation of the bones of the pelvis, there are, unit-
ing the sacrum and ilium, an anterior sacro-iliac ligament, which
consists of short fibres  passing from one  bone to the other;  a
posterior sacro-spinous ligament extending from  the spinous pro-
cesses of the ilium  to the third and fourth transverse processes
of the sacrum;  and an anterior  and posterior sacro-sciatic liga-
ment; the posterior, which is much the  larger, arises from the
posterior inferior spinous process of the ilium, the margin of the
sacrum,  and the first bone of the coccyx, and is  inserted into
the inner margin of the tuberosity of the ischium; the anterior,
which is in front of the posterior, extends from  the side  of the
sacrum to the spine of the ischium.   The articulating surfaces
of  both  the sacrum and ilium  are covered with cartilage.
   The obturator  ligament passes over the thyroid foramen 
66
OF THE ARTICULATIONS.
closing it up, with the exception of a small opening at its upper
part for the passage of the obturator vessels and nerves.
  In addition to the foregoing there is an ilio-lumbar ligament,
a lumbo-sacral  ligament, an  anterior  and posterior  coccygeal
ligament, and a sub-pubic ligament, the  names  of which suffi-
ciently indicate their attachments.
  The articulation of  the pubes—symphysis pubis—consists
chiefly of a fibro-cartilaginous substance, like that of the ver-
tebrae.
  The Ribs in their articulation posteriorly with  the vertebrae
have an anterior or radiated ligament, extending from the head of
the rib to the two contiguous  vertebrae and the intervening car-
tilage; a capsular ligament enclosing the head of the rib;  an
inter-articular ligament, extending from the ridge  on the head
of the rib to the inter-vertebral substance;  a capsular ligament
connecting the transverse processes to the tubercle of the rib;
an internal, middle, and external  costo-transverse ligament, ex-
tending from the transverse process  to the adjacent rib.
  In the  articulation  of  the  ribs anteriorly with  the sternum
there is: an anterior radiated  ligament, which passes from  the
cartilages of the true ribs to the sternum;  a posterior radiated
ligament,  having the same connections;  and a  costo-zyphoid
ligament, which extends  from the  cartilages of the  sixth  and
seventh ribs to the zyphoid or ensiform cartilage.
  In the articulation of the  shoulder there are:  uniting  the
clavicle and sternum, a  capsular ligament,  within which,  and
dividing the joint into two  cavities, is  a wedge-shaped  inter-
articular cartilage; an inter-clavicular ligament, connecting the
two clavicles; and a rhomboid ligament, extending from inferior
edge of the clavicle to the cartilage of the  first rib.
   Uniting  the scapula and clavicle are: a  capsular ligament,
connecting the  acromion  process of the  scapula, and the outer
end of the clavicle;  a coraco-clavicular  ligament, consisting of
two parts, one called conoid,  the other trapezoid, which extends
from the coracoid process to the  external extremity of the clav-
icle; a bifid ligament, which  goes from  the  coracoid  process to 
                  OF THE ARTICULATIONS.                67

the clavicle and the cartilage of the first rib;  a coraco-acromial
ligament connecting  the coracoid and acromion processes;  and
a coracoid ligament which passes across  the coracoid notch.
   Uniting the scapula  and humerus, are, a loose capsular liga-
ment which invests  the glenoid cavity and  the  neck of the
humerus;  a coraco-humeral ligament,  a part of the capsular,
which extends to the coracoid process; and a glenoid ligament
which consists of a ring of fibro-cartilage  attached to the edge
of the glenoid cavity, to increase its depth.
   In the articulation of the  elbow joint there are,  a capsular
ligament, which surrounds the head of the humerus,  radius
and ulna; an  internal lateral ligament, passing from the internal
condyle to the coronoid and olecranon processes of the ulna; an
external lateral ligament, extending from the  external condyle
to the lateral ligament; an angular or coronary ligament, which
surrounds  three-fourths of the head of  the radius, and  extends
to either side  of the lesser sigmoid cavity; and an interosseous
ligament, which fills up the space between the radius and ulna
throughout nearly their whole length.
   The articulation of the  wrist, which is formed by the greater
sigmoid  cavity of the radius, and the scaphoid, semilunar and
cuneiform bones, has a capsular ligament, an  anterior and a pos-
terior ligament, and  an internal and external  lateral ligament.
The individual bones of the carpus are connected by  palmar and
dorsal ligaments.
   The bases of the metacarpal bones  are also attached  to the
second row by palmar and dorsal ligaments.  The pisiform bone
and the thumb have distinct capsular ligaments.
   The fingers are attached to the metacarpal  bones by an inter-
nal  and external lateral  ligament; an anterior or palmar liga-
ment, and a posterior ligament furnished by the extensor tendon.
   The phalangeal bones are joined together by a similar arrange-
ment of ligaments.
   In the  articulation of  the hip joint, formed by  the head of
the  thigh bone  and the acetabulum,  the following ligaments
enter.  The cotyloid ligament,  which is a thick prismatic  ring 
68
OF THE ARTICULATIONS.
 surrounding the margin of the acetabulum  and increasing its
 depth.  The ligamentum teres—round  ligament—which is at-
 tached  to  a pit on  the head of the femur, whence it passes  in
 two fasciculi to be inserted  into the notch of the acetabulum;
 the  cotyloid ligament  and  the capsular  ligament,  which  en-
 circles the acetabulum and  the  neck of the  femur, and is the
 strongest ligament in the body.
   In the  articulation of the knee joint there are,  an anterior
 ligament,  called also  the ligament  of the patella, which is a
 continuation of the quadriceps muscle, is firmly attached to the
 patella, and inserted into the tubercle  of the  tibia; a posterior
 ligament,  also called  ligament  of Winslow, which extends ob-
 liquely from the external condyle to the  back part of the  inter-
 nal tuberosity of the tibia;   two semilunar cartilages, which are
 prismatic rings attached to the margins of the tibia, to  deepen
 its articular surface;  two crucial ligaments, which cross each
 other, the one extending from the front of the spine of the tibia
 to the posterior part of the  inner face of the  external condyle,
 the other  passing from behind  the spine of the tibia to  the an-
 terior part  of the external face  of the internal  condyle  of the
 femur;  and an internal and  external lateral ligament on either
 side of the joint.
   The tibia and fibula are  united; at the superior extremity,
 by an anterior  and posterior ligament, which  pass  obliquely
 between the heads of the two bones before and  behind;  along
 their length by an interosseous ligament, which fills up the space
 between the bones,  except  a small opening  at  the upper ex-
 tremity to transmit the anterior  tibial artery;  and at the  lower
 extremity,  by an anterior and  posterior ligament similar  in ar-
 rangement to those connecting the heads of the bones.
   The ankle joint is united by an internal  and an external late-
ral ligament;  the  internal,  also called deltoid is triangular in
 shape, and has its  apex attached to the  internal malleolus and
its base to the os calcis, astragalus,  and  calcaneo-scaphoid liga-
ment ; the  external  consists  of  three fasciculi which arise from 
OF THE SKIN.
69
the external malleolus, and are inserted into the astragalus and
os calcis.
   Articulation of the tarsus.—The astragalus is  united  to the
os calcis by a thick, strong, interosseous ligament, and by a pos-
terior ligament; the os calcis to the scaphoid by a superior and
an inferior calcaneo-scaphoid ligament; the os calcis and cuboid
by a superior and  inferior calcaneo-cuboid ligament; and the
astragalus and scaphoid by a semicircular ligament which  passes
from the neck of the astragalus  to the edge of the concavity of
the scaphoid.  The  three  cuneiform bones are joined to the
scaphoid, and to each other by dorsal, plantar  and interosseous
ligaments.
   Articulation of the metatarsus.—The first of these bones has
a strong capsular ligament, attaching  its base to the internal
cuneiform; the second and  third have the base attached to the
middle and external cuneiform by dorsa1  and plantar ligaments;
and the bases of the fourth and fifth are joined to the cuboid by
dorsal and plantar ligaments. The heads of the metatarsal bones
are united to the  phalanges by two lateral and a plantar liga-
ment, and superiorly  by an expansion of the extensor tendon;
and to each other by a strong transverse ligament.
   In the articulation  of the  phalanges there is an arrangement
of ligaments corresponding to that of the hand.

                        Of  the  Skin.

   The skin covers  the entire body, and besides affording  protec-
tion to the various  parts, serves also as an organ of touch and
secretion.
   It  is continuous with the mucous membrane, and at the ori-
fices of the canals leading into the body, as the mouth, nose, &c,
is readily  converted  into it.  Its color  and thickness vary  in
different races  and individuals, and in different parts of the same
individual.  Climate  has a great influence over it, the tendency
of parts exposed to tropical  heat and light  being to turn  dark.
        11 
70
OF THE SKIN.
   The skin  is covered  by  a  great number  of wrinkles;  the
largest, those which appear on the forehead, face, &c, are caused
by the contractions of muscles, and the flexion  of the  joints;
others of a  finer description  are  produced by the contractile
nature of the skin.
   Numerous hairs, perspiratory ducts, and pits showing the ori-
fices of sebaceous glands, and follicles, are contained in the skin;
the perspiratory ducts or pores are not visible  to the naked eye.
The facility with which  the  skin slides backwards and forwards
on most parts of  the  body is owing to the looseness of the cel-
lular tissue beneath it.
   The skin consists of two layers, the  cutis vera or true skin,
also called chorion,  and the epidermis or cuticle.  Formerly a
third layer, the rete mucosum, was  admitted;  but more recent
observations have demonstrated this to be merely a layer of the
cuticle.
   Of the two layers the true skin is the thicker and deeper;  it
is closely adherent to the cellular tissue, and perfectly white and
semi-transparent  in all persons.  The external surface is covered
with fine conical  projections, called villi or papillae tactus ; the
papillae are  most numerous and distinct in those parts where
there is much motion. On the hands and feet they are arranged
in double rows,  which  occasion  the  semi-circular and spiral
wrinkles of the cuticle on these parts.  Each papillae consists  of
an artery, vein, and  nerve,  and the sensibility of a part is in
proportion to their number.
   The texture of the true  skin is  fibrous; the irregular inter-
lacing of fibres producing a mass of net-work or areolae, through
the meshes of which the hairs, nerves, blood-vessels, &c.  are
transmitted.  Its  composition is of condensed cellular tissue  the
yellow fibrous  element predominating where  great elasticity is
required, as in the arm pit;  and the white  element where resis-
tance is wanted,  as in the  sole of  the  foot.  It unites  readily
with tannin, and forms leather.  Boiling converts it into gelatine. 
OF THE  SEBACEOUS GLANDS.
71
  Fig. 8. Magnified representation of the
skin, a, Cuticle or epidermis; b, papillae tac-
tis or villi; c, cutis vera or true skin.

   The cuticle  or  epidermis varies in
thickness according  to  the  amount of
pressure to which it is subject; in the
palms  of the hand,  and the soles of
the feet in  individuals, who  perform
manual labor,  it becomes very thick.
It is not organized, neither vessels nor
nerves being traceable into it, but is
composed of particles arranged in la-
minae,  or layers; the  deepest being
granular, the next somewhat flattened,
and those upon the surface mere horny
scales which are constantly being shed,
and replaced  again  by others.   The
coloring matter is  contained in the
lowermost layer, and is very abundant
in  negroes,  moles,  freckles, &c.   The
facility  with which  the  cuticle may be
divided into different layers, owing to
its laminated  arrangement,  formerly
caused the innermost layer to be  con-
sidered  distinct, and to receive a  sepa-
rate name, that of rete  mucosum.

    Of the Sebaceous Glands.
  These consist of a blind, pouch-like
duct, which is lined by an epithelium
containing granules of sebaceous mat-
ter in its particles, and has an  orifice
opening  into  hair  follicles,  or upon
the  general surface.   They are most
abundant on  the  scalp and  face,  particularly about the nose.
There are none on  the palms  of the hands and  the  soles of
the feet.
  The secretion is of an oily nature, and serves to lubricate the
hair and skin; it is this which gives to linen that has been worn
a long time a greasy appearance, causes water when  applied to
the surface of the body to collect in drops, and gives  rise  to the
 
72
OF THE NAILS AND HAIRS.
strong disagreeable smell in negroes, and persons who do not pay
proper attention  to  cleanliness.  Parasitic animalculae are fre-
quently found in  the ducts of these glands.

                       Of the Nails.
  The nails take  the place of  the  cuticle on the ends  of the
fingers and toes, and like the latter are readily separable  from
the true skin by maceration.  They correspond  with the hoofs
and talons of the lower orders of animals.
  They consist of a root, body, and free extremity.  The root is
that.part which is concealed; it has a thin irregular edge,  is
white, thin,  soft, and about one-fifth of  the whole length of the
nail.  The body is that portion between the root and free extrem-
ity ; its under surface adheres closely to  the skin, which produces
it, and is hence called the  matrix;  it is  also soft  and marked
by longitudinal grooves.
  The white part of the nail near the root is called the crescent
or lunula, and is caused  by the absence of vascularity.  At its
root the nail is received into  a groove formed by the cutis vera.

                       Of the Hairs.
   Hairs are found on  almost every part of the skin except the
palms of the hands and soles of the feet.  They vary in size and
color  in different races, sexes, and  individuals, and  in different
parts  of the body. Those on  the head attain  the greatest length,
and grow more  closely together than any  others—in females
they grow longer, and are  more abundant than in males.  Those
of the face (the beard), when allowed to grow, are next in length.
and are  thicker  than the others,  and more disposed to curl.
Generally the eyes and hair correspond in color, and the darker
the hair the coarser.   It has been  computed that a fouth  of  an
inch square  has  upon  it 147 black hairs, or 162 hazel, or 152
white.  In  some individuals the hairs are  so much developed
as almost to conceal the skin.
  Each hair consists of a bulb  and a  shaft or stalk;  the bulb is
the extremity contained within  a follicle of the skin, and the 
OF THE HAIRS.
73
shaft is the part that projects  beyond the surface. The human
hair is solid and not globular as is generally supposed. It is con-
tinuous with the cuticle lining the follicle, and is arranged  in
lamina or scales, which overlap each other like the  shingles of
a house; the middle portion has a looser and more porous struc-
ture than the external,  and has  received the name of medulla,
while the external is termed the cortex.   The hair is nourished
from the bottom of the  follicle, as the nail is from  the matrix,
or the cuticle from the true skin.
   The  hairs, when large,  are used as organs of touch, and in
some animals, the whiskers  of the cat, for instance, possess some
degree  of sensibility, which  is owing to the projection of a
conoidal papilla of  the follicle furnished with nerves, into the
bottom of the  bulb. As a general rule,  however, they are void
of sensibility.  The hairs  receive no blood-vessels; their moisture
is chiefly owing to  the secretion of the sebaceous follicles passing
through them by capillary attraction. In those instances in which
the hair has suddenly become white from mental emotion, it has
been by some, supposed  to be owing to the  secretion of a fluid
acid, which  penetrates the  tissue of the  hair in  this way,  and
destroys its color.
   The erection of  the hair in some animals is caused by the
contraction of the  subcutaneous  muscle; and a similar  effect in
man, produced by  great fright, is owing to the contraction of the
 occipito frontalis muscle. Moisture lengthens the hairs and dry-
ness shortens them.
    When the hair falls off,  it is occasioned by the drying up of
 the fluids of the follicle or  its death; in  the baldness of old per-
 sons, the latter generally takes place, and consequently all efforts
 to restore it will be fruitless.  But when the hairs fall  off from
 sickness, the follicles remain, and a new crop is  soon produced.
 When the  hair becomes  white from age, the change  of color
 begins at the free  extremity ; but if the color is restored again,
 the change  begins at the root.   In the disease known as Plica
 Polonica, which consists in a matting together of the hair  by a
 glutinous substance from the cutaneous  glands,  if  the hairs are 
74
OF THE TEETH.
cut close  to  the skin they bleed;  this  is owing to  the  elonga-
tion of the vascular papilla at their roots by disease.

                       Of the Teeth.
  The permanent teeth are thirty-two in number, sixteen being
placed in the alveolar processes of each  jaw.   They are the har-
dest part of the human body.  The  part of a tooth above the
gum is called its crown; the narrow portion surrounded by the
gum its neck;  and the  portion within  the alveolus  its fang, or
root.   There are  four classes of teeth, as follows: two incisors,
or cutting teeth, on each side of each jaw next the middle line;
one cuspid, or pointed place  next to these outwardly;  two bi-
cuspid, or double pointed;  and three molars,  or grinding teeth.
Fig. 9.  Permanent teeth.
  The incisors have a bevelled edge which  in  early life is ser-
rated; their roots are single  and conoidal; those of the upper
jaw are the largest.
  The cuspid (pointed), or canine, which are placed between the
incisors and bi-cuspides, have a conoidal body and longer roots
than any of the others.  Those of the upper jaw are commonly
known as eye-teeth, and those of the lower as stomach-teeth.
  The bi-cuspides are next in size to the  molars;  their  bodies
have  two conical tubercles, or  grinding points, the external  of 
OF THE TEETH.
75
which is  the  larger.  The root is flat and deeply grooved on
either side.   The two posterior superior  have each two roots;
the others generally but one.
   The molars, of which there are six in  each jaw, have large
quadrilateral bodies, surmounted by four or five grinding points;
their roots  are shorter  than  those of the bi-cuspides, and are
divided into two, three, four,  or even five branches.   The third,
called the wisdom-tooth, is generally smaller than the other two.
   In the  centre of each tooth is  a cavity, which is filled by a
pulp, chiefly composed of an artery, vein, and nerve, which enter
through the small  orifice at  the extremity of the  root.  This
pulp is soft, of a gray color, and extremly sensitive.
   Three  textures enter into  the structure of each tooth—the
ivory, or bony portion, the enamel, and  the  cementum.  The
first, which forms the principal part of the tooth, is arranged in
radiating fibres; it contains  neither blood-vessels,  nor nerves,
nor  are its particles  absorbed  as those of bone.   Chemically, it
consists of phosphate of lime, gelatine, and water.  The enamel
is the hardest portion, it covers the body of the  tooth, is white,
brittle,  and semi-transparent, thicker  on  the  grinding  surface,
and terminates by a thin edge at  the neck.  It is also arranged
in radiating fibres,  and has  neither blood-vessels,  nor nerves.
The cementum, is a thin coating extended over the  root of the
tooth, which in structure resembles bone.
   The  periods at which the permanent teeth make their ap-
pearance  are as follows:  the four first molars, and  the two inferior
incisors  from  the 6th to the 8th year; the two superior central
incisors from  the 7th to the 9th year;  the four  lateral  incisors
from the  8th  to the 10th year; the four  first bi-cuspides from
the  9th to the 11th year; the four cuspidati from  the  12th to
the  13th  year; the four second bi-cuspides from  the 11th to the
13th year;  the four second molars from the 12th to the 14th
year; and finally the four last molars from the 18th to the 30th
year, or even later in some instances. 
76
OF THE MUSCLES.
Fig. 10.
  Fig. 10.  The deciduous, or milk-teeth,  a a central incisors; bb lateral
incisors; ce cuspidati, or eye- and stomach-teeth; dd first molars;  ee
second molars.

  The rudiments of all the teeth, both of the first and  second
set, fifty-two in number, are contained in the gum  of the infant.
The first set,  called the deciduous, or milk-teeth, are  twenty in
number, viz. four incisors, two cuspidati, and four molars in each
jaw.  As with the temporary teeth there is  a good deal of irre-
gularity in the time of their appearance; usually the  four cen-
tral incisors appear from the  5th to the 10th month; the four
lateral  incisors from  the 8th  to the 13th month;  the four first
molars  from the 10th to the 14th month;  the  four cuspidati
from  the 12th to the  18th month;  and the  four  second  molars
from  the 24th to the 30th month.  The teeth of the  lower jaw
generally make their appearance a short time before those of the
upper.   About the seventh year, the time at which the  first of
the permanent teeth make their appearance, the first  set begin
to loosen and fall out,  generally, in the order in which they came.

                      Of the  Muscles.
   The muscles are the organs  by which the various motions of
the body are performed; they  are constituted of the  substance
commonly called flesh,  and possess the power  of  shortening
themselves, called contractility, and which  produces motion. 
OF THE MUSCLES.
77
Each muscle is composed of a number of fasciculi (bundles* of
fibres) of various size;  these  again  are  made up of filaments.
Every muscle and fasciculus is enveloped, and held together by
a portion of cellular membrane, called its sheath, which is tough
and  elastic,  and becomes more delicate the smaller the fasciculus
or filament it surrounds.
   The uses of the sheaths are  to  facilitate  the sliding of the
muscles upon each other, and by their pressure  to add to  their
strength and tenacity.   Towards their extremities the muscles
are attached to a white, shining, fibrous structure  termed tendons,
which serve to fasten them  securely to  the  surfaces of bones;
the extremity, which is the more fixed,  is termed the head, or
origin, and that which is the more movable, the tail, or inser-
tion /  and the middle is the belly, or swell.  The fibres of the
most simple muscles are longitudinal.   In others the  fibres are
disposed in rays  which converge  to a  tendinous point, hence
called radiate muscles; others again have their fibres converg-
ing  to one or both sides of a tendon like the plumes of a  pen;
these are called the penniform, and the  bi-penniform.
   There  are  two classes of muscles,  the  voluntary, or  those
which are influenced by the will, and the involuntary, or  those
not  governed  by the will.   The first class, which is much the
most numerous, are placed between the skeleton  and  the  skin,
and constitute the chief bulk of the body; the second class are
contained within  the great  cavities of  the skeleton,  and  enter
into  the  formation of the  digestive, circulatory, and  urinary
organs, performing most of the internal movements of the ani-
mal economy.   The color  of the muscles  of voluntary motion
is of a decided red, that of  the involuntary muscles  is lighter;
the  fibres of the latter, also, cros^ each  other and interlace.
   The muscles are divided into four parts, viz. those of the head
and neck;  those of the trunk; those of the upper extremities;
and those of  the lower extremities.
12 
78           MUSCLES OF  THE  HEAD AND  NECK.
Muscles of the Head and Neck.
Fig. 11.
                      First, of the Face.

  The occipito frontalis is a thin muscle passing from the back

to the front of the head immediately beneath the scalp; it has

four bellies, and arises from the superior semi-circular ridge of

the occiput, and is inserted into the superior margin of the orbi-

cularis oris, and corrugator supercilia, and into the internal an-

gular process of the  os frontis and nasi.  It pulls the  skin of

head  backwards and forwards, and elevates the eye-brows, mak-

ing transverse wrinkles.
                                     Fig. 11.  View of the muscles
                                   of the  head and neck.   1, 2, 3
                                   Occipito frontalis;  4 orbicularis
                                   palpebrarum ; 5 "corrugator super-
                                   cilii; 0 compressor naris ; 1 orbi-
                                   cularis oris; 8 levator labii supe-
                                   rioris alasque nasi; 9 levator an-
                                   guli oris; 10 zygomaticus minor;
                                   11 zygomaticus major; 12 depres-
                                   sor labii inferioris; 13 depressor
                                   anguli oris; 14 levator mentii; 15
                                   masseter; 16 temporalis; 18 buc-
                                   cinator; 24 mylo-hyoideus;  25
                                   sterno-cleideo-mastoideus.


                                     The compressor naris arises
                                   from the root of the ala nasi,
                                   and is inserted into its fellow
                                   on the dorsum of the nose,
                                   and into the lower  part of
                                   the  os nasi.   It serve  both
                                   to  compress  and  dilate the
                                   nostril.

   The orbicularis palpebrarum is a sphincter surrounding  the

 orbits of the eyes; it arises from  the nasal process of the supe-

 rior maxillary bone, the os unguis, the internal  angular process

 of  the os frontis, and the superior margin of the internal palpe-

 bral  ligament;  and  is inserted into the orbital and nasal  pro-

 cesses of the superior maxillary, and into the inferior margin of

 the palpebral ligament.   It closes the eyes.

   The  corrugator supercilii arises  from the  internal  angular
 
MUSCLES OF THE  HEAD AND NECK.          79
process of the os frontis, and  is inserted  into the occipito fron-
talis and orbicularis.   It is small and  pointed, and makes the
vertical wrinkles of the forehead.
   The levator labii sujierioris alaeque nasi  is placed at the side
of the nose; it arises from the nasal and orbitar processes of the
superior maxillary bone, and is inserted into the upper lip and
the wing of the nose.   It draws the upper lip and wing of the
nose upwards.
   The levator anguli oris  is  small and concealed by the  last;
it arises  from the superior maxillary bone below the infra-orbital
foramen, and is inserted into the angle  of the mouth.  Its use
is to elevate the  angle of the mouth.
   The zygomaticus minor arises from the fore part of the malar
bone,  and is inserted into the upper  lip.   It draws the corner
of the mouth obliquely upwards and outwards.
   The zygomaticus major arises from the malar bone outside of
the last, and is inserted into the corner of the mouth.   Its use
same as the last.
   The depressor labii superioris alaeque nasi arises from the al-
veolar processes of the incisor and canine teeth, and is inserted
into the wing of the nose and upper lip.  It depresses the upper
lip and the wing of the nose.
   The depressor anguli oris  arises from  the base of  the lower
jaw at the side of the chin, and is  inserted  into the corner of
 the mouth.  It  draws the corner of  the mouth downwards.
    The depressor labii inferioris arises from the base of the lower
jaw, beneath the last, and is inserted into the whole side of  the
 lower lip.   It draws the lip downwards.
    The levator menti,  or labii inferioris arises from the alveolar
 processes of the lateral incisor  and canine teeth,  and is inserted
 into the lower lip.  It elevates the lip.
    The buccinator arises from the coronoid  process of the lower
 jaw, the tuber of the upper jaw, and  the  alveolar processes of
 both jaws, and is inserted into  the corner of the mouth and lips.
 It draws the corner of the mouth backwards. 
80          MUSCLES  OF THE HEAD AND NECK.
   The orbicularis oris is a circular muscle, which surrounds the
mouth, constituting  the  principal part of the  lips;  it has  no
long origin but is attached to the surrounding muscles, and acts
as the  antagonist to most of them.
   The masseter arises from the upper maxillary, malar, and the
zygomatic process  of the  temporal bones, and is inserted into
the angle and outer surface of the lower jaw.  It closes the jaws,
and also draws the lower jaw backwards and forwards.
   The temporalis arises from the temporal fascia, and from the
sides of the temporal, frontal, and parietal bones, and is  inserted
into the coronoid process of  the lower jaw.  It pulls the lower
jaw upwards.
   The pterygoideus externus arises from the pterygoid,  spinous,
and temporal processes of the sphenoid bone, and  from the tuber
of the upper  maxillary,  and is inserted  into the neck of the
lower jaw.   It draws the lower jaw upwards.
   The pterygoideus internus arises from the  pterygoid  fossa,
Eustachian tube, and internal pterygoid process, and is  inserted
into the inner surface of  the neck of the  lower jaw.  It draws
the jaw upwards.

                    Second, of the Neck.
   There are two layers of cellular tissue in the neck, called the
superficial, and the deep seated fascia;  the first is immediately
beneath the skin, and a continuation of the fascia covering the
whole  body;  the second  is more condensed, and  extends from
the ligament nuchae to the sternum, investing the several muscles
and blood-vessels.
   The platisma myoides is a broad thin muscle, placed  between
two laminae of the superficial fascia, and is attached  to  the  cel-
lular tissue below the clavicle, and to the  muscles at the side of
the face and lower jaw.  It  elevates the skin of the neck.
   The sterno-cleido-mastoideus arises  from the  upper part of
the sternum, and  the  sternal end of  the clavicle, and passino-
obliquely across the neck  is inserted into the  mastoid  process,
and the adjoining ridge of the occipital bone.   It forms a pro- 
MUSCLES OF THE  HEAD AND NECK.          81
minent ridge on the outside of the neck.  Its use is to draw the
chin to the sternum.
   The sterno-hyoidcus arises from  the sternum, clavicle, and car-
tilage of the first rib, and is inserted into the lower edge of the
hyoid bone.   It draws the hyoid bone towards the sternum.
   The sterno-thyoideus arises  from the sternum and cartilage of
the first rib, and is inserted into the side of the thyroid cartilage.
It draws this  cartilage downwards.
   The thyro-hyoideus  arises  from the  side of the  thyroid car-
tilage, and is inserted into the base and cornu of the os hyoideus.
It draws the os hyoideus and  thyroid cartilage together.
   The omo-hyoideus arises from the upper edge of the scapula,
and is inserted into the base of the os hyoideus.   It draws the
os hyoideus downwards.
   The digastricus arises from the fossa at the base of the mas-
toid process of the temporal bone, and is inserted into the base
of the lower jaw at the side of its symphysis;  its middle is ten-
dinous, and passes through the stylo-hyoid muscle.   Its use  is
to  raise the  hyoid bone, and  open  the mouth, even  when the
lower jaw is fixed.
   The stylo-hyoideus arises from the middle and lower part  of
the styloid process of  the temporal bone, and is inserted into the
base and  cornu of the os hyoides.   It draws the os hyoides up-
wards and backwards.
   The stylo-glossus arises from the  upper and internal part  of
the styloid process, and is inserted into the side  of  the root  of
the tongue.   It draws the tongue backwards.
   The stylo-pharyngeus arises from  the inner side of the root  of
the styloid process, and is inserted into the side of the pharynx
between  the  superior and middle constrictors, and  is inserted
into the posterior margin of the thyroid cartilage.  It draws the
larynx and pharynx upwards.
   The mylo-hyoideus arises from  the root of the alveolar process
of the lower jaw, and is inserted into a white tendinous line,
placed  between  it and its  fellow.   It forms the floor of the 
82           MUSCLES OF  THE  nEAD AND  NECK.
mouth.   Its use is to draw the os hyoides upwards and project
the tongue.
   The genio-hyoideus is placed beneath the last, and arising
from the tubercle  on the posterior  side  of  the chin, is inserted
into the body of the hyoid bone.
   The following seven pairs of muscles are placed at  the front
and sides of the cervical vertebrae.
   The longus colli arises from the three upper dorsal vertebrae,
and the transverse processes of the five lower cervical  vertebrae;
and is inserted into the  bodies of all the cervical vertebrae.   It
bends the neck forwards and to one side.
   The rectus capitis anticus major arises  from the  transverse
processes of the third, fourth, and fifth cervical vertebrae, and is
inserted into the cuneiform process of the os occipitus. It bends
the head  forwards.
   The rectus capitis anticus minor arises from the front of the
first cervical vertebrae, and is inserted into the basilar  process of
the occiput.  It bends the head forwards.
   The rectus  capitis lateralis arises from the front of  the trans-
verse process of the atlas, and is inserted into the ridge leading
from the condyle  to the  mastoid process of the occiput.  It draws
the head slightly  to one side.
   The scalenus anticus  arises from  the transverse processes of
the fourth,  fifth, and sixth cervical vertebrae, and is inserted into
the upper surface of the first rib near its middle.  It bends the
neck forwards, or elevates the first rib.
   The scalenus medius  arises from  the transverse processes of
all the  cervical vertebrae, and is inserted into the upper surface
of the first rib from the middle to the  tubercle.  Its  use  same
as the last.
    The  scalenus posticus arises from the transverse processes of
the fifth and  sixth cervical vertebrae,  and is inserted  into the
upper face  of the second rib, beyond its tubercle.  It bends the
neck, and raises the second rib.  The use  of the three scalenii
muscles,  acting together, is to elevate the ribs, and bend the neck
 to one side. 
MUSCLES OF THE  TRUNK.
83
                  Muscles of the Trunk.

          First,  those of the front  of the  Thorax.
  The pectoralis  major forms  the large fleshy cushion of the
chest.   It arises from  the first two  bones of the sternum, the
cartilages of  the fifth and sixth ribs, the  anterior two-thirds of
the clavicle, and the tendon of  the external oblique muscle, and
is inserted by a broad  thin  tendon into the outer edge of the
bicipital groove of the humerus.  It  draws the arm inwards and
forwards, and depresses it when raised.
  The pectoralis minor is beneath the last;  it  arises  from the
upper edges of the third, fourth, and fifth ribs, and is inserted
into the inner faces of the coracoid process of  the scapula.  It
draws the scapula inwards and downwards.
   The subclavius arises from the  cartilage of the first rib, and
is inserted into the lower face of the clavicle.   It is placed im-
mediately beneath the clavicle, and  draws it downwards.
   The  serratus magnus, or serratus major anticus is a broad
muscle at the sides of the ribs;  it  arises from the nine upper
ribs by fleshy digitations, the five lower of which are  connected
with the internal oblique muscle, and is inserted into the base
of the  scapula.  It draws the  scapula forwards.
   The intercostales fill up  the spaces—eleven  in number—be-
tween the ribs.  There are two to each  space,  an external, and
 an internal.   The external arises from the transverse process of
 the vertebrae, and the inferior acute edge of the  rib,  and is in-
 serted  into the superior rounded edge of the rib below; its fibres
 passing obliquely forwards and downwards.  The internal arises
 from the inferior edge of the rib, and  is inserted into the  supe-
 rior rounded edge of the  rib below;  its fibres pass obliquely
 backwards and downwards.  The use  of the  intercostales is to
  draw the ribs together.
    The triangularis sterni is on  the posterior surface  of the car-
  tilages of the ribs; it arises from the ensiform cartilage and the
  second bone of the sternum, and is inserted into the cartilage  of 
84
MUSCLES OF THE TRUNK.
the third, fourth, fifth, and sixth ribs.   Its use is to depress the
ribs, and thereby diminish the cavity of the  thorax.
  Fig. 12.  View  of the  muscles  in front of the  thorax and abdomen.
1 Pectoralis major; 2 deltoid; 3 latissimus dorsi; 4 origin of the serratus
magnus; 5 subclavius; 6  pectoralis minor; 1 coraco-brachialis; 8 biceps;
9 coracoid process  of the scapula;  10 serratus magnus; 11 external inter-
costal muscle ;  12 external oblique; 13 aponeurosis of the external oblique;
14 and 15 Poupart's ligament;  16 rectus;  17 pyramidalis;  18 internal ob-
lique;  19 tendon of the internal oblique  and transversalis;  20 passage of
the spermatic cord.

                Second, muscles of  the abdomen.

   Between the skin and the muscles of the  abdomen is a layer
of condensed cellular  substance, called  the fascia superficialis 
MUSCLES OF  THE  TRUNK.
85
abdominis: it maybe traced upwards over the thorax to the
neck and  face, and downwards  to  the thigh.  It is generally
blended with fat, and  in the groin encloses the lymphatic glands,
and the external pudic vessels between its laminae.
  There are five pairs  of abdominal muscles, viz. the  external
oblique,  internal  oblique, rectus abdominis, pyramidalis,  and
transversalis.
  The obliquus externus  arises  from the eight inferior  ribs, by
tendinous and fleshy heads, the  five upper  of which are  inter-
locked with those  of  the serratus  anticus,  and the three  lower
with  those  of the latissimus dorsi;  its fibres  pass obliquely
downwards and forwards, and are inserted into the whole length
of the linea alba, and into the anterior half  or two-thirds of the
crest  of the ilium : the  tendon also  extends anteriorly to the
body  and symphysis  of the  pubes,  forming thereby Poupart's
ligament.
  The linea alba, in  the  middle line of the body, is formed by
the union of the tendons  of the three broad muscles on  either
side of the abdomen.   On either side of the linea alba,  and two
or  three  inches from it,  is another line formed by the  same
tendons,  called linea semilunaris.  The use  of the  external
oblique is to compress the viscera of the abdomen, and  approxi-
mate  the pelvis and thorax.
  The obliquus internus lies beneath the last, and its fibres pass
in an opposite direction; it arises from the three inferior spinous
processes of the lumbar vertebrae, all  those of the sacrum, the
crista of the ilium, and the upper  half of  Poupart's ligament;
and is inserted  into  the cartilages of  the six inferior ribs, the
ensiform cartilage, and into the whole length of the linea alba.
At the linea alba the tendon is  divided into two  laminae,  which
enclose the rectus muscle.  Its use is the same as that of the
internal oblique.
   The transversalis abdominis is underneath the last, and arises
from  the transverse processes of the last dorsal  and four upper
lumbar vertebrae, the crest of the ilium, the  outer half of Pou-
part's ligament, and from the cartilages of the six or seven lower
         13 
86                MUSCLES OF THE TRUNK.

ribs;  and is inserted into the ensiform cartilage, and linea alba.
At  the pubes it is inserted in common with the tendon of the
internal oblique  behind the external abdominal ring.  Just above
this insertion it is divided into two lamina to enclose the pyrami-
dalis muscle.  It compresses the viscera of the abdomen.
  The rectis  abdominis  arises from the symphysis and body of
the pubes, and passing upwards between the layers of the tendon
of the external oblique, increasing in breadth  as it ascends, is
inserted  into  the  ensiform cartilage, and  the fifth,  sixth and
seventh ribs.  It has several tendinous intersections crossing it,
called  linea transversae.   Its use is to draw the thorax towards
the abdomen.
  The pyramidalis is placed at the lower and front part of the
rectus, and is about three inches long; it arises from the  body
of the pubes, and is inserted into the linea alba.  Sometimes it
is wanting.  It gives strength  to the lower part of the abdomen.
  The cremaster is commonly considered as a portion of the in-
ternal oblique, as previous to the descent of the testicle  it forms
the lower edge of this muscle. It envelops the testicle and cord,
and is inserted into the tendons of the internal oblique and trans-
versalis.  It draws  up the testicle.
  The fascia transversalis is placed between the abdominal
muscles and the peritoneum;  it is thin and tough,  and has an
opening in it, to  transmit the spermatic cord, which is called the
internal abdominal ring.

Third, muscles of  the upper and posterior part of the abdomen.
  The diaphragm is a movable, muscular septum, or division
placed  between the cavities of the thorax and abdomen.  Above
it is in contact with the pericardium and lungs, and below, with
the liver, stomach, and spleen.  It consist of two portions, called
the greater and lesser muscle.   The greater arises from the ensi-
form cartilage, and the six inferior ribs on each side, its fibres
converge towards  the centre to be inserted into the cordiform
tendon.  The lesser has two bellies, called the crura, the one on
the right side being the larger; it arises from the second, third, 
MUSCLES OF  THE  TRUNK.
87
and fourth lumbar vertebrae, and is also inserted into the cordi-
form tendon.  This tendon, so called from its resemblance  to a
heart,  is large and  shining,  and nearly horizontal in the erect
posture; it has its apex toward  the sternum, and its notch to-
wards  the  spine;  its summit is about on a line with  the lower
end of the  second bone of the sternum.
  There are three openings or foramina in the diaphragm; the
first, situated in the  back part of the muscle near the spine, is
called  the  foramem  oesophageum.   It is elliptical in shape, and
transmits the oesophagus  and par vagum nerves.  The  second,
called the foramen quadratum,  is in the centre of the cordiform
tendon and transmits the ascending vena cava.  The third, the
hiatus aorticus, is in front of  the vertebrae, and between the
crurae;  it  gives passage to the  aorta,  thoracic duct,  and  great
splanchnic nerves.
  The quadratus lumborum arises from the crista of  the ilium,
and is inserted into the last dorsal and all the lumbar vertebrae,
and into the  lower edge of the last rib.  It bends the loins  to
one side, and pulls down the last rib.
  The psoas parvus arises from the last dorsal  and the first
lumbar vertebrae, and is inserted into the linea innominata and
fascia iliaca. It draws up the sheath of the femoral vessels. Some-
times it is  absent.
  The psoas magnus arises from the transverse processes of all
the lumbar vertebrae, and from the bodies  of the four upper
lumbar and the last dorsal vertebrae;  and is inserted into the
lesser trochanter of the  femur, and for about an inch  below it.
  The iliacus internus arises from the transverse process of the
last lumbar vertebrae, the costa and crest of the ilium, and from
the capsula of the hip joint;  and is inserted  into the tendon of
the psoas magnus.  It assists the latter muscle in bending the
body forwards and drawing the thigh upwards.

                Fourth, muscles of the  back.
  The trapezius is a broad muscle immediately under the skin
of the  back; it arises from the  occipital protuberance and the 
88
MUSCLES OF THE  TRUNK.
superior semicircular ridge of the occiput, from the spinous pro-
cesses of the neck by the ligamentum nuchae, and from all those
of the  back;  and is  inserted  into the  external  third  of the
clavicle, and the acromion process and spine of the scapula.  It
draws the scapula towards the spine.
  The latissimus dorsi covers  the whole of the lower part of
the back; it arises from the seven inferior  spinous processes of
the back, from all those of the loins and sacrum, and from three
or four  of the last  ribs; and is  inserted into the posterior ridge
of the bicipital groove along with the teres minor.   It draws the
humerus downwards and backwards.
  The  serratus  inferior posticus  arises from  the  two inferior
spinous processes of the back, and the three superior of the loins,
and  is  inserted  into the four inferior  ribs.  It draws the ribs
downwards.
  The rhomboideus minor arises from the three inferior spinous
processes of the neck;  and is inserted into the base of the sca-
pula opposite the spine.
  The rhomboideus major  arises  from the last spinous process
of the neck, and the four superior of the  back; and is inserted
into  the base of  the scapula below the spine. These two muscles
draw the scapula upwards and backwards.
  The serratus superior posticus arises from  the  three inferior
spinous processes of the neck, and the  two superior of the back;
and  is inserted  into the second, third, fourth and fifth ribs.  It
draws the ribs upwards.
  The levator scapulae arises from  the three, four, or five supe-
rior transverse processes of  the neck;  and is  inserted into the
angle of the scapula and its base above the spine.   It draws the
scapula upwards.
  The splenius arises from the spinous processes of the  five in-
ferior cervical and the four  superior dorsal vertebrae; and is in-
serted  into the occipital  bone between the  semicircular ridges,
and  into the  transverse processes of  the two superior cervical
vertebrae. The part which  goes to the head is called splenius 
                   MUSCLES  OF THE  TRUNK.                 89

capitus, and  that which  goes  to the neck, splenius colli.   It

draws the head and neck backwards.

                              Fig. 13.
     Fio-. 13.  View of the muscles of the back.  1, 2 The trapezius; 3 acro-
   mion°process and spine of scapula; 4 latissimus dorsi;  5 deltoid; 6 infra-
   spinatus, and teres minor and major; 7 external oblique; 8 gluteus medius;
   9 glutei maximi;  10 levator anguli scapula?;  11 & 12  rhomboideus minor
   and major; 13 splenius capitis ;  14 splenius colli;  15 vertebral aponuerosis
   16 serratus posticus inferior; 17 supra spinatus; 18 infra spinatus ; 19 teres
   minor; 20 teres major; 21 long head of the triceps; 22 serratus magnus ;
~  23 internal oblique.

      The  sacro-lumbalis and  longissimus  dorsi arise in common

   from the spinous and  transverse processes of the loins  and 
90
MUSCLES OF THE TRUNK.
sacrum, and from  the crest of the ilium; and the first is in-
serted into the angles of the ribs.  The latter,  which is nearest
the spine, is inserted into all  the  transverse  processes of the
vertebrae of the back except the first, and into the under-edges
of all the ribs beyond their tubercles, except the two last.  They
keep the spine erect, and draw down the ribs.
   The spinalis dorsi arises  from the three lower spinous pro-
cesses of the back,  and the two upper of the loins; and is  in-
serted into the nine upper spinous  processes of the back except
the first; it is almost entirely tendinous.  Its use is to keep the
spine erect.
   The cervicalis descendens  arises from  the four superior ribs,
and is inserted  into the  fourth, fifth, and sixth transverse pro-
cesses of the back.  It draws the neck backwards.
   The transversalis cervicis  arises  from the five superior trans-
verse  processes of the back; and is inserted into the five middle
transverse processes of  the neck.  It draws the head and neck
backwards.
   The trachelo-mastoid arises  from the three upper transverse
processes of the back, and the five  inferior of  the neck; and is
inserted into the mastoid  process.
   The complexus arises from transverse  processes of the four in-
ferior cervical, and of the  superior dorsal vertebrae;  and is
inserted into the os occipitus between its semicircular ridges.  It
draws the head backwards.
   The semi-spinalis cervicis arises from the transverse processes
of the six upper dorsal vertebrae; and is inserted into the spinous
processes of the five middle cervical vertebrae.  It  draws the
neck obliquely backwards.
   The semi-spinalis dorsi arises from  the transverse processes
of the seventh, eighth, ninth, and tenth  dorsal vertebrae, and is
inserted into the spinous processes of the two lower cervical, and
five upper dorsal vertebrae.  It draws the  spine obliquely back-
wards.
   The multifidus spinas  arises from the oblique and transverse
processes of all the sacral, lumber and dorsal vertebrae, and is 
MUSCLES OF THE  TRUNK.
91
inserted into  the spinous  processes of all the vertebrae of the
loins and back, and of the  four inferior of the neck.  It twists
the spine backwards, and keeps it erect.
  Fig. 14.  Posterior views of the neck,           Fig. 14.
thorax, abdomen, and pelvis. 1, 2,3 Sacro-
lumbal, and longissimus dorsi ;  4 spinalis
dorsi;  5 cervicalis descendens;   6 trans-
versalis  cervicis ;   7  trachelo  mastoid;
8 complexus; 10 semi-spinalis dorsi; 11 se-
mi-spinalis cervicis; 12 rectus capitis pos-
ticus major;   13 rectus capitis posticus
minor; 14 obliquus superior; 15 obliquus
inferior; 16 multifidus spinse; 17 levatores
costarum; 18 inter-transversalis.

   The rectus capitis posticus major
arises from  the spinous process of
the dentata, and is inserted  into the
inferior  semicircular ridge  of the
occiput  and a part  of  the surface
below it.  It  turns the head, and
draws it backwards.
   The rectus capitis posticus minor
arises from the tubercle of the atlas,
and is inserted into  the occiput at,
and below the inferior semicircular
ridge. It draws the head backwards.
   The obliquus superior arises from
the transverse  process of the atlas,
and is inserted  into the outer end  r.
of the inferior semicircular ridge of   >^v
the occiput.  It draws the head back-
wards.
   The obliquus inferior arises from
the spinous  process  of the  dentata,
and is inserted into  the  transverse
process of the first cervical vertebrae.  It rotates the first vertebrae
on the second.
   The  inter -  spindles are  short muscles, placed between  the
spinous  processes of  all the vertebrae.  They are double in the
neck; tendinous  in  the back;  and single and well marked in
the loins.  They keep the spine erect.
   The inter-transversalis are placed between all the transverse
processes.   They draw these processes together.
 
92         MUSCLES OP  THE UPPER  EXTREMITIES.
  The levatores costarum.  There are twelve  of  these  small
muscles on either side of the spine; they arise  from the  trans-
verse processes of the last cervical, and the eleven superior dorsal
vertebra, and are inserted into the upper edge of the two next
ribs below.  They elevate the ribs.

             Muscles of the  upper extremities.
  The muscles  of  the  upper  extremity are covered with the
brachial fascia, which extends from  the  shoulder to the  hand.
It forms  at the wrist the  anterior and  posterior annular liga-
ments, which holds down the  flexor tendons of the hand  and
fingers. In the hand it forms the palmar aponeurosis.
               First, muscles  of the shoulder.
  The deltoid passes over the top of the shoulder,  giving  to it
its rotundity: it arises from the spine  of the scapula, the acro-
mium process, and the outer third of the clavicle, and is inserted
into  the triangular  roughness  near the middle of the humerus.
It raises the humerus.
  The supra-spinatus scapulae arises from the whole of the fossa
supra-spinata, and is inserted into the inner facet of the greater
tuberosity of the humerus.  It raises the arm, and turns it out-
wards.
  The infra-spinatus scapulae arises from the whole of the fossa
infra-spinata, and is inserted into the middle facet of the greater
tuberosity of the humerus.  It rolls the humerus outwards and
backwards.
  The teres minor arises from  the lesser costa  of  the scapula,
and is inserted into the outer facet of  the greater  tuberosity of
the humerus.  It rotates the humerus outwards,  and draws it
downwards and backwards.
  The teres major arises from the posterior  surface  of the angle
of the scapula, and from a part of  its inferior costa; and is in-
serted into the posterior ridge of the bicipital groove along with
the tendon of the latissimus dorsi.
  The subscapularis arises from the  whole of  the inferior or
thoracic surface of the scapula, and  is inserted  into the  lesser 
MUSCLES OF THE  UPPER EXTREMITIES.         93
tuberosity of the humerus.  It rotates the humerus inwards and
draws it downwards.
                Second,  muscles of the arm.
  The biceps flexor cubiti  has  two heads, one the long head,
arising from the superior extremity of the glenoid cavity of  the
scapula, and passing through the joint and bicipital groove ;  the
other,  called the short head, arising from the coracoid process
of the scapula.  It is  inserted into the posterior rough parts of
the tubercle of the radius.  Its use is to flex the fore-arm.
  The coraco-brachialis arises in common with the short head
of the biceps from the middle facet of  the coracoid process of
the scapula, and is inserted by  a rough ridge into the  internal
side of the middle of the humerus.  It draws the arm upwards
and inwards.
  The brachialis internus arises from  the anterior and  lower
half of the humerus,  and is inserted  into the  rough surface
at the root of the  coronoid process of the ulna.  It flexes the
fore-arm.
  The triceps extensor cubicti arises by three  heads,  the first,
called the longus, from a rough ridge on the inferior edge  of the
scapula; the second, the brevis, from a ridge on  the back part
of the  humerus just below the head; and  the third, the brachia-
lis internus, from the inner side of the  humerus near the inser-
tion of the teres major.  It is inserted into the back-part of the
olecranon process.   It extends the fore-arm.
   The anconeus arises from the external condyle of the humerus,
and is inserted into the ulna below the olecranon process.   It
extends the fore-arm.
               Third,  muscles of the fore-arm.
   There are  eighteen of these;  eight on  the front of  the fore-
arm, which are  the flexors, and ten on  the back part,  which
are the extensors.   The last arise principally from the external
condyle.
   On  the front are :
   The pronator radii teres, arising from the internal condyle of
       14 
I
94
MUSCLES OF THE UPPER EXTREMITIES.
the humerus,  and the coronoid process of the ulna; and is in-
serted into the middle and back part of the radius.
   The flexor  carpi  radialis,  arising from the internal condyle
of the humerus,  the adjacent fascia,  and from the upper part
of the ulna, and is inserted into the base of the metacarpal bone
of the fore-finger.  It flexes the hand.
Fig. 16.
Fig. 15.
                                               Fig. 15.  View of the
                                             superficial  muscles on
                                             the front of the fore-
                                             arm.  1  Lower part  of
                                             the biceps;  2 part  of
                                             the brachialis anticus ;
                                             3 part  of  the  triceps;
                                             4 pronator radii teres;
                                             5 flexor carpi radialis; 6
                                             palmarus longus; 7 part
                                             of the  flexor sublimus
                                             digitorum; 8 flexor car-
                                             pi ulnaris;  9 palmar fas-
                                             cia;  10 palmaris brevis
                                             muscle;  11  abductor
                                             pollicis ; 12 part of the
                                             flexor  brevis  pollicis;
                                             13 supinator longus; 14
                                             extensor ossis metacar-
                                             pi, and extensor primi
                                             internodii pollicis, curv-
                                             ing around the edge of
                                             the fore-arm.
                                                Fig. 16. View of the
                                             deep seated  muscles on
                                             the  front  of the  fore-
                                             arm. 1 The internal la-
                                             teral ligament of the
                                             elbow-joint; 2 anterior
                                             ligament; 3 orbicular li-
                                             gament of the head of
                                             the radius ; 4 flexor pro-
                                             fundis digitorum  mus-
                                             cle ; 5 flexor longus pol-
                                             licis;  6 pronator qua-
                                             dratus; 7 adductor pol-
                                             licis ;  8 dorsal interos-
seous muscle  of the middle finger and  palmar interrosseous of the ring
finger; 9 dorsal interrosseus muscle  of the ring finger and palmar inter-
osseous of the little finger.

   The flexor carpi  ulnaris, arising from  the  internal  condyle

and from the ridge at the internal  side  of the  ulna;  and is in-
 
MUSCLES OF  THE UPPER EXTREMITIES.         95
serted into the os pisiforme, and sometimes  also into the base
of the metacarpal bone of the little finger.  It bends the hand,
and draws it towards the ulna.
   The flexor sublimis digitorum perforatus arises from the in-
ternal condyle of the humerus, the coronoid process of the ulna,
and the tubercle of the radius;  and is inserted by four tendons
into the second phalanges of the fingers. It bends the hand and
fingers.
   The flexor profundus  digitorum perforans  arises from the
anterior flat surface of the ulna, from the  coronoid process, and
the interosseous  ligament; and  is  inserted by  four tendons,
which pass through the  slit in those  of the flexor sublimis, into
the third phalanges of the fingers.  It bends the last phalanges
of the fingers, and also  the hand.
   The flexor longus pollicis arises from the middle two-thirds of
the radius, the interosseous ligament, and  the  internal condyle
of the humerus;  and is inserted into  the base of  the second
phalanx of the thumb.  It bends the last joint of the thumb.
   The pronator quadratus arises from the inner surface of the
ulna, near its lower extremity, and passing obliquely across the
fore-arm, is inserted into the corresponding surface of the radius.
It rotates the radius inwards.
   On the back of the fore-arm are:
   The supinator radii longus, arising from the ridge leading to
the external condyle;  and  is inserted  into a rough ridge  just
above the  styloid process of the radius.  It rotates the radius
outwards.
   The extensor carpi radicdis longus arising from the ridge of
the external condyle of the humerus; and is inserted into the
posterior part of the root of the metacarpal bone of the fore-
finger.  It extends the hand.
   The extensor carpi radialis brevis, arising from the external
condyle  of the humerus, and from the  external lateral liga-
ment; and  is inserted into the posterior part of the  base of the
metacarpal bone of the second finger. It extends the hand.
   The extensor carpi ulnaris, arising from the external condyle 
96         MUSCLES OF  THE  UPPER EXTREMITIES.
and from the  fascia, is inserted into the ulnar side of the base
of the metacarpal bone of the little  finger.  It extends the hand.

        ^'S' *''          Fig. 17.  View of the muscles on the back of
                      the fore-arm.  1 Lower part of biceps;  2 part of
                      the brachialis anticus ;  3 insertion of the triceps
                      into the olecranon; 4 supinator longus;  5  ex-
                      tensor carpi radialis longior; 6 extensor carpi
                      radialis brevior; 7 tendons showing the inser-
                      tion of the two last muscles; 8 extensor com-
                      munis digitorum;  9 extensor minimi digiti;  10
                      extensor carpi ulnaris;  11  anconeus;  12 part
                      of the  flexor carpi ulnaris; 13 extensor ossis
                      metacarpi and extensor primi internodii;  14 ex-
                      tensor seeundi internodii; 15 posterior annular
                      ligament, beneath which are the tendons of the
                      extensor communis.

                         The extensor digitorum  communis,
                      arising from the external condyle;  and
                      is inserted by  four tendons,  which  are
                      connected by slips, near the roots of the
                      fingers,  into all  the phalanges  of the
                      fingers.   It  extends  the  joints  of the
                      fingers.
                         The supinator  radii brevis,  arising
                      from the  external condyle and from  the
                      ridge on the posterior radial  edge of the
                      ulna; and is inserted into the tubercle
                      and the oblique rough ridge of the radius.
                      It rotates the radius outwards.
                         The extensor ossi metacarpi pollicis
                      manus, arising  from the posterior part
                      of the ulna,  the interosseous  ligament,
                      and from the back part of the  radius.
and  is  inserted  into  the base of  the  metacarpal bone of the
thumb, and into  the trapezium.  It extends the metacarpal bone
of the thumb.

   The extensor minor pollicis manus,  arising from the back of
the ulna below its middle and from the interosseous ligament;
and is inserted into the first phalanx of the  thumb.   It extends
the first phalanx.
   The extensor major pollicis manus, arising from the back of
the ulna above  its  middle,  the interosseous ligament  and the
 
MUSCLES OF THE HAND.
97
back of the radius; and is inserted into the base of the second
phalanx of the thumb.  It extends  the second phalanx.
  The indicator, arising  from the back of the ulna and from
the interosseous  ligament; and is  inserted into the back of the
fore-finger, as far as the base of the third phalanx.  It  extends
the fore-finger.

               Of the Muscles of the Hand.

  The palmaris brevis is just beneath the skin at the inner side
of the hand; it arises from the anterior ligament of the  wrist,
and from the palmar aponeurosis; and is inserted into  the skin
at the inner margin of the hand.  It  contracts the  skin of the
hand.
  The lumbricales  are  four small muscles,  resembling  earth-
worms, which arise from the tendons of the flexor profundus,
and are inserted into the radial side of the first phalanx of each
finger.  They bend the first phalanges.
   The abductor pollicis manus arises from the annular ligament
and from the ends of the scaphoid and trapezium;  and  is  in-
serted into the base of the first phalanx of the thumb.  It draws
the thumb from the fingers.
   The opponens pollicis  arises from the trapezium and the an-
 nular ligament; and  is  inserted into the radial edge  of the
 metacarpal bone of the thumb.   It draws the metacarpal bone
 inwards.
    The flexor brevis pollicis manus  has two bellies,  the  first
 head  arises from the trapezium, trapezoides, and annular liga-
 ment, and is inserted into the  outer  side of the first phalanx
 of the thumb ;  the second head arises from the magnum, unci-
 forme, and the base of the metacarpal bone of the middle finger,
 and  is  inserted into  the inner  side of the base  of the first
 phalanx of the  thumb.  The sesamoid bones  are included  in
 these tendons.   It  bends the first phalanx to the thumb.
    The adductor pollicis manus arises from the ulnar margin of
 the metacarpal bone of  the middle-finger, and  is inserted into 
98
MUSCLES OF  THE  HAND.
 the inner side of the base of the first phalanx of the thumb.  It
 draws the thumb towards the fingers.
              FiS- 18-               Fig. 18. View of the muscles of
                                  the palm of the hand.  2 Abductor
                                  pollicis manus; 3 opponens polli-
                                  cis ; 4, 5 flexor brevis  pollicis ma-
                                  nus; 6 adductor pollicis  manus;
                                  77 lumbricales;  10 abductor mi-
                                  nimi digiti manus; 11 flexor par-
                                  vus minimi digiti.

                                    The following three mus-
                                  cles are situated at the ulnar
                                  side of the hand, constituting
                                  the ball of that side.
                                    The abductor minimi di-
                                  giti manus arises  from the
                                  pisiform bone  and annular
                                  ligament, and is inserted in-
                                  to the  ulnar side of the first
                                  phalanx of  the little  finger.
                                  It draws the little finger from
                                  the rest.
   The flexor parvus minimi digiti manus arises from the unci-
 form  bone and annular ligament, and is inserted into  the ulnar
 side of the base of the first phalanx of the little finger. It bends
 the little finger.
   The adductor metacarpi minimi digiti  arises from the unci-
 form  process  and annular  ligament,  and is inserted into the
 metacarpal bone of the  little finger along its whole length.  It
 brings the metacarpal bone towards the wrist.
   There are seven interosseous muscles, which fill  up  the inter-
 stices of the metacarpal bones.  Three of them are  adductors
 and placed on the palmar side;  and four are abductors  placed
 on the dorsal side.
   The adductors arise from the  base of the metacarpal bone of
 one finger, beginning at the index, and are inserted into the
base of the first phalanx  of  the same finger.
   The adductors are penniform, and  arise by two heads from
the adjoining sides  of the  metacarpal bones, and are inserted
 
MUSCLES OF THE LOWER EXTREMITIES.        99
into the bases of the first phalanges;  two of them, the second
and third, go to the middle finger.

         Of the Muscles of the lower  extremities.
  Like the rest of the body the  lower extremities are invested
by  cellular membrane, reaching from the crest of the  ilium to
the foot.  It has received the general name of fascia lata, and
is exceedingly strong and dense.  That  portion in front  of the
thigh is termed iliac and pubic;  that which surrounds the knee
involucrum ; that of the leg crural; and that in the sole of the
foot plantar fascia.  In  front of  the ankle it forms the annular
ligament, and under the sinuosity  of the os calcis,  where  it
binds down the flexor tendon, the ligamentum lancinatum.  It
also furnishes sheaths  for the muscles.
   The  tensor vaginae femoris muscle arises  from the anterior
superior spinous process  of  the ilium; and is  inserted  into the
fascia of the thigh.  It makes the fascia tense, and rotates the
foot inwards.
   The sartorius arises from the anterior superior spinous process
of the ilium;  and is inserted into the inner side of the head of
the tibia.  It is the longest muscle in the body.  It bends the
leg, and draws it inwards.
   The rectus  femoris arises from the anterior inferior spinous
process of the ilium, and is inserted into the upper surface  of
the patella, and through the ligament  of the patella into the
head of the tibia. It extends the leg.
   The vastus  externus  arises from the  trochanter major and
linea aspera, and is inserted  into the outer and upper  part of
the patella. It extends the leg.
   The vastus internus arises from the whole length of the linea
aspera, and covering the entire  inside of the thigh is inserted
into the internal edge of the tendon of the rectus, and into the
external  and  upper  part  of the patella.  It likewise extends
the leg.
   The cruraeus arises from  the front of  the thigh and from the 
100       MUSCLES  OF THE  LOWER EXTREMITIES.
linea  aspera;  and  is inserted  into  the  upper surface  of the
patella.  It extends the leg.
  The four last  named  muscles form a common tendon  (the
ligamentum patellae), in which is included the patella, before it
is inserted into the head of the  tibia.   In consequence of this
arrangement, and of these muscles, having a common use,  they
are  often described  as the quadriceps femoris.
  The gracilis arises from the front and  ramus of  the  pubes,
and is inserted into the inside of the head of the tibia.  It flexes
the  leg.
  The pectineus arises from the upper face  and front  of the
pubes, and is inserted into the linea aspera below the trochanter
minor. It draws the thigh inwards and forwards.
  The adductor  longus arises from the upper front part of the
pubes, and is inserted into the  inner edge of the middle third
of the linea aspera.
  The adductor brevis arises from the body and ramus  of the
pubes, and is inserted into the inner edge of  the  linea aspera,
along its upper third.
  The adductor magnus arises from the body of the pubes, and
the  ramus of the pubis and ischium;  and is inserted  into the
whole length of the  linea aspera.  These three adductors  have
the  same use, that of drawing the thigh forwards and inwards.
  The gluteus magnus or maximus arises from the crista of the
ilium, the sides of the sacrum and coccyx, and  from the great
sacro-sciatic ligament; and  is inserted into the  upper  part of
the linea aspera, and the fascia of the thigh. It draws the thigh
backwards, and keeps the trunk erect.
  The gluteus medius arises  from the crest  of the ilium, its
dorsum between the crest and semicircular ridge, from the space
between the anterior spinous processes, and from the fascia femo-
ris;  and is inserted into the upper surface of the trochanter
major and the shaft of the bone in  front of it.  It draws the
thigh backwards and outwards.
  The gluteus minimus  arises from  the  dorsum  of the ilium
between the semicircular ridge  and capsular  ligament;  and is 
MUSCLES OF THE LOWER EXTREMITIES.       101
inserted into the upper part of the trochanter major.  It abducts
the thigh, and also rotates it inwards.—The three gluteii mus-
cles  form most  of the fleshy part of the hip.
   The pyriformis arises from  the anterior face of  the second,
third and fourth bones of the sacrum, and is inserted into the
superior middle  part of the  trochanter major.  It rotates the
limb outwards.
   The  Gemini  are two small muscles; the upper  arises from
the root of the spinous process of the ischium;  the lower from
the back part of the  tuberosity of the  ischium; they are both
inserted into the root of the trochanter major.  They also rotate
the limb outwards.
   The obturator internus arises from the margin of the thyroid
foramen, the posterior face of the thyroid ligament, and from the
iliac fascia; and is inserted into the pit on the back part  of the
femur at the root of the trochanter major.  It rotates the limb
outwards.
   The  quadratus femoris arises from the tuberosity of the
ischium, and  is inserted into  the ridge between the two tro-
chanters of the os femoris. It rotates the limb outwards.
   The obturator externus arises from the anterior margin of the
thyroid foramen, and from the anterior face of the thyroid liga-
ment; and  is inserted into  the  cavity at  the  root of the tro-
chanter major of the bs femoris.  It rotates the  thigh outwards.
   The biceps flexor cruris  forms  the outer hamstring; it arises
by two heads; a long one from  the tuberosity of the ischium in
common with the  semi-tendinosus, and a  short one  from the
lower part of the linea aspera.  It is  inserted into the head of
the fibula.  It flexes the leg on the thigh.
   The semi-tendinosus arises from the tuberosity of the ischium,
and is inserted into the side of the tibia just below its tubercle.
It flexes the leg  on the thigh.
   The semi-membranosus arises from the outer and upper part
of the tuberosity of the ischium;  and is inserted into  the inner
and back part of the tibia  just  below the joint.  It flexes the
leg on the thigh.
        15 
102
MUSCLES  OF  THE  LEG.
                    Muscles of the Leg.
  The tibialis anticus  arises from  the outer side of the head
and from the spine of the tibia, and from the interosseous liga-
ment; and is inserted, at the inner side of the sole of the foot,
into  the base of the internal cuneiform bone  and the base of
the metacarpal bone of  the great toe.  It bends the foot, and
presents the sole obliquely outwards.
  The extensor longus digitorum pedis arises from the head of
the tibia, from the head  and anterior margin of the fibula, and
from  the interosseous ligament; and is inserted after dividing
into four tendons, into the phalanges of  the toes.  It  extends
the toes, but flexes the foot.
  The peroneus tertius arises from  the lower third of the ante-
rior angle of the tibia;  and is inserted  into  the base  of the
metatarsal  bone  of the  little toe.   It is rather a part of the
extensor longus than a  distinct muscle.   It assists in bending
the foot.
  The  extensor proprius pollicis pedis  arises from  the lower
three-fourths of the fibula, and  the interosseous ligament; and
is inserted into the base of the first and second phalanx of the
great  toe.  It extends the great toe.
  The peroneus longus arises from  the outside of the head and
upper third of  the fibula; and is inserted into the base of the
metatarsal  bone of the great  toe.  It extends the foot, and in-
clines the sole outwards.
  The peroneus brevis arises from the lower two-thirds of the
outer surface of the fibula; and is inserted into the base of the
metatarsal  bone of the  little toe.  It extends the foot and pre-
sents  the sole obliquely downwards.
  The gastrocnemius has two heads, one  of  which arises from
each of the condyles of the humerus; it is inserted by the tendo
Achillis into the os calcis.
  The soleus arises  from the posterior part of the upper two-
thirds of the fibula, and from  the middle third of  the tibia;
and is inserted into the tendo  Achillis. 
MUSCLES OF  THE LEG.
103
Fig. 19.
Fig. 20.
  Fig. 19. View of the
anterior muscles  of the
leg. 1 Tendon of the qua-
driceps femoris; 2 ante-
rior angle of the  tibia;
3 tibialis anticus ;  4 ex-
tensor longus  digitorum
pedis;   5  extensor pro-
prius pollicis pedis; 6 pe-
roneus  tertius; 7 pero-
neus longus: 8 peroneus
brevis;  9, 9 borders of
the soleus; 10 gastrocne-
mius.

  Fig. 20. View  of the
deep seated muscles on
the  back of  the  leg.  s'
1  Lower  extremity of
the femur; 2 ligament of
Winslow; 3 tendon of the
semi-membranosus; 4, 5
internal and external la-
teral ligaments; 6 popli-
teus  muscle;  7  flexor
longus digitorum;  8 ti-
bialis profundus; 9 flexor
longus pollicis; 10 pero-
neus longus; ll peroneus
brevis;  12 lower  end of
the  tendo Achillis;  13
tendons  of  the  tibialis
posticus and flexor longus
digitorum. To show these
muscles, the  gastrocne-
mius, plantaris and soleus
muscles have been re-
 moved.

    The plantaris arises by a very long tendon from the femur,

 just above the external condyle;  and is inserted into  the  os

 calcis in front of the tendo Achillis.
    The last three muscles  have the same action, to wit, to extend

 the foot.  They constitute the calf of the  leg and are sometimes

 called the triceps surae.
    The popliteus  arises from the external face of the external

 condyle, and  is  inserted  into the  oblique ridge on the back of

 the tibia, just below its head.   It bends  the leg, and rotates it

 in wards.
    The flexor longus digitorum  pedis perforans  arises from the

 back of the tibia below its oblique ridge, and after dividing into
 
104
MUSCLES OF THE  FOOT.
four tendons is inserted into the bases of the last phalanges of
the four lesser toes.  These tendons perforate those of the flexor
brevis.   It flexes the toes, and  extends the foot.
   The flexor longus pollicis pedis arises from the  posterior face
of the tibia, commencing about  three inches below its head, and
continuing nearly to the ankle; and is inserted into the second
phalanx of the great toe.  It bends the great toe.
   The tibialis posticus arises by two heads from  the tibia and
fibula, also from the interosseous ligament;  and is inserted into
the tuberosity of the scaphoid bone.   It extends the foot.

                   Muscles of the Foot.

   The extensor brevis digitorum pedis  arises from  the greater
apophysis of the os calcis; and  is inserted by four tendons into
the backs of the four greater toes.   Its  tendons join those of
the extensor longus.  It extends the toes.
   The flexor brevis digitorum pedis arises from  the tuberosity
of the os calcis and the plantar  fascia, and is inserted into  the
second phalanges of the four smaller toes.  Its tendons are per-
forated  by  those  of the  flexor longus.  It bends  the second
joint of the toes.
   The flexor accessorius arises from the inside of the sinuosity,
and the front of the tuberosity  of the os  calcis;  and is inserted
into the outside  of  the tendon of  the os  calcis at its division.
It assists in flexing the toes.
   The  lumbricales pedis  are four small  muscles, which  arise
from the tendon of the flexor longus; and are inserted into the
inside of the first  phalanx of each  of the lesser toes.  They
assist in flexing the toes.
   The abductor pollicis pedis arises from  the internal tuberosity
of the os calcis, the internal side of the navicular and internal
cuneiform bones, and from the plantar fascia; and is inserted
into the inner side of the base of the first phalanx of the great
toe, including the internal sesamoid bone.  It draws the  great
toe from the others. 
MUSCLES OF THE  FOOT.
105
  The flexor brevis pollicis pedis has two bellies; it arises from
the calcaneo-cuboid ligament, and the internal cuneiform bone;
and is inserted by two tendons into the internal  and external
sesamoid bones, and into the first phalanx of the great toe.
  The adductor pollicis pedis arises from the  calcaneo-cuboid
ligament, and the basis of the second, third, and fourth meta-
tarsal bones of the lesser toes;  and is inserted into the external
sesamoid bone, and the tendon of the flexor brevis.   It draws
the great toe towards the others.
  The abductor minimi digiti pedis arises from the outer tube-
rosity of the os calcis, and the metatarsal bone of the little toe;
and is inserted into the  base  of  the first  phalanx of  the little
toe.   It draws the little toe from the others.
   The flexor brevis minimi digiti pedis arises from the calcaneo-
cuboid ligament, and the fifth metatarsal bone; and is inserted
into the head of the metatarsal bone, and  the base  of the first
phalanx of the little toe.  It bends the little toe.
   The transversalis pedis is a small muscle, which lies across
the anterior extremities of the metatarsal bones;  it arises from
the capsular ligaments of the first joints of  the fourth and fifth
toes; and is inserted into the external  sesamoid  bone.   It  ap-
proximates the heads of the metatarsal bones.
   The interosseus muscles are seven in number;  four of them
are upon the dorsal, and three upon the plantar surface of  the
foot.  There  are two to the first smaller toe, two to the  second,
two to the third, and one to  the  fourth or little toe. The dorsal
interossei arise by double heads from the adjacent sides of  the
metatarsal  bones; and  are inserted into the base of the first
phalanx.   The first is an adductor being inserted into the inner
side of the second toe; the  other  three  are inserted into  the
outer side of  the second, third,  and fourth toes, and are conse-
quently abductors.
   The plantar interossei arise from the base of the metatarsal
bones of the  three outer toes; and are  inserted into  the inner
side of the base of the  first phalanx  of the same toes.  They
draw the toes inwards, or adduct them. 
106
ORGANS OF  DIGESTION.
                   Organs of Digestion.
  Mouth.—The  mouth is bounded anteriorly and laterally by
the lips and cheeks;  its roof is formed by the hard and soft
palate;  and its floor by the mylo-hyoid muscles; posteriorly it
extends to  the  pharynx, and  communicates  with  the fauces.
The space between the  lips and the teeth  is  sometimes called
the vestibule of  the mouth.   The  mouth is lined by a mucous
membrane, beneath which are a number of muciparous  glands.
This membrane  is thrown into folds (frena) at several points,
the one beneath the tongue is called frenum linguae.
  The lips (labia) are composed of muscular fibres and  fat, and
covered externally by skin.   The  upper is  longer and thicker
than the lower, and has a vertical depression on the middle front
surface, called philtrum.
   The gums are formed of the lining membrane  of the mouth
much thickened.
   Tongue.—The tongue is the special organ of taste, and is also
of material importance in speech and mastication.   It is a mus-
cular body, symmetrical, oblong,  and flattened;  its  size and
shape are variable.
   The posterior extremity is  called its base, or root, the  anterior
its point, or tip, and the middle its body.  The root is attached
to the hyoid bone.
   The  mucous  covering is very thick  on  the upper surface of
the tongue, and thin  on the lower.  On the upper surface are a
number of large papillae; those on the posterior  border, eight
or nine in number, arranged like  the letter V, are the largest,
and called the papillae maximas; others are termed capitatae,
mediae, villosae, and filiform;  the latter are  the smallest, and
are found principally at the middle of the  tongue.  The papillae
mediae are the most abundant. The structure of all is the same.
Their orifices are easily seen  by the naked  eye.
   The  following muscles compose the tongue : the stylo-glossus,
 the hyo-glossus, the genio-hyo-glossus, lingualis, superficialis lin-
guae, transversalis linguae, and verticales linguae.  The first three
 form the principal part of its bulk. 
ORGANS OF DIGESTION.
107
  Palate.—The palate is divided into two parts, the hard, and
the soft palate.  The first separates the mouth  from  the nose,
and is composed of the palate processes of the upper  maxillary
and palate bones, covered by the common  lining membrane  of
the mouth.   It has transverse ridges extending  to the alveolar
processes, and also one in the median line.
  The second, or soft palate, called also pendulous palate, con-
sists of a loose membrane stretched transversely across the back
of the mouth, at the posterior margin of the hard palate.  Its
middle portion, called the uvula, is free and projects downwards
for a half or  three-fourths of an inch; on each side of the uvula
there are  two crescenting folds of mucous membrane, called the
lateral  half-arches, the space between which is the fauces.
Between the anterior and  posterior arches on each side  are the
tonsil glands, which consist of a collection of mucous follicles.
Each tonsil is about the  size and shape of an almond.
   There are  several small muscles entering into the composition
of the soft palate.
   The  constrictor isthmi faucium, a small muscle on each side,
arising from  the middle  of  the  anterior half-arch, and inserted
into the side of the root of the tongue. It diminishes the open-
ing into the  pharynx.
   The palato-pharyngeus, is situated  in the posterior half-arch,
arising from  its middle to be inserted into the side of the pharynx.
It draws  the soft palate  downward and the pharynx upwards.
   The circumflexus, or  tensor palati, arises from the  spinous
process of the sphenoid bone and the Eustachian tube, and is
inserted  into the middle of  the soft palate, and into the cres-
centic edge of the palate bone; its tendon winds round the hook
 of the internal pterygoid process. It extends or spreads  out the
 palate.
   The levator palati arises from the petrous portion of the tem-
 poral bone and the Eustachian tube,  and  is inserted into the
 soft palate.  It draws the palate upwards.
    The azygos uvula is in the centre of the soft palate and uvula.
 It shortens the uvula. 
108 SALIVARY GLANDS, ETC.—THE PHARYNX AND (ESOPHAGUS.

              Salivary Glands of the Mouth.
  There are three salivary glands situated  on each side of the
neck, bordering on the mouth, for the secretion of saliva.  They
are the parotid,  submaxillary and sublingual.   Their color is
of a light pink.
  The parotid is  the largest, and is very irregular in shape.  It
occupies the space behind the  ramus of  the lower jaw, and the
mastoid process.  Externally it is covered by the skin; it  is of
a lobulated structure. Its duct, called the duct of  Steno, is about
the size of a crow's quill, and passes along the outer face of the
masseter muscle, in a line drawn from the lobe of the ear to the
end of the nose, and perforates the cheek  by a very small orifice,
opposite the second molar tooth of the upper jaw. The external
carotid artery and the temporal vein pass up through its deeper
portion; and the portia dura nerve also traverses  it from behind
forward.
  The submaxillary  gland is not more than half the size of the
former, and is somewhat ovoidal in form, and lobulated in struc-
ture.   It is  situated in the depression on the inner face of the
lower jaw, and covered externally by the  skin, superficial fascia
and platisma myoid muscle.
  Its duct, called the duct of Wharton, empties into the mouth,
under the tongue, at the anterior margin of  the fraenum linguae,
by  a very small orifice.
  The sublingual gland, which is smaller than the last, oblong
in shape, lobulated in  structure, is situated under  the tongue,
covered only by the  lining membrane of the mouth.  It dis-
charges by several ducts near the duct of the  submaxillary gland,
              The Pharynx and Oesophagus.
  The pharynx is a  large membranous cavity situated between
the vertebral  column and the posterior  part of the nose and
mouth,  and extending  from the base of the cranium to the
fourth or fifth cervical vertebrae.  It is about five inches long,
and funnel shaped, being larger above than  below; its muscular
attachments keep it always open. 
THE PHARYNX AND CESOPHAGUS.          109
  It has three coats, a muscular, a cellular  and a mucous one.
The muscular coat is internal, and consists of three muscles on
each side, placed one above the other, and called constrictors.
  The inferior constrictor arises from the side of the cricoid and
thyroid cartilages, and is inserted into its fellow of the opposite
side on the back of the  pharynx;  the upper fibres are oblique,
the lower horizontal.
  The middle constrictor arises from the cornu of the os hyoides
and  the lateral thyreo-hyoid ligament, and  is inserted into its
fellow at the posterior median line.
  The superior constrictor  arises  from the  pterygoid process of
the sphenoid bone, from the upper and lower jaw, from the buc-
cinator muscles and the root of the tongue; and is inserted into
its fellow behind, and also into the cuneiform process of  the os
occipitus. Its fibres are more horizontal than those of its fellows.
   The successive contractions of these  muscles convey the food
from the mouth  into the oesophagus.
   The stylo-pharyngeus muscles, described  among  those  of the
neck, by contracting shortens the pharynx.
   The cellular coat  connects the muscular with  the mucous,
and merely  serves for  the transmission of  nerves and  blood-
vessels.
   The internal or mucous coat, which is a continuation of that
of the mouth, nose and Eustachian tube, like it is covered by a
delicate epidermis, and studded with mucous follicles and glands.
   The (Esophagus is the canal situated between the spine and
larynx, which  conveys the food from  the  pharynx to the sto-
mach.  Its length is about nine or  ten inches; and its diameter
when inflated,  near an  inch, though this is  not uniform, as it
gradually increases  as it descends.  In descending, it  passes
through the posterior mediastinum, and at its lower part, where
it passes through the diaphragm, inclines slightly to the left
side.   Its upper part is the narrowest portion of the alimentary
canal; and consequently foreign bodies, if  not arrested  in the
neck, readily pass through the remainder of the alimentary canal.
   It is composed, like the pharynx, of three coats, a muscular,
        16 
110
THE ABDOMINAL  VISCERA.
Fig. 21.
a cellular, and a mucous. The muscular is external, and thicker

than any  other  portion  of  the canal; it  consists of two layers,

the fibres of  the external  layer being longitudinal; those  of

the internal, circular.

  The cellular coat unites the others.  The mucous coat is con-

tinuous with that of  the pharynx, has a  thick epithelium, con-

tains numerous  mucous glands and follicles, and when in a state

of rest, presents a number of longitudinal folds.

                                 Deglutition, or swallowing, is
                               effected by the  contraction  of
                               the longitudinal muscular fibres,
                               which shorten the passage, and
                               by the successive contractions of
                               the  circular fibres  from above
                               downwards.  In  vomiting, the
                               contractions  commence  below
                               and go upwards.
                                 Fig. 21.  Lateral  view of the pha-
                               rynx. 1 Trachea; 2  cricoid cartilage ;
                               3 crico-thyroid membrane;  4 thyroid
                               cartilage; 5 thyro-hyoid membrane ;
                               6 os hyoides;  7 stylo-byoid ligament;
                               8 oesophagus; 9 inferior constrictor;
                               10  middle  constrictor;  11  superior
                               constrictor; 12 stylo-pharyngeus mus-
                               cle ; 13 upper concave margin of the
                               superior constrictor; 14 pterygo-max-
                               illary ligament; 15  buccinator  mus-
                               cle;  16  orbicularis oris;  17  mylo-
                               hyoideus.
                 Of the Abdominal Viscera.

   The cavity of the abdomen extends from the diaphragm above
to the pelvis below; and is divided for descriptive purposes into
nine different regions, by the drawing of two parallel vertical
lines through the anterior inferior spinous processes of the ilia,
and intersecting these by two other horizontal  lines, the one
drawn over the  crests  of the ilia, and the other over the most
prominent part of the cartilages of the ribs.  This makes three
regions above, three in the middle, and three below.  The region
in the centre of the upper row is called the epigastric, and con-
tains  the left lobe of the  liver and a portion of the stomach; 
THE ABDOMINAL VISCERA.
Ill
those on either side are termed the right and left hypochondriac,
the first contains the right lobe of the liver,  and the second con-
tains  the  spleen, and a portion of the stomach and liver.  The
central  region of  the middle row is called the umbilical, and
contains the small intestines; those on the sides are the right
and left lumbar, the first contains the right kidney and ascend-
ing colon, the second the left kidney and descending colon. The
region in the centre of  the lower row, is the hypogastric, and
contains a portion of the small intestines and the bladder; those
on the sides are the right and left iliac regions, or the iliac fos-
sae, of which the first or right contains the caecum or caput coli,
and the second the sigmoid flexure of the colon.
   Peritoneum.—The whole of the interior surface  of the ab-
domen  is lined, and  the contained viscera covered  by a thin,
transparent,  serous  membrane,  called the  peritoneum, which,
like all the serous membranes, is a closed sack.  Its office is to
secrete  a  small quantity of fluid to  lubricate the viscera, and
thus enable them to move readily upon each other, and the walls
of the cavity; it also forms ligaments and connections by which
the viscera are held in their places.  Although the viscera appear
to  be contained within  the cavity of the peritoneum, they are
not so in  reality, but are all on its outside. A familiar and good
illustration of the  manner  in which  the  various  viscera are
covered by the  peritoneum, is afforded in the application of a
double  night cap to the head.  One part of the cap is close to
the head  and compares with the peritoneal  coat  of  one of the
viscera; the other is loose and compares with the peritoneum,
where it comes in  contact with the walls of the abdomen.
   Those  portions  of the peritoneum, which pass between one
viscus and another,  generally consists of two lamina, and are
called omenta.
   There  are four of these  processes or omenta, viz. the lesser
omentum, or gastro-hepatic, passing  between  the stomach and
liver, and attached to the lesser curvature of the stomach; the
great omentum, or gastro-colic, which extends between the sto-
mach and colon, being attached to the greater curvature of the 
112
THE ABDOMINAL VISCERA.
former, and including the  latter between its lamina—it is  the
largest  of the omenta, and is spread over the intestines like an
apron — it is known as the caul, and in corpulent persons con-
tains a great deal of fat; the colic-omentum or mesocolon, which
holds the large intestine to the posterior wall of the abdomen ;
and the gastro-splenic, which extends  from the stomach to  the
spleen.
   The mesentery serves to connect the  small  intestines to  the
walls of the abdomen; it consists of two  laminae of peritoneum,
and its inferior edge equals in length the entire intestine. The
superior mesenteric arteries and  veins, lymphatic glands and
vessels, branches  of  the  sympathetic nerve, fat, &c, are con-
tained between the lamina of the mesentery.
   Stomach.—The stomach is situated in the epigastric and left
hypochondriac regions. It is a conoidal sac, having an  upward
curve;  it has an  anterior  and  posterior face, being somewhat
flattened in front and behind; two curvatures, the upper of which
is the lesser, and the  lower the greater; two orifices, of which
one, called  the cardiac, is at the superior part of the left  ex-
tremity, and is a continuation of the oesophagus into the stomach,
and the other, the pyloric, is at the right extremity, and is con-
tinuous with the small intestine; and two extremities, of which
the  left is  much  the largest,  and is  a rounded cul-de-sac or
tuberosity,  and the left is a gradual  diminution of the organ
from its middle  to the duodenum.   Near the right  end of  the
stomach is a dilatation, which  is sometimes  called  the  antrum
pylori.
   The  stomach is retained in its place by the hepatico-gastrie
and the gastro-splenic omentum, and by its  continuity with  the
oesophagus and  duodenum.  Its dimensions are variable, depend-
ing  much upon the mode of life;  generally, however, its capa-
ciousness is  between that of a pint and a quart.  It is composed
of four coats, a peritoneal, muscular, cellular, and mucous.
   The peritoneal  coat affords  a complete investment  for the
stomach, and is closely attached to it,  except at the curvatures
where its looseness allows of the distention of the other coats. 
THE ABDOMINAL VISCERA.
113
  The muscular coat is  thicker than that of the intestines, but
not so thik as  that  of the oesophagus; its  fibres are arranged
both in a longitudinal and circular direction.  The longitudinal
fibres are chiefly found along  the lesser curvature, and the cir-
cular fibres, which cover the entire organ, are most numerous
near the pyloric extremity.
                            Fig. 22.
  Fig. 22.  A vertical and longitudinal section of the stomach  and duo-
denum.  1 Oesophagus;  2 cardiac orifice of the stomach; 3 greater end of
the stomach; 4 Lesser or pyloric end; 5 lesser curvature ; 6 greater curva-
ture; 7 antrum pylori; 8 folds or rugas of the mucous membrane; 9pyloris;
10 oblique portion of the duodenum;  11 descending portion; 12 pancreatic
duet, and ductus communis  choledochus; 13 opening of these  ducts;  14
transverse portion of the duodenum; 15 commencement of the jejunum;
the valvulae conniventes are shown in the duodenum and jejunum.

   The cellular  coat  connects the muscular with  the  mucous,
and  serves  for  the transmission  of blood-vessels and nerves to
the mucous coat.
   The mucous coat,  also called  villous, is the most  internal, and
is continuous with that of the oesophagus; it is of  a light pink
color, and  presents  a velvety  appearance,  hence the name vil-
lous has been applied to it.  When the stomach is not distended,
this coat is thrown  into longitudinal folds  or rugae, which  are 
114
THE INTESTINES.
most numerous along the greater curvature, and near the pyloric
orifice.  A circular fold of mucous membrane at the pyloric ori-
fice, which lessens its size, is called the pyloric valve.  The office
of this coat is to secrete the gastric juice.

                      The Intestines.
   The whole length  of the  intestinal canal  is  from thirty to
thirty-five feet.   It extends from the pyloris to the anus, and is
divided into large and small intestine.

                      Small Intestine.
   The small intestine commences at the pyloris, and terminates
by a lateral  opening  into  the  large  intestine  in  the right iliac
region.  It comprises four-fifths of the length of the whole canal,
and is from  twenty to twenty-four feet long. It is cylindrical in
shape, and about an inch in diameter, although there is a gradual
decrease in diameter from above downwards.
   Like the stomach, the small intestine has four distinct coats.
   The peritoneal coat is the most external; and after completely
investing  the intestines, it is continued in two  laminae to be
attached to  the lumbar vertebrae, thereby  constituting  the
mesentery.
   The muscular  coat is next to the peritoneal, and is thin and
pale; the superficial  fibres are longitudinal, though indistinct;
the internal are circular.
   The cellular coat, like that of the stomach,  connects the peri-
toneal  with  the  mucous, and  serve  to transport blood-vessels,
nerves and lacteals.  When dried it  appears like cotton, as also
does the  corresponding coat in the other portions of the ali-
mentary canal.
   The mucous coat is internal, and much longer than the others,
which  allows it be thrown into numerous folds or duplicatures;
these folds  generally pass quite around the intestine, and  over-
lap each other, like  the shingles of a house.   They are  called
valvulae conniventes, and their office is  to retard the  progress
downwards  of alimentary matter,  and to increase the absorbing 
SMALL INTESTINE.
115
and exhaling surface.  The surface of the mucous membrane is
covered with numerous papillary projections, called villi; and
each villius is composed of an artery, vein and lymphatic.  The
lymphatics do not open directly upon the surface of the mucous
membrane, but the chyle is conveyed out of the intestine by the
intervention of cells.
  The cellular  coat is studded with mucous glands, whose ducts
open upon the surface  of the mucous coat.   They are mostly
microscopical.  Some of them, which are visible  to the naked
eye,  and  called the glands  of Brunner, are found  scattered
throughout the intestine, although existing in most abundance
in the  duodenum.   Others still larger, called Peyer's glands,
are found chiefly in the lower part of the small intestine. They
consist of a cluster of smaller glands, and are consequently often
called aggregated.   Those of Brunner are also sometimes called
solitary.
  The small  intestine is divided by anatomists, though without
much reason, as it  is a continuous tube,  into the duodenum,
jejunum,  and ilium.
  The duodenum, so named from its being about twelve fingers'
breath,  or twelve inches long, is that portion next  the stomach.
Its direction  is curved, forming a segment  of a circle, the con-
cavity of which looks  towards the left side.  The mucous coat
of the duodenum is tinged with bile, and contains a great num-
ber of valvulae conniventes, and the glands of Brunner.
  The  ductus communis choledochus,  from the liver and  pan-
creas, empties  into the duodenum, about four inches from the
pylorus.
  The  jejunum and ilium  form the  remaining three-fifths of
the small intestine, the former being  two,  and the latter one-
fifth  of the  length; the only differences in their  appearance
are that the jejunum contains a large number of valvulae conni-
ventes, and is rather larger in its diameter than the ilium.
  The small  intestine,  as stated, is attached to the  posterior part
of the abdomen by a process  of peritoneum, called the mesentery.
This attachment, called the root of the mesentery, is about six 
116
LARGE INTESTINE.
 inches in length, and extends from  the  left side of the second
 lumbar vertebrae to the right iliac fossa.
                      Large Intestine.
   The large intestine receives the effete matters from the small,
 and comprises about one-fifth of the length of the whole  intes-
 tinal canal.  It commences at the inferior end of the small in-
 testine, and  describing a circle, which surrounds two-thirds  of
 the abdomen,  terminates at  the  anus.   Its diameter is  much
 greater than that  of the small intestine, and it also  presents a
 sacculated appearance.
   It is composed, like the small intestine, of four coats.
   The peritoneal  coat is continuous with the mesocolon and
 affords a  complete  investment, except at  the lower part of the
 rectum, and the descending portions of the colon, where the latter
 comes in  contact with the abdomen.
   The muscular coat consists of longitudinal and circular fibres;
 the former are collected into three fasciculi, or bands, which ex-
 tend to the rectum.
   The cellular coat unites  the muscular and mucous  coats, and
 contains the  blood-vessels and nerves.
   The mucous coat is smooth, having neither villi nor valvulae
 conniventes.   It contains numerous follicles, called the follicles
 of Lieberkiihn. It also contains some solitary  glands.
   The large  intestine is divided into three parts, the ccecum,
 the colon, and the  rectum.
   The caecum is the commencement of the large  intestine, and
 is about two  inches in length.  It  is confined by the mesocolon
 in the right iliac fossa.  It is often called  the caput coli, or head
 of the colon.  Attached to its rounded extremity is a  worm-like
 process  of intestine, from three to four inches  long,  called the
 appendix vcrmiformis. This appendix is usually filled with flatus.
   At the  side of the coecum is an elliptical opening,  called the
ilio-colic  valve, by which the small  intestine empties into the
large. When the coecum is distended, this valve becomes closed,
and prevents  the return of foecal matter into the small intestine. 
THE LIVER.
117
  The colon comprises the principal part of the large intestine;
it commences  at  the  ilio-colic valve, and ascends  on the right
side of the abdomen  to  the margin of the false  ribs, it then
passes transversly across, beneath the stomach, to the left side,
whence it descends to the left iliac fossa, and terminates in the
sigmoid flexure.
  The rectum commences at the  left sacro-iliac symphisis, at
the termination of the long, loose convolution of the colon, called
the sigmoid flexure, and  passes  down in front of the sacrum to
the anus.
  Its muscular coat  is much thicker and redder than that of
any other portion of the intestines; the external fibres are longi-
tudinal, and the internal circular.  At  the lower  extremity of
the rectum, the circular fibres are multiplied so much as to form
a complete internal sphincter muscle.
   The mucous coat is thick, red, and spongy, and five or six
inches above the anus on each side, is thrown into a semi-circular
fold,  somewhat resembling the valvulae conniventes, which in
some degree prevent the involuntary discharge of faeces.   Just
above the anus  are a number  of small pouches, having  their
orifices pointing downwards. The rectum is larger in the middle
than  at the ends.

                         The Liver.
   The liver occupies the whole  of the right hypochondriac, and
a portion of the  epigastric and  left hypochondriac regions. It
is the largest  glandular organ in the body, and secretes the bile.
In shape it is oblong and oval;  its weight is  from four to five
pounds, and it measures about ten inches in length, six or seven
in  width, and four or five  in  thickness.  Its long diameter is
across  the body.  Its color is a reddish brown, with occasional
blue or black spots on its under surface  and about its edges.
   The upper  surface is  regularly convex, fitting closely to the
concave under surface of the diaphragm ; and the  lower con-
cave ; the right end is also much thicker than the left. A broad
ligament, called  suspensory, formed from its peritoneal covering, 
118
THE LIVER.
holds the liver in contact with the diaphragm.  The anterior part
of this  ligament is the ligamentum teres, and the posterior the
coronary ligament.  In the anterior edge of  the liver is a notch,
and in the posterior edge a deep depression for the spinal column.
On its under surface, extending  from the notch in front to the
depression behind,  is  the umbilical flssure, or sulcus, so called
from having accommodated the umbilical vein in the fcetal state;
at right angles with this is the transverse flssure, which contains
the hepatic  artery and duct, surrounded by cellular membrane,
and called the capsule of Glisson.
                           Fig.  23.
  Fig. 23.  Representation of the upper surface of the liver. 1 Right lobe;
2 left lobe; 3 anterior, free border, and fundus of gall bladder; 4 posterior
border; 5 broad ligament; 6 round ligament; 7, 7 lateral ligament; 8 origin
of the coronary ligament;  9 inferior vena cava;  10 point of the lobulus
Spigelii.
   The liver is divided into two lobes, a right and left lobe, the
division being  marked above  by the suspensory ligament, and
below  by  the umbilical  fissure.  The  right lobe is much the
larger, and has several elevations on its under surface; the prin-
cipal  of which are the lobulus Spigelii, lobulus quadratus, and
the gall bladder.
   Four sets of vessels ramify through the substance of the liver,
making it extremely vascular.
   The portal vein collects the blood from the stomach, intestines, 
THE LIVER.
119
pancreas, and  spleen, and after reaching the  transverse  fissure,
divides into two branches, called the right and left sinuses, one
of which is distributed to each lobe of the liver.
   The hepatic artery, also, conveys blood to  the liver; it is a
branch of the cceliac, and at the transverse fissure divided into
three or more branches previous  to penetrating the substance
of the liver.
   The hepatic veins arise by capillaries in the acini of the liver,
and after collecting  into three  large  trunks, empty into the
ascending vena cava at the posterior margin of the  liver.  These
veins are destitute of valves, and have very thin parietes.
   The hepatic duct also commences by capillaries in the liver;
when it reaches the transverse  fissure  it is about the size of a
writing  quill.   It joins  the duct of the gall bladder at an acute
angle;  and the  union of the two forms the  ductus communis
choledochus, which  empties  into  the  duodenum three  or four
inches from the stomach.
                             Fig. 24.
  Fig. 21.  Representation of the under surface of the liver.  1 Right lobe;
2 left lobe; 3 lobulus quadratus; 4 lobulus Spigelii;  5 lobulus caudatus;
6 longitudinal fissure; 7 pons hepaticus;  8 fissure for the ductus venosus;
9 inferior vena cava; 10 gall bladder; 11 transverse fissure; 12 vena cava;
13 depression for the curve of the colon; 14 double depression made by the
right kidney and its supra-renal capsule;  15 rough surface on the posterior
border of the liver;  16 notch separating the lobes anteriorly; 17 depression
on the posterior border for the spinal column. 
120
THE GALL BLADDER.
  The minute structure of the liver is made up of a numerous
collection of irregular  lobules, or acini.   This arrangement  is
best seen on tearing the organ.  Each lobule is said to be about
the size  of a millet seed, and to represent of itself a  perfect
gland, being formed by the termination of the blood-vessels, and
by the origin of a branch of the  hepatic  duct, called the porus
biliaris.  These lobules are held together  by means of a cellular
tissue, which is called the parenchyma.

                     The Gall Bladder.
  The gall bladder is  the reservoir for the bile; it is attached
to the under surface of  the  right lobe  of the  liver to the right
of the umbilical  fissure, and has its long diameter inclining
slightly to the right side.  It is a pyriform sac, and about three
inches in length.  Its rounded extremity, called the fundus, pro-
jects somewhat beyond  the anterior border of the liver.  Its pos-
terior extremity, or neck, is narrow and  twisted  to retard the
passage of a fluid through it.
   It has three coats, a peritoneal, a cellular, and a mucous  one.
The peritoneal coat is but a partial one, covering  its inferior
surface only.
   The middle is of strong cellular membrane;  and the internal
mucous coat is thrown into irregular delicate folds, and tinged  of
a deep green or yellow  color by the bile.
   The duct of  the gall bladder, called the cystic, is shorter and
smaller than the  hepatic, which  it joins at an acute angle; the
union of the two forming the ductus communis choledochus, which
is from two to three inches long,  and about the  size of a goose
quill.  As mentioned it empties into the duodenum, in an oblique
manner, after  passing  through the right extremity of the  pan-
creas.  Its orifice is very small, and marked  by  a tubercle  on the
inner side of the duodenum.
   The bile is of a deep yellow, sometimes green color, and bitter
taste.  When  recently secreted, it is  thin  and fluid; but after
remaining  for some time  in the gall bladder it becomes as thick
as molasses, and increases, also, in the intensity of its color and 
THE SPLEEN.—THE  PANCREAS.
121
in bitterness.  This is owing to the absorption of its watery par-
ticles by its mucous coat.
   The chief use of the bile is to aid digestion by dissolving the
fatty matters, and rendering them capable of being taken up by
the lacteals.
                        The Spleen.
   The  spleen is situated in the posterior part of the left hypo-
chondriac region.  Immediately above it is  the diaphragm, below
it the colon, and to the right the large end of the stomach and
the  pancreas.  It is of a semi-oval figure,  and of a deep blue  or
brown color. Its external surface is convex; its internal slightly
concave, and has an imperfect  fissure in  its centre, where the
blood-vessels enter.  Sometimes, also, its  margins  are  notched.
The usual size of the  spleen is four or five inches in length, by
two or three in breadth. In some individuals several spleens are
found, the additional ones  in such cases being quite small.  It is
kept in its place by ligaments, formed of the peritoneum, which
pass between it and the diaphragm, stomach and colon.
   In structure it presents  a dark, brown pulp, which is held to-
gether by cells formed of the internal coat.  It has two coats,
an external peritoneal one, and an internal thin, gray  and elas-
tic one.
   The splenic artery, which is  the largest branch of the coeliac,
furnishes it with blood; its vein empties into the vena portarum.
   The spleen has no secretion, and its use is not well ascertained.

                        The Pancreas.
   The pancreas secretes saliva,  and is the largest salivary gland
in the body. It is placed horizontally across the spine, in front
 of the  last dorsal and first lumbar vertebrae,  and behind the
 stomach.  Consequently it is in the lower back part of the epi-
 gastric  region.   Its length is from  six to seven inches, and its
 width  about two.  It is flattened before and behind.  The ante-
 rior face looks obliquely upwards, and the posterior face obliquely
 downwards.  The right extremity is  enlarged into a head or 
122
PHYSIOLOGY  OP DIGESTION.
tuber,  sometimes called  the lesser pancreas, and is  in contact
with the curvature of the duodenum; the left extremity is con-
nected with the spleen.
   The color of the pancreas, like that of the other salivary glands,
is of a light  gray or pink  hue; and  its structure is lobulated,
the lobules being held together by intermediate cellular tissue.
   It has no peritoneal coat, but is included between two lamina
of the  mesocolon.   Its duct, called sometimes the duct  of Wur-
sungius, empties  into the duodenum near the orifice of  the duc-
tus communis choledochus, and sometimes into the latter. The
arteries of the pancreas are branches of the splenic, and its veins
also empty into the splenic.

                  Physiology of Digestion.
   Before the food  is fitted for purposes  of nutrition, it has to
undergo several changes in the digestive  organs.
   The first stage in the process of digestion  is called prehension,
or the taking of  food into the mouth.   This is chiefly accom-
plished by the hand, some  assistance being rendered by the front
teeth,  lips, cheeks and tongue.
   The second stage is mastication (chewing), by which the food
is rendered sufficiently fine to be taken into the stomach, and
acted  on by its juices.  The food is kept between the teeth by
the lips and cheeks externally, and by the tongue internally, and
the closure of the  soft palate  upon the tongue prevents it from
passing into the oesophagus.  The motion of  the lower teeth upon
the upper reduce it to the requisite fineness.
   While the food is being masticated, it is mixed with the saliva
and juices  of the  mouth, which  soften it  and aid in its reduc-
tion.  This is called insalivation.
   The third  stage  is  deglutition  or  swallowing, which, when
the food has been sufficiently comminuted and moistened in the
mouth, is effected by a simultaneous action  of  the  muscles of
the tongue, cheeks, floor of the mouth, soft palate and pharynx.
The elevation of the soft  palate prevents the food from passing
into the posterior opening of the nostrils (nares); and it is pre- 
PHYSIOLOGY  OP DIGESTION.
123
vented from passing from the pharynx into the trachea by the
closure of the glottis (opening of the trachea) by the epiglottis.
After entering the oesophagus, the alternate relaxing and con-
traction of the circular bands of muscular fibres gradually force
it downwards  into the stomach.  In the  effort of  vomiting, the
action of the oesophagus is reversed—the contraction of its mus-
cular fibres commencing at its lower extremity. The spasmodic
cough which sometimes  takes place while eating or drinking, is
owing to some particles of the aliment entering the  larynx or tra-
chea, which cannot  occur unless  the glottis  is  opened by the
inhalation  of air.  An attempt to speak when the mouth contains
food is generally the cause.
   The fourth  stage in the process of digestion is chymification,
or the conversion of  the food into a homogeneous pulpy mass,
generally of the consistence of cream, called chyme. This change
is effected  in the stomach; as soon as the food enters this organ,
it is thoroughly mixed with  the  gastric juice, by the alternate
contraction and  relaxation of the fibres of the muscular coat,
which produce a great variety of motion.  The contraction of the
muscular coat as well as the  secretion of the gastric juice from
the follicles of the mucous coat,  is occasioned by the stimulus
of the food.   No gastric juice is contained in the organ when in
a state of rest, but its secretion is  always excited by the presence
of a foreign body.   While the process is  going on, the food is
prevented  from escaping from the stomach  by the closure of its
orifices.
   The gastric juice is colorless, slightly viscid, and has an acid
reaction. By  analysis it has been  found to contain free muriatic
and acetic  acids, and phosphates and muriates of  potassa, soda,
magnesia and lime.   Although  the presence of dilute acids in
the gastric fluid is essential to its action, the active agent  is an
organic compound, called pepsin.
   This agent undergoes no change itself, but induces changes
in other substances, disposing them to dissolve in the acids of
the stomach,  and form with them definite chemical compounds.
   The degree of solubility of different substances in the juices 
124
THE KIDNEYS.
of the stomach varies.   As a general rule, animal  food  is more
soluble than vegetable—though this is not  invariably the case.
Fatty substances undergo but little change in the stomach; they
require admixture with  the bile, whereby a  saponaceous com-
pound is formed, to fit  them for absorption by the chyliferous
vessels.
   The time required by the rstomach  to convert the food into
chyme, varies from three to  five hours according to the nature
of the food.
   The fifth stage is chylification. After the food  is reduced to
chyme in the stomach, it passes through the pyloric orifice into
the duodenum, where it is mixed with the  bile and pancreatic
juice,  and by  their action converted into  chyle and  residual
matters. The chyle is a whitish or whey-like fluid, with a creamy
pellicle.  As the contents of the intestine are gradually carried
along the canal by an action, called peristaltic—induced by the
alternate contraction and relaxation of the muscular coat—the
chyle is absorbed by the lacteals through the villi of the mucous
coat, and the residual foecal matters pass into the large intestine,
where it accumulates  until finally expelled from  the  system.
After leaving the intestinal canal, the chyle is carried by  the
lacteals through the mesenteric glands or ganglia, and  emptied
into the receptaculum chyli at the commencement of the  thora-
cic duct, along which  it  passes to  enter the circulation at  the
junction of the internal jugular and subclavian veins.

                       The Kidneys.
   The kidneys are two glands, for the secretion of urine, one of
which is situated on each  side of the spine, in the  back part of
the lumbar region.  They extend from  the  last dorsal to  the
third lumbar vertebrae; the right  one being  somewhat  lower
than the left, to accommodate the right lobe  of the liver.   In
shape the kidney is oval, resembling the kidney bean; its posi-
tion is  upright, with the excavation,  called hilum, presenting
towards the spine.  It is a hard, solid body of a reddish brown
color.  The length is about four inches, and  the breadth two. 
THE KIDNEYS.
125
The kidneys are placed without the cavity of the peritoneum,
and surrounded with an abundance of fat,  and cellular tissue.
Their proper covering is a deuse  fibrous capsule which envelops
them completely, and penetrates into the fissures.
  The kidney consists of two different structures, which may be
readily seen by cutting it open longitudinally.  One, the exter-
nal,  is called  cortical, the other, the internal, medullary.  The
cortical substance is about one-fourth of an inch thick, and forms
the whole circumference of the kidney.  It consists of a number
of tortuous tubes of Ferrein, which secrete the urine,  between
which  are numerous minute blood-vessels.
   The medxdlary substance is of a darker color than the cortical,
and consists of from twelve  to eighteen cones (named after Mal-
pighi), which are arranged  in  three rows with their apices con-
verging towards the hilum or fissure.   These  apices  are called
papillae renales, in consequence of their projecting like so many
small  nipples. Each cone forms a sort of distinct gland, and
can be subdivided into numerous tubes, called the tubes of Bel-
lini, into which the tortuous tubes of Ferrein, from the cortical
substance, empty.  As the urine  oozes from the orifices of the
papillae,  it is received into a membranous cup, the infundibulum,
which surrounds each papilla.  From  these infundibulae, four or
five of which are united into a common trunk for that purpose,
and called a calyx, the urine passes  into  a common receptacle,
called  the pelvis, which is formed by the junction of about  three
calyces.
   The pelvis is in the centre of the kidney, and  of a  conoidal
shape; from  it the  excretory duct of  the kidney, called the
ureter, conveys  the urine to  the bladder.  The ureter is cylin-
drical, and about the size of a writing quill;  it  has  two coats,
an internal mucous one, and an external fibrous one.  They are
thin, white, and extensible.
   The ureter descends between the peritoneum and psoas magnus
muscle, and enters  the inferior fundus of the  bladder obliquely,
by a very small orifice.
       18 
126       SUPRA-RENAL  CAPSULES---THE  BLADDER.

                  Supra-Renal Capsules.
  There are  two small bodies, placed one upon the upper end
of each kidney.  They are of a yellowish brown color, and tri-
angular pyramidal shape, the base being  concave to  rest upon
the kidney. They have no excreting duct, nor is their use known.
It is supposed, as they are larger in  the  foetus than the adult,
that  their use is confined to foetal life.

                       The Bladder.
  The bladder receives and serves  as  a reservoir for the urine.
It is placed in the pelvis immediately behind the pubes.  When
distended, its shape is generally oval, the large end being down-
wards;  in women and young children it  is nearly spherical;  it
is also, mostly,  more capacious in woman than in man.  The
dimensions of the bladder varies; when healthy it will  gene-
rally hold near a pint.  It  is  bounded in  front by the  pubes,
above by the small intestine, behind  by the rectum, and below
by the prostate gland and seminal vesicles.  A conical  ligament,
called the urachus, extends  from  the superior extremity of the
bladder to the  umbilicus;  on each side of the urachus, in the
folds of the peritoneum, are the round ligaments, which were the
umbilical arteries in  foetal life.
  Besides these ligaments, the pelvic aponeurosis also assists to
retain the bladder in its place.  Its upper extremity is  called the
superior fundus, its lower  extremity the inferior fundus, and
between the two is the body. The  neck is at the junction of the
bladder with the urethra.
   The walls of the bladder consists  of four coats, viz. a peritoneal,
a muscular,  a cellular, and a mucous one.
   The peritoneal coat covers the  superior  fundus, and the pos-
terior part of the body.  The muscular coat consists of  pale fibres
which  pass in various directions.   It  is somewhat thicker than
that of the intestines; and its contractions expel the urine.
   The  cellular  coat connects the muscular and mucous coats,
and  is dense, strong,  capable of much distention, and impervious
to water. Through it the vessels and nerves are transmitted. 
THE PROSTATE GLAND.
127
  The mucous coat, also called the villous, is much more smooth
than that of the intestines; it is of a light pink color, and con-
tains  a great number  of small mucous follicles.  An angular
space within  the  cavity of the bladder, included  between the
orifices of the ureters and the orifice of the urethra, is  called
the vesical triangle.  A projection in the anterior angle, caused
by the third lobe of the prostate, is called uvula vesicae.
  The sphincter vesicas consists of a semi-circular and transverse
band of muscular  fibres  surrounding the neck of the bladder.
Its office is to keep the  orifice closed.
   The urethra is  the  membranous canal  which conducts the
urine from the bladder, in the male it also conducts the semen;
it consists of an  internal mucous coat,  continuous with that of
the bladder, and an external muscular one.  Its course is curved.
In the male, the  portion which extends from the neck  of the
bladder through  the  prostate gland, is  called the prostatic por-
tion, and is about  an inch in length; in it  are the  uvula  vesica,
and the  caput gallinaginis  or verumontanum—the  latter is a
triangular elevation of mucous membrane, at the base of which
are the orifices of the ejaculatory ducts.  The  next portion  is
about three-fourths of an inch  in length, quite narrow,  and  is
the membranous  portion; the remaining portion,  which is the
longest,  passes through  the penis; when it enters  this organ,
 there is  an enlargement, called  bulbous.  The urethra  of the
 female is much shorter than that of the male;  it passes from
 the neck of the bladder downwards  and forwards under the sym-
 physis pubis, and has its  sexternal orifice at the superior, anterior
 angle of the vagina.  The orifice is marked  by a slight elevation.

                     The Prostate Gland.
    This is a hard body, about the size and shape of a  horse chest-
 nut, fixed to the neck of the bladder.  It rests upon the rectum
 behind, and in front is bounded by the triangular ligament.  It
 consists  of three  lobes,  through the middle  one  of which the
 urethra  passes.   It  secretes a  thick,  white mucous,  which is
 discharged into the urethra. 
128
ORGANS OF RESPIRATION.
                  Organs of Respiration.
  These are the larynx, the trachea, and the lungs.
  Larynx.—The larynx  is a cartilaginous tube, forming  the
commencement of the windpipe.  It is placed  in the upper and
anterior part of the neck immediately below the os hyoides. The
oesophagus is situated immediately behind it, separating it from
the vertebrae of  the neck; and on each side are placed the  pri-
mitive carotid arteries and the internal jugular veins. It gives
passage to the air to and from the lungs, and also regulates  the
voice; its superior portion is prismatic, and its inferior circular.
In males it is larger, proportionably, than  in females.
  The five following cartilages compose it,  viz. one thyroid,  one
cricoid, two arytenoid, and one epiglottis.
  The thyroid is  the largest of  the five, and is  placed  at  the
upper and anterior part  of the neck, about one inch below  the
os hyoides.  It consists  of two symmetrical, quadrilateral  plates
which unite in  an acute angle at the  median line,  and consti-
tute the prominence in the upper part of  the throat known as
the pomum Adami (Adam's apple),  which is much larger in
men than women.   In the upper  part  of  this prominence is  a
deep notch.  On either  side the  superior  margin is curved like
the letter S, and to it is attached  the middle thyreo-hyoid liga-
ment ; the inferior margin is also curved, but in a less degree,
and  to it is attached the middle crico-thyroid ligament. The
posterior margin is elongated above and below into processes or
cornua, of which the superior are the longer, and called cornua
magna, and are  attached  to the  lateral thyreo-hyoid ligament;
and  the inferior, which are short and curved, are called  the
cornua minor, and articulate with the lateral crico-thyroid liga-
ments.
  The cricoid cartilage  is  situated below the thyroid, and  forms
the base of the larynx;  it is an oval ring, with the lower margin
nearly straight and horizontal, and connected to the first ring of
the trachea;  the superior  margin is oblique on account  of  the
breadth being three times as great behind as  in front; on each 
ORGANS  OP RESPIRATION.
129
side of the superior part of the posterior margin is a small con-
vexity for articulating with the arytenoid cartilages. Externally
the posterior  surface is flattened,  and from  it arises the crico-
arytenoid muscle.
  The arytenoid cartilages are placed at the upper and posterior
portion of  the larynx, and in shape  resemble triangular pyra-
mids curved backwards.  Their bases articulate with the  cricoid
cartilage. When joined together, the two cartilages resemble the
mouth of a pitcher, from which they received their  name;  to
the anterior surface, which is uneven, the superior and inferior
thyreo-arytenoid ligaments.
  The epiglottis cartilage is situated on the posterior face of the
base of the hyoid bone,  and  is partially enclosed  by the two
sides of the thyroid cartilage.  Its  form  is that of an oval disk;
the upper edge is  thin and rounded; the lower part is also thin
and elongated, and attached to the  thyroid cartilage. Its attitude
is vertical, immediately behind the base  of  the tongue, and pro-
jecting somewhat  above it; the anterior  surface is slightly con-
cave, and the posterior convex.
  Besides  these cartilages there is  sometimes a small one, called
corniculum laryngis, attached  to the apices of each of the ary-
tenoid cartilages.
  Numerous ligaments hold these cartilages together.  Four of
these within  the larynx, are the thyreo-arytenoid ligaments ; the
two inferior are commonly called the vocal cords,  and  extend
one on each  side from the  angle of  the thyroid to the base of
the arytenoid cartilages;  the  space included  between them is
the rima glottidis.  The  two  superior  ligaments, also one on
each side, are placed three or four lines above the inferior, and
extend from the angle of thyroid to the  middle of the arytenoid
cartilages.  All of these  ligaments are small, round,  fibrous
threads, covered by a reflection of  the lining membrane  of the
larynx.  The action of the small muscles of the  larynx  render
them more or less tense.
  The following pairs of  muscles belong to the larynx, viz. the
thyreo-hyoid,  the  cryco-thyroid, the posterior crico-arytenoid, 
130
ORQANS OP  RESPIRATION.
the  lateral crico-arytenoid, the  thyreo-arytenoid, the  oblique
arytenoid, the transverse arytenoid, the thyreo-epiglottideus, and
the aryteno-epiglottideus.
   Their names sufficiently indicate their attachement; they serve
to move the various cartilages, and modulate the voice.
   The  larynx is lined internally by a mucous membrane con-
tinuous  above with  that  of the  pharynx, and below with that
of the trachea.
  Fig. 25.  A view of the larynx, trachea, and bronchia, with an outline
ef the lungs. 1, 2, 3 Outline of the lungs; 5 thyroid  cartilage; 6 cricoid
cartilage; 7 trachea;  8 right bronchus;  9 left bronchus; 10  muscles con-
necting the thyroid and cricoid cartilages; 19, 19 the subdivisions of the
right and left bronchial tubes;  20, 20 capillary vessels. 
           THE TRACHEA.—THE THYROID GLAND.        131

                       The Trachea.
  The trachea is a cylindrical canal, four or five inches in length
by about three-fourths of an inch in diameter, extending from
the larynx as low as the third dorsal vertebrae, and terminating
in two ramifications called bronchia.  It is  composed of from
sixteen to twenty distinct rings of cartilage united by an elastic
ligamentous tissue.   These rings are deficient in  the posterior
third of their  circumference, which is completed by a muscular
structure, whose fibres are transverse, and the contractions of
which, diminish the diameter  of  the larynx, and thereby facili-
tate expectoration. Each ring is about a-fourth of an inch broad,
and half a line thick.  The trachea is lined by a mucous mem-
brane continuous with that of the larynx.
   The structure and arrangement of the bronchia is the same
as that of the trachea.  The right bronchus is larger and of a
larger diameter than the left.  At the orifice of each branch there
is a semi-lunar cartilage, which forms somewhat more than half
of its circumference, and the  office of which is to keep the ori-
fice  open.   The bronchia, after ramifying into numerous  sub-
divisions, terminate in the lobules of the lungs.  The structure
of the smaller ramifications is somewhat modified; the  cartilages,
instead of being formed of one piece, are composed of several
pieces, and are placed  farther apart; finally, they  disappear
entirely, and the bronchia  are membranous only.

                    The Thyroid Gland.
  This gland is situated in front of the first and second  rings of
the trachea, and at the sides of the larynx.  It consists of two
lobes, one on each side, united by a thin, narrow portion stretched
across in front of the upper part of the larynx, called the  isth-
mus. It  is of a dark brown color, and granular structure.  It is
also covered by a capsule which gives it a polish.  Its  use is not
known.
  In some districts of country it becomes very much enlarged,
constituting the disease known as bronchocele  or goitre. 
132
THE LUNGS.
                        The Lungs.
  The lungs are the essential organs of respiration, and  are
situated one on each side of  the chest, occupying the principal
part of its cavity. They are conical in shape, and separated from
each other by the  heart and by a membranous septum, called
the mediastinum; the diaphragm separates them from  the  ab-
domen.  On the external surface they are concave, corresponding
with the walls of the chest; internally they are concave to receive
the convexity of the heart.  The superior extremity is a tapering
cone, terminating above the level of the  first rib; the  inferior
extremity is broad and concave, and rests upon the diaphragm.
The color of the lungs is a light pink, with specks or patches of
black.
  The right lung is somewhat shorter than the left, though more
voluminous; and is divided into three lobes, while the  left  has
but  two.
  Each lung is supported in  its place by its root, which is com-
posed of the pulmonary artery, pulmonary veins, bronchial tubes
and vessels, and the pulmonary plexus of nerves.
  In structure the lungs are divided into numerous lobules, and
these again into  minute air-cells, all of which are held together
by cellular tissue, through which the blood-vessels, nerves and
lymphatics ramify.  The shape of the air-cells is polyhedral, and
a certain  number of them  communicate with each other,  by
lateral openings, and with a single branch of the bronchial tube.
They are lined by mucous membranes.  The intermediate cellular
substance is called parenchyma.
  The pulmonary artery, which conveys  the dark, venous blood
to the lungs, terminates in capillaries which ramify on the walls
of the air-cells;  from these walls arise the pulmonary veins, by
which the arterial blood,  purified in  its passage through  the
capilaries, is returned to the heart.
  The bronchial arteries are the nutritious arteries of the lungs;
they arise from the thoracic aorta.
  The lymphatics, which are numerous, arising from the surface 
THE PLEURAE.
133
and the substance of the lungs, terminate in the bronchial glands,
which are placed at the roots of the lungs, and at the bifurcation
of the bronchia.
   The nerves are  branches of the sympathetic and eighth pair.

                             Fig.  26.
  Fig. 26.  Front view of the heart and lungs.  1 Right ventricle of the
heart; 2 left ventricle; 3 right auricle; 4 left auricle;  5 pulmonary artery;
6 right pulmonary artery; 7 left pulmonary artery; 8 remains of the duc-
tus arteriosus of the foetus;  9 arch of the  aorta;  10 superior vena cava ;
11 arteria innominata; 12 right subclavian vein;  13 right common carotid
artery and vein; 14 left vena innominata;  15 left carotid artery and vein;
16 left subclavian vein and artery; 17 trachea; 18 right bronchus;  19 left
bronchus; 20, 20 pulmonary vein;  7, 19, 20 form  the root of the left lung;
and 18, 20 the root of the right lung;  21 superior lobe of the right lung;
22 its middle lobe; 23 its inferior lobe; 24 superior lobe of the  left lung;
25 its inferior lobe.

                          The  Pleurae.

  Each  lung is invested by a serous membrane which maintains
its structure and gives to  it its  shining appearance.  After en-
closing  the lung as far as the  root,  it is reflected upon  the
parietes of the chest. The portion that covers  the lungs is  called 
 134   MEDIASTINUM.—THYMUS GLAND.—RESPIRATION.

 the pleura pulmonalis, and  that in contact with the chest the
pleura costalis. The diaphragm and the root of the lung is also
 covered by it.
                     The  Mediastinum.
  The space  included between the pleura of the two lungs is
 called the mediastinum.  It is in the middle line  of the  thorax,
and is divided into the anterior, middle and posterior.
  The anterior mediastinum is the  triangular space between the
 sternum and heart; it contains the remains of the thymus gland,
 and some loose cellular tissue.
  The middle mediastinum contains the heart,  the  ascending
aorta, the superior vena cava, the bifurcation of the  trachea, the
pulmonary arteries and veins, and the phrenic nerves.
  The posterior mediastinum extends from the heart  to the
spinal column, and  contains the descending aorta, the superior
intercostal, and greater  and lesser azygos veins, the thoracic
duct, the oesophagus, the great splanchnic nerves,  and the pneu-
mogastric nerves.
                    The Thymus Gland.
  The thymus gland is placed  in the anterior mediastinum ;  it
is of a triangular shape and pink color.  Its structure is lobu-
lated.  Its use is not known; up to the second year of age  it
grows, after which it gradually diminishes  and almost  entirely
disappears.  In all probability it is of importance in foetal life.

                Physiology of Respiration.
  The function of respiration consists in the  conversion  of
venous into arterial blood.  This change, by which carbonic acid
is given off from, and  oxygen taken  into the system, takes place
in the lungs.  In  the  periphery of the  body the  circulating
fluid becomes dark colored,  and  is taken up by the radicles of
the veins, and after being mixed with the lymph and chyle, is
carried to the lungs, where  it is brought into  contact with the
atmospheric air, which restores its red color, and fits it for  pur-
poses of nutrition. 
PHYSIOLOGY OP RESPIRATION.
135
  The manner in which this is accomplished is  the following :
the walls or sides of the air cells are very thin and transparent,
and the capillaries are so placed between two adjacent cells, as
to come in contact with  the air from both.  The carbonic acid
of the venous  blood then  passes out through the walls of the
air  cells by exosmose or exudation,  to unite with the nitrogen
of the air,  for  which  it has a  strong affinity, and be exhaled
from  the lungs;  and  the  oxygen  of the air contained  in the
air cells passes through  their parietes by endosmose, or imbibi-
tion, to unite with the blood, giving to  it its bright red arterial
color, thus vitalizing it, or fitting it for the various purposes of life.
  The carbonic acid given off in respiration is chiefly furnished
by the continual decay of the tissues.  The carbon of the food,
however, is also directly converted into  carbonic acid to a con-
siderable degree,—varying in quantity according to the amount
of animal heat required.
  Inspiration, or the action by which air is taken into the lungs,
and expiration, or the action by which the air received in inspi-
ration is expelled from  the lungs, are performed by the  expan-
sion and contraction of the  chest.
  In  the first inspiration, the diaphragm is  the  principal agent
in the dilatation of the chest;  when in a state of rest, this mus-
cle is  much arched, but by contracting it  becomes more plane,
and by flattening its  arch  increases the cavity  of the thorax,
while at the same time, by  forcing down the abdominal viscera,
it causes the  protrusion of the abdomen, witnessed in inspira-
tion.  The intercostal  and other of the  muscles of the chest
produce the lateral dilatation, which is however  slight in  ordi-
rfhry natural inspiration, but is considerable when the inspira-
tions  are  deep and forced.  In  a natural, quiet inspiration,
the expansion kof  the  chest  is  almost  wholly  accomplished
by  the diaphragm.   This  is also the case in old  persons, the
ossification  of  the  cartilages  of  the  ribs  preventing  lateral
expansion.
  In  general there are from sixteen to eighteen  inspirations per
minute, though the number varies  greatly under different cir- 
136
PHYSIOLOGY  OF RESPIRATION.
cumstances.  The average proportion, numerically, of the pulsa-
tions of  the  heart  to  the respiratory movements is about four
and a  half to odc  At about every fifth inspiration the move-
ments  of the  thorax are considerably increased.
   In the second, or expiration, the parts concerned in inspira-
tion return again to their natural  state;  the elasticity of the
cartilages of  the ribs, the rings of the bronchia, and of the  air
cells themselves, all aid in accomplishing this, as  does also the
contraction of the abdominal, and some of the thoracic muscles.
   After  each expiration, a short interval of repose  succeeds;
the length  of this interval has been estimated as follows.  By
representing  the whole period  of time occupied in one respira-
tory act,  from the beginning of one inspiration to the beginning
of the  next,  by ten, the  inspiration may by estimated at five,
the expiration at four,  and the interval of repose at one.
   The  amount of air inhaled at each inspiration is estimated to
be about twenty cubic  inches, which, allowing sixteen inspira-
tions per minute, would give 19,200 cubic inches in one hour,
parsing through the lungs of an  individual,  or 460,800 cubic
inches  in twenty-four hours.
   A certain portion of air, called residuary, always remains in
the lungs, and upon it  their lightness depends.  It has been cal-
culated that  after an ordinary expiration more than a hundred
cubic  inches  remain,  and after the strongest expiration more
than thirty.  After the lungs have been once inflated by a full
inspiration, no  power whatever  can remove  the air from them
so as to cause them to sink  in  water.  The  residuary air will
not support life a longer time than three or four minutes.
   " The  movements of respiration are partly voluntary, antl
partly  involuntary.   Partly voluntary, in order that they may
be inservient to  the  production of vocal  sounds,  and to the
actions of  speaking, singing, &c.   Partly  involuntary, lest in
sleep or in  moments of forgetfulness, the movements of respira-
tion should be suspended, and fatal results ensue."
   The  nerves which govern  the  respiratory movements are
derived from  the medulla oblongata at the  base of the brain. 
            CIRCULATORY SYSTEM.—THE HEART.         137

                    Circulatory System.
  The organs concerned in  the circulation, are the heart,  the
arteries, the veins, and  the lymphatics.

                        The Heart.
  The heart, the centre of the circulation, is a hollow muscular
organ, situated in the thorax between the sternum and the spine;
being  bounded  at  the  sides by the lungs, and resting on the
centre of the diaphragm below.  In  shape it is conoidal, having
the apex inclined to the left side, and  in contact with the walls
of the thorax about the junction  of the fifth rib with its cartil-
age.  The  side which  rests upon the diaphragm is somewhat
flattened.  The length of the heart is about five inches and a half,
and its diameter at the  base three inches and  a half. Its ordi-
nary weight is  about six ounces.  It has four cavities, two of
which are  called auricles, and two  ventricles.   The heart  has
two functions, viz. to receive the blood and throw  it into  the
lungs, and to receive it again after  it has  been oxygenated in
the lungs, and distribute it  throughout the body.  The  auricles
are the  receptacles of  the blood, and the ventricles propel it
through the system.
   The auricles form the base, and the ventricles the  body of
the organ;  the anterior extremity of the left ventricle, which
extends somewhat beyond the right, constitutes its apex.
   A membrane, called the  pericardium, surrounds the heart,
and also invests the roots of the  large vessels connected with it.
This  membrane consists of two layers, an internal and an ex-
ternal one;  and is only attached to the base of the heart, the
remainder of the organ  being only loosely enveloped by it.
   The right auricle is  an oblong cuboidal cavity, having supe-
riorly  an elongated process, which bears  some resemblance to
the ear of an animal, from which the term auricle has probably
originated; anteriorly  it has a  convexity or  pouch, called  its
sinus.  Posteriorly, at  its superior angle, the  descending vena
cava enters,  and at its inferior  angle the ascending vena cava.
Its parietcs are thin, and composed of muscular fibres arranged 
138
THE HEART.
in parallel lines, resembling the  teeth of a comb, whence their
name musculi pectinati.  Between the orifices of the two vena
cava, an elevation exists called the  tuberculum Lowcri.  A de-
pression on the partition between the two auricles is called the
fossa ovalis; in foetal life an opening existed at this place, called
the foramen ovale.  Between  the right  auricle and ventricle is
a round hole about an inch in diameter, called the ostium veno-
sum, for the passage of the blood.
   The right ventricle receives the blood from the right auricle.
It is a somewhat triangular cavity, having  its base downwards,
with thick  parietes, and is also  larger  than  any of the  other
cavities of the heart.  It is placed anterior  to the left ventricle,
from which it is  separated by  a thick septum.  The internal
surface of the cavity is composed of  large fleshy fibres, called
columnae carnas,  from a number of which  several tendinous
chords (chordae tendineae) proceed to be inserted into the loose
edge of the tricuspid valve.  This valve is situated between the
auricle and  ventricle, opening into the  latter, and is formed  of
a doubling of the lining membrane of the ventricle.  It is cir-
cular, and attached around the  ostium venosum; at its loose
margin are three points  or processes, from  which it derives its
name tricuspid. When the heart contracts, this valve closes the
ostium venosum, and prevents the blood from  returning into the
auricle, and hence it passes into the pulmonary artery.  The
orifice of the pulmonary artery is circular, and about an inch  in
diameter; it is furnished with  three valves,  called from their
shape semilunar; they are formed from the internal coat of the
artery, and open outwards; in the centre of their loose edges is
a small cartilage, called the corpus aurantii,  the office of which
is to perfect the closure of the valves.  The use of the valves is
to prevent the blood returning from  the artery into the ventricle,
when the latter dilates.  Behind each valve is a pouch, called
the  sinus of Valsalva.   The pulmonary artery  passes upwards,
and backwards to the under side of the arch of the aorta, and
there divides  into two branches,  one for each lung, the  branch
for the right lung being the longest and largest.  The diameter 
THE HEART.
139
of the pulmonary artery is the same as that of the  aorta, but
its parietes are thinner.
   The left auricle is concealed by the right and by the ventri-
cles.  Its shape is quadrangular or square, and into each of its
four angles one of the pulmonary veins enter.   Its parietes are
muscular, smooth, and  rather  thicker than those of the right
auricle.  Its ear-like appendage is narrower  and more crooked
than that of  the  right  auricle, and  the musculi pectinati  also
enter into its  structure.  The opening  between it and the left
ventricle is likewise called ostium venosum.   The partition  be-
tween the auricles is sometimes imperfect in  the adult.
   The left ventricle  is  a conical  cavity, and  forms the apex of
the heart.  Its parietes are much thicker than those of the right
ventricle.  Internally,  its  surface  is  roughened by numerous
columnas carnae,  which become tendinous  (chordae tendinae)
where they are attached to the bicuspid or mitral valve.  This
valve, which consists of two folds or leaflets  of  the lining mem-
brane of the ventricle, has  its base attached to the margin of the
ostium venosum, and its edges  opening downwards into the ven-
tricle : consequently when the ventricle contracts, it  closes the
opening, and  the blood passes  out  by the aorta.  The orifice of
the  aorta  is  supplied  with three  semilunar valves, arranged
precisely like those  at the  mouth of the pulmonary artery.
   The nutritious vessels  of the heart are  the right and left
coronary arteries.   The veins  accompanying them empty into
the right auricle.  The nerves are branches of the sympathetic,
supplied by the cardiac plexuses.
   The pericardium is a  membranous  sac, consisting of two
layers, in which the heart  is loosely enveloped.  The external
 layer  is fibrous,  white,  and  inelastic;  the internal layer is
 serous, lines  the  external, and  is  reflected  over the heart  and
 roots  of the vessels.  It gives to  the heart its smooth shining
 appearance, and the fluid it secretes  lubricates the surface of the
 organ and allows it to move freely in the pericardium.
    The cavities of  the heart  are lined  by a serous membrane
 similar to that of the blood-vessels. 
140     BLOOD-VESSELS.—THE ARTERIES.—THE AORTA.

                       Blood-Vessels.
  There are two sets of blood-vessels, one of which, the arteries,
carries the red or  oxygenated blood from the heart and distri-
butes it to the different parts of the body;  and the other, the
veins, carries dark blood, collecting it  from the various parts of
the body, and returning it to the heart.
                       The Arteries.
  The  arteries  are composed of three  coats, an  external,  a
middle, and a serous one.
  The external coat is formed  of cellular tissue, and  is firm
and strong, not yielding on the application of a ligature.
  The middle coat is fibrous  and elastic, having  its fibres
arranged circularly.  It is readily divided  by a  ligature.
  The internal coat is a delicate serous membrane, easily  torn.
Its secretion lubricates the surface of  the artery, and  facilitates
the passage of blood.
  The small arteries which ramify on  the coats of the arteries
to nourish them, are called vasa vasorum. The sympathetic fur-
nishes the arteries with nerves.

               The Aorta, and its Branches.
  The aorta is the main trunk of the  arterial system ; it arises
from the upper and posterior end of the left ventricle,  and  pass-
ing upwards and backwards towards the left side forms a curva-
ture, called its arch, the summit of which is about an inch lower
than  the  upper  end of  the  sternum.   Near the origin of the
arch there is generally an enlargement or dilatation of the aorta,
called its  greater sinus. After forming its arch the aorta passes
to the left side of the spine, about the third or fourth dorsal
vertebra, and descends through the thorax to the hiatus aorticus
of the diaphragm, through which it passes  into the  abdomen,
and terminates in front of a space between the fourth and fifth
lumbar vertebrae, by dividing into  two large trunks called the
primitive iliacs. In its descent through the thorax and abdomen,
it is in contact with the left side  of the bodies of  the  vertebrae. 
THE AORTA,  AND ITS  BRANCHES.          141
It receives the name of thoracic aorta, while  passing  through
the thorax, and abdominal, while passing through the abdomen.
  The coronary arteries are the first branches  given off by the
aorta;  they are distributed to the heart.
  The arteria innominata is the next branch;  it is given off
from the  arch  of the  aorta, and after ascending about an inch
and a half obliquely towards the right side, divides  in  front of
the trachea into the right carotid, and right subclavian.  The
right  carotid ascends  nearly  as  far as the  os  hyoides,  and
divides into the external and internal carotids.
  The left carotid arises from the arch of the aorta, and passing
to the left side of the neck divides, as the right, into the ex-
ternal and internal carotids.
  The external  carotid is distributed to the more superficial
parts of the head and neck, and the internal goes to the brain
and eye.
  The following principal branches  are given off from the ex-
ternal  carotid, viz. the superior thyroid which goes to the thyroid
gland; the lingualis to the tongue; the facial to the face; the
inferiorpharingeal to  the pharynx;  the occipital to the integu-
ments  on  the back part of the head; the posterior auricular to
the integuments of the side of the  head; and the anterior, pos-
terior, and middle temporal, which go to the muscles and integu-
ments  on  the side and  back part of the head.
  The internal maxillary artery commences at the bifurcation
of the  external carotid, and winds around the neck of the lower
jaw to supply the back portions of the  mouth  and palate.  Its
course  is very tortuous, and it  gives off numerous branches, of
which  the following are the principal: the tympanitic, to the
tympanum, or drum of the ear, through the glenoid fissure; the
meningea parva, to the dura mater through the foramen ovale;
the meningea magna or media, to the dura mater through the
spinal  foramen; the inferior dental, to the teeth through the
posterior  mental foramen; the deep temporal, two in  number,
which  go  to the temporal muscle;  the pterygoid and buccal to
the muscles and lining membrane of the cheek; the  superior
       20 
142
SUBCLAVIAN ARTERY.
alveolar or maxillary to the molar teeth, antrum and gums;
the infra orbital enters  the infra-orbital canal, and  is distri-
buted to the canine and incisor teeth, to the antrum, and to the
muscles in front of the upper jaw; the superior palatine  goes
to the mouth and palate; the superior pharyngeal to the  pha-
rynx and Eustachian tube ; and the sphenopalatine to the lining
membrane of the nose,  entering  through the  spheno-palatine
foramen.
   The vertebral and internal carotid arteries supply the brain;
the former  enter through the foramen magnum occipitus, and
uniting form a  large trunk, called the basilar,  which passes
along the median line of the pons  varolii, giving  off several
branches; the principal  being the superior cerebellar, and the
posterior cerebral arteries.
   The carotid enters the cranium  through the  carotid canal,
and divides  into  the ophthalmic, middle  cerebral, and anterior
cerebral  arteries.
   The arteries  are  united in front and behind  by branches
called  anterior and posterior  communicating,  and  by this a
circle, called the  circle of Willis, is formed.

                     Subclavian Artery.
   On the left side the subclavian  arises from the arch of the
aorta, and on the right from  the innominata.  The right is con-
sequently shorter, and more  superficial than the left.
   The subclavian passes out of the thorax over the first rib,
and usually gives off five  branches, viz.
   The vertebral, which is the first and largest, and which passes
through  the  foramina of the  spinous processes of the  six upper
cervical vertebrae, and enters the cranium through the occipital
foramen.
   The inferior thyroid, which  goes  to  the  thyroid  gland, and
also gives off the ascending cervical to the muscles of the  neck.
   The superior intercostal, to the  two upper intercostal spaces.
   The internal  mammary, which enters the thorax, and  pass- 
SUBCLAVIAN ARTERY.
143
ing down over the cartilages of  the ribs,  gives off branches to
the thorax, diaphragm, and abdomen.
   The posterior cervical, which  passes to the back of the neck
to be distributed on the muscles there.
   After  giving off these branches the subclavian artery goes to
the axilla or arm-pit, passing between the first rib and the sub-
clavius muscle, where it loses the name of subclavian and takes
that of axillary.
   The axillary  artery, also usually sends off  five branches,
though there is much irregularity in this  respect.
   The supra-scapidar, to the muscles of the scapula.
   The external mammaries, mostly four in  number,  to  the
shoulder, axilla, and muscles on the front of the thorax.
   The scapular to the arm-pit, and  the  muscles on the back of
the thorax.
   The anterior circumflex to the parts  in front of the joint;
and the posterior circumflex to the posterior parts of the joint
and the  deltoid muscle.
   From the axilla to the elbow joint the artery descends at the
inner side  of the arm on the edge  of the biceps flexor muscle,
and is called brachial.
   The brachial artery gives off four branches.
   The profunda major to the outer portions of the arm.
   The profunda minor to the internal face of the triceps at its
lower part, and to the internal condyle.
   The  nutritious artery to the bone  through  the nutritious
foramen.
   The anastomotic, which passes around the internal condyle,
and anastomoses with the ulnar  recurrent.
   At the elbow joint the  brachial artery divides into the radial
and ulnar arteries.
   The radial is the smaller of the two, and except at the wrist
is the more superficial.  It descends at the outer side of the arm
between  the  tendons of the supinator  radii longus and flexor
carpii radialis muscles.   In its course it gives off  the following
branches, viz. 
144
SUBCLAVIAN ARTERY.
   The radial recurrent, which is distributed about the joint,
and anastomoses with the profunda major.
   The superficialis volae, which is distributed to the palm of
the hand.
   The dorsalis carpi to the back of the wrist.
   The magna pollicis to the thumb;  this is one of the terminal
branches of the radial.
   The radialis indicis is connected at its origin  with the last,
and is distributed on the radial side of the fore-finger.
   The palmaris profunda  is the third terminal  branch  of the
radial; it crosses the hand beneath the flexor tendons, forming
the arcus profundus, from which branches are sent to the inter-
ossei muscles, and uniting  at the ulnar side of the hand with
the cubitalis manus of the ulnar artery.
   The ulnar artery is deep seated; it passes from the internal
condyle along the inner side of the arm between  the tendons of
the flexor carpi ulnaris,  and flexor sublimis muscles.  At the
wrist  it is superficial,  and  its pulsations may be distinctly felt;
it  passes over the annular ligament, and, in the palm, forms the
superficial arch.
   The following are the branches it sends off:
   The ulnar recurrent, which  is distributed  to the  muscles of
the internal condyle, and anastomoses with the anastomotic.
   The interosseus, which divides into an anterior and a poste-
rior interosseous branch; the anterior descends the arm,  in con-
tact with the interosseous ligament,  giving off branches in its
course to the deep seated muscles; near  the wrist it perforates
the ligament, and is distributed to the back of  the  wrist and
hand; the posterior branch soon perforates the interosseous liga-
ment, to be distributed to the extensor muscles of the fore-arm.
   The dorsalis manus is given off at  the lower end of the fore-
arm, and distributed upon the back of the hand.
   The superficial  arch  (arcus  sublimis) is formed by the con-
tinuation of the radial artery beneath the  palmar fascia,  from it
a branch is sent to the ulnar side of the  little finger, followed
by three others (digital arteries), each of  which  on  arriving at 
BRANCHES OP THE THORACIC  AND ABDOMINAL AORTA.  145

the heads of their metacarpal bones, divides into two branches, a
digito-radial, and a digito-ulnar, to supply the sides of the fingers.

              Branches of the Thoracic Aorta.

   In descending through the chest the aorta gives  off the fol-
lowing branches.
   The  bronchial  arteries,  generally  but   one  for  each lung,
though  sometimes two or more, pass into the root of the lungs,
and are distributed  along  the ramifications of the bronchia.
They are the nutritious arteries of  the lungs.
   The oesophageal arteries, mostly five or  six small  twigs, arise
one after the other from the aorta,  and go  to the oesophagus.
   The intercostal arteries, ten  on each side, supply the ten infe-
rior intercostal spaces, the two upper spaces being  supplied  by
the subclavian.  Those for  the right  side are longer than the
left in consequence of having to cross the spine behind the oeso-
phagus and  the vena azygos.   Each  artery passes along the
grooves in the lower margin of the rib  for about two-thirds of
the length of the latter.

             Branches  of the Abdominal Aorta.

   The aorta in its descent through the abdomen gives off several
branches viz.
   The phrenic,  two in number, which go to the diaphragm, and
are chiefly distributed on its concave surface.
   The cceliac, a large trunk, about half an inch in length, which
is given off opposite the junction of the last dorsal with the first
lumbar vertebra.  It divides  into  three branches—the  gastric,
hepatic, and splenic.
   The gastric  is the smallest branch and goes to the lesser cur-
vature of the stomach.
   The hepatic goes to the liver, entering through the transverse
fissure;  it gives off  a  branch to the  greater curvature of the
stomach, called the  right gastroepiploic; and another to the
gall bladder, called the cystic. 
146       BRANCHES  OP  THE  ABDOMINAL AORTA.
                 p.   „h.                     Fig. 27. The abdominal
                   £'                     aorta and its branches.
                                           1 Phrenic arteries ; 2 coe-
                                          liac artery ;  3 gastric ar-
                                          tery ; 4 hepatic artery ;  5
                                          splenic artery; 6 supra-
                                          renal artery of the right
                                          side ; 7 right renal artery;
                                          8 lumbar arteries; 9 su-
                                          perior mesenteric; 10 sper-
                                          matic arteries; 11 inferior
                                          mesenteric; 12 sacra me-
                                          dia;  13 common iliacs;
                                          14 internal iliac of  the
                                          right side;  15 external ili-
                                          ac ;  16 epigastric artery;
                                          17 circumflex iliac ; IS fe-
                                          moral artery.

                                            The  splenic, which
                                          is the largest branch
                                          of the  cceliac, goes to
                                          the spleen;  it gives off
                                          several small branches
                                          to the pancreas, and
                                          the vasa  brevia,  and
                                          left gastric arteries to
                                          the  left  half of  the
                                          greater  curvature  of
                                          the stomach.

                                            The superior mesen-
                                          teric  arises  from  the
                                          aorta  about  half  an
                                          inch below the cceliac,
                                          and is nearly as large;

it is distributed to the whole of  the small intestine, and to  the

right side of the large; three branches go to the latter, viz.  the

ileo-colic to the coecum, and  a portion of the ileum;  the colica

dextra  to  the  ascending  colon;  and  the colica media to  the

transverse  colon.

  The capsular arteries, generally but one on  each side, go to

the supra-renal capsules.

  The renal or emulgent arteries, mostly one for each  side,  are

large, and  go outwards transversely to the  kidneys; before  en-

tering the fissure of the kidneys  they divide into three or four

branches.
 
BRANCHES  OF THE  ABDOMINAL  AORTA.        147

                 Fig. 28.
  Fig. 28.  Distribution of the superior mesenteric artery.  1, 2 Duodenum ;
3 pancreas;  4jejunum;  5 ileum; 6 coecum and appendix vermiformis;
7 ascending colon; 8 transverse colon; 9 commencement of the descending
colon; 10 superior mesenteric artery;  11 colica media; 12 the branch which
anastomoses with the colica sinistra;  13 the branch of the superior mesen-
teric, which anastomoses with the pancreatico-duodenalis; 14 colica dextra;
15 ileo colic;  16, 16 branches to the small intestines.

   The spermatic arteries arise  from the aorta just below the
emulgents, or sometimes from the latter, and pursuing a tortuous
course, pass through the abdominal rings, and divide into several
branches before reaching  the  testicle.   In the female  the  sper-
matics are chiefly distributed  to  the  ovaries.
   The inferior mesenteric usually arises from the aorta about an
inch above its termination.  It is much  smaller than  the superior
mesenteric, and divides into three principal branches, called the 
148         THE  PRIMITIVE,  OR COMMON ILIACS.
superior, middle, and inferior left colic arteries, which are dis-
tributed to the left side of the colon.  It also gives off a branch,
the superior hsemorrhoidal, to the upper part of the rectum.
   The lumbar arteries, commonly five on each  side, correspond
with the intercostales, and are distributed chiefly to  the loins.
   The middle sacral artery is a small artery arising from the
bifurcation of the aorta, and  passing down  the sacrum  to the
coccyx.

             The  Primitive,  or common Hiacs.
   The aorta, as mentioned, divides at the fourth  lumbar vertebra
into the two iliacs, which pass outwards and downwards  to the
sacro-iliac junction, where they divide  into the internal and ex-
ternal iliac.
   The internal iliac, or hypogastric, is a short trunk descending
from the sacro-iliac junction into the  cavity of the pelvis, and
giving off numerous branches, of which the following are the
principal:
   The ilio-lumbar, which is distributed to the loins.
   The lateral sacral, which divides into four  branches  to enter
the anterior sacral foramina.
   The obturator artery, which passes  out  of the pelvis  at the
obturator  foramen, and  is distributed by two  branches  to the
obturator  and adductor muscles.
   The middle hasmorrhoidal, which goes to the rectum  to the
vesiculae seminales, and to the prostate gland.
   The vesicle  arteries consisting of several branches, which go to
the bladder.
   The gluteal artery, which is a large  trunk and one of the ter-
minating branches of the internal iliac, passes out of the pelvis
at the upper part of the sacro-sciatic notch, to be distributed by
two or three branches to the glutei muscles.
   The ischiatic artery, which is the anterior of the two  termi-
nal branches  of the  internal  iliac, passes  out of the  pelvis
through the sciatic notch, supplying the floor of the pelvis and
back of the thigh.  Before leaving the pelvis the ischiatic artery 
     THE EXTERNAL ILIAC.—THE FEMORAL  ARTERY.     149

gives off a large branch, called the internal pudic, which is dis-
tributed to the muscles of the perineum and to the penis.
  The internal pudic gives off several branches, viz.
  The lower haemorrhoidal, to the anus and rectum.
  The transversus perineal, to the muscles and integuments of
the perineum. In the lateral operation for stone it is always cut.
  The ureihro-vulvar, to the corpus spongiosum  of the penis.
  The dorsi penis, to the back of the penis.
  And the cavernous artery, to the corpus cavernosum.

                    The External Iliac.
  The external iliac artery extends from the sacro-iliac junction
to Poupart's  ligament,  under which  it  passes to the lower ex-
tremity, and  is then called the femoral artery.  Near Poupart's
ligament it gives  off two branches; one, called the  epigastric,
ascends obliquely upwards and inwards, to be distributed upon
the anterior  parietes of the abdomen.  In its course it passes
between the two abdominal rings, and consequently in the opera-
tion for hernia is in  danger of being cut.
   The other, the circumflex iliac, also passes  obliquely upwards
to the crest of the  ilium, and is distributed  to the  muscles of
the loins and abdomen.

                    The Femoral Artery.
   This artery is a continuation of the external iliac;  it extends
from Poupart's ligament down the inner side of the thigh, about
two-thirds of its length, where it perforates  the tendon  of the
adductor magnus muscle, and takes the name of popliteal. The
femoral artery sends off the following branches :
   The  superficial  artery of the  abdomen  goes obliquely to the
integuments of  the lower part  of the abdomen, and is there
distributed.
   The  external  pudics, two or three small arteries which go to
the  integuments.
   The  profunda, a large artery going to the muscles  of  the
upper part of the thigh.  It gives off a large branch called  the
        21 
150   THE POPLITEAL ARTERY.—THE ANTERIOR TIBIAL,  ETC.

external circumflex, which supplies the muscles  on the outside
of the thigh; and another,  called the internal circumflex, to
the muscles on the inside of the thigh.  Several smaller branches,
called  perforating arteries, are  given  off by the profunda and
the internal circumflex.
   The anastomic artery is sent off by the femoral, and descend-
ing to the knee anastomoses with the  internal articular arteries.

                   The  Popliteal Artery.
   The popliteal is a continuation of the femoral artery, and ex-
tends  from the adductor  tendon to  the opening in the inter-
osseous ligament below the head of the tibia, where it  divides
into the anterior and posterior tibial.
   It gives off the superior, middle, and inferior articular arteries
to the knee joint; and  the gemellar, two in number, to the
heads of the gastrocnemius muscle.
                    The Anterior Tibial.
   The anterior tibial artery perforates the interosseous ligament,
 and descends the leg in front  of it to the ankle joint, giving
 off in its course numerous branches, as follows:
   The recurrent tibial, which goes  upwards, and anastomoses
 with the  arteries about the knee joint.
   The internal malleolar, to the inner side of the ankle joint.
   The external malleolar, to the outer side of the ankle joint.
   The tarsal,  to the external ankle and to the  tarsus.
   The metatarsal, to the  toes by three branches.  It forms  an
 arch at the roots of the  metatarsal bones.
   The dorsal, to the outer side of the great toe, and the inner
 side of the second toe.
   And the pedal, a branch  passing through the first interosseal
 space to  the sole of the foot to join the external plantar artery.

                     The  Posterior Tibial.
    This artery descends  from  the head  of the tibia to the os
  calcis in  a line from  the middle  of the ham to the external
  ankle.  It is beneath the  muscles of the calf of the leg. 
      THE  VEINS.—VEINS OP THE HEAD  AND  NECK.     151

  The peroneal arises  from the posterior tibial, and dividing
into several branches is distributed  to  the  muscles on the back
of the leg.
  On reaching the os calcis, the posterior tibial artery divides
into the internal and external plantar arteries.
  The internal plantar is a small artery, which  passes along
the inner margin of the foot, and is distributed to the great toe.
  The external plantar is considerably larger than  the last, and
passes obliquely across  the sole of the foot to the outer margin,
forming  an  arch  from  which branches  {digital  arteries)  are
given off to the interosseous spaces, and to the toes.

                         The Veins.
   The veins  collect the blood from the different  parts  of  the
body, and convey it to the heart.  They are much more numerous
than  the  arteries; the deep seated arteries generally having
two accompanying veins called venae comitas.  All the venous
blood is emptied into the right auricle through two large trunks,
called the ascending and descending vena cava.   The veins of
the head,  upper  extremities, and  thorax,  unite  to  form  the
descending vena cava.
   The  parietes of the veins, like the arteries, are formed of
three coats;  these coats, however, are much thinner than those
of  the arteries, which render the veins flaccid when  empty and
easily distinguishable  from the arteries, the elastic middle coat
of  which enables them  to retain the cylindrical shape.
  -  The veins are likewise furnished with numerous valves, formed
of  two or  three crescentic folds of  the lining membrane, which
open towards the heart.
    In the  brain  and the bones the canals or channels which
 convey the venous blood, are termed  sinuses, and  are lined by
 the internal coat  of the veins.

                Veins  of the Head and Neck.
    Most of the veins  of the head and neck have the same names
 as the arteries they accompany. 
152           VEINS  OF THE HEAD AND NECK.
  The internal maxillary, occipital., temporal, and other of the
principal trunks join  together  to form the external jugular,
which is a superficial vein extending from the parotid  gland to
the subclavian vein, into which it empties behind the outer end
of the clavicle.   The external jugular  is covered externally by
the skin, superficial fascia, and platysma-myoides muscle.
  The internal jugular vein is larger  than the external; it ex-
tends from the base of the occiput to the posterior face of the
clavicle near its sternal end, where it unites with the subclavian
to form the  vena innominata.   It receives the blood from the
sinuses of the cranium, and from some of the superficial veins.
                  Fig. 29.
 
SINUSES  OF  THE DURA  MATER.
153
                Sinuses  of the Dura Mater.
  The channels, or passages, by  which the  blood is removed
from  the brain, are formed between the lamina of the dura
mater, and termed sinuses.
  The principal are:
  The superior  longitudinal sinus, a channel of a triangular
shape, commencing at the foramen coecum by  a small vein from
the root of the  nose, and gradually increasing in size forms an
arch in the middle  line of  the arch of the cranium, which  ter-
minates at the internal occipital cross in an enlargement called
the torcular herophili, where it receives the  blood from other
sinuses.
  The inferior longitudinal sinus, is situated  between the lobes
of the cerebrum in  the falx  cerebri; it also forms an  arch,  and
empties  into  the straight  sinus  at  the  anterior edge  of  the
tentorium.
  The straight  or fourth sinus, extends along the median  line
of the tentorium, from the falx cerebri to the torcular herophili.
  The vena azygos, is a short trunk formed by the venae Goleni
which empties into the fourth sinus.
  The lateral sinuses, on either side,  commence at  the torcular
herophili, and pass over the occipital, parietal, and temporal
bones  to  the  posterior foramen  lacerum,  through which they
pass out  of the cranium, and form  the commencement of  the
internal jugular vein.
  The circular sinus, surrounds the pituatary gland in the sella
turcica, communicating on either side with the  cavernous sinuses.
  The cavernous sinuses, receive the blood from the ophthalmic
veins; they are  venous cells of a  spongy structure, situated on
either side of the sella turcica.
  The superior  and inferior petrosal sinuses, are small channels,
traversing the petrous portion of  the temporal bone  to  empty
into the lateral sinus.
  The anterior, occipital sinus, passes across the basilar process
of the occipital bone, forming a communication between the  two
inferior petrosal sinuses. 
154      THE VEINS OF THE UPPER EXTREMITIES.

  The posterior occipital sinus extends from the torcular  hero-
phili in the lower edge of the falx cerebri to the foramen  mag-
num, where it divides and empties into the  lateral  sinus  on
either side.
  The name of emissaries of Santorina has been given to the
small veins, which pass through  the  minute foramina in the
bones of  the cranium, to communicate  with the sinuses of the
brain.

           The Veins of the Upper Extremities.

  These  veins are superficial and deep seated;  the latter accom-
pany the arteries, and take the same name; two veins usually
accompany one artery.
  The superficial veins lie between the  skin  and  the brachial
aponeuroses.  They anastomose frequently with each other, com-
mence generally  on the back of  the fingers, and finally unite
into two  principal branches, called the  cephalic and basilic vein.
  The cephalic vein commences  on the thumb, fore-finger, and
back of the hand, and passes up the radial side of the fore-arm
to the elbow, where it is  joined  by the  median cephalic, and
pursuing its course up the outer side of  the arm, empties into
the subclavian vein beneath the clavicle.
  The basilic vein commences on the little finger, and passes up
the ulnar side of the fore-arm to  the  elbow, where  it receives
the median basilic, and continuing its course up the arm  along
the inner margin of the biceps muscles, where  it is  joined by
the venae comites, and becomes the axillary vein.
  The median vein collects the  blood  from  the palm of the
hand, wrist, and front of the fore-arm, and ascends in  front of
the fore-arm to within a  few inches of  the elbow joint, where it
divides into two branches,  one of which called the  median ce-
phalic runs outwardly to join the cephalic vein; the  other, the
median basilic, goes inwards to join the  basilic vein.
   The axillary vein is formed by the union  of the basilic and
the brachial veins; it passes up the arm  in the same sheath with 
THE VEINS OF THE LOWER EXTREMITIES AND ABDOMEN.  1 55

the axillary artery to the axilla, where, like the artery, it takes
the name of subclavian.
   The superior or descending vena cava is formed by the junc-
tion of the right and left innominata; it empties into the right
auricle of the heart.

            The Veins of the Lower Extremities.

   The veins of the lower extremity, like those of the upper, are
superficial  and deep seated, and  the  latter  generally take the
name of the artery they accompany.
   The popliteal vein commences behind the head of the tibia,
and extends upwards along with the popliteal artery to the per-
foration  in the tendon of the  adductor  magnus muscles, after
which it takes the name of femoral.
■  The femoral vein is a continuation of the popliteal, and passes
upwards along with the  artery of the same name to Poupart's
ligament, where it becomes the external iliac vein.
   The small or external saphena vein is superficial, commencing
 by the union  of several small branches at the outer side of the
 top of the  foot and ankle, and passing up the posterior and outer
 side of the leg to the ham, empties into the popliteal vein.
   The great or internal saphena vein is also superficial; it com-
 mences by a number of  roots from the sole, and the inner and
 upper part of the foot, and ascending along the internal face  of
 the leg, and  thigh to within  about an inch and a half of Pou-
 part's ligament empties into the femoral vein.

                   Veins of the Abdomen.
   The principal of these are the external and internal iliacs;
 the spermatics of the  testicles;  the renales or  emulgents from
 the kidneys;  the  hepatic in three branches, from the liver, all
 of which  empty directly into the ascending vena cava; the vesi-
 cal plexus from the bladder, and the uterine  plexus  from  the
 uterus, which empty into the internal iliac; and the hsemorrhoi-
 dal veins from the rectum, which empty into  the inferior me-
 senteric. 
156
THE PORTAL VEIN.
  The inferior or ascending vena cava commences between the
fourth and fifth lumbar vertebrae, by the union of the iliac veins,
and ascending along the spinal column at the right of the aorta,
receives in its course the abdominal veins,  and passing through
the diaphragm into the chest, empties into the right auricle  of
the heart.

                      The Portal Vein.

  The portal vein collects the blood from all the viscera of the ab-
domen, and entering the transverse fissure of the liver, is included
with the biliary duct  and hepatic artery, in a common invest-
ment of cellular tissue, called the capsule  of Glisson;  it rami-
fies through the substance of that organ previous to entering the
general circulation.
  The veins which contribute to form the  portal are: the supe-
rior  and inferior mesenteric, the splenic,  the gastric, and the
pancreatic; the trunk of the  portal  vein, which  is about four
inches in length, extends from the posterior face of the pancreas
to the transverse fissure of the liver.

           Peculiarities of the  Foetal Circulation.
  The circulation  of the foetus,  in consequence of the  absence
of respiration, differs very materially from  that function in the
adult.  For its nutrition and development an alliance through
the circulatory organs  of the mother  is necessary.
  The peculiarities of the foetal circulation consist in: the duc-
tus  venosus, a vein leading from the umbilical vein along the
margin of the liver to the ascending vena  cava;  the communi-
cation of the right and left auricles through the foramen ovale;
and the ductus arteriosus, a branch from the pulmonary artery,
which conducts the blood returned from the head into the aorta
just behind the origin of the left subclavian artery.  When the
current of the blood is changed  after birth, by respiration, the
ductus venosus and arteriosus, shrivel up into ligamentous cords,
and the aperture between the auricles is closed by the  adhesion
of its valve. 
       PECULIARITIES OF THE FOETAL  CIRCULATION.     157

  The placenta is the organ through which the effete blood of
the foetus is regenerated, or aerated. It is closely attached to the
uterus of the mother, and the change in the blood is probably
effected by interstitial circulation, as there appears to be no direct
connection of blood-vessels between the mother and foetus.  The
umbilical cord extends  from  the placenta to the umbilicus of
the child, and consists of one umbilical  vein and two umbilical
arteries; the latter are twisted around the former, and conduct
the blood to the placenta; the former conveys the aerated blood
back again to the child.  Thus it will be observed, that the um-
bilical vein and  the ductus venosus carry arterial blood;  and
the umbilical arteries and  the ductus arteriosus carry venous
blood.
   Commencing at the  placenta, the circulation of the  foetus
pursues the following course.  The blood passes along the um-
bilical vein to the umbilicus of the child; it then penetrates the
abdomen, after which it divides into two currents, one of which
goes through the ductus venosus into  the ascending vena cava;
the other passes  through the vena portarum  to the  liver.  The
portion sent to the liver, after ramifying through that organ, is
collected by the  hepatic veins, and likewise discharged into the
ascending cava.
   The contents  of  the ascending cava are  emptied into the
right auricle  of  the heart, from which  it passes into the left
auricle through the ostium venosum.   From  the left auricle it
passes into the left ventricle, by which it is distributed by means
of the aorta throughout the system.  That portion of the blood
which goes to the head and upper extremities,  is collected in the
descending vena cava, and also discharged into the right auricle,
from whence it  passes into the  right ventricle, from  which  a
small portion goes into the pulmonary artery, and the remainder
into the aorta through the ductus arteriosus.
   It  will be  perceived, therefore,  that  all parts of the body
receive mixed arterial and venous blood,  with  the single excep-
tion of the liver, to which  organ the blood  is  sent from the
placenta  unmixed.
       22 
158                " THE  LYMPHATICS.
  The umbilical arteries are continuations of the internal iliacs;
they pass up at  the  sides of the bladder and  go to the navel,
from which  point, as mentioned, they form part of the umbilical
cord.   After  the  change  in  the  circulation,  at  birth,  they
become the round ligaments of the bladder.

                     The Lymphatics.
  The lymphatics, so called from  the transparent color of the
fluid they carry, are  found in all parts of the body;  their office
is that of interstitial absorption, by which  the effete  parts  of
the body are removed,  and room made for  new depositions.
They are small, transparent, cylindrical vessels, rarely exceeding
a line in diameter.   Like the arteries, they have three coats,
and when  distended they present  a knotted appearance, which
is owing to  their being furnished with valves and sinuses.
  In the intestines the  lymphatics, which commence in the vil-
lous coat, are frequently called lacteals, and contain the chyle.
  The lymphatic is also spoken  of as the absorbent system.
  Numerous lymphatic glands  exist  in the mesentery, groin,
axilla, and neck, into which the lymphatic vessels  enter, and
pass out again. They form frequent anastamoses with each other,
and become larger and less numerous, as they proceed from their
origins.
   All the lymphatic vessels from the various parts of  the body
collect into two large trunks, one of  which is placed  on each
side of the body.
   The trunk on the right side receives the lymphatics from the
right side of the head and neck, and the right  upper extremity
and lung; it is short, and discharges its contents into the venous
system at the junction of the  right internal  jugular and sub-
clavian vein.  The  trunk on the left side, called the thoracic
duct, receives the contents of  the lymphatics and  chyliferous
vessels of  the rest  of  the body; it is the principal lymphatic
vessel of the body, and  commencing in the abdomen with an
enlarged extremity, called receptaculum chyli, which receives
the contents of the  lacteals and the  lymphatic vessels of the 
PHYSIOLOGY OF THE CIRCULATION.          159
lower extremities, it passes into the thorax  through the dia-
phragm, and ascending through the posterior mediastinum  in
front of the  spinal column, along with the aorta, empties  its
contents at  the  junction of the  left subclavian and internal
jugular veins.

               Physiology of  the Circulation.
   By the circulation of the blood  is understood  that function
by which the arterial blood, fitted for nutritive  purposes in the
lungs, is distributed to every part of the body.  The organs and
vessels,  by which this function is accomplished, viz. the  heart,
arteries, veins, and  the  capillary vessels, intermediate between
the arteries and  veins, constitute the vascular system.
   The heart is  the centre of  the circulation, and may be con-
 sidered  as a double  organ, or as two distinct hearts brought
 together for convenience of package,—the right one containing
 black or venous blood only, and the left one red  or arterial blood
 only.  The circulation from the two hearts, or  the two sides of
 the heart, are entirely distinct; that from the right is called  the
 lesser or pulmonic circulation, and that from the left, the greater
 or systemic.
    Commencing  at the heart, the route of the circulation is as
 follows; the venous blood from all parts of the body is collected
 in the right auricle, from which it passes through the auriculo-
 ventricular orifice  into  the right ventricle; thence it is sent
 through the pulmonary artery to the lungs to  be aerated, after
 which it  is collected by the pulmonary  veins, and carried to
 the  left auricle, out  of  which  it  passes through the auriculo-
 ventricular orifice into the left  ventricle, from whence it is  dis-
 tributed by means of the aorta throughout the system.
    The  chief  propelling  power of the circulation is the alter-
 nate contraction and dilatation  of the heart.  This motion of
 the  heart is constant and unremitting during life; its cessation,
 even for a short time, terminating existence.  It is independent
 of the nervous system, and also of the stimulus of the blood,
 as it continues  after all nervous communication is  cut off,  and 
160          PHYSIOLOGY OF THE CIRCULATION.
when the heart is empty, and in fact after it has been removed
from the body.   The ventricles  are the principal  agents  in the
propulsion of the blood,  for which purpose  they have  strong
muscular parietes;  the  auricles have but  slight  contractile
powers, their chief use being as receptacles.  The contraction of
the auricles and ventricles is not synchronous.  The two auricles
act together, as  do also  the  two ventricles.  The contraction
of the auricles which forces the blood into the ventricles, is im-
mediately followed by the contraction of the ventricles,  during
which the auriculo-ventricular valves are  closed to prevent the
regurgitation of  the  blood into the auricles, and  consequently
it passes into the aorta and pulmonary artery.  Dilatation of all
the cavities  succeeds their contraction.   The term systole has
been given to the contraction  of the heart, and that of diastole
to its dilatation.  The pulse is  caused by the  projection of the
blood into the arteries from the ventricle, and corresponds  with
the contraction or systole. The contractile nature of the  mus-
cular coat of the arteries aids in the propulsion  of the  blood,
and also in the  production of the pulse.  In  the capillary and
venous circulation there is no pulse.
  By the time  the blood reaches the capillaries, the force of the
heart is lost.   Of the  circulation carried on  in this system of
vessels but little  more can be  said than that it is due  to  vital
action.  The nutritive properties of the arterial blood  are  here
yielded up, and the effete portions enter the veins  to be returned
to the heart and lungs, there  to be given off, or again vitalized.
  The forces which aid in returning the blood to  the heart are:
the suction power of the heart, muscular motion, and inspiration.
When the heart dilates, and when the chest is  expanded  by the
descent of the diaphragm, a vacuum is created, which the blood
rushes towards the chest to fill.
  At every contraction of a muscle, the veins of the  part are
pressed upon, and their valves  allowing  the flow of the blood
but in one direction, towards the heart, it must consequently be
driven on in that direction.
  The muscular  force of the heart has been variously estimated 
PHYSIOLOGY  OF THE CIRCULATION.          161
 by different observers, some allowing it to be equal to but ten or
 fifteen pounds, other estimating it at thirty or forty. A true esti-
 mate is of course exceedingly difficult to arrive at, as it is greatly
 modified  by age., sex, temperament, and a variety of causes.
   The usual number of contractions of the heart, or pulsations,
 per minute, in the adult  is from  seventy to  seventy-five.  In
 youth they are more  frequent, and in old age less so.
   In the female sex the pulse  is also more  rapid than in  the
 male.  Temperament, muscular exertion, mental emotion, &c,
 all exercise a controlling influence  over the action of the heart.
   On applying the ear over the region of the heart, two distinct
 sounds are perceptible, during each beat of the heart.  The first
 is a  dull, lengthened sound; the second quick and sharp;  they
 follow each other in  quick succession, and  are succeeded  by a
 short interval of repose, after which they recur again, and so on.
 The first is synchronous with the contraction, and the second with
 the dilatation of the ventricles. About one-half the whole period
 between the commencement of one pulsation, and the commence-
 ment of the next is occupied by the first sound; one-fourth  by
 the second;  and the remaining  fourth is the period of  repose.
 The causes of the first sound are : the rush of the blood through
 the orifices of the aorta and pulmonary artery;  the  passage of
 the blood over the rough internal surfaces of the ventricles; the
 flapping of the auriculo-ventricular valves; the sound of muscular
 contractions; and the impulse of the heart against the chest.
   The  second sound is caused  by the closure of the valves, at
 the mouths of the aorta and pulmonary arteries.
   At each contraction of the heart, it is projected forwards, and
 strikes against the parietes of the thorax, in the region of the
 fifth and  sixth ribs; the shock  this occasions is called the im-
pulse of the heart.
   There is some  variation in the capacity of the cavities of the
 heart, the right auricle and ventricle being  somewhat more
 capacious than the left.
   Tht circulation was discovered by William Harvey  of London,
 in 1719. 
162      NERVOUS  SYSTEM.—THE SPINAL MARROW.

                     Nervous System.
  In  this system are  included the  brain, spinal marrow,  and
nerves.
  The material or tissue of which it is composed, is called neu-
rine, and is of a soft, pulpy consistence.
  This tissue consists  of two portions, one of which is white or
medullary, and of fibrous structure; the other gray or ciueritious,
and globular in structure.
  The nerves  are  composed of the medullary substance,  and
consist of parallel fasciculi or bundles of fibres, capable of being
subdivided into filaments.  Each nerve, as well as each particular
fibre, is enveloped in a sheath, called the neurilemma.
  A  ganglion  is a  knot occurring  in the course of a nerve, and
by which they  obtain an increase of volume and power. Ganglia
are of different sizes and shapes, and consist of a union of white
and gray matter.
  An anastomose is the junction of the filaments of the same
nerve, or of different nerves.
  A plexus is the junction or interchange of the larger fasciculi
of the same nerve, or of different nerves, forming a network.

                   The Spinal Marrow.
  The spinal marrow is contained within the vertebral canal, and
extends from the atlas or first vertebra of the neck  to the first
or second lumbar  vertebra.  Its  general form  is cylindrical,
though it is somewhat flattened in front and behind, and  has
an  enlargement in the neck and loins. Its diameter, with the
addition of its membrane, is much smaller than  that  of  the
spinal canal,  by which provision injury from pressure is guarded
against.
   It is divided, longitudinally, into two symmetrical parts, by
an anterior and a posterior fissure.  The posterior fissure is some-
what deeper than the  anterior.   It has also a lateral fissure  on
each side, placed somewhat posterior to the middle, and passing
inwards and forwards.
   The spinal marrow  is composed  of  medullary  and cineritious 
THE SPINAL  MARROW.
163
matter, the former being internal, and the latter external;  the
cineritious matter is also much more abundant than the medullary.
   From the sides of the spinal marrow, thirty pairs of nerves
are sent out, which, like the vertebrae, are divided into cervical,
dorsal, lumbar, and sacral.  Of these, eight pairs belong to the
neck, twelve  to  the  thorax,  five to the loins, and five to the
sacrum.   Sometimes there is an additional pair, making thirty-
one in all.
   Each nerve arises by two roots, one of which comes from the
anterior cord of the  spinal marrow, and the  other  from  the
posterior  cord.  The posterior root is larger than the anterior,
and upon it is a ganglion; the roots are separated by a process
of pia mater, called the  ligamentum denticulatum,  and after
penetrating the dura mater  by separate foramina, unite to form
a single trunk.
   The lumbar and sacral pairs arise  from the lower extremity
of the spinal  marrow, and form a cluster resembling the tail of a
horse, hence the name of cauda equina has been applied to them.
   Three membranes envelop the spinal cord; one, the external,
is called the dura mater; another, the internal, is the^x'a mater,
and the third, which is between the others, is  the arachnoidea.
The dura mater is continuous with that of  the brain, and  ter-
minates below in a closed extremity;  it is a white fibrous mem-
brane, affording a loose investment to the spinal canal, except
at the first cervical vertebra, to which it adheres firmly. Between
it  and  the parietes of the canal  is placed a quantity of loose
cellular tissue containing fat and  serum.
   The tunica arachnoidea is placed next to the dura mater; it
is very thin and transparent.
   The pia mater adheres closely  to the spinal marrow; it  is a
cellular membrane, made up  almost  entirely of blood-vessels;
it sends processes into the anterior and posterior fissures of  the
medulla spinalis; below it  terminates in round  cord-like  pro-
cesses continuous with  the roots of the nerves constituting  the
cauda equina. It is also continued along the nerves constituting
their neurilemma or sheath. 
164
THE BRAIN.
                      The  Brain.
  The brain is contained within the bones of the cranium, and
is oval in shape.
  It is composed of cineritious and medullary matter, and con-
sists of four principal parts, viz. the medulla oblongata, which
is a continuation of the spinal marrow, or its superior part;  the
pons Varolii, called alsoprotuberantia annularis, which is placed
at the superior extremity of the medulla oblongata; the cerebrum.,
which  occupies seven-eighths of the cavity of the cranium; and
the cerebellum, which is situated at the base of the  cranium.
   Like the spinal marrow, the brain also is enclosed in three
membranes,—the dura mater, tunica arachnoidea, and pia mater.
   The dura mater is the most external, lining the whole of the
cavity of the cranium, to the bones of which it is firmly attached.
Its structure is fibrous.  It consists of two lamina,  from the in-
ternal of which several processes are formed. One of these, the
falx cerebri, is situated under the middle line  of the  head, and
extends from  the crista galli in front to the tentorium behind,
separating the hemispheres of the brain.   Its breadth in front is
about an inch, and behind about two, or two and a half inches.
Another process is called  the tentorium, and like the last is
crescentic  in  shape; it is stretched horizontally across the cra-
nium, separating the cerebellum from the posterior  lobes of the
brain.  In front it is continuous with the falx cerebri.  The falx
cerebelli is a small triangular process, extending from the lower
surface of  the tentorium to the foramen magnum;  it separates
the two lobes of the cerebellum.
   The tunica arachnoidea is placed between the dura mater
and pia mater; it is a thin, transparent, serous membrane, and
adheres closely to the pia mater.
  The pia mater is a cellular membrane, placed  next  to  the
substance of the brain, and extending to the bottom of the fis-
sures between the convolutions, consequently its internal surface
is very irregular; its external surface, being in contact with the
arachnoid membrane is smooth and shining. 
     THE  MEDULLA  OBLONGATA.—THE  PONS VAROLII.   165

  This membrane is made up almost entirely of blood-vessels.
Clusters of small, white, granular bodies, called glands of Pac-
chioni are contained in its meshes, the use of which is  not
known.
                  The Medulla Oblongata.
  The medulla oblongata, as mentioned, is the upper part of the
spinal cord; it extends from the margin of the atlas to the pons
Varolii, and is about an  inch in length, and three-fourths of an
inch in breadth  at the base; it gradually increases in size as it
ascends.  Like the medulla spinalis, it is divided by an anterior
and  a posterior fissure into symmetrical halves, and  each half
consists of three  portions, viz. the corpora pyramidalia,  two
cord-like cylindrical  portions, one  on each side  of  the anterior
fissure, and united at their lower extremities by an interchange
of fibres.   The  corpora  olivares,  are  two oval bodies situated
posterior  to the pyramidalia and separated  from  them by a
fissure.  The corpora restiformia are elliptical elevations, situated
at the posterior part of the medulla oblongata, and separated
from each other by the posterior fissure.  They are about one
inch in length, and  united  below by transverse fibres of medul-
lary matter.

                     The Pons Varolii.
   The pons Varolii, or annular protuberance, is  a large cuboidal
mass of medullary matter, placed at the top and in front of the
medulla oblongata, and resting on the basilar process at the base
of the cranium; its  internal fibres are longitudinal,  being a con-
tinuation  of those of the  medulla oblongata; externally they are
transverse.  A superficial fossa divides it into two  symmetrical
halves.  Four crura proceed from it, two to the cerebrum,  and
two  to the cerebellum.

                      The Cerebellum.
   The cerebellum is situated in  the posterior fossa of the  cra-
nium, beneath the posterior lobes of the cerebrum, and separated
from it by the tentorium.
       2:J 
166
THE CEREBRUM.
    It is oblong and flattened, having its long diameter transverse,
 and constitutes about one-sixth part of the brain.  It is divided
 by a longitudinal  fissure  into two  lobes  or  hemispheres.   On
 making a vertical section through one of the lobes, an arbores-
 cent arrangement is presented, caused by the intermingling of
 the gray and white matter, to which the name of  arbor vitae
 has been given.  A fasciculus of medullary matter, called  the
 crus cerebelli, connects each  lobe of  the  cerebellum with  the
 pons Varolii; another fasciculus, called  the valve of the  brain,
 extends from the corpus restiforme of the medulla oblongata  to
 the under surface of the cerebellum.
   Externally the cerebellum is formed of cineritious, and inter-
 nally of medullary  matter.

                       The Cerebrum.
   The cerebrum is a large ovoid mass, six or seven times  as
 large as the cerebellum, and weighing from three to four pounds.
 It  is divided into two parts or hemispheres by the deep  fissure
 above  (superior longitudinal fissure),  and each  hemisphere  is
 subdivided on its under surface into three lobes—anterior, poste-
 rior, and middle.  The anterior and middle lobes rest upon the
 anterior and middle fossa of the cranium, and the posterior lobes
 upon the tentorium.  The fissure of Sylvius is between the an-
 terior and middle lobes.  The surface of the cerebrum consists
 of a number of convolutions or gyri, separated from each other
 by  deep fissures (sulci), which give it an exceedingly irregular,
 tortuous appearance.
  The periphery of the convolutions to the  depth of about a
 fourth of an inch is composed of cineritious substance, and  the
 interior of medullary substance.
  The longitudinal  fissure completely separates the two anterior
lobes  from each other, extending between them to  the base of
the brain; the posterior lobes are also separated in  the same
manner.  But between the middle lobes, a broad arched band of
medullary matter, called the corpus callosum, extends from side
to side at the bottom of the longitudinal fissure, connecting the 
THE CEREBRUM.
167
two hemispheres.  This band is mostly composed of transverse
fibres.  The crura cerebri, coming from  the anterior margin of
the pons  Varolii, also pass from  the middle  fissure  to each
hemisphere.  They are two thick, cylindrical,  white  cords of
longitudinal fibres, which terminate  in  the convolutions after
expanding in all directions so as to constitute the principal part
of the hemispheres.   Between  the crura are two white globular
bodies, about as large as a pea, called the eminentia mammil-
lares.  In front  of these is a soft mass of cineritious matter
called  the tuber cinereum.  The term infundibulum  has been
given to  a reddish, hollow, conical  body, the base of  which is
on the tuber cinereum and the apex,  extending  to the pituitary
gland.  This latter is  a light colored, vascular body, consisting
of two lobes situated in  the sella Turcica.   A  triangular arch
of medullary matter, the base  of which is continuous  with  the
posterior  part  of  the  corpus callosum,  and the apex  joined to
the eminentia mammillares  by  two crura, is called the fornix.
A vertical septum, consisting  of two lamina,  and separating
the lateral ventricles, having its upper extremity attached to the
fornix,  and  its lower to the  corpus callosum,  is called the
septum lucidum.
   The velum interpositum is a reflection of the pia mater imme-
 diately beneath the fornix; the plexus choroides  is a  net-work
 of veins  contained in its edges.   The pineal gland is a small,
 reddish, conical body, placed upon the tubercula  quadrigemina,
 and connected with the  optic thalamus; it often contains  par-
 ticles of  calcareous matter.  The ancients imagined it to be the
 seat of the soul.  The tubercula quadrigemina are four promi-
 nences situated  on the  upper  part  of the crura cerebri, and
 behind the optic thalamus; a  passage under them  is the aque-
 duct of Sylvius.  The thalami  optici, two in number, are  situ-
 ated on  the superior face of the crura cerebri;  they are convex
 above and internally, and are composed of a mixture of medul-
 lary and cineritious matter.  Their  posterior  extremities have
 three rounded prominences, called corpora geniculata.
   The corpora striata are  two  oblong  masses  of gray matter, 
168
NERVES OF THE  CRANIUM.
situated in front of the thalami optici, and at the bottom of the
lateral ventricles.
  In the brain are five ventricles, or  cavities;  two  of them are
called lateral, and the others, the third, fourth and fifth.
  The lateral ventricles are situated in the centre of the hemi-
spheres, and are separated from each other by the septum  luci-
dum.   They  are horizontal and very irregular in shape; the
roof is formed by the corpus callosum, and the floor by the for-
nix, thalami optici, and corpora  striata.  Each contains three
depressions, called cornua,  of which  one is anterior, one poste-
rior, and one inferior;  an oblong eminence on the inner side of
the posterior cornua is called hippocampus minor, or ergot; and
a ridge on the floor of the inferior cornua is called hippocampus
major.  The lateral ventricles communicate with each other, and
with the third ventricle by  the foramen of Monro.
  The third ventricle is situated between the thalami optici; it
is a narrow, oblong cavity bounded above by the velum inter-
positum and the fornix, and below by the tuber cinereum, crura
cerebri, and eminentia mammillares.  It communicates with the
lateral ventricles by  the foramen of Monro, and with the fourth
by  the aqueduct of Sylvius.
  The fourth ventricle is an irregular triangular cavity, situated
between the  pons Varolii,  cerebellum, and medulla oblongata;
above, it is bounded by the valve of the brain and the tubercula
quadrigemina; its floor is formed by the calamus scriptorius.
It communicates with the third ventricle.
  The fifth ventricle is placed between the lamina of the septum
lucidum, and has no communication with the other ventricles.

                  Nerves of the Cranium.
  There are nine pairs of nerves  arising from the  cranium,
which  are designated numerically, as well  as by their function
or distribution.
  The olfactory nerve, or first pair  arises by three  roots  from
the base of the brain at the corpora  striatum which unite in
the fissure of Sylvius. It passes  forward, converging towards its 
NERVES OF THE  CRANIUM.
169
fellow, to the cribriform plate of the ethmoid bone, where  it
forms a large, soft bulb from which it sends filaments into the
nose to supply the Schneiderian membrane.
  The optic nerve or second pair, arises by a single broad  root
from the thalamus opticus and the tubercula quadrigemina, and
going forward to the anterior part of the third ventricle, forms
a junction with  its fellow in the form of the letter X, called the
chiasm or crossing of the optic nerves, after which it enters the
orbit of the  eye  to join the retina.
  The motor occult, or  third pair, arises from the crus cerebri,
and passing into  the orbit through the sphenoidal foramen, is
distributed to most of the muscles of the eye-ball.
  The patheticus, or fourth pair,  arises by two roots from the
valve of the brain, and entering the orbit through the sphenoidal
foramen, is distributed to the  superior  oblique muscle of the
eye-ball. It is  the smallest of the nerves, coming from the en-
cephalon, and is not larger than a sewing thread.
   The trifacial, trigeminus, or fifth pair, arises by three roots,
from the medulla oblongata, and emerging from the side of the
 pons Varolii, enters a canal of the  dura mater at the fore part
 of the petrous  portion of the temporal bone, where it forms a
 ganglion, called the ganglion  of Gasser,  from  which  proceed
 three branches, viz. the  ophthalmic, superior maxillary, and
 inferior maxillary.
    The  ophthalmic  branch  emerges through  the sphenoidal
 foramen, and is distributed to the orbit,  lachrymal gland, and
 integuments and muscles of the forehead.
    The superior maxillary branch passes  through  the  foramen
 rotundum,  and is distributed to the upper jaw and face.
    The inferior  maxillary branch emerges  at the foramen ovale,
 and is distributed to the  tongue, and to the muscles and teeth
 of the lower jaw.
    The motor cxternus oculi, or sixth pair, arises from the corpus
 pyramidale by  two roots, and passing forward through the caver-
 nous sinus, it enters the orbit through the sphenoidal  foramen,
 and is distributed to the abductor occuli muscle. 
170
THE SPINAL  NERVES.
   The seventh pair includes  the facial and auditory nerves,
and arises from the corpus restiforme and  calamus scriptorius.
Both branches enter the internal meatus.   The fascial, which is
likewise calledportia dura, passes out through the stylo-mastoid
foramen, and penetrating the  parotid gland, is distributed by
numerous branches to the face.  The auditory is also called the
portio mollis.  It is distributed to the internal ear.
   The eighth pair  includes the glossopharyngeal, the pneumo-
gastric, and the spinal  accessory.  It arises  by filaments from
the corpus olivare, medulla oblongata, and  the medulla spinalis.
The glossopharyngeal  passes  through the  posterior foramen
lacerum, and is distributed to the side and root of the  tongue,
and to the tonsils and pharynx.  The pneumo-gastric also passes
out through the posterior foramen lacerum, and descending  the
neck, included in the sheath with the vessels, enters the thorax
and is distributed to the lungs and  stomach.  The spinal acces-
sory also emerges from the posterior foramen  lacerum, and is
distributed to the muscles and integuments of the neck.
   The hypo-glossal  nerve, or ninth pair, arises  by several fasci-
culi from the medulla oblongata, and passing through the  pos-
terior condyloid foramen of the os occipitus, is distributed to
the muscles of the tongue.

                    The Spinal Nerves.

   The nerves  arising from the spinal cord are  divided into the
cervical, dorsal, lumbar, and sacral.  As mentioned in the account
of the spinal cord, they arise by two roots,  one coming from the
anterior portion of the cord,  the other from the  posterior por-
tion—the anterior is the motor root, the posterior  the sensitive
root.  After the union of the roots in the intervertebral foramen,
the spinal nerves divide into two trunks, the posterior of which
are much the smaller and go  to the muscles of the  back;  the
anterior are large, and uniting with the ganglions of the sym-
pathetic,  form plexuses, from which the principal  nerves of the
muscles of the trunk and extremities are derived. 
CERVICAL NERVES.
171
                 Cervical  Nerves.
  The first nerve given off from  the medulla  spinalis, is called
the sub-occipital;  it passes out between  the occiput and atlas;
its anterior fasciculus is the  smaller, and following  the  course
of the vertebral arteries, is partly distributed to the muscles on
the front of the vertebrae, and partly joins the pneumogastric
and  hypoglossal nerves, and the cervical ganglion of the sym-
pathetic;  its posterior  fasciculus  is distributed to the muscles
on the back of the neck. The next seven are the cervical nerves
proper, of which the three superior anastomose freely with each
other, and form a cervical plexus at the  side of the neck, from
which numerous branches are sent  to the  muscles and skin of
the neck.  The phrenic nerve, also, arises from this plexus, and
passing down through  the  anterior mediastinum, divides into
several branches, and is distributed to the diaphragm.
  The four inferior cervical nerves and the  first dorsal, after
sending off filaments to the sympathetic, unite to form in the
axilla the  brachial plexus.   From this plexus  the  following
branches are given off which  supply the  shoulder, axilla, and
upper extremity. The scapular branch goes backwards, passing
through the  coracoid notch, and  supplies the muscles  of the
shoulder and scapula. It is quite small.
  The subcapular and thoracic branches, generally five or  six
in number, supply the muscles of the parietes of the thorax and
those under the shoulder.
  The circumflex, or axillary branch, winds around  the hume-
rus in company with the posterior  axillary artery, and  is dis-
tributed to the deltoid muscle.  The internal cutaneous and the
external musculo-cutaneous are two small branches, which pass
down the arm, and are distributed to the muscles and integu-
ments of the fore-arm.
  The radial nerve,  also called  musculo-spiral,  winds around
the humerus, passing between the heads of the triceps muscle,
which it supplies with branches,  and then descends to the fore-
arm and is spent upon its muscles, and  upon the wrist and 
172         DORSAL NERVES.—LUMBAR NERVES.

thumb.   The radial nerve also descends to the fore-arm, pass-
ing under the internal coudyle, and is distributed to the integu-
ments on the ulnar side of the back of the hand, the little finger
and the ulnar side of the ring finger.  The median nerve is the
largest  of  the  branches  given off by  the  brachial plexus; it
descends the arm at the inner edge of the biceps muscle, along
with the brachial artery; on reaching the elbow it passes between
the heads of the pronator teres muscle, and descending the fore-
arm between the flexor sublimus and profundus muscles, giving
off branches  in  its  course, is finally distributed to the thumb,
and to the fore, middle, and one side of the ring finger.

                Dorsal or Thoracic Nerves.
   There are twelve pairs of these; the first pair passing  out
through  the  intervertebral foramen between the  first and  the
second dorsal vertebrae, and the twelfth between the last dorsal
and first lumbar vertebra.  The posterior branches go backwards
between the transverse processes  of the vertebrae, and are  dis-
tributed  to the muscles  on  the  back  of the thorax and those
lying along the spine.  The anterior branches which are  the
larger, pass along the intercostal  grooves, and are  distributed
to the muscles of the thorax.
   The first dorsal nerve sends a branch to the axillary plexus.
The second and third send branches, called intercostal humeral,
to be distributed upon the integuments of the arm.

                     Lumbar Nerves.
   Of these there are five  on each side; the posterior branches
are small, and go to supply the muscles of the  loins; the ante-
rior branches unite  to form the lumbar plexus, which is placed
between  the  psoas magnus  and quadratus  lumborum muscles.
From this plexus a number of branches are given off: two or
three  of these  are  quite small, and  go to  the muscles of  the
abdomen.  The  external spermatic branch  goes  to the groin,
and supplies the glands and the cremaster muscle.  The external
cutaneous goes to the commencement of Poupart's ligament, at 
SACRAL NERVES.
173
the commencement of which it emerges from the abdomen, and
is distributed to the integuments and muscles on the inside of
the thigh.
  The anterior crural  is the largest branch arising from the
lumbar plexus; it passes out of  the  abdomen under Poupart's
ligament,  at the outside of the femoral artery. Just above this
ligament several  branches are given off which are distributed
to the  muscles and integuments of the pelvis and thigh.  Three
of these branches  are called the anterior, middle, and internal
cutaneous nerves, and are distributed to the integuments.  The
saphenus  nerve is a branch of the anterior crural, that accom-
panies the femoral artery till the latter perforates the adductor
tendon, after which it accompanies the saphena vein to  the foot,
giving off in its, course branches to the integuments of the inner
side of the leg, and to the upper and inner parts of the foot.
   The obturator branch accompanies the obturator artery, and
passing out at the obturator foramen, is  distributed to the
adductor and obturator  muscles.

                       Sacral Nerves.
   There are  generally  five pairs of sacral  nerves,  sometimes
however there are six.  Their anterior fasciculi  unite with a
part of the last  dorsal, to form the sacral or sciatic jilcxits,
which is situated  at the side of the rectum, in front of the pyri-
formis muscle.
   A number of branches are given off from the plexus,  of which
a few small ones go to the viscera and muscles within the pelvis.
There  are also given off the two glutei nerves which pass out at
the sciatic notch,  and are distributed to the glutei muscles; the
inferior long pudendal, which winds around  the  tuberosity of
the ischium, and  is distributed to the integuments of the peri-
neum ; the posterior cutaneous, which is distributed to the integ-
uments on the back of the thigh and leg;  and  the  super Un-
ion g pudental or internal pudic, which accompanies the internal
pudic  artery,  and  supplies the organs of generation  and the
perineum.
       24 
174
THE SYMPATHETIC NERVE.
   The great sciatic, or ischiatic nerve, also arises from the sacral
 plexus.  It is much the largest nerve in the body, and passing
 out from the pelvis under the pyriformis muscle, it  descends
 the back part of the thigh about half way to the knee, and then
 divides into two large branches, called peroneal and popliteal.
 In its course the sciatic gives off several branches to the integu-
 ments and muscles of the upper part of the thigh.
   The popliteal nerve continues straight  down to  the middle
 and posterior part of the knee joint, and at the head of the tibia,
 divides into the external peroneal and  the anterior  tibial, the
 first of which descends upon the fibular side of the  leg  to the
 foot and ankle, and the last passes down in front of the inter-
 osseous ligament, and is distributed to the muscles upon the
 foot.   The posterior tibial nerve is a continuation of the popli-
 teal, and descending the  back  part  of the leg  along  with the
 posterior tibial artery to the sole of  the foot, divides  into the
 external and internal  plantar  nerves  which supply the sole.
 The external saphenus is  also a branch of the popliteal, near
 the ankle it becomes superficial, and is  distributed  to the exter-
 nal ankle and foot.

                  The Sympathetic Nerve.
   The sympathic nerve consists of two series or chains  of gang-
lia placed on either side of the lateral part of the bodies of the
vertebrae, and extending  from the  base of the cranium to the
coccyx. With the exception of the neck, there is a ganglion for
each intervertebral space;  the ganglia are united to  each other
by nervous cords, and send off numerous  filaments to the adja-
cent organs.  Each ganglion is considered as a distinct nervous
centre.  This nerve supplies all the internal organs, and by
means of plexuses is connected and distributed with all the other
nerves of the body. Besides the ganglia  situated along the spine,
there are  others  placed  about  some of the large vessels of the
abdomen, and also in other parts of the body.
   In the cranium are five ganglia belonging to the sympathetic,
viz. the ganglion of Ribes, situated upon the anterior communi- 
THE SYMPATHETIC NERVE.
175
eating artery, and connected with the carotid plexus by means
of a filament of the sixth nerve.  The carotid plexus surrounds
the carotid artery in the carotid canal, and is joined by the deep
petrous branch of the vidian nerve;—the lenticular ganglion,
situated between the optic nerve and the external rectus muscle,
and communicating with the nasal nerve, a branch of the  third
pair,  and  with  the carotid plexus;—the spheno - palatine or
MeckeVs ganglion, which gives off  the vidian nerve, the  deep
petrous portion of which, as  mentionned, joins the carotid plexus,
and the superficial petrous joins the submaxillary ganglion; this
ganglion also communicates with  the superior maxillary nerve,
and from it the palate, gums, and fauces, are supplied.  A small
oval ganglion,  called the otic ganglion, is attached to the inner
Burface of the inferior maxillary nerve below the foramen ovale,
from  which communicating  branches go to the superior and in-
ferior maxillary, and to the vidian and tympanitic nerves, and
which also supplies the  tensor  tympani, and the tensor palati
muscles.  A ganglion, called the ganglion of Laumonier, is also
frequently found in  the carotid plexus.
   In the neck are  three ganglia, called  the  superior, middle,
and inferior cervical.  The first  is  long and spindle shaped; it
is situated along the sides of the third and fourth cervical verte-
brae,  behind the sheath of the vessels of the neck.  Its branches
are numerous, and communicate with the first, second, and third
cervical nerves,  with the carotid  plexus and the second cervical
ganglion, with the facial eighth and ninth pair, and the pharyn-
geal  plexus,  and with  the  cardiac  ganglion,  by means of  the
superior cardiac  nerve.
   The middle cervical  ganglion is smaller and  more flattened
than  the preceding; it is  placed in  front of the fifth or sixth
cervical vertebra. In some  instances it is wanting.  It has, also,
numerous connections;  its  branches join the anterior fasciculi
of the third,  fourth, and  fifth  cervical nerves,  and  also  the
superior  and inferior cervical ganglia and  the middle cardiac
plexus.
   The inferior cervical ganglion is placed near the head of the 
176
TIIE SYMPATHETIC  NERVE.
 first rib and varies in form and size; it is mostly  larger than
 the last. Like the two last, it also gives off numerous filaments;
 it is  connected with  the  sixth, seventh, and eighth nerve, and
 from  it proceeds the inferior cardiac  nerve,  which joins  the
 middle cardiac nerve and  the cardiac plexus.
   The cardiac plexus is situated beneath the arch of the aorta.
 It is formed almost entirely by branches from the three cervical
 ganglia, the most of them coming from the middle one,  or  the
 middle cardiac nerve.  It is a single plexus, formed by the  nerves
 from  both sides of the neck.   Filaments from  the  par vagum
 and the descendens  noni nerves are also blended with it.  From
 this plexus the heart is supplied with nerves.
   In  the thorax are twelve ganglia, which are situated  at  the
 commencement of each intercostal space near the  heads  of  the
 ribs.  They are smaller than the cervical ganglia, and are con-
 nected with each other, and also with the anterior  fasciculi of
 the spinal nerves.
   The great splanchnic nerve is formed by filaments derived
 from  the sixth to the tenth ganglion; it descends through  the
 posterior mediastinum,  and  penetrating the diaphragm along
 with the aorta, forms on each side of the aorta  a large ganglion
 composed  of a number of smaller ones, called the semilunar
ganglions.
   The small splanchnic nerve is derived from the tenth and
 eleventh thoracic ganglia,  after passing through the diaphragm,
 it joins the semilunar ganglion and the  renal plexus.
   The solar plexus  is a network of nerves situated on the sides
 of the aorta,  and  extending  downwards as far as the renal
arteries.  It is composed of the several filaments connecting  the
semilunar ganglion. From it proceed a number  of smaller gang-
lia, which accompany  the several  arteries. The diaphragmatic
plexus accompanies the phrenic arteries; the superior coronary
plexus accompanies the corresponding artery to  the stomach •
the splenic plexus accompanies the splenic artery to the spleen,  &c.
The superior and inferior mesenteric, the renal plexuses, &c,
are distributed in the same manner. 
           PHYSIOLOGY OF  THE NERVOUS SYSTEM.       177

  Along the sides of the lumbar vertebrae are placed the lumbar
ganglia, generally  five in number.   They are  also united to
each other, and to the spinal nerves.
  The sacral ganglia,  mostly three in number,  are situated on
the anterior face of the sacrum.  The lumbar and sacral ganglia
unite with branches from  the  lumbar and aortic plexuses, and
form the hypogastric plexus,  from which all the pelvic viscera
are supplied.

            Physiology of the Nervous  System.
   The certcbrum.—In the  cerebral hemispheres, the highest
and most important of the functions of the animal economy—
those of the mind—are seated.  In  them the faculty of atten-
tion, or the power of directing the mind to  impressions made
on  the senses, resides.  The cineritious or gray matter which is
found in the convolutions on the periphery of the  cerebrum, is
the portion which possesses these elevated functions. This gray
matter, wherever found, whether in the brain and spinal mar-
row, or in the ganglions along the course of the nerves, is con
sidered as a nervous centre,  or the generator  of nervous  in-
fluence, while the white or medullary matter carries this influence
to the different parts of the body.
   The more numerous and complex the  convolutions in gene-
ral, the greater the degree of intelligence.
   In infants they are imperfectly developed, and their increase
is proportionate to the mental improvement;  if  their  growth
be arrested by any cause,  the mental powers are feeble.  Idiots,
besides having small  brains,  have but a limited development
of the convolutions.  The arrangement of the brain into convo-
lutions admits of a large surface of cineritious matter in  a small
space. It also  allows of a  more ready access to the  blood-vessels
on  the one side, and a more free communication on the  other,
with the fibres by which its influence is distributed.  The entire
surface of a human cerebrum  of average  size, when the convo-
lutions are unfolded,  has  been estimated  to  be equal to about
670 square inches. 
178       PHYSIOLOGY OF THE NERVOUS SYSTEM.
  The hemispheres possess but little or no sensibility, they may
be wounded, and partially or entirely removed, without  giving
rise to pain;  when severely injured, however, a state of stupor,
attended by  general  functional derangement, mostly  results.
Instances have occurred in which portions of the cerebrum  have
been removed without destroying life or impairing the intellect.
   The cerebellum.—With respect to the functions of this portion
of the brain there is much diversity of  opinion;  the majority
of observers, however, agree in regarding it as the  seat of the
animal or lower  propensities.  It is urged  in support  of this
view, that in individuals who have given free indulgence to their
passions, the relative size of this organ is much increased.
  On the other hand, some  contend that is has  but little  or
nothing to do with these propensities, but that its function is to
regulate and harmonize the  muscular  movements, especially
those of a  voluntary character.  Like the cerebrum, the  cere-
bellum is void of sensibility.
  The medulla  oblongata.—Placed intermediate between the
brain and  spinal marrow, the medulla  oblongata serves  as a
medium  through which they act on each other.  The  corpora
pyramidalia, or anterior pyramids, connect  the motor fibres of
the cerebrum with the anterior lateral columns of  the spinal
cord; near the lower extremity of the medulla oblongata, these
fibres decussate,  or cross from side to side, a large portion of
those, coming from the right side of the  cerebrum, passing over
to the left side of the cord, and vice versa.  Hence the frequent
occurrence of paralytic affections on the side  of the body opposite
to that affected  in the brain.  It  is also alleged that,  besides
being  the point  at which sensation  terminates and  excitement
to motion begins, the medulla oblongata possesses the power of
originating motion in  itself, independent of the cerebrum, and
that it presides,  especially, over respiration  and deglutition.
   The medulla spinalis.—The functions of the spinal cord  are
to convey nervous influence to and  from  the brain, and  also to
originate nervous influence independently of the brain.   All  the
nerves  of the body are united into one common trunk in  the 
PHYSIOLOGY  OF THE NERVOUS  SYSTEM.       179
white or medullary matter of the cord; though each filament of
every nerve runs a separate and distinct course from its starting
point to its  termination.  Hence the brain influences not only
the nerves at the base of the cranium, but all the spinal nerves
through the  medium of  the  spinal cord.  As  previously  men-
tioned, the  spinal nerves arise  by two roots from the anterior
and posterior columns of the spinal cord; a part of the fibres of
the  posterior root, which is distinguished by having a ganglion
on it, pass on to the brain conveying impressions to this organ;
and part terminate in the gray matter of the spinal cord, con-
veying impressions to it.  This root is called the sensory root;
it is also the afferent root.  The  anterior is the efferent or motor
root; part of its fibres come from the brain, conveying voluntary
motion, and part of them originate  in the gray matter  of the
spinal marrow.  To these fibres  of both roots, which appear to
act independent of the brain, constituting with the gray  matter
of the  spinal cord*a distinct nervous centre, the term  reflex
system has been applied.
    Thus it will be seen  that each nerve has  four  sets of  fibres:
 one set, called sensory, passing upwards to the brain, conveying
 sensations  to that organ; a second set, called motor, conveying
 the influence of volition and emotion from the brain; a  third
 set, called excitor, terminating in the spinal cord and conveying
 impressions to it; and a fourth set also of motor fibres, conveying
 the motor influence from the spinal marrow to the muscles.
    In  the reflex system,  or that of which the spinal  cord  is the
 centre, it will be understood that  the cord  has the power  of
 reflecting the  action of the sensitive upon the motor  nerves,
 without itself possessing sensation, that being a faculty which
 belongs exclusively to the brain.
    The sympathetic nerve.—This nerve is both  motor and sen-
 sory ;  it exercises  a controlling influence over the involuntary
 functions, and being connected  also with the cerebro-spinal sys-
 tem, it brings the organic functions in relation to the animal. 
180
SENSATION.—SENSE  OF TOUCH.
                         Sensation.
   Sensation is defined to be "the perception of an impression;"
it is to the brain alone that this faculty belongs, hence the term
sensorium is often applied to  this organ.  There are two kinds
of sensations,  one internal, the other external;  the  first  arise
from impressions  made within  the body,  as the  sensations of
hunger or thirst, or such as arise from some  temporary want of
the system; the second are those which arise from impressions
made on the external surface of the body, as the sense of touch
or sight.  Sensation occurs in  the  brain, and not in the part
impressed.
   Sensations are likewise divided into general and special.  By
general sensation, which is distributed all over the body, we feel
those impressions  made by surrounding objects, which produce
the various modifications  of pain  and pleasure,  variations  of
temperature, and the sense of contact and resistance.  By special
sensation is understood that which arises from impressions of a
peculiar  character upon  nerves  which are adapted to receive
them alone.  Each nerve of  special sensation requires its own
peculiar stimulus  to call it into action, and is consequently in-
capable of taking part in the  action of another.  Thus  light is
required  for the eye, sound for the ear, &c.  Nerves  of  special
sensation  have no general sensibility, they may be wounded
without causing the individual any pain.
   There  are five special senses, viz. touch, taste, smell, hearing,
and seeing.

                     Sense of Touch.

   This sense enables us to become acquainted with the hardness
or softness, the roughness or smoothness, shape, size, and weight
of a body.  The idea of resistance would seem to be the only
idea conveyed  to the mind by the sense of  touch, as by it these
properties of  bodies  are made  known.  The sense of touch is
more highly developed in the lips,  tip of the tongue, and the
palmar surface of the extremities of  the fingers, these parts being 
SENSE  OF TASTE.
181
abundantly supplied with nerves  of  general sensation,  than in
other parts of the body;  it is also  more generally distributed
throughout the  animal kingdom than any of the other senses.
The nerves of touch are the posterior roots of the spinal nerves,
and  portions of the  fifth and eighth pairs  of cranial nerves;
these are also the  nerves of general sensation; they are dis-
tributed to the papillae of the  skin, and covered by the epidermis
to protect them from too violent external impressions from ex-
ternal bodies.  All bodies to be cognizable to the  sense of touch,
must be brought into contact with the sensory surface; the only
exception to this  rule is with respect to the sense of tempera-
ture, for which, in the opinion of some physiologists,, there is a
special set of nerves.

                      Sense of Taste.
   The mucous membrane of the  tongue and fauces is the organ
of taste, the anatomical character of which has been previously
described.
   As in the sense of touch, so in that  of taste,  the substances
to be examined must be brought in contact with the organ.
When substances having a strong savour are brought in contact
with the tongue, the papillae become erect and turgid, giving to
the surface of the organ a decided roughness.  For the exercise
of this  function it is necessary that the substance to be tasted
should be soluble; otherwise  the feeling of  contact merely is
excited.  Impressions of  taste remain longer than those of the
other senses;  though the after-taste may be different from the
original.
   There is no special nerve of taste ; the  tongue being supplied
by the  fifth  and  eighth pairs,  which would seem  to  convey
impressions of taste as  well  as  give to  the tongue its general
sensibility.  The first of these nerves is distributed more to the
front, and the second more to the back of the organ; those im-
pressions which produce nausea are conveyed by the latter. The
motions  of the  tongue are performed  through the ninth pair,
though this nerve  has nothing to do with  the sense of taste; as 
182
SENSE  OF SMELL.
its division causes loss of motion of  the organ,  without at all
impairing the special sense.
  Both the senses of touch and taste are deadened by cold air;
the latter  is also considerably impaired  by any injury  of the
sense of smell.

               Sense of Smell, or Olfaction.
  The nose is the organ of smell; it consists of two portions,
one external, projecting upon the face,  the  other  an internal
cavity.  The external portion is formed  by the nasal bones, the
nasal process of the superior maxillary bones, by five cartilages,
and by the integument.  The bones have been already described.
Two of the cartilages  are  placed on either side, and one in the
middle; the latter constitutes the cartilaginous septum between
the nostrils, and  is thick, flat, and triangular.  The lateral car-
tilages are also triangular, and articulate above and behind with
the bone, in front with  the septum,  and below with  the alar
cartilages.  The  alar cartilages form  the  lower part of the nose,
called the nostrils;  they are irregularly semi-eliptical, and keep
the  nostrils open.  The mucous membrane lining the  nose is
thick, soft,, and red; it is termed pituitary or Schneiderian, and
is continuous with the mucous membrane of the mouth, Eusta-
chian tube, lachrymal canal, and frontal sinus.  The hairs situated
 at the entrance of the nose are called vibrissas.
   By the sense  of smell we are made acquainted with the
 odorous particles of bodies suspended or dissolved  in the atmo-
 sphere.  Being seated in the nose, at the entrance of the respira-
 tory passages, it serves as a protection against the  introduction
 of injurious matters.   Another use of this sense, and the prin-
 cipal one, is to aid  the  impression of taste in conveying intelli-
 gence of the properties of food.  The sense of smell is limited
 to that portion of the mucous or Schneiderian membrane of the
 nostrils which covers the superior and  part of  the middle tur-
 binated bones, the olfactory nerve being distributed only to this
 portion.   Hence this region is called the olfactory  region.  The
 advantage of having the sense  situated high up in the nostril, 
SENSE  OF HEARING.
183
is to protect it from mechanical injury, and also from the contact
of too cold or too dry air, both of which  impair it very mate-
rially.   Odorous particles are  brought  in  contact  with the
Schneiderian membrane  by the act of inspiration, and  are  so
minute that they can not be detected by the most delicate expe-
riments.  The fifth pair of nerves give to the  mucous membrane
of the nose its general sensibility.
  The sense of smell, like that of taste, is not an intellectual
one; it is however, susceptible of cultivation; individuals by it
are  frequently capable of recognizing others.   It is usually much
more acute in the lower  orders of animals than in man.

              Sense of Hearing, or Audition.
  The ear is the organ of hearing.  It  consists  of three parts;
the external ear, the middle ear or tympanum, and the internal
car.  The external  is  composed of the pinna, which is the
movable part on the side of the head, and the meatus, or canal,
a passage leading from the pinna.  The outer rim of  the pinna
is called  the  helix, within which is a prominence called the
anthelix.   At the upper part this prominence divides,  leaving
a space termed the scaphoid fossa.  The deep, central cup within
the anthelix, is the concha.  A small eminence,  situated at the
end of the helix, and in front of the  concha, and containing a
small tuft of hair, is the  tragus—so named from its resemblance
to a goat's beard.   Opposite  to  this eminence, and below the
concha, is the antitragus. The pendulous portion is the lobe; it
consists of cellular and adipose tissue.  The oval, elastic plate of
fibro-cartilage is  attached in front, by the anterior  ligament  to
the zygomatic process, and behind, by the posterior ligament to
the mastoid process.  Several  small muscles enter into the com-
position of the pinna, but as they are,  comparatively, of but
little importance, their description may be dispensed with.
  The meatus is about  an inch in length ; it  is a bony canal
lined by cartilage, narrow in the middle, and curved downwards.
The skin lining it  is studded with hairs,  and glands which
secrete wax or cerumen. 
184
SENSE  OF HEARING.
   The middle ear, or tympanum, is an irregular cavity situated
 in the petrous portion of the temporal bone, and filled with air
 which enters by the Eustachian  tube; it contains a chain of
 small bones, and openings into the mastoid cells.  In front it is
 bounded by the membrana tympani, or drum of the ear.
   The membrana tympani,  or drum, is a thin, transparent, oval
 membrane which separates  the external ear from the cavity of
 the tympanum.  It is placed obliquely across this cavity, and is
 slightly convex internally, and concave  externally.  It consists
 of three lamina; the external is continuous with the cuticle, the
 internal with the mucous membrane lining the cavity, while the
 middle is strong and fibrous, and attached by its circumference
 to the bone.
   The middle  ear  has two orifices  communicating  with it;
 one, the  fenestra ovalis, leading to  the vestibule; the other,
 the fenestra rotunda, opening into the cochlea; both  of these,
 however, are closed by membranes to prevent the escape of fluid
 contained in the inner chambers.   The Eustachian tube is a
 straight canal, about two inches in length, which empties into
 the pharynx; its commencement  is bony, and  its termination
 cartilaginous.
   The bones of the tympanum  are four in  number, viz. the
 malleus, or hammer, which is imbedded  in the tympanum; the
 incus, or anvil,  somewhat resembling  a molar tooth ;  the  orbi-
culare; and the stapes or stirrup. These bones articulate with
each other in the order named, and are also connected by three
small muscles, called the tensor and laxators tymj>ani, and the
stapedius.  The  contractions and relaxations  of these muscles
move the bones, and relax or make tense the tympanum.
   The internal ear, or labyrinth, is composed  of  three parts,
 viz. the vestibule, the semicircular canals, and the cochlea.
  The vestibule is a small triangular cavity situated within the
wall of the tympanum; into it behind, the semicircular canals
 open by five orifices, and in  front the cochlea by a single one.
 The fenestra ovalis is on its outer wall, and  on its inner are 
SENSE  OF HEARING.
185
several small holes for the passage of a portion of the  auditory
nerve. The aqueduct of the vestibule also opens into it.
  The semicircular  canals are three bony passages,  the  ex-
tremities of which open into the vestibule by five orifices. Two
of these canals are vertical, and one horizontal.
  The cochlea resembles  a  snail shell, and forms the  anterior
portion of the labyrinth; it consists of a bony and gradually
tapering canal about an inch and a half in length, which makes
two turns and a half spirally around an axis called the modiolus.
The canal of the cochlea is divided into two passages by a bony
and membranous plate,  called the lamina  spiralis; these pas-
sages  communicate with each other at the apex of the  cochlea.
The aqueduct of the cochlea  opens  by one extremity into  the
upper part of the canal, and by the other upon the inferior sur-
face of the petrous bone.
  The membranous  labyrinth has the same form as the bony
vestibule, cochlea, and semicircular canals, which cavities it lines;
it consists  of  several layers, and contains a limpid fluid called
after  Cotonius.
  The auditory nerve divides in the internal meatus into two
branches, which ramify through the  membranous labyrinth and
terminate on the inner surface of the membrane.
  The sense of hearing is that function by which the mind takes
cognizance of the vibratory motions of bodies which  give rise to
the phenomena of sound.  These  vibrations may be communi-
cated to  the ear through the air, or through the intervention of
some  solid  substance  brought into  contact with the  organ of
hearing.
  The precise function of all the parts of the  ear is not known.
  The function of the external car is to  collect and  concentrate
sonorous vibrations or sounds, and conduct them inwards.
  The use of the membrana tympani  is  to receive  the sounds
and transmit  them to the  chain  of bones, and also to modify
their  intensity.   It is not, however, essential to hearing as it
may be perforated or destroyed without very materially impair-
ing  the sense.
       26 
186
SENSE  OF VISION.
  The chain of bones serves to  conduct the sounds across the
cavity of the tympanum to the internal ear.
  The tympanum  isolates the chain of bones,  and allows free
vibration to the membranes  at each end of it.   The use of the
Eustachian tube is to admit air into the cavity of the tympanum,
which prevents undue tension of the membrane, by rendering the
pressure on both sides equal; and  to carry off the secretions of
the middle ear which it discharges into the throat.
  In regard to the functions of  the internal ear,  or labyrinth,
but little  is known; in it the sounds reach  the auditory nerve,
and are thus transmitted to  the brain.
  The idea of  the distance  and direction of sounds is mostly
acquired by habit.  The acuteness of hearing varies very  much
in different individuals,  and  may  be much increased  by culti-
vation.
                     Sense of Vision.

  By this sense we are enabled to perceive the  form, size, color,
position, &c, of the bodies  which surround us.   The medium
through the agency of which this is accomplished, is called light.
The eye is the organ of sight.
   The globe, or ball of the eye, is a spherical body about an inch
in diameter, from before  backwards and somewhat less  trans-
versely.   It is surrounded  by a fibrous membrane continuous
with the sheath of the optic nerve behind.
   The sclerotic coat is a dense, white,  fibrous membrane,  which
invests about four-fifths of  the  eye, giving to it its form, and
serving for the attachment  of the muscles.   Behind  it  is per-
forated by the optic nerve.   In front it receives the cornea by a
circular, bevelled edge.
   The cornea is  the transparent, projecting portion which fills
up the circular opening in the anterior part of the sclerotica; it
constitutes  about one-fifth of the eye-ball,  and is composed of
several lamina, or layers.
    The choroid coat is a thin vascular membrane which lines
 the sclerotica, and is of precisely  the same  extent as that tunic. 
SENSE  OF VISION.
187
It consists of three layers, and is filled with black coloring matter
called pigmentum nigrum.
   The ciliary processes  are situated at the anterior portion of
the choroid coat surrounding the lens.  They consist of seventy
or eighty short triangular folds.
   The iris is a thin circular membrane, varying in color in dif-
ferent  persons,  hence its  name, forming  a vertical septum, or-
partition, between the anterior and posterior chambers of the eye.
In its centre is an opening, called the pupil.  Its posterior sur-
face is  in contact with the ciliary  processes, and thickly coated
with pigmentum nigrum.  Its external border is attached to the
ciliary ligament at the base of the  ciliary processes.
   The  retina is a  soft  white membrane, situated within the
choroid coat; it  extends from the optic  nerve behind to ter-
minate in  an irregular edge  around the centre of the cilia in
front.   Internally it is in  contact  with the vitreous humor.  It
is a nervous structure, and  generally considered as an  expansion
of the optic nerve.   This nerve enters the ball of the eye on the
inner side of its axis;  and through it the central artery of the
retina enters, and after passing through the vitreous humor, is
distributed  to  the retina and  lens.   The point where the optic
nerve is connected with the retina is incapable of vision. Im-
mediately at this point, also, there exists upon  the retina a yel-
low spot, called after Soemmering.
   A thin membrane between the choroid coat and the retina, is
the membrana  Jacobi.
   The aqueous humor is a transparent, albuminous fluid,  filling
the chambers of the eye.  The anterior chamber is  the  space
 between the cornea in front, and the iris and pupil behind; the
 posterior chamber is between the iris and pupil in front, and the
 crystalline lens and ciliary processes behind. Both chambers are
 lined by a delicate membrane which secretes the aqueous humor.
 If the  aqueous humor  is  by accident discharged,  it will  be
 replaced again  without loss of sight.
    The crystaline lens is placed immediately behind the pupil,
 and is surrounded by the ciliary processes; it is a double convex 
188
SENSE OF VISION.
lens, with the posterior surface more convex than  the anterior.
It is soft and transparent, and  composed of concentric laminae
or layers which increase in hardness as they approach the centre.
The lens is invested by a transparent membrane, called its cap-
sule.  In childhood it is spherical, and in old age it is flattened.
   The vitreous humor is  more dense than the aqueous, being of
a jelly-like consistence.  It is transparent and globular in form,
constituting  the  principal bulk of the eye.  It is held in cells
formed by  a delicate  membrane,  called  the  hyaloid.  If the
vitreous humor  is let out, it cannot be restored, and  the eye is
entirely destroyed.
                         Fig. 30.
  Fig.  30.  An antero-posterior vertical section of the eye.  1 The scle-
rotic coat; 2 the cornea; 3 the  choroid coat; 4, 5 the ciliary body and
processes;  6 the iris; 7 the pupil;  8 the retina; 10 anterior chamber;
11 posterior chamber; 12 crystalline lens; 13,14 vitreous humor; 15 central
artery of the retina; 16 optic nerve.

  The eyebrows are elevations of integument, covered with stiff
short hairs : they protect the  eye from too vivid light and  from
the perspiration that accumulates on the forehead.
  The eyelids or palpebrae,  are composed of skin, muscular
fibres,  and  cartilage;  the  latter, called tarsal cartilages, are
small  and crescentic in shape, and  placed  in  the edges of the
lids; they serve to preserve the shape of the lid. When the lids
are in contact, they have a triangular canal between them. 
SENSE  OF VISION.
189
  The cilia, or eyelashes  are  short, curved hairs  placed  in  the
margins of the lids to protect the eyeball.  A mucous membrane,
called the conjunctiva, lines  the lids, and also extends over the
anterior surface of the  ball.
  The Meibomian glands are small bodies, twenty or thirty in
number,  placed between  the  conjunctiva  and  the inner  surface
of the lids.  They discharge a viscid fluid by numerous orifice
along the edges of the  lids, and their secretion prevents the over-
flow of tears at night.
  A small red elevation in the internal angle of the eye, about
the size of a grain of barley, is the caruncula lachrymal is.   It
consists of a number of small glands.
  The lachrymal gland is  situated at the upper and outer  por-
tion of the orbit; it is of a light  pink color,  and about the size
of a filbert.  It secretes the tears,  which are discharged through
ten or twelve ducts opening along  the edge of  the upper lid.  By
this secretion the eye is constantly kept moist.
  The lachrymal canals, one for each lid, commence by a very
minute orifice, called puncta lachrymalia, near the inner angle
of the eye.  They conduct the tears into the lachrymal sac.  The
lachrymal sac is  the enlarged upper extremity of the nasal duct.
This latter is a canal,  about  three-fourths of an inch  in  length,
passing downwards and  backwards from  the inner angle of the
eye through the bones of the face to the inferior meatus of the
nose.  It carries off  the  tears.
  The movements  of the  eye  are performed  by six muscles,
which arise from the walls  of the orbit, and are inserted  into
the sclerotic coat. Four of them are straight,  and are called the
superior, inferior, internal, and external: and  two  are  oblique
—a superior and inferior.   The superior oblique muscle plays
over a tendinous pully attached to the upper margin of the orbit.
   In order to comprehend  fully  the functions of the different
parts of  the eye, a knowledge of  the laws of  light and optics is
necessary,  for which the reader  is referred to the  works  of
natural philosophy, as these subjects  belong rather to  natural
philosophy than  to physiology. 
190
SENSE OF VISION.
  The use of the sclerotic coat is  to give form to the body of
the eye, and also to protect the inner and more delicate parts.
  The choroid coat serves chiefly to transmit the nerves and
blood-vessels.
  The pigmentum nigrum on the inner surface of the choroid
coat absorbs  the rays of light after they have made their im-
pressions on the retina.
  The use of the iris  is  to  regulate the quantity of light ad-
mitted through the pupil, which it is enabled to do by its power
of contraction and expansion.
  The aqueous humor, crystalline lens, and vitreous humor, are
transparent media through  which the rays of light pass to reach
the retina; their office  is  to  refract rays of light so that they
will fall upon the retina in the most favorable manner; the most
of the refracting power is possessed by the lens.
  The use of the retina is to receive the impressions of light,
and transmit them to the brain.
  In near-sighted persons the refracting power of the eye is too
great, the rays of light being brought to a focus before reaching
the retina. This defect is remedied by the use of a double con-
cave lens. In far-sighted persons, on the contrary,  there  is not
sufficient refractive power,  and the focus is formed behind the
retina.  To  obviate  this defect,  convex lenses should be used
to concentrate the rays.  The former defect, that of near-sighted-
ness or myopia commonly occurs in young persons, and is often
corrected  by age; the latter, far-sightedness or presbyopia, is
most frequently met with in persons somewhat advanced in years.
  The fifth pair of nerves  furnishes the eye with general sensi-
bility ; the optic  nerve being a nerve of special sensibility only. 
INDEX.
A.		Cervicalis descendens	page 90
		Chlorine . . . .	. 14
Abductor brevis	Dage 100	Chondrine	. 12
longus	. 100	Circulatory system .	. 137
magnus	. 100	Circumflexus .	. 107
minimi digiti manus.	. 98	Clavicle .	. 108
minimi digiti pedis .	. 105	Coccyx .	. 26
pollicis manus .	. 97	Comparative Anatomy	7
pollicis pedis	104, 105	Physiology	7
Abductors	. 98	Complexus	. 90
Albumen ....	. 11	Composition of bone	. 22
Anatomy and Physiology	9	Constrictor isthmi fauciui	a . 109
Anconeus....	. 93	Coraco brachialis	. 93
Astragalus	. 59	Corrugator supercilii	. 78
Azygos uvulae .	. 107	Cranium .	. 33
		Cremaster	. 86
B.		Crureus .	. 99
		Cuboid bone	. 59
Biceps flexor cruris .	. 101	Cuneiform	. 51
flexor cubiti	. 93	Cuticle, or Epidermis	. 71
Blood-Vessels .	. 140		
Bone ....	. 15	D.	
Bones of the face	. 38		
of the foot	. 58	Deltoid muscle	. 92
of the fore-arm	. 50	Depressor anguli oris	. 79
of the hand	. 51	labii inferioris .	. 79
of the head	. 33	labii superioris alseqi	le nasi 79
of the leg .	. 56	Development of bone	. 21
of the lower extremitie	s . 55	Diaphragm	. 86
of the metatarsus	. 60	Digastricus	. SI
of the toes	. 61	Dorsal, or thoracic nerve	s .172
of the trunk	. 23	vertebrae .	. 25
of the upper extremiti	js . 47		
Braebialis internus .	. 93	E.	
Branches of the abdominal	aorta 145		
of the thoracic aorta	. 145	Elaine	. 12
Buccinator	. 77	Elasticity of tissues	. 19
		Elementary composition	of man 10
c.		Ethmoid bone .	. 38
		Extensibility of tissues	. 19
Calcium, or Lime	. 14	Extensor brevis digitoru	m pedis 104
Carbon ....	. 13	carpi radialis brevis	. 95
Carpus ....	. 51	carpi radialis longus	. 95
Cartilage ....	15, 63	carpi ulnaris	. 95
Caseine ....	. 11	digitorum communis	96
Cellular, or areolar tissue	. 17	longus digitorum pe	dis . 102
Cervical nerves	. 171	major pollicis manu	s . 96
vertebrae .	. 24	minor pollicis manu	3 . 96
 
192
INDEX.
Extensor ossi metacarpi pollicis
      manus   .     .     .  page 96
    proprius pollicis pedis    .  102
External cuneiform ...   60
Facial and auditory nerves, or
      seventh pair
Fascia superficialis
    transversalis
Fibrine
Fibro cartilage
Fibula
Flexibility of tissues
Flexor accessorius  .
    brevis digitorum pedis
    brevis minimi digiti pedis
    brevis pollicis manus
    brevis pollicis pedis .
    carpi radialis
    carpi ulnaris
    longus digitorum pedis per
      forans
    longus pollicis
170
 40
 84
 80
 11
 5:!
 58
 19
104
104
105
 97
105
 94
 94

103
103
    longus pollicis pedis .   95, 104
    parvus minimi digiti manus  98
    profundus digitorum  perfo-
      rans    ....   95
    sublimis digitorum perfora-
      tes     ....   95
Follicles.....16
Fontanels.....44
Formation of callus ...   23
Frontal bone  ....   33

                G.
Ganglions
Gastrocnemius.
Gelatine ....
Gemini  ....
General remarks on the head
Genio hyoideus
Glands   ....
Glosso pharyngeal, pneumogas-
  tric, and spinal accessory, or
  eighth pair of nerves
Gluteus magnus
    medius
    minimus  ,
Gracilis  .
Gums
H.
Haematosine
Humerus .
 16
102
 12
101
 43
 82
 10
170
101)
100
lot)
100
106
Hydrogen     .     .     .  page
Hyoid bone   ....
Hypo-glossal nerve,  or  ninth
  pair.....
13
47
170
Iliacus internus
Ilium
Indicator .
Inferior constrictor
    maxillary .
    turbinated bone
Infra spinatus scapula
Innominatum .
Intercostales  .
Internal cuneiform
Inter-spinales .
Interosseus muscles
Inter-transversalis
Intestines
Iron .
Ischium  .
 87
 28
 97
109
 42
 41
 92
 28
 83
 60
 91
105
 91
114
 14
 29
                L.

Large intestines
Larynx
Latissimus dorsi
Levator anguli oris
    costarum .
    labii superioris
    menti
    palati
    scapulae
Ligaments
Linea alba
Lips.
Longus colli
Lumbar nerves
    vertebrae  .
Lumbricales
    pedis.
Lunare
          .   116
          .   128
          .    88
     ...    79
          .    92
alaeque nasi   79
          .    79
          .   107
          .    88
          15,  53
          .    85
          .   106
          .    82
          .   172
          .    25
          .    97
          .   104
          .    51
M.
Magnesium
Magnum .
Malar bones
Manganese
Margarine
Masseter .
Membrane
M eta carpal bones
Middle constrictor
    cuneiform .
Motor oeuli  externus, or sixth
  pair of nerves
 14
 52
 41
 14
 12
 80
 16
 52
109
 60

169 
INDEX.
193
Motor oculi, or third pair of		Orbits of the eye . . page 45	
nerves .... page 169		Organs of Digestion	106
Mouth.....	106	of respiration .	128
Multifidus spinae	90	Os calcis.....	59
Muscles.....	. 15	Oxygen .....	13
of the abdomen	84		
of the arm	93	P.	
of the back	87		
of the foot	104	Palate.....	107
of the fore-arm	93	bones ....	40
of the hand	97	Palato-pharyngeus .	107
of the head and neck	78	Palmaris brevis	97
of the leg ....	102	Parietal bones ....	34
of the lower extremities .	99	Parotid gland ....	108
of the pharynx.	109	Patella.....	58
of the shoulder.	92	Patheticus, or fourth pair o:	
of the soft palate	107	nerves .....	169
of the trunk	83	Pectineus....	100
of the upper extremities	92	Pectoralis major	83
Muscular tissue	18	minor	83
Mylo-hyoideus	81	Peculiarities of the foetal circu-	
		lation ....	156
N.		Pelvis ....	28
		Periosteum	22
Nasal bone	40	Peritoneum	111
cavities	45	Peroneus brevis	102
Nerves ....	. 16	longus	102
of the cranium .	168	tertius	102
Nervous system	. 162	Phalangeal bones	. 52
tissue	. 18	Pharynx and CEsophagus	. 108
Nitrogen ....	. 13	Phosphorus Physical and vital properties o	. 23 f
O.		tissues ....	. 18
		Physiology of digestion .	. 122
Obliquus externus .	. 85	of the circulation	. 159
inferior	. 91	of the nervous system	. 177
internus .	. 85	of the respiration	. 134
superior	. 91	Pisiform bone .	. 41
Obturator externus .	. 101	Plantar interossei	. 105
internus	. 101	Plantaris ....	. 103
Occipital bone .	. 34	Platisma myoides	. 80
Occipito frontalis	. 78	Popliteus ....	. 103
CEsophagus	. 109	Porosoty of tissues .	. 22
Of the abdominal viscera	. 110	Potassium	14
articulations	62-69	Pronator quadratus .	. 95
bones	. 20	radii teres.	. 93
hair ....	. 72	Psoas magnus .	. 87
muscles	. 76	parvus	. 87
nails ....	. 72	Pterygoideus externus	. 80
sebaceous glands	. 71	internus	. 80
skin ....	. 69	Pubis ....	29
teeth ....	. 74	Pyramidalis	. 86
Olfactory nerves, or first pair	. 168	Pyriformis	. 101
Omo-hyoideus .	. 81		
Opponens pollicis	. 97	Q	
Optic nerves, or second pair	. 169		
Orbicularis oris	. 80	Quadratus femoris .	. 101
palpebrarum	. 78	lumborum .	. 87
27			
 
194                         INDEX.
               R.

Radius   ....   page 50
Rectus abdominis  .
    anticus capitis major
    anticus capitis minor
    capitis lateralis.
    capitis posticus major
    capitis posticus minor
    femoris    .
Remarks on the lower extremities
    on the upper extremities  .
Rhomboideus major
    minor    ....
Ribs......

               S.
31
Sacral nerves .	173		
Sacro lumbalis and longissimus		Temporal bone	
dorsi.....	89	Temporalis . .	
Sacrum.....	26	Tensor vagina femoris	
Salivary glands of the mouth .	108	Teres major	
Sartorius muscle	99	minor	
Scalenus anticus	82	The anterior tibial artery	
posticus . . . .	82	aorta and its branches	
Scaphoid ....	59	arteries	
Scaphoides	51	bladder	
Scapula ....	47	brain	
Semi-membranosus .	101	cerebellum	
spinalis cervicis	90	cerebrum .	
spinalis dorsi .	90	external iliac artery	
tendinosus	101	femoral artery .	
Sensation.....	180	gall bladder	
Sense of hearing, or Audition	183	heart	
of smell, or Olfaction	182	kidneys	
of taste . . . .	181	liver .	
of touch .	180	lungs	
of vision .	186	lymphatics	
Serratus magnus	83	mediastinum	
posticus inferior	88	medulla oblongata	
posticus superior	88	pancreas .	
Silicum ....	14	pleura	
Sinuses of the dura mater	153	pons varolii	
Small intestines	114	popliteal artery	
Sodium ....	14	portal vein	
Soleus ....	102	posterior tibial .	
Sphenoid bone'	36	primitive, or common	iliacs
Spinalis dorsi .	90	prostate gland .	
Splenius ....	88	spinal marrow .	
Stearine ....	12	spinal nerves	
Sterno-cleido-mastoideus.	80	spine.	
hyoideus .	81	spleen	
thyroideus	81	sympathetic nerve	
Sternum ....	. 30	thymus gland .	
Stomach ....	. 12	veins.	
Structure of bone .	. 27	Thigh bone, or Femur	
Stylo-glossus .	. 81	Thorax	
Stylo-hyoideus.
    pharyngeus
Subclavian artery and its
  sions
Subclavius
Sublingual gland
Submaxillary  .
Subscapulars  .
Sulphur  .
Superior maxillary bones
    radii brevis
    radii longus
Supra-renal capsules
    spinatus scapula
Sutures  of the head
Synovial membrane.

                T.
 page  81
   81, 109
divi-
      142
       83 
INDEX.
195
Thyro-hyoideus
Thyroid gland .
Tibia
Tibialis anticus
    posticus
Tongue  .
Trachea  .
Trachelo-mastoid
Transversalis abdominis
    cervicis
    pedis.
Trapezium
Trapezius.
Trapezoides
Treatise on Anatomy and
  siology .    .     .
Triangularis sterni .
Triceps extensor cubiti
Trifacial, or fifth pair of nerves
page 81
    131
     56
    102
    104
131
 90
 85
 90
105
 52
 87
 52
Phy
  7
 83
 93
172
Ulna .... page 50	
Unciform bone.	52
Unguiform bones	40
V.	
Vastus externus	99
internus	99
Vegetable Physiology	7
Veins of the abdomen	155
of the head and neck	151
of the lower extremities	155
of the upper extremities	154
Vessels ....	16
Viscus ....	17
Vital properties of tissues	19
Vomer ....	41
Zygomaticus major .
79 
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