HINTS 
elementary physiology 
ON .CRANIUM. 
...MAXILLA. 
,7 CERVICAL VERTEBR/E. 
.CLAVICLE. 
..SCAPULA. 
.HUMERUS. 
;,12 DORSAL VERTEBRA:. 
.5 LUMBAR VERTEBR/E. 
jsJLIUM. 
RADIUS. 
I..ULNA. 
PELVIS. 
ISCHIUM. 
PUBES. 
.BONES OF THE CARPUS. 
.BONES OF THE METACARPUS. 
PHALANGES OF THE FINGERS. 
...FEMUR. 
...PATELLA, 
...TIBIA. 
FIBULA, 
BONES OF THE TARSUS. 
..BONES OF THE METATARSUS. 
..PHALANGES OF THE TOES. HINTS 
ON 
ELEMENTARY PHYSIOLOGY 
BY 
FLORENCE A. HAIG-BROWN 
WITH 21 ILLUSTRATIONS 
PHILADELPHIA 
P. BLAKISTON, SON & CO. 
1012 WALNUT STREET 
1897 PREFACE 
My friend and fellow-worker, Miss Florence A. 
Haig-Brown, has asked me to write a few words by 
way of preface to her “ Hints on Elementary 
Physiology.” Ido so with a double good will, for 
the sake of the writer, and for the sake and memory 
of her sister, Miss Helen Haig-Brown, a very long- 
standing patient and dear friend, who after a 
successful career as Probationer and Sister at St. 
Thomas’s Hospital was taken from us when enter- 
ing on a wider sphere of usefulness. “The Hints” 
are, as is stated by Miss F. A. Haig-Brown, founded 
upon notes taken by the two sisters of the Lectures 
and Demonstrations given by the medical officers 
of St. Thomas’s Hospital entrusted with the duty 
of giving such elementary instruction to the proba- 
tioners as may help to fit them for the discharge of 
their duties in the wards. The sisters seem not 
only to have received instruction, but to have 
made, so to speak, a common fund, and what they 
have acquired and have found useful, the survivor 
has condensed for the help of her successors at PREFACE. 
St. Thomas’s and of her associates at the St. Mary- 
lebone Infirmary. The reception, the interchange, 
and the transmission of the lamps of knowledge 
are, as has long ago been recognised, an orderly 
and effective means for the promotion and for the 
application of Science. This book seems to me to 
embody to the full such a method, Its aspect is 
that of the learner. It registers the impressions 
received by attentive minds in the hours spent in 
the class-room. It is intended clearly to be help- 
ful, but not final or complete, to be useful as a 
guide, available for reference, stimulating in much 
of its terseness and brevity to wider reading and 
study. As an evidence of earnest diligence in 
preparation for what is one of the most responsible, 
and certainly the very hardest possible, occupation 
in life, it calls for all praise and respect. The 
qualities of the book will, I am well assured, com- 
mand the success which I most heartily wish for it. 
William M. Ord. CONTENTS 
CHAP. 
PAGE 
I. PROTOPLASM X 
11. THE FORMATION OF BONE .... 8 
111. THE BONES OF THE SKELETON . . . 15 
iv. the bones of the skeleton (continued) . 23 
V. THE CIRCULATORY ORGANS .... 34 
VI. THE RESPIRATORY ORGANS .... 47 
VII. THE DIGESTIVE ORGANS ..... 55 
VIII. THE EXCRETORY ORGANS .... 66 
IX. THE SECRETORY ORGANS .... 75 
X. THE MUSCULAR AND NERVOUS SYSTEM . . 8l 
XI. THE ORGANS OF SIGHT, SMELLING, HEARING 
AND TASTE 89 
XII. INFLAMMATION 102 
XIII. FOOD AND ITS USES ..... XOg 
XIV. VENTILATION 117 LIST OF ILLUSTRATIONS 
FIG. 
Frontispiece—The Skeleton 
* section through Ossifying Cartilage and Young Bone g 
PAGE 
2. Interior of Right A uricle and Ventricle exposed by the 
removal of a part of their walls ... 36 
3- Diagram of the Circulation of the Blood and the 
4. Diagram of the Portal Vein arising in the alimentary 
tract and spleen, and carrying the blood from 
these organs to the liver 
44 
Absorbent Vessels 
5- The Orifices of the Heart seen from above, both the 
auricles and the great vessels being removed . 43 
6. Diagram of the Respiratory Organs , . 
7. Transverse section of part of the wall of a medium- 
sized Bronchial Tube 
5° 
8. A Dissection of the side of the face, showing the 
Salivary Glands ... q 
9• Diagram of Alimentary Tract, <Bc. . 
!o. Diagram showing the course of the Main Trunks of 
the Absorbing System . . 
Ir' Section of the Kidney of Man . ... 68 LIST OF ILLUSTRATIONS. 
FIG. 
12. Glomeruli of the Kidney with the origin of the Tubuli 
Uriniferi 70 
PAGE 
13. Section of the Skin showing the roots of three hairs 
and two large Sebaceous Glands ... 72 
14. Cells of the Liver . . 77 
15. Portion of the Mucous Surface of the end of the 
Human Ileum ...... 79 
16. Striated Muscle Tissue of the Heart ... 82 
17. Transverse section of Nerve Fibres . . - 85 
18. Ophthalmoscopic view of Fundus of Eye . . . 90 
19. Diagram of the minute changes in Inflammation . 101 
20. Diagram showing the proportion of the principal food- 
stuffs in a few typical comestibles . . .115 HINTS ON 
ELEMENTARY PHYSIOLOGY 
CHAPTER I 
PROTOPLASM 
In order to understand the mechanism of our 
bodies,it is essential to know something of Anatomy, 
which, through dissection, teaches us how the 
various parts are formed and something of Physio- 
logy, which teaches us the functions of the various 
parts; and if we clearly understand the working 
of the body in natural health, we can then group 
more clearly the causes and reason of Pathology or 
disease. 
If we compare any of the higher animals or men 
with the lowest known forms of living being, we 
cannot help being struck with the amazing struc- 
tural complexity of the one and the extreme sim- 
plicity of the other. 
The body of anything living, whether animal or 
vegetable, is built up of cells, which may be com- 
pared to bricks building up its structure. The 2 
ELEMENTARY PHYSIOLOGY 
amoeba is the lowest form of animal life, and is an 
apparently homogeneous lump of soft jelly; but it 
feels, it digests, it breathes, it discharges effete 
matter, it grows, it has the powers of locomotion 
and procreation ; in fact, it fulfils all the primary 
and essential functions of life. Human beings, on 
the other hand, and all higher organisms, are 
supplied with special organs to fulfil these various 
functions: 
(1) With nervous organs. 
(2) With digestive organs. 
(3) With respiratory organs. 
(4) With excretory organs. 
(5) With circulatory organs, &c. 
A cell is composed of Protoplasm (living matter), 
an albuminous fluid, of which the chemical consti- 
tuents are: 
(1) Carbon. 
(2) Oxygen. 
(3) Hydrogen. 
(4) Nitrogen. 
With these are associated in various proportions : 
(1) Sulphur. 
(2) Chlorine. 
(3) Phosphorus. 
(4) Calcium. 
(5) Sodium. 
(6) Magnesium. 
(7) Iron. 
Protoplasm {llthe physical basis of life”) exists 
in the human body as the white corpuscles of the 
blood, which have no wall and no nucleus. It is 
also found in all embryonic tissue, but by a process 
of development, or differentiation, the cells become 
nucleated. A nucleated cell has a Avail of more PROTOPLASM 
3 
condensed protoplasm, and in the centre has a 
nucleus which appears to play an important part 
in reproduction. Cells are always formed from 
one another by multiplication ; they are never de 
novo (spontaneously developed). 
The second stage is aggregation of cells, as seen, 
for instance, in sponges. 
The nucleus divides and a fresh cell is formed, 
and so on ad infinitum. 
Powers of Cells. 
A cell can take in nourishment. 
A cell can secrete and excrete. 
A cell can move. 
A cell can multiply. 
Therefore a cell is an organism, or matter which 
has life. 
Cells vary in character in the different tissues, 
according to the functions they have to perform. 
Some are round. 
Some, long. 
Some, stellated. 
Some, ciliated. 
Some, flaky. 
Cells are divided into different groups : 
(1) Epithelial cells. 
(2) Connective tissue cells. 
(3) Tubular cells. 
Some, oval. 
Each of these is subdivided into several varieties : 
(1) Epithelial tissue cells are characterised by 
the circumstance that the cells which compose them 
are in contact layer upon layer. They vary a great 4 
ELEMENTARY PHYSIOLOGY 
deal according to the situations they occupy and 
the functions they perform. The epidermis, or 
outer layer of skin, consists of epithelial tissue, and 
is entirely protective. It consists of several layers 
of cells, round at the bottom, becoming more 
flattened, and the upper layer becoming flakes. 
In connection with the skin are numerous tiny, 
tubular glands, which are lined with delicate epi- 
thelial tissue; nails and hair are varieties of this 
tissue. 
Such tissue also lines all cavities and all mem- 
branes : 
(i) Synovial membrane. 
(2) Mucous membrane. 
(3) Serous membrane. 
It also lines all ducts, blood-vessels, and 
lymphatics. 
In the stomach and intestines the epithelial tissue 
absorbs as well as protects. 
In the respiratory passages the cells are fur- 
nished with cilia, or small hairs. 
In the glands of the liver, kidneys and skin the 
epithelial cells are globular. 
(2) Connective tissue consists of nucleated masses 
of protoplasm which are often exceedingly minute, 
always surrounded by a wall of some thickness, 
and are either rounded or isolated from one another, 
or stellate, and furnished with processes communi- 
cating with those of the neighbouring cells. 
The essential morphological distinction between PROTOPLASM 
5 
epithelial and connective tissue is, that in the 
former the cells are in absolute contact; in the 
latter they are separated from one another in a 
greater or less degree by some intervening sub- 
stance of either inorganised deposit, or portion of 
the higher living tissues. 
According to the nature and amount of this 
intervening substance, or to peculiarities presented 
by the cells, connective tissue may be divided into 
several varieties. 
(a) Common connective tissue, as found in fasciae 
and tendons ; the protoplasm is scanty and stellate, 
and the intervals, which are large, are occupied by 
wavy bands of white fibrous tissue and more or 
less yellow elastic-fibre, both of which are either 
simple secretions from the living protoplasmic 
masses, or the mummies of defunct cells. 
This variety of connective tissue yields gelatine. 
(b) Cartilage : In common cartilage the cells are 
round or oval and separated from one another by 
a dense, homogeneous, elastic substance, which 
appears to be formed by the progressive thickening 
of the cell walls and by their coalescence. 
This variety of connective tissue yields chon- 
drine. 
(c) Bone : In a transverse section of bone, when 
magnified, we see large round spaces called Haver- 
sian canals, which serve for the passage of blood- 
vessels, lymphatics and nerves from the exterior to 
the interior of the bone. Round the Haversian 6 
ELEMENTARY PHYSIOLOGY 
canals are irregular, dark spaces, called “lacunae ” • 
connecting one lacuna with another are fine lines 
called “ canaliculi ” which also communicate with 
the Haversian canals. The intervals between the 
canaliculi are filled with bone earth; the lacunae 
represent the living bone cells. 
(d) Fat, sometimes called adipose tissue, in which 
the cells contain oil. 
(e) Mucous tissue, as seen in the foetus, in the 
tissue of the umbilical cord, also in the vitreous 
humour of the eye; in this form of connective 
tissue the intervals are filled with mucus which 
contains mucine. 
(3) Tubular tissue is considered a higher develop- 
ment, and is formed by the juxtaposition and 
coalescence of cells, which have in some manner 
undergone a higher process of development. 
Under this head we have nerves, muscular fibre, 
capillary vessels and lymphatics, and complex organs 
such as muscles, bones, glands, brain, heart, liver, 
which are composed of all the various tissues. 
For instance, the muscular fibres are tubular, 
united by fascia which is connective tissue, supplied 
with blood-vessels and lymphatics which are lined 
with epithelial tissue. 
The different organs tend to arrange themselves 
into groups or systems such as : 
(1) Circulatory organs. 
(2) Secretory organs. 
(3) Excretory organs PROTOPLASM 
7 
(4) Digestive organs. 
(5) Organs of locomotion. 
(6) Nervous organs, which govern and control 
all the others. 
The motor cells have always one long fibre which 
enters into muscle and makes it contract, acting as 
a battery and supplying force. 
In order that the cells should properly perform 
their function, the protoplasm of which they are 
composed must be healthy. 
Unhealthy function is soon perceived and gives 
rise to what we call symptoms, meaning signs of 
disease. 
It is by the multiplication of cells without the 
power to control their differentiation that we get 
cell diseases, namely, Tumours. A Tumour is a 
degenerating mass of cells. Enchondroma, a carti- 
laginous tumour. Neuroma, a nerve tumour, and 
when found in the foetus this loss of power brings 
about malformation or fusion of parts. CHAPTER II 
THE FORMATION OF BONE 
Bone is composed of two kinds of constituents 
(1) Organic or animal matter. 
(2) Inorganic or earthy matter. 
The animal material consists of gelatine, albumen 
fibrin, and blood-vessels. 
The earthy material consists of : 
(1) Phosphate of calcium. 
(2) Carbonate of calcium. 
(3) Fluoride of calcium. 
(4) Phosphate of magnesia. 
(5) Chloride of sodium. 
(6) Oxide of sodium. 
In the adult there should be two parts of inor- 
ganic matter to one part of organic matter. In 
children there is a larger proportion of organic 
material, therefore their bones are soft and do not 
fracture so easily, but rather bend. 
Thus in the disease of Pickets, to which young 
children are subject, the bone indeed grows, but 
the inorganic material is not formed and the bones a. Cartilage cells. 
h. Degenerating cartilage cells. 
c. Cell space, empty. 
d. Spiculse of calcareous deposit, 
Fig. 1.—Section through ossifying cartilage and 
young bone. (Cadiat.) 
e. Blood corpuscles. 
/. Osteoblasts. 
g. Ditto of periosteum 
h. Bone cells. ELEMENTARY PHYSIOLOGY 
remain soft and pliable. Such, too, is the case in 
Mollities ossium, when the bones contain too little 
organic material. In elderly people there is a 
larger proportion of inorganic material than in 
younger people ; hence their bones are very brittle; 
they fracture easily and re-union is very difficult, 
as it is the organic material of bone which furnishes 
the plastic material for the union of the divided 
ends. 
Bone is composed of two kinds of tissue, Com- 
pact tissue, the outer layer, which is dense in texture 
like ivory. 
Cancellous tissue, the inner layer, which consists 
of slender fibres like lattice-work. 
Every bone is covered by a fine membrane, called 
the periosteum and lined by a still finer membrane 
called the endosteum. 
Bones are richly supplied with nerves and blood- 
vessels, and these are brought to the bone by means 
of the periosteum. On the surface of the bone 
there are foramina (openings) to be seen, into 
which the periosteum dips so as to allow the passage 
of the nerves and blood-vessels to the interior of 
the bone. 
The periosteum consists of two layers: the 
outer formed chiefly of connective tissue, contain- 
ing a few fat cells; the inner of elastic fibres and 
blood-vessels. THE FORMATION OF BONE 
Uses of Bone. 
(i) Bones determine the general shape and pro- 
portion of the body. 
(2) Bones give attachment to the muscles and 
form levers, by means of which the muscles act 
to move the body from one position to another. 
Bones are considered as both active and passive 
agents of locomotion. 
(3) Bones form cavities for the protection of 
important organs; they must therefore be strong, 
elastic, and light. 
Bones may be classified as ; 
(1) Long Bones, found in the extremities and 
serving for locomotion. 
(2) Flat Bones, as in the head and sternum, 
serving for protection. 
(3) Short Bones, such as the bones of wrist or 
ankle, where strength and limited action are re- 
quired. 
(4) Irregular Bones, as the vertebrae, which 
cannot be classed under any of the preceding 
heads. Long bones have a cylindrical hollow in 
the centre which contains the medulla or marroio. 
Long bones contain yellow marrow, whilst short 
and flat bones contain red marrow. 
Cancellous tissue also contains a red marrow 
which is an organ of physiological importance. 
Bone grows in width by means of 'periosteum. There 
is no periosteum at the end of bone. Bone grows ELEMENTARY PHYSIOLOGY 
in length by means of cartilage, and the point of 
the cartilage at which the bone grows is called the 
epiphysis (growing on). There are about two 
hundred bones in the human skeleton; but more 
than two hundred would be found in a child’s 
body, less than two hundred in an adult’s, for the 
bones coalesce with advancing age. 
Bone enters largely into the formation of joints. 
A Joint is composed of : 
(i) Bone. 
(3) Synovial membrane. 
(2) Cartilage. 
(4) Ligaments. 
(1) Bone is the principal element in joints; in 
long bones the extremities forming the articulation 
are generally enlarged and formed of cancellous 
tissue, covered by a thin layer of compact tissue. 
This outer tissue, called Articular Lamella, differs 
from ordinary bone in having larger lacunae, no 
Haversian canals and no canaliculi. 
(5) Muscles around joint. 
(2) Cartilage appears to the naked eye very much 
like the white inside of a cocoanut, or the hard- 
boiled white of an egg; under the microscope it 
is almost formless, but in certain parts there are 
cells enclosed in capsules ; its use is to act as a 
buffer and to break the shock of movements. It 
has no nerves and consequently no sensation, and 
is devoid of blood-vessels. It receives its nourish- 
ment from the synovial membrane and below from THE FORMATION OF BONE 
13 
the bone itself. (Cartilage and synovial membrane 
are the parts most commonly diseased in a joint.) 
In caries, or ulceration of bone, not only do the 
cartilage and synovial membrane disappear but the 
bone itself decays. If the synovial membrane be 
injured, the cells secrete not only synovia but 
serum. This causes swelling, or “ water in a 
joint.” 
(3) Synovial Membrane is a very thin layer of 
connective tissue, finer than the finest tissue paper. 
It is abundantly supplied with blood-vessels. On 
its surface is a layer of cells which separate the 
synovia from the blood-vessels and pour it on to 
the cartilage, so acting like joint-oil and keeping 
the cartilage smooth ; in connection with the syno- 
vial membrane are hollow fringes which are very 
active in secreting the synovial fluid. 
(4) Ligaments are found in connection with all 
joints; they consist of bundles of white fibrous 
tissue, closely interlaced with each other, present- 
ing a shiny, silvery appearance; they are pliant 
and flexible, but strong and tough, and help to 
bind and keep in place the bones which form the 
joint. 
(5) Muscles, with their extremities or tendons 
are also agents in keeping the joint surfaces in 
their place. 
There are six kinds of joint movement: 
(1) Abduction. 
(2) Adduction. 14 
ELEMENTARY PHYSIOLOGY 
(3) Circumduction. 
(4) Extension. 
(5) Flexion. 
(6) Rotation. 
Joints may be divided into two classes : 
(1) Movable, comprising— 
(a) Ball-and-socket joint (as in the hip). 
(b) Hinge joint (as in the knee). 
(c) Gliding joint (as in wrist and ankle). 
(2) Immovable, where the bones are in direct 
contact, as in the head and face. CHAPTER 111 
THE BONES OF THE SKELETON 
The Skeleton may be divided into three parts : 
(1) The Head (cranium and face). 
(2) The Trunk (thorax and abdomen). 
(3) The Extremities (upper and lower). 
The Bones of the Head are eight in number 
(1) Frontal (front bone). 
(2) Parietal (two side bones). 
(3) Occipital (back bone). 
(4) Temporal (two temple bones). 
(5) Sphenoid (wedge bone). 
(6) Ethmoid (sieve bone). 
The bones of the head are flat and tabular, and 
are intimately connected with each other by means 
of natural sutures (stitches). 
The flat bones of the head consist of three 
layers : 
(1) The outer table. 
(2) Diploe. 
(3) The inner table. 
The outer table consists of dense compact tissue. 16 
ELEMENTARY PHYSIOLOGY 
The diploe consists of cancellous tissue, and acts 
as a buffer. 
The inner table is extremely brittle, like glass, 
hence it is called the vitreous. 
The frontal hone has a fancied resemblance to a 
clam shell; it consists of two plates—the vertical, 
which forms the forehead, and the horizontal, which 
forms part of the roof of the orbit. In the centre 
of the horizontal or orbital plate is the nasal spine, 
to which the bones of the nose articulate ; below 
the spine is the nasal notch ; on either side of the 
nasal spine is the supra-orbital arch, and above the 
arch again is the supra-dliary ridge, which forms 
the eyebrows. 
The nasal notch is for the articulation of the 
ethmoid bone. 
The supra-ciliary ridges are hollow and con- 
nected by cavities with the nose. 
On the outer side of the supra-orbital arch is 
the external angular p>rocess, for the articulation of 
the malar or cheek bones. 
Behind the external angular process is a depres- 
sion for the lachrymal gland. 
Sometimes in the middle line of the vertical plate 
of the bone are seen some sutures, indicating the 
original separation of the two halves of the bone. 
The frontal bone articulates behind with the two 
parietal bones ; in front with the two malar bones ; 
also with the two nasal bones; and with the 
sphenoid and ethmoid bones. THE BONES OF THE SKELETON 
17 
The Parietal hones.—The name is derived from 
a Latin word meaning side-wall. They are situated 
on each side of the vault, the two forming together 
a beautiful arch for the protection of the brain ; 
each is four-cornered, hollowed out from above 
downward, and from front to back. 
They have an outer and inner surface and four 
borders. The outer surface is smooth and dense ; 
the inner surface is less smooth and marked by 
depressions for the convolutions of the brain and 
by numerous grooves for the middle meningeal 
artery. Three of the borders are serrated or 
toothed, the upper borders articulating with each 
other ; the anterior articulating with the frontal 
bone, and the posterior with the occipital bone; 
the lower border is thin and bevelled at the 
expense of the outer table and articulates with the 
temporal bone; at the posterior inferior angle is 
another sinus for the middle meningeal artery. 
The Occipital hone.—This occupies the back and 
base of the skull; it rests upon the upper end of the 
spinal column; it forms one bone with the sphe- 
noid in the adult, and is usually separated by saw- 
ing through the hasilar process which unites them. 
In shape it is very irregular, four-sided, perfo- 
rated near its anterior angle by a large oval hole, 
called the Foramen Magnum ; it has two surfaces, 
four borders and four angles, the exterior surface 
is for the most part tough ; in the middle line is a 
tubercle called the external occipital 'protuberance ; ELEMENTARY PHYSIOLOGY 
on either side of the foramen magnum are oval, 
convex bodies called condyles, which rest in de- 
pressions on the first of the vertebrae ; in front of 
each condyle is a smaller foramen for the passage 
of nerves; behind each condyle is another foramen 
for a vein passing into the lateral sinus; the basil- 
lar process of the bone is its continuation forward 
into the sphenoid, the inner surface is smooth ; 
two ridges run across it, and where they cross they 
form the internal occipital protuberance. 
The occipital hone articulates in front with the 
two parietal and the two temporal bones, and at 
the base with the sphenoid and atlas. The sphenoid, 
or wedge hone, fits in at the base of the skull, in 
front of the occipital bone and behind the frontal 
and facial bones ; it somewhat resembles a bat with 
wings spread and legs hanging down. 
The centre part is called the body, and on either 
side stretch the alee majores; in front of the body 
are the alee minores ; springing from the centre of 
the body and hanging down are the pterygoid pro- 
cesses ; in front of the body is a projection called 
the ethmoidal spine, which fits it into the back of 
the ethmoid. At the roots of the lesser wings are 
small foramina for the passage of the optic nerve. 
On the upper part of the body is a depression 
called the sella turcica, or Turk’s saddle. The 
sphenoid bone sends out processes to touch all the 
other bones of the cranium, and also some of the 
bones in the face. THE BONES OF THE SKELETON 
19 
The Temporal hone is usually divided into three 
portions; a thin vertical division, called the 
squamous portion, at the lower end of which is a 
process running forward named the zygoma ; below 
and behind the squamous portion is a nipple-like 
process called the mastoid; at the inner surface 
and running towards the base of the brain is the 
petrous portion. 
Between the mastoid and zygoma is the externa 
auditory foramen ; exactly behind the zygoma is a 
deep groove called the glenoid cavity, for the 
articulation of the condyle of the lower jaw; 
behind the mastoid process is a groove, the jugular 
fossa ; in the petrous portion is the inner auditory 
foramen. 
The Ethmoid, or sieve hone, occupies the cleft in 
the frontal bone between the two orbits, and forms 
the upper part of the nasal cavity; it consists of a 
horizontal plate which occupies the base of the 
skull; a vertical plate which forms the upper part 
of the septum of the nose and two lateral masses 
consisting of cells or cavities; on its upper surface 
is a perforated plate called the cribriform plate, and 
a projection resembling a cock’s comb, named the 
crista galli. 
There are three fossee in the base of the skull in 
which the brain rests : 
(1) The posterior fossa (the deepest). 
(2) The middle fossa (less deep). 
(3) The anterior fossa (the most shallow). 20 
ELEMENTARY PHYSIOLOGY 
Bones of the Face. 
The bones of the face are fourteen in number 
(r) 2 Superior maxilla?. 
(2) 1 Inferior maxilla. 
(3) 2 Nasal bones. 
(4) 2 Malar bones. 
(5) 2 Lachrymal bones. 
(6) 2 Palate bones. 
(7) 1 Vomer. 
(8) 2 Turbinated bones. 
The Superior maxillai form the greater part of 
the face between the orbit and the mouth. Each 
consists of a hollow body called the antrum or cave, 
a vertical plate which runs inwards and upwards, 
the inner and upper part forming the malar pro- 
cesses, the lower border and the vertical plate 
forming the alveolar processes, with sockets for the 
roots of the teeth. Running inwards and back- 
wards from the alveolar process is the palatine 
process forming two-thirds of the hard palate. The 
roof of the antrum forms part of the socket of the 
eye; at the inner and lower border of the orbital 
plate is a groove for the nasal duct, which com- 
municates with the nostril. 
The superior maxillae articulate with the frontal 
bone, with the two nasal bones, with the two 
lachrymal bones, with the two malar bones, with the 
two turbinated bones, with the vomer, and with the 
ethmoid bone. THE BONES OE THE SKELETON 
21 
The Inferior maxilla constitutes the lower jaw; it 
is developed in two halves, which in process of time 
unite, this union is called the symphysis of the 
lower jaw ; it presents the appearance of a horse- 
shoe, consisting of a body, two horizontal rami, and 
two vertical rami; the lower border of the body is 
called the chin ; it is peculiarly strong ; the upper 
border contains the alveolar process for the teeth 
of the lower jaw ; the union of the horizontal and 
vertical rami is called the angle of the jaw. 
The nasal hones form the bridge of the nose ; 
they are oblong in shape and articulate with each 
other and with the superior maxilla;; the upper 
border with the frontal bone, whilst the lower 
border is thin and jagged for the attachment of 
cartilage. 
The malar hones form the prominence of the 
cheek; they enter into the formation of the orbit, 
also into the formation of the temporal and zygo- 
niatic fossse. They are four-sided, and have four 
angles ; the superior exterior angle articulates with 
the frontal bone ; the inferior exterior angle ar- 
ticulates with the zygoma, forming the zygomatic 
arch; the anterior and also the posterior inferior 
angles articulate with the superior maxilla. The 
outer surface is very strong, forming a prominence 
which acts as a safeguard to the eye. 
The Lachrymal hones are situated at the inner 
and lower border of the eye; they are the 
most delicate bones in the body—they present a 22 
ELEMENTARY PHYSIOLOGY 
grooved appearance for the support of the nasal 
duct. 
The palate, bones are situated at the hack of the 
nasal fossa, between the superior maxillae and the 
pterygoid processes. They serve to lengthen back- 
ward the hard palate, and serve also for the 
attachment of the various muscles of the pharynx. 
The vomer, or plough-share, is placed in the 
median line below the body of the sphenoid, and 
forms the back part of the septum of the nose. 
The turbinated are spongy bones, curved and 
twisted upon themselves, and are found in either 
nostril. They serve to give greater surface to the 
mucous membrane, which is very vascular, and 
transmits the olfactory nerves. They, with the 
lateral masses of the ethmoid, form the three 
divisions of the nose : 
(i) Upper meatus. 
(2) Middle meatus. 
(3) Lower meatus. CHAPTER IV 
THE BONES OF THE SKELETON—{continued) 
The bones belonging to the vertebral column are 
twenty-four in number. 
The vertebral column is the pivot on which the 
body turns; it is an organ of support and also an 
organ of protection—it is shaped like a pyramid, 
forming three curves. 
2 Convex curves. 
i Concave curve. 
The vertebrce are divided into : 
7 Cervical (neck). 
12 Dorsal (back). 
5 Lumbar (loin). 
Between each vertebra there are inter-vertebral 
discs which act as buffers; these buffers are 
formed of yellow elastic tissue and fibrous tissue. 
Each vertebra consists of a body, from which 
springs an irregular arch, which arch forms the 
spinal foramen for the spinal cord ; on either side 
at the commencement of the arch spring seven 
processes, two above the pedicles, which jut out 24 
ELEMENTARY PHYSIOLOGY 
from the side and are called transverse or lateral 
processes \ nearer together'and between the lateral 
processes are the lower articular processes ; in front 
of them and still nearer together are the two 
upper articular processes ; between the two lower 
and the two upper are two plates of bone, called 
lamince, which form the roof of the arch ; they are 
pinched up together and form the spinous process. 
Each vertebra therefore consists of 
(a) i Body. 
(b) 2 Pedicles. 
(c) 2 Transverse processes. 
(d) 2 Upper articular processes. 
(e) 2 Lower articular processes. 
(f) i Spinous process. 
(g) 2 Laminae. 
(h) i Vertebral foramen. 
The five lumbar vertebrae are the largest, their 
bodies are broad and thick, pedicles strong, 
laminae short, spinous process horizontal. 
The twelve dorsal vertebrae are smaller than the 
lumbar ; their bodies are somewhat triangular; 
pedicles nearly on a level with the upper margin 
of the body ; their laminae are broad and thick, 
their spinous processes long and oblique; their 
transverse processes clubbed, having facets on them 
for the articulation of the ribs; their spinal 
foramina are round. 
The cervical vertebrae are the smallest; their 
transverse processes are perforated for the passage THE BONES OF THE SKELETON 
25 
of the vertebral arteries ; their spinous processes 
are short and bifurcated ; their bodies very small. 
The first cervical vertebra, called the atlas, is 
fixed to the head by means of ligaments; it has 
not any body, but has two side masses connected 
in front and behind by an arch forming an almost 
complete ring. 
The second cervical vertebra is likewise very 
peculiar ; it is called the axis ; it has a body from 
the upper surface of which projects a tooth-like 
body, the odontoid process, which serves as an axis 
for the atlas to revolve upon ; its transverse pro- 
cesses are short and perforated; its spinous pro- 
cess bifurcated and channelled below. 
The seventh cervical vertebra is remarkable for 
its long spinous process and is therefore called 
vertebra prominens. 
A brim divides the pelvis into two parts, the 
true and false pelvis : the false above, the true 
below. The pelvis directs the weight of the body 
on to the lower extremities, it consists of : 
The Pelvis. 
(1) The sacrum. 
(2) Two innominate bones. 
The sacrum is the direct continuation of the 
vertebral column, being in fact the fusion of five 
or six bones, which in the feet us are separate. It 
is placed between the last lumbar vertebra above 
and the coccyx below, with an innominate bone 
on either side. It is a triangular, wedge-shaped 26 
ELEMENTARY PHYSIOLOGY 
bone, with base above, and apex below ; the inner 
surface is smooth and concave, whilst the upper edge 
projects forwards and is called the “ promontory,” 
it presents indications by means of transverse lines 
of the original division of the bone. At the extre- 
mities of the lines are foramina, continuous with 
those of the vertebral column, for the transmission 
of the nerve trunks. The posterior or dorsal surface 
is convex, presents down the middle line spinous 
processes, and on either side laminae which form the 
continuation of the spinal fox-amen. The lateral 
masses on either side consist of coalesced trans- 
verse processes. 
The upper axxd outer angles present peculiarly 
roughened surfaces, alternately convex and con- 
cave for articulation with the innominate bone, 
the sacro-iliac synchondrosis. At the apex of the 
sacrum is the coccyx, consisting of four or five 
rudimentary vertebrae; the first piece is broad 
and articulates with the sacrum, the second articu- 
lates with the first, the third and fourth are mere 
nodules, coalescing with the second. 
In middle life the first piece is usually separated 
while the rest are fused together. 
In advanced life they are all united together 
and with the sacrum, sooxxer in males than ixx 
females. 
The innominate hone is an irregularly shaped 
bone forming part of the pelvis ; in the child it is 
developed in three parts. THE BONES OF THE SKELETON 
27 
(i) The ilium. 
{2) The ischium. 
(3) The pubic bone or pubes. 
These three bones form a cup-like cavity called 
the acetabulum. 
The ilium is the flattened portion which sup- 
ports the flank. 
The ischium is the strong portion which sup- 
ports the buttocks and on which we rest when 
sitting. 
The pubes is the front portion and supports the 
organs of generation. 
Between the ischium and the pubes is a large 
hole, named obturator or foramen ovale. 
The upper border of the ilium is called its crest; 
the crest ends in front in a thick angle, the 
anterior superior spine, to which is attached a 
ligamentous structure, called Forepart's ligament, 
which runs to the angle of the pubes. 
Below the notch is the anterior inferior spine ; 
tracing the crest backwards is the posterior 
superior spine, then an excavation, the ischiatic 
notch. 
The lower portion of the ilium enters into the 
formation of the acetabulum with the ischium and 
pubic bone. 
The ischium consists of a body which also enters 
into the formation of the acetabulum. Forwards 
and downwards is its tuberosity on which we rest 
■when sitting ; curving upwards and forward is its 28 
ELEMENTARY PHYSIOLOGY 
ascending ramus which articulates with the pubic 
bone and helps to form the foramen ovale. 
The pubic bone has a body and two branches ; the 
upper branch assists in the formation of the 
acetabulum, the lower branch articulates with the 
ischium. 
The two pubic bones unite in front by means of 
a fibro-cartilaginous disc to form the symphysis 
pubis. 
The Bones of the Extremities. 
The femur, or thigh-bone, is the longest, largest, 
and strongest bone in the skeleton. 
The femur, as all other long bones, consists of a 
shaft and two extremities—the upper extremity 
presenting a head, neck, and the greater and lesser 
trochanters ; the head is globular and forms rather 
more than a hemisphere ; its surface is smooth and 
coated with cartilage. The neck is a flattened 
pyramidal process of bone, which connects the 
head with the shaft; it varies in length and 
obliquity at various periods of life and under 
different circumstances. 
The trochanters are prominent processes of bone 
which afford leverage to the muscles which rotate 
the thigh on its axis. 
The great trochanter is a large, quadrilateral, 
irregular eminence situated at the outer side of the 
neck, at its juncture with the upper part of the 
shaft; it has two surfaces and four borders. THE BONES OF THE SKELETON 
29 
The lesser trochanter is a conical eminence; its 
summit is rough, and gives insertion to the psoas 
muscle. The shaft is almost perfectly cylindrical 
in form; it is a little broader above than in the 
centre and is highly arched. 
The lower extremity is larger than the upper, is 
of a cuboid form, and divided into two large 
eminences called the condyles (knuckles) with a 
notch between, called the intercondyloid notch. 
The skeleton of the leg consists of three bones : 
(1) Patella. 
(2) Tibia. 
(3) Fibula. 
The patella, or knee-cap, is a flat, triangular bone, 
situated at the anterior part of the knee joint; it 
is composed mainly of dense cancellous tissue, and 
protects the front of the joint. It has two facets 
(small plane surfaces) for the articulation of the 
condyles of the femur. 
The tibia, or shin bone, is situated at the front and 
inner side of the leg, and in length and size is only 
second to the femur ; it also consists of a shaft and 
two extremities. The upper extremity, or head, is 
large and expanded on each side into two lateral 
eminences, the tuberosities, which present two 
smooth, concave surfaces which articulate with the 
condyles of the femur. 
The lower extremity is much smaller than the 
upper and presents five surfaces. It forms the 
inner ankle. 
The fibula, or splint bone, is situated at the outer 
side of the leg, and is, in proportion to its length, 30 
ELEMENTARY PHYSIOLOGY 
the most slender of the long bones; it has a shaft 
and two extremities. 
The upper extremity is small and placed below 
the level of the knee-joint, and is excluded from its 
formation; the lower extremity inclines a little 
forward and forms the outer ankle. 
The foot consists of three divisions ; 
(i) Tarsus. (2) Metatarsus. (3) Phalanges. 
The bones of the tarsus are seven in number. 
(1) Calcaneum. (5) Internal cuneiform. 
(2) Astragalus. (6) Middle cuneiform. 
(3) Cuboid. (7) External cuneiform. 
(4) Scaphoid. 
The metatarsal hones are five in number; they 
are long bones, and each has a shaft and two ex- 
tremities. The phalanges of the foot resemble 
those of the hand, both in number and general 
arrangement; there are two in the great toe and 
three in each of the other toes. 
Bones of the Upper Extremity. 
The humerus is the longest and largest bone of 
the upper extremity. It has a shaft and two ex- 
tremities ; the upper extremity is the largest part 
of the bone; it has a rounded head, and is joined 
to the shaft by a constricted portion called the neck 
and two other eminences, the greater and lesser 
tuberosities. 
The lower extremity is flattened and curved 
slightly forwards, and has a general surface which, THE BONES OF THE SKELETON 
31 
with the bones of the forearm, forms the elbow- 
joint. 
The radius is the outer bone of the forearm ; it 
is a long bone which articulates with the humerus ; 
it is largest at the lower end where it comes in 
contact with the first row of carpal bones. 
The ulna is a long, irregularly shaped bone, 
articulating above with the humerus and below with 
the radius ; at its upper end is a projection which 
forms the joint of the elbow; it is called the 
olecranon, and gives attachment to the muscles 
coming from above. The space between the radius 
and the ulna is called the interosseus space. 
The carpus consists of eight small bones of irre- 
gular shape, so bound together by ligaments as 
to allow of gliding movements between them; they 
articulate with the radius and ulna above, with 
each other, and with the metacarpal bones below ; 
the carpus as a Avhole is arched, and may be divided 
into two rows, four bones in each. 
First row. 
(1) Scaphoid (boat-like). 
(2) Semilunar (half-moon). 
(3) Cuneiform (wedge-shaped). 
(4) Pisiform (pea-shaped). 
Second row. 
(1) Trapezium (square). 
(2) Trapezoid (table-shaped). 
(3) Os magnum. 
(4) Unciform (hook-shaped). 
The bones of the wrist are numerous, in order to 
give greater mobility to the part. 32 
ELEMENTARY PHYSIOLOGY 
The metacarpal bones are placed between the 
wrist and the fingers, and are composed of five 
bones. That belonging to the thumb is called the 
first, and that of the little finger is called the fifth. 
They articulate above with the carpus and below 
with the first bone of the thumb and the fingers, 
the whole together form the palm of the hand and 
ball of the thumb. 
The phalanges consist of three small bones form- 
ing each finger ; the thumb has only two. 
The clavicle, or collar-bone, takes its name from 
a fancied resemblance to an ancient key (clavis); 
one is placed on each side of the upper part 
of the chest; its inner end is articulated to the 
sternum, and its outer end to the scapula ; its use 
is to support the shoulder. 
The scapula, or shoulder-blade, is a flat bone 
of a triangular shape, placed at the back of the 
shoulder; on its outer surface runs a ridge which 
divides it into two unequal parts. The scapula 
is attached to the spinal column and ribs by 
strong muscles, and it articulates at its upper 
and outer edge with the clavicle and with the 
humerus. 
The thorax, or chest, is formed by the sternum in 
front, twelve ribs on either side, and twelve dorsal 
vertebrae behind. 
The sternum, or breast-bone, occupies the front of 
the chest, and supports the inner ends of the clavicle; 
seven of the costal cartilages are connected with THE BONES OF THE SKELETON 
33 
the sternum on each side. The sternum has been 
likened to a sword, the upper part being called the 
manubrium, or handle, the middle part the gladiolus, 
or blade, whilst appended to the latter is a small 
point of fibro-cartilage, called the ensiform. 
The ribs, or costa?, form the greater part of 
the wall of the thorax ; they are twenty-four in 
number, twelve on each side, and articulate behind 
with the twelve dorsal vertebra-. 
The upper seven are called true ribs ; they are 
attached in front to the sternum by costal cartilages. 
The next three (eighth, ninth, and tenth) are 
connected with the costal cartilages of those above. 
The last two are free, and are called floating ribs, 
each being tipped with costal cartilage. 
The true ribs are more easily broken than the 
false, because the false are more yielding. CHAPTER Y 
THE CIRCULATORY ORGANS 
The organs of the circulation are the 
(1) Heart. (4) Capillaries. 
(2) Arteries, (5) Lymphatics. 
(3) Veins. (6) Various ductless glands. 
The heart is a hollow muscular organ, about the 
size of the closed fist of the person to whom it 
belongs. It varies much in size. The weight in 
a male is about 10 to 12 ounces, in a female about 
8 to 10 ounces. 
The heart is situated in the mediastinum, or 
centre of the thorax, in an upper direction from 
right to left. 
It is invested by a double serous membrane 
called the pericardium. 
The upper part of the heart is broad and called 
the base, whilst the lower end, round and pointed, 
is called the apex. 
The upper surface of the heart is somewhat 
convex, whilst the under stirface is flattened and 
rests upon the diaphragm. THE CIRCULATORY ORGANS 
35 
The heart is held in place by the large vessels 
which spring from it. 
The heart is divided internally from the base to 
the apex by a muscular wall, or septum, into the 
right and left sides. Each side of the heart is 
sub-divided into two chambers, the upper called 
auricles, and the lower called ventricles. 
The openings between the auricles and ventricles 
are called auriculo-ventricular openings and they 
are guarded by means of valves. 
The valves on the right side of the heart are 
called tricuspid, because they are divided into three 
folds or cusps. 
Those on the left side are called bicuspid, or 
mitral, valves, from a fancied resemblance to a 
bishop’s mitre. 
The walls of the heart are muscular and vary in 
thickness according to the amount of work they 
have to do. 
The walls of the auricles therefore are compara- 
tively thin, as they simply receive blood and pass 
it on to the ventricles, whereas those of the right 
ventricle are thicker, because they force the blood 
into the pulmonary artery and the lungs, whilst 
those of the left ventricle are thickest of all, 
because they have to force blood through the aorta 
all over the body. Each cavity of the heart is 
supposed to be capable of containing about gij of 
blood. 
The heart substance is composed of layers of j?igi 2- Interior of Right Auricle and Ventricle exposed by 
the removal of a part of their walls. (Allen Thomson.) 
1. Superior vena cava. 
2. Inferior vena cava. 
6. Pulmonary artery, in the 
wall of which a window 
has been cut. 
2'. Hepatic veins. 
3, 3', 3". Inner wall of right 
auricle. 
4, 4. Cavity of right ventricle. 
4'. Papillary muscle. 
5> s'> 5". Flaps of tricuspid 
valve, 
7. On aorta near the ductus 
arteriosus. 
8, 9. Aorta and its branches. 
10, 11. Left auricle and ven- 
tricle. THE CIRCULATORY ORGANS 
37 
muscular fibres : an inner layer of oblique fibres, a 
middle layer of circular fibres, and an outer layer 
of longitudinal fibres, which all contract evenly 
together. 
Fat fills up the spaces between the muscles like 
a cushion. 
Rising from the walls of the ventricles internally 
there are small muscular pillars called papillary 
muscles, which terminate in fine thread-like tendons 
called chordae tendinece, and the extremities of these 
are attached to the edges of the valves; therefore 
when the papillary muscles contract they pull on 
the chordae tendinese and these help to open the 
valves and allow of the passage of the blood from 
auricle to ventricle. 
Arteries always carry blood from the heart, and 
as a rule convey pure, bright-red (arterial) blood. 
Veins always carry blood to the heart, and as a 
rule contain impure dark (venous) blood. 
Arteries and veins are furnished with three 
linings or coats ; 
(i) An inner coat of epithelial tissue. 
(2) A middle coat of muscular fibres (very weak 
in veins). 
(3) An outer sheath of connective tissue. 
Veins, especially those of the lower extremity, 
are also provided with valves which assist in re- 
turning venous blood to the heart. 
Capillaries (capillus = a hair) form a network 
of thread-like vessels and intervene between the ELEMENTARY PHYSIOLOGY 
smallest arteries and the radicles or commence- 
ments of veins; they have exceedingly thin walls, 
through which their contents ooze out to nourish 
the tissues. 
Lymphatics are very fine vessels which originate 
in the tissues, they lie with open mouths and 
absorb lymph or any superabundant nourishment 
from the blood ; at intervals they run into glands in 
which their contents undergo certain changes, and 
which help to form the corpuscles of the blood. 
The spleen is a ductless gland situated on the 
left side of the body under the diaphragm, and its 
function is supposed to be the manufacture of the 
white corpuscles of the blood. 
All venous blood is collected by means of small 
veins which run into larger vessels and finally 
empty themselves into one of the two large trunk 
veins ; those below the heart empty themselves into 
the inferior vena cava, those above the level of the 
heart empty themselves into the superior vena 
cava. 
The Circulation. 
Impure venous blood is brought through two 
openings to the right auricle by means of the 
superior and inferior venae cavae. The auricle 
dilates to receive it, then contracts on its contents ; 
at the same time the papillary muscles in the 
ventricle contract, and by means of the chordae 
tendineae open the tricuspid valve and allow of the THE CIRCULATORY ORGANS 
39 
passage of the blood from the right auricle to the 
right ventricle—the ventricle dilates to receive the 
blood, then contracts on its contents, closes the 
tricuspid valve to prevent regurgitation, opens the 
semilunar valves, and drives the blood into the 
pulmonary artery by which it is carried to the 
lungs. The pulmonary artery divides into the 
right and left pulmonary arteries, which subdivide 
into smaller and smaller branches, finally ter- 
minating on the walls of the air-cells, where 
the blood comes into contact with oxygen and 
is purified of its carbonic acid ; the purified 
blood is taken up by other capillaries which run 
into veins and finally empty themselves into the 
left auricle; the left auricle dilates to receive the 
blood, then contracts, the mitral valve opens and 
allows of the passage of the blood into the left 
ventricle ; the left ventricle dilates to receive the 
blood, then contracts, shutting the mitral valves 
and opening the semilunar valves into the aorta, 
into which it propels the blood, and by which 
vessel and its branches the blood is carried to all 
parts of the body. 
The sides of the heart are symmetrical and act 
synchronously (at the same time). Auricles dilate 
and contract simultaneously. Ventricles dilate and 
contract simultaneously. Corresponding valves are 
open at the same time. The movement by con- 
traction is called the systole. The period between 
two successive contractions is called the diastole. 40 
ELEMENTARY PHYSIOLOGY 
Fig. 3.—Diagram of the Circulation of the Blood and 
the Absorbent Vessels. (Yeo’s “ Physiology.”) 
P«. Small pulmonary arte- 
rioles. 
P.A. Pulmonary arteries. 
P.V. Pulmonary veins. 
P.C. Pulmonary capillaries. 
Y. Wide systemic veins. 
A. Larger systemic arte- 
ides. 
K.H. E’ght systemic heart. 
L.H. Left systemic heart. 
Lr. Liver. 
LA. Lymphatics. 
Lc. Lacteals. 
I. Intestines. 
A'. Smaller systemic arte- 
rioles. 
S.C. Systemic capillaries. THE CIRCULATORY ORGANS 
41 
Course of the Aorta and its principal branches. 
At its very commencement the aorta gives off 
two branches, the coronary arteries, which turn 
back over the surface of the heart to nourish that 
organ itself; the aorta then takes an upward 
direction and arches over the root of the left lung; 
this arch is divided into three parts : 
(1) The ascending aorta. 
(2) The transverse aorta. 
(3) The descending aorta. 
From the transverse arch of the aorta three 
branches are given off: 
(1) The innominate artery. 
(2) The left carotid artery. 
(3) The left subclavian artery. 
The innominate artery is very short and soon 
bifurcates, forming the right subclavian and the 
common carotid. 
The common carotid runs up the side of the 
neck, and when on a level with the thyroid carti- 
lage bifurcates and forms the external and internal 
carotid arteries; the external carotid runs up the 
side of the face in front of the ear, giving off 
branches to the anterior portion of the face and 
also branches to the scalp. 
The internal carotid enters the skull by the tem- 
poral bone, supplies blood to the brain and its 
membranes, forming with other arteries the circle 
of Willis. The right subclavian passes under the 42 
ELEMENTARY PHYSIOLOGY 
clavicle, takes a downward course to the axilla, 
where it is called the axillary artery, then passes 
downwards and forwards to the bend of the elbow, 
and is here called the brachial artery; about an inch 
and a half below the elbow it bifurcates, forming 
the radial and ulnar arteries. The radial artery 
takes its course along the outer side of the arm to 
the root of the thumb ; here it dips deeply down 
and forms the deep palmar arch, giving off branches 
to the dorsal part of the hand and to the fingers. 
(At the wrist the radial artery is very superficial, 
and is called the pulse, which is the beat of an 
artery synchronous with the contraction of the ven- 
tricles.) 
The ulnar artery takes its course along the inner 
side of the arm, passes beneath the annular liga- 
ment and forms the superficial palmar arch, which 
gives off branches to the palm of the hand and 
front part of the fingers. 
A portion of the descending aorta takes its course 
downwards through the thorax on the left side of 
the vertebral column; this portion is called the 
thoracic aorta ; on its way it gives off branches right 
and left to the intercostal muscles, and also branches 
to nourish the lungs and other contents of the 
thorax ; it then passes through the diaphragm and 
enters the abdomen, where it is called the abdominal 
aorta; through the abdomen the course is more 
to the front of the vertebral column. The first im- 
portant branch given off from the abdominal aorta THE CIRCULATORY ORGANS 
43 
is the cceliac axis, which is short and immediately 
divides into three branches, the gastric artery for 
the stomach, the splenic artery for the spleen, the 
hepatic artery for the liver; a little lower down 
branches are given off to the kidneys, right and left 
renal arteries, and also branches to nourish the 
mesentery and the intestines. When the abdominal 
aorta reaches the level of the fourth lumbar verte- 
bra it bifurcates, forming the right and left com- 
mon iliac arteries. These are about 2\ inches long, 
each of which in turn bifurcates to form an external 
and internal iliac artery. The internal iliac takes 
a downward and backward course into the pelvis, 
whilst the external iliac takes a forward course into 
the pelvis and passes under Poupart’s ligament into 
the thigh, then downwards on the inner side of 
the femur where it is called the femoral artery, 
through the space behind the knee where it is called 
the popliteal artery, and where it bifurcates into the 
anterior and posterior tibial arteries. The anterior 
tibial artery passes down the front of the tibia and 
supplies the upper or dorsal part of the foot and the 
toes; the posterior tibial artery passes down behind 
the tibia and supplies the inner ankle and plantar 
portion of the foot. {Systemic Circulation.') 
There are certain parts of the body which have 
an independent circulation of their own, the venous 
blood of which is not carried at once to the vena 
cava; the blood carried to the stomach, intestines, 
spleen and pancreas being gathered into veins 44 
ELEMENTARY PHYSIOLOGY 
which unite into in a single trunk, the portal vein 
or vena portte. 
Fig. 4.—Diagram of the Portal Vein (pv) arising in the 
alimentary tract and spleen (s), and carrying the blood 
from these organs to the liver. 
The portal vein distributes its blood to the liver, 
mingling it with that supplied to the capillaries of 
the same organ by the hepatic artery; from these 
capillaries it is conveyed by small veins which unite THE CIRCULATORY ORGANS 
45 
into a large trunk, the hepatic vein which opens 
into the inferior vena cava. (Ported Circulation.) 
We can therefore see that the function of the 
'pulmonary circulation is the aeration of the blood 
in the lungs; that the function of the systemic 
circulation is to convey blood to all parts of the 
body; that the function of the portal circulation 
is the elaboration of nutriment. 
Fig. s.—The Orifices of the Heart seen from above, both 
the auricles and the great vessels being removed. 
(Huxley.) 
PA. Pulmonary artery and its semilunar valves. 
Ao. Aorta and its valves. 
PA V. Tricuspid, and LA V. Bicuspid valves. 46 
ELEMENTARY PHYSIOLOGY 
The heart has no influence over the lymphatics; 
they are under the control of the nervous system ; 
fluid passes along them by capillary attraction, 
assisted by the pressure of the actions of the 
muscles. The walls of the heart and blood-vessels 
are under the control of special branches of the 
sympathetic system, the vaso-motor nerves, of which 
some fibres have the special function of dilating, 
others of contracting, the vascular walls. CHAPTER VI 
THE RESPIRATORY ORGANS 
Respiration is carried on by means of : 
(1) The mouth. 
(2) The nose. 
(3) The larynx. 
(4) The trachea. 
(5) The bronchi. 
(6) The lungs. 
Accessory to these organs are : 
(1) The diaphragm. 
(2) The intercostal muscles. 
The mouth and nose are lined with a mucous 
membrane which is highly vascular, so that the 
air passing through them is both moistened and 
warmed before it enters the air passages. 
The larynx contains the organ of voice, and is 
situated at the base of the tongue and at the 
upper part of the trachea ; it is composed of nine 
cartilages connected by ligaments and moved by 
numerous muscles, lined by mucous membrane 
and supplied with nerves and blood-vessels. The 
chink, or opening, into the larynx is called the rima 
glottidis, and it is guarded by the epiglottis, a thin 
lamella or plate of elastic fibro-cartilage, shaped 
like a leaf and situated at the back of the tongue. 48 
ELEMENTARY PHYSIOLOGY 
During respiration the epiglottis remains in a 
vertical position, but in the act of swallowing it is 
drawn down over the glottis to prevent any foreign 
body entering the air passages : 
The nine cartilages of the larynx are : 
i Thyroid, 
r Cricoid. 
2 Arytenoid. 
i Epiglottis. 
2 Cornicula laryngis. 
2 Cuneiform. 
The function of the larynx is to protect the 
vocal cords and the entrance to the air passages. 
There are four vocal cords, two false and two 
true. The two superior or false cords are folds of 
mucous membrane attached in front to the angle 
of the thyroid cartilage and behind to the anterior 
surface of the arytenoid cartilages. The two in- 
ferior or true vocal cords are strong fibrous bands 
covered with mucous membrane, and are similarly 
attached. 
Between the false and true vocal cords is a space 
or cavity called the ventricle of the larynx. The 
anterior part of this ventricle leads up by a narrow 
canal into a pouch of mucous membrane called the 
laryngeal pouch. 
If any foreign substance passes through the 
glottis it will very likely lodge in this pouch and 
produce irritation and coughing until it is ejected. 
The vocal cords may be said to act as janitors to 
the respiratory organs. 
The itrachea, or windpipe, is a cartilaginous 
and membranous tube, about inches long, THE RESPIRATORY ORGANS 
49 
two-thirds of which consists of imperfect carti- 
laginous rings, and the remainder of fibrous mem- 
brane. The fibrous membrane is chiefly at the 
Fig. 6.—Diagram of the Respiratory Organs. The wind- 
pipe leading down from the larynx is seen to branch 
into two large bronchi, which subdivide after they 
enter their respective lungs. 
back where the trachea comes into contact with 
the oesophagus; there are from sixteen to twenty 
of these rings connected by membrane and extend- 
ing from the level of the fifth cervical to the level 
of the third dorsal vertebra. Hear the trachea 
bifurcates into the two bronchi, one for each lung. 
Each bronchus after entering its lung divides and 
subdivides dichotomously (by constant double fork- ELEMENTARY PHYSIOLOGY 
ing), the smaller branches being called bronchial 
tubes; these are elastic and cartilaginous and are 
lined with mucous membrane. 
Eig. 7.—Transverse section of part of the wall of a medium 
sized Bronchial Tube, x 30. (F, E. Schultze.) 
a. Fibrous layer containing plates of cartilage, glands, &c. 
b. Coat composed of unstriated muscle, 
c. Elastic sub-epithelial layer. 
d. Columnar ciliated epithelium. 
When the tubes become as small as one-forty - 
eighth of an inch in diameter, they lose their carti- 
laginous property and finally terminate in elongated 
muscular dilatations called intercellular passages. 
These open into air cells which form the ultimate 
tissue of the lung. The walls of these air cells 
are a fine membrane, over which are spread the 
capillaries of the pulmonary artery. It is here 
that the venous blood is brought into contact with 
oxygen and so purified of its carbonic acid gas. THE RESPIRATORY ORGANS 
51 
The lungs occupy the greater part of th 3 cavity 
of the thorax or chest, and are situated to the right 
and left of the heart. 
Each lung is invested by a serous membrane 
called the pleura, which encloses the organ as far 
as its root and is then reflected upon the inner 
surface of the thorax. 
The portion of the pleura that invests the lung 
is called the pleura pulmonalis, or visceral pleura, 
whilst that portion which lines the inner surface 
of the thorax is called the pleura costalis, or 
parietal pleura ; the space between these two por- 
tions is called the pleural cavity. 
In pleurisy, or inflammation of the pleura, this 
cavity is filled with a serous fluid, the product of 
inflammation; in more severe inflammation it is 
filled with pus, the product of a further degree of 
inflammation called suppuration {empyema). 
The tissue of the lung itself is very elastic and 
of a light, spongy, porous character; when healthy 
it floats in water, but in the foetus, before respira- 
tion takes place, and also in certain diseases of the 
lungs, such as congestion and inflammation, which 
render the lung solid, it sinks. 
When pressed between the fingers the lung 
imparts a peculiar sensation together with a 
crackling sound, caused by the air in the tissue. 
In infancy the lung is a pale rose-pink colour, but 
as life advances it becomes more or less mottled 
with grey. 52 
ELEMENTARY PHYSIOLOGY 
The right lung is divided into three lobes; it 
is conical in shape, with its base below, concave 
and semi-lunar in form as it rests on the arch of 
the diaphragm. The apex forms a blunted point, 
reaching into the root of the neck above the 
margin of the first rib. The anterior surface is 
smooth and convex, its inner border concave ; the 
posterior border is rounded and broad and is received 
into the deep groove formed where the ribs articu- 
late with the dorsal vertebrae ; the anterior border 
partly overlaps the heart. The right lung is 
broader than the left owing to the position of the 
heart: it is also shorter by an inch to accommodate 
the liver; but it is, nevertheless, of greater capacity. 
The left lung is smaller, longer, and narrower 
than the right, and is divided into two lobes. Its 
base, apex, surface, and borders, correspond with 
those of the right lung. 
A little above the middle of the inner border 
of each lung is its root, by which the lung is con- 
nected with the heart and trachea. 
This root is formed by the bronchus, pulmonary 
arteries, nerves, and lymphatics; here also the 
pulmonary veins pass out. 
The root of the right lung is situated behind 
the superior vena cava and the upper part of the 
right auricle; the root of the left lung lies 
beneath the arch of the aorta. 
As already stated, the lungs are very elastic, so 
that the amount of air they contain varies. In 
a normal condition they are capable of holding THE RESPIRATORY ORGANS 
53 
about two hundred cubic inches of stationary air, 
together with about thirty cubic inches of tidal air 
(or about five to seven pints of air). 
The quantity of air taken in after a very deep 
inspiration is about one hundred cubic inches, or 
about two and a half pints. Air received into the 
lungs undergoes four changes : 
(i) It is rendered wanner and moister by pass- 
ing over the mucous membranes lining the air 
passages. 
(2) Its proportion of C02 is increased. 
(3) Its oxygen is diminished. 
(4) Its organic matter is increased. 
Air taken into the lungs should consist of oxygen 
one-fifth and nitrogen about four-fifths and a mi- 
nute proportion of C02, and watery vapour, 11,0. 
Air exhaled from the lungs will be found to 
contain 002 in excess, no oxygen, a certain amount 
of NH4HO and some watery vapour. The C02 given 
off is in proportion to the organic matter. 
Chief uses of Oxygen inhaled by the Lungs. 
(1) As the oxygen enters the air-cells, it is 
absorbed by the capillaries which permeate their 
walls; it enters into chemical combination with 
certain constituents of the blood, especially 0, and 
forms C02, which is given off by expiration. 
(2) Some of the oxygen is carried along the 
blood stream by means of arteries and capillaries 
and comes into contact with waste material—i.e., 
urea and uric acid, which are oxydised forms of 54 
ELEMENTARY PHYSIOLOGY 
effete muscles and tissue, and which must be 
removed from the body. 
(3) The remaining good purpose served by the 
oxygen which the vessels absorb in the lungs is, 
to convert part of the surplus fat and starch into 
C02 and as no chemical combination can take 
place without heat being evolved, this change 
tends to maintain the warmth of the body. In 
healthy adults the act of respiration takes place 
about eighteen times per minute or once to every 
four beats of the heart. 
In women and children respiration is quicker 
and louder than in men ; in children averaging 
twenty-five per minute. 
In men respiration is more easily perceptible in 
the lower part of the chest; in women in the 
upper part. 
It is well to observe that the main source of 
oxygen in the atmosphere is green plants. The 
chlorophyll which they contain, under the influ- 
ence of sunshine, has the special property of acting 
upon the C02 and H2O which are in the air, in such 
a way as to fix the Carbon and Hydrogen and set 
free the Oxygen, which is in turn given back to the 
air. Animals eagerly inhale this Oxygen and in 
return for it give off Carbonic Acid Gas, so that 
by this beautiful and simple interchange of gases 
animal and vegetable life are sustained, each by the 
other; each at the expense of the other, but with 
mutual advantage. CHAPTER YII 
THE DIGESTIVE ORGANS 
In order that we may have sufficient nourishment 
for the blood supply of our bodies, it is necessary 
that our blood should be renewed ; this is effected 
by means of the digestive tract or alimentary 
canal (Lat. alimentum = nourishment). 
The alimentary canal, or passage through which 
food is conveyed to the tissues, begins at the 
mouth and ends at the anus. It is a musculo- 
membranous tube comprising the : 
(1) Mouth. 
(2) Pharynx. 
(4) Stomach. 
(3) (Esophagus. (6) Large intestine. 
To these may be also added what are sometimes 
(5) Small intestine. 
called the accessory organs of digestion ; 
(a) The teeth (thirty-two in number). 
(b) The salivary glands (three pairs). 
(1) The parotid glands (in front of the ear). 
(2) The submaxillary glands (beneath the jaw). 
(3) The sublingual glands (under the tongue). 
The word digestion, which comes from the Latin 56 
ELEMENTARY PHYSIOLOGY 
digerere, to carry into different parts, signifies the 
separation, by various chemical processes, of the 
Eig. B.—A Dissection of the side of the face, showing the 
Salivary Glands. 
a. Sublingual gland. 
h. Suhmaxillary glands with their ducts opening on the 
floor of the mouth beneath the tongue at (rf). 
c. Parotid gland and its duct, which opens on the inner 
side of the cheek. 
nourishing part of the food from that which is not 
nourishing, and the absorption of such nourish- 
ment after it had been dissolved or broken up 
into minute globules suitable for the maintenance 
of the tissues. This is brought about by— 
(1) Mechanical action, 
(2) Chemical action. 
(3) Absorptive action. 
Food is taken into the mouth and wrought 
upon by the mechanical action of the teeth; at the THE DIGESTIVE OEGANS 
57 
same time it comes into contact with the saliva, 
which is a fluid secreted by the salivary glands 
and which is being perpetually poured into the 
mouth to keep it moist. 
On the introduction of food into the mouth, the 
flow of saliva is immediately increased, and it not 
only softens the food but acts chemically upon the 
starchy portions of it by converting them into sugar. 
Now in the saliva there is a substance called 
ptyalin, which acts as a ferment (ferment some- 
thing which in very small quantities is able to 
produce great changes in large quantities) and which 
having a chemical affinity for starch, takes hold of 
it and converts it into a species of sugar, called 
dextrine. Starch is not readily absorbed, dextrine 
is ; hence the reason of the change. 
Food, after being masticated by the teeth and 
acted upon by the saliva, is collected into a bolus 
and passed by the tongue to the back of the 
mouth; the uvula or'extremity of the soft palate 
is pushed backwards to close the cavity leading to 
the nose; the epiglottis at the root of the tongue 
closes over the glottis to prevent anything entering 
the larynx, thus the bolus of food is passed over 
it, seized by the muscles of the pharynx, and 
conveyed by means of the oesophagus or food 
carrier into the stomach. 
The greater part of the alimentary canal consists 
of three coats— 
(i) The peritoneal coat(aperfectly smooth surface). •Fig. 9.—Diagram of Alimentary Tract, &c. Angles of 
mouth slit to show the back of the buccal cavity and 
the top of the pharynx. 
c. Cardiac. 
p. Pyloric parts of stomach. 
d. Duodenum. 
i. Jejunum and ilium. 
ac. Ascending colon. 
tc. Transverse colon. 
dc. Descending colon. 
r. Eectum. 
a. Anus. THE DIGESTIVE ORGAN'S 
59 
(2) The muscular coat (composed of fibres). 
(3) The mucous membrane (for absorptive pur- 
poses). 
Food is conveyed along the alimentary canal by 
peristaltic action, which is movement in successive 
jerks caused and controlled by the longitudinal 
and transverse action of the muscular contraction 
of the walls of the canal. 
The stomach is a muscular oblong bag, capable 
of holding two to three pints, and is situated in 
the upper left side of the abdomen immediately 
below the diaphragm, to which it is attached by a 
ligament. 
That end of the stomach communicating with 
the oesophagus is called its cardiac opening; the 
outlet at the further end is termed the pylorus or 
pyloric opening. The space between these two 
openings is called the lesser curvature, whereas the 
lower border is called the larger curvature. 
The mucous membrane of the stomach is 
arranged in tubular rows or folds called rug to, 
in which lie a number of glands, the function of 
which is to secrete gastric juice and mucus, which 
serves to moisten and protect the membrane itself. 
The gastric juice has been proved to consist of 
water, saline matter, hydrochloric acid, and pepsin. 
The hydrochloric acid supplies the acid medium in 
which alone pepsin can be effective. 
The moment food reaches the stomach its mus- 
cular walls contract and set up a churning motion, ELEMENTARY PHYSIOLOGY 
which rolls the food pulp from side to side, thus 
bringing it into contact with the gastric juice, 
which acts on the albuminous portions of the food 
and reduces them to a semi-fluid condition. If 
food not thoroughly acted upon by the juices 
reaches the pyloric end, it causes the valve to close 
by contraction, but when the process of digestion 
is properly completed, the food reduced to a 
greyish semi-fluid mass, called chyme, passes 
through this valve into the intestine. 
All liquids are absorbed in the stomach by 
minute vessels which ramify through the walls, 
therefore food, such as soup, beef-tea, &c., is ab- 
sorbed at once and not passed through the pylorus. 
The small intestine measures twenty feet in length, 
and is held up by a reflection of peritoneum, called 
the mesentery. It is divided into three parts— 
(i) The duodenum (about ten inches long). 
(2) The jejunum (nearly three-fifths). 
(3) The ileum (nearly two-fifths). 
In the interior of the duodenum wo find the 
mucous membrane drawn up into a large number 
of transverse folds, and presenting a velvety appear- 
ance from the fact of its being covered by minute 
papillae termed villi. In the centre of each villus 
we find the true absorbent vessel, which is called a 
lacteal.” 
The lacteals are the lymphatics of the intestines. 
These folds, or valvulae conniventes, serve two pur- 
poses ; first, to delay the food pulp in its passage, THE DIGESTIVE ORGANS 
61 
and, secondly, to afford a greater surface for absorp- 
tion. During its passage through the duodenum 
food is subject to two agencies—the pancreatic 
juice and the bile. 
The pancreatic juice is a fluid secreted by the 
pancreas; it acts upon all foods, but its chief 
chemical property is the same as that of the saliva. 
If any starchy matters have been allowed to pass 
through the mouth untouched by the saliva they 
are seized upon by the pancreatic juice and con- 
verted into sugar. Albumens which may have 
escaped the action of the gastric juice are converted 
into peptones; and fats are emulsified. 
Bile is a fluid secreted by the liver (one to two 
pints in twenty-four hours, a certain portion of 
which is stored up in the gall-bladder). It is 
carried from both of these by means of ducts—the 
hepatic duct and the cystic duct—and these form a 
common duct which opens into the duodenum close 
by the pancreatic duct. 
At the same time, from the surface of the intes- 
tine itself, a peculiar, half liquid, slimy mucus 
exudes, called intestinal juice (succus entericus). 
With these three juices the chyme mixes as it passes 
on, loses its acid character and becomes alkaline, 
assumes a milky appearance, and is then called 
chyle. The bile has three functions— 
(i) It works upon the fatty portions of the 
food; forming them into an emulsion, in which 
form alone they can be absorbed. 62 
ELEMENTARY PHYSIOLOGY 
(2) It acts as an antiseptic, and prevents de- 
composition of the food-pulp. 
(3) It promotes the peristaltic movement of the 
intestines. 
The chyle is first conveyed to numerous glands 
in the neighbourhood of the small intestine, 
called mesenteric glands. The lacteal vessels 
proceeding from these glands empty themselves 
into the receptacle of the chyle, which is 
a large cavity, opposite the last dorsal ver- 
tebra. 
From this cavity a duct, called the thoracic duct, 
ascends upwards through the thorax and unites 
with the venous system at the innominate vein on 
the left side below the neck. At the opening into 
the vein there is a valve which allows the chyle to 
How into the blood-stream, but not to regurgitate. 
As the chyle passes up the thoracic duct the fat 
diminishes, and minute white bodies, or cells, make 
their appearance, growing more and more like 
blood corpuscles. 
By the addition of bile to the chyme the con- 
tents of the duodenum are rendered alkaline. 
When fat in its passage through the body comes 
into contact with alkalies it becomes soapy and 
suitable for absorption. 
Distributed over the mucous membrane of the 
small intestine are Beyer’s patches—groups of 
glands somewhat globular in character. They are 
the seat of inoculation in typhoid fever. The THE DIGESTIVE ORGANS 
63 
typhoid bacillus fixes his “ habitat ” there, and 
thrives and multiplies. When food has passed 
through the small intestine it reaches the large 
intestine, which is divided into— 
(1) The caecum. 
(2) The colon (ascending, transverse, descend- 
ing). 
The opening of the ileum into the caecum is 
guarded by the ileo-caecal valve, and close to this 
valve is a blind ending of the caecum, called the 
vermiform appendix (in some persons, particularly 
liable to inflammation = appendicitis). 
(3) The rectum. 
The last coil of the descending colon is called the 
sigmoid flexure, also sometimes the seat of disease. 
The structure of the large intestine is similar to 
that of the small, only it is not provided with villi, 
as the nourishing part of food has been mainly 
absorbed before entering it. 
Food in the small intestine is fluid, gradually 
becoming firmer, but after passing the ileo-csecal 
valve it becomes solid and slightly acid again, 
owing to the presence of lactic acid, the purpose of 
which seems to be to dissolve out any remaining 
gluten (especially vegetable matter) which the 
contents of the bowel may contain, thus completely 
exhausting it of all nutrition. 
The residue, being non-nutritious, is gradually 
passed along the colon as fecal matter, and, coming 
down the rectum, is finally discharged by the anus. Fig. 10.—Diagram showing the course of the Main Trunks 
°of the Absorbent System. The lymphatics of lower 
extremities (d), meet the lacteals of intestines (lac; 
at the receptaculum chyli (R.C.), where the thoracic 
duct begins. The superficial vessels are shown in 
the diagram on the right arm and leg (s), and the 
deeper ones on the left arm (D). 
The glands are here and there shown in groups. The 
small right duct opens into the veins on the right 
side. The thoracic duct opens into the union of the 
great veins of the left side of the neck (t). THE DIGESTIVE ORGANS 
The glands of the large intestine secrete mucus 
to lubricate its surface, and to further the progress 
of the food. 
The peculiar odour of fsecal matter is ascribed to 
the presence of indol, which probably comes from 
the pancreas. 
Absorption of Constituents of Food. 
Sugars and Starches are absorbed either in the 
mouth, stomach, or small intestine. 
Fats are absorbed chiefly by the lacteals of the 
small intestine. 
Albumens are mainly altered in the stomach, 
being changed into peptones, and acted upon by the 
hydrochloric acid of the gastric juice. 
Salts, if soluble in acid, are absorbed in the 
stomach ; if in alkali, in the small intestine. 
Water is absorbed gradually throughout the 
entire length of the canal. 
Alcohol, when taken into the system, is carried 
direct to the liver, and absorbed by the blood- 
vessels. CHAPTER VIII 
THE EXCRETORY ORGANS 
The organs of excretion are those which separate 
impure matters from the blood and eliminate them 
from the body. 
The principal excretory organs are— 
(i) The lungs. 
(2) The kidneys. 
(3) The skin. 
The lungs and skin excrete volatile matters, 
carbonic acid gas, and watery vapour. 
The kidneys excrete solid matters, such as 
urea, uric acid, sundry animal products such as 
colouring matter, saline and gaseous sub- 
stances ; all held in solution by a large quantity 
of water. 
The lungs belong more correctly to the respira- 
tory organs, but are important also as excretory 
organs, for the oxygen which we inhale combines 
with the carbon, derived from waste products in the 
blood, and forms a poisonous gas, C02, or carbonic 
acid gas, which with water is exhaled or excreted THE EXCRETORY ORGANS 
67 
as breath. From impairment of the action of the 
lungs we find that— 
(2) The body has a tendency to cool. 
If respiration ceases we find that a person dies 
(x) Blood is not oxydised. 
in two or three minutes fx*om carbonic acid poi- 
soning. 
Asphyxia, or Apnoea (= cessation of breathing), 
show interference with the pulmonary circulation, 
and death in such cases would be due to carbonic 
acid poisoning. 
Dyspnoea, or difficulty of breathing, 
Carbonic acid poisoning especially affects the 
nervous system, hence the violent delirium which 
may accompany pneumonia; and some have attri- 
buted the vivid pictures which are presented 
before the mental eyes of a drowning person to 
the same cause. 
The Kidneys. 
The kidneys are placed in the loins, one on 
each side of the vertebral column ; they are fixed 
behind to the muscles of the back and are held in 
place in front by a fold of peritoneum. (The serous 
membrane, which lines the abdominal and pelvic 
cavities, and invests the viscera contained therein.) 
If under any circumstances this fold of peri- 
toneum gets stretched, it allows a kidney to fall 
forward and become displaced; it may even find 
its way down to the pelvis (as in floating kidney). 68 
ELEMENTARY PHYSIOLOGY 
The kidneys are the principal organs of the 
body for eliminating certain secretions, which if 
retained in the body prove injurious. 
a. Cortical substance composed chiefly of convoluted 
tubules and Malpighian bodies. 
b. Pyramids of medullary substance, composed of straight 
tubes and loops of Henle, radiating towards cortex. 
c. Papillae, where the tubes open into pelvis. 
d. Commencement of ureter, leading from central sac or 
pelvis. 
Fig. ix.—Section of Kidney of Man. (Cadiat). 
Each kidney is about four inches in length, THE EXCRETORY ORGANS 
69 
two to two and half inches in breadth and one 
inch in thickness. A well-developed healthy 
kidney weighs about six ounces. In the middle of 
the concave side of each kidney there is a notch 
called the hilum, which allows the passage of 
vessels, nerves, and urine (by excretory duct) into 
and out of the kidney. 
When a vertical section is made of the kidney 
we see that it consists of a central cavity sur- 
rounded by kidney substance. This central cavity 
is called the sinus and is lined by a prolongation 
of the fibrous coat which surrounds the exterior of 
the kidney and which also enters it through the 
hilum. The ureter or excretory duct dilates into 
a basin-like cavity called the pelvis ; into the pelvis 
sundry conical elevations project, called pyramids. 
Their summits present multitudes of minute open- 
ings, terminations of the urinary tubules, of which 
the thickness of the kidney is chiefly made up. 
If the tubules be traced from their opening to the 
outer edge of the kidney, they are found at first 
to lie parallel with each other in bundles, which 
radiate towards the surface and subdivide as they 
go, but at length spread out irregularly and be- 
come interlaced. From this circumstance the 
medullary or middle part of the kidney looks 
different from the cortical or superficial part, 
which latter is more abundantly supplied with 
vessels and is therefore darker in colour. 
The greater number of the urinary tubules Fig. 12.—Glomeruli of the Kidney with the origin of the 
Tubuli Uriniferi. 
a, a. Capsules of Malpighi, enclosing the glomeruli; b. Con- 
torted portion of the tubuli; c. Straight or interlobular arteries ; 
d. Afferent vessels, conveying blood to the Malpighian cor- 
puscles ; e. Glomeruli formed by the ramification of the afferent 
arteries ; /. Capsule from which a portion has been removed to 
show the glomerulus within it; g. Efferent vessels ; h. Efferent 
vessels, the divisions of which i break up into the capillary net- 
work, k, of the kidney. THE EXCRETORY ORGANS 
71 
ultimately terminate towards the surface in dilata- 
tions called Malpighian capsules. 
Into each capsule enters a small renal artery, 
which breaks up into a bunch of capillary vessels, 
called a glomerulus, which nearly fills the capsule. 
Blood is carried from the glomerulus by a small 
vein which runs into other veins and these finally 
empty themselves into the inferior vena cava. It 
is obvious that the more full the glomerulus of 
blood, the more rapid will be the escape of urine. 
Hence it is found that when blood flows freely to 
the kidney, the urine is secreted (formed) freely, 
but that when the blood supply to the kidneys is 
scanty, the urine is also scanty. The vein which 
leaves the glomerulus is much smaller than the 
artery (which is unusual), and that also accounts 
for a slower progress of the blood. 
The function therefore of the kidneys is : 
(i) To get rid of the water in the body by 
filtration. 
(2) To get rid of albuminous matter not used 
Normal urine should be acid, clear, of a yellow 
colour, and should contain no albumen and no sugar. 
It does contain urea in solution, a small quantity 
of uric acid and sundry other animal products of less 
importance. Specific gravity 1020. 
up in digestion. 
Urea is the essential solid constituent of urine, 
considered to be a result of the action of the liver 
upon some of the nitrogenous substances in the 72 
blood. Urea and uric acid are both composed of 
carbon, hydrogen, oxygen, nitrogen, but urea is far 
the more soluble in water and greatly exceeds the 
uric acid in quantity; there being 500 grs. of urea 
to 10 or 12 grains of uric acid. The total solids 
excreted by the kidneys daily equals about 1000 
grains, of which one-half is urea. 
ELEMENTARY PHYSIOLOGY 
The Skin. 
The skin forms a polished surface to all the 
Fig. 13.—Section of Skin showing the roots of three hairs 
and two large sebaceous glands (d). (Cadiat.) 
body but is variously constituted in different parts. 
The skin consist of three layers— THE EXCRETORY ORGANS 
73 
(i) Epidermis, cuticle, or scarf skin. 
(2) Derma, vera cutis, true skin or corium. 
(3) Subcutaneous tissue, the amount of which 
The ejridermis is composed of cells which have 
no blood-vessels, no nerves, no glands; it is a 
purely sheathing structure to protect the second 
layer or derma. Epithelial cells are flat and fit 
together like tesselated pavement. At the lower 
part of the epidermis is the basement membrane, 
rete mucosum, or rete Malpighii, composed of oval 
cells and containing pigment in the form of small 
granules. 
determines the mobility of skin. 
The derma, or true skin may be divided into two 
layers, the upper layer being composed of papillae, 
conical in shape, well seen on the back of the 
tongue; each papilla has its blood-vessel, a large 
distribution of nerves and dense tactile organs, 
which readily convey impression to the brain. 
Each papilla is also the rudiment of a hair. The 
second layer of the derma is composed of connective 
tissue bands interlacing with each other, permeated 
by blood-vessels, glands and fat. 
The skin has two sets of secreting organs— 
(1) Sudoriparous, or sweat glands. 
(2) Sebaceous (sebum lard) or fat glands. 
These latter are connected with the hair follicles, 
and open on the surface of the skin, thus keeping 
it smooth and moist; muscles are attached to the 
sac containing the hair follicle, which contract from 74 
ELEMENTARY PHYSIOLOGY 
cold or fright, producing goose skin. In deeper 
parts of the skin, where the connective tissue is 
loose, fat or adipose tissue collects, and serves to 
economise heat, to facilitate movement, and acts 
also as a reserve fund. 
The function of the skin is the perspiration 
(breathing through) of aqueous vapour from the 
body. Insensible perspiration is always going on; 
about three pints per diem are passed off. 
Sensible perspiration is due to exertion, activity, 
indulgence in drink, or to the emotions; thirty 
pints and more may be passed off daily. 
Perspiration is of great importance, because it 
means loss of heat to the body and therefore affects 
the temperature. 
The amount of perspiration excreted daily from 
the skin in the form of watery vapour and C02 is 
more than that excreted by the lungs; 11 parts 
being given off by the skin to 7 by the lungs. 
The body also throws off daily by the skin solid 
matter about 300 grains, C02 about 400 grains; 
the solid matter is largely urea. 
This is the function of the sudoriparous glands. 
The skin is chiefly an excretory organ, but has also 
secretory and absorptive powers. A certain 
amount of oxygen is absorbed by the skin. CHAPTER IX 
THE SECRETORY ORGANS 
By secretion is meant the separation of a special 
substance from the blood for further use in the 
economy of the body. 
A gland is an organ, or part of the body, of 
which the special function is secretion. 
The principal organs of secretion are : 
(i) The liver. 
(2) The pancreas. 
(3) The salivary glands. 
(4) The mucous glands. 
The liver is a large reddish-brown organ, situ- 
ated in the right hypochondriac region, and 
extending across the epigastrium to the left hypo- 
chondriac region ; its tx-ansverse diameter is ten to 
twelve inches, and it is about three inches thick. 
The liver is the largest and heaviest gland in the 
body, and weighs from fifty to sixty ounces. 
It consists of five lobes, sub-divided into lobules. 
These lobules are covered with areolar tissue and 
are held together by it. 76 
ELEMENTARY PHYSIOLOGY 
This areolar or connective tissue of the liver 
and its vessels and nerves are nourished by a 
special artery from the abdominal aorta, the 
hepatic artery. 
The liver is supplied with the blood from which 
it derives its secretions by the portal vein, a vessel 
which collects blood from the stomach, spleen, and 
pancreas. 
The portal vein divides and sub-divides in the 
liver till it forms a plexus of minute vessels from 
which originate the radicals of the hepatic vein, a 
vessel which conveys blood from the liver to the 
inferior vena cava. 
The spaces between the blood-vessels of the 
liver are filled with minute cells, about one 
thousandth of an inch in diameter, called hepatic, 
or liver cells. The blood capillaries run between 
these, and all changes which occur in the blood as 
it circulates through the liver are brought about 
by the action of the cells, which are separated 
from the blood only by the exceedingly thin walls 
of the arterioles. 
The materials which are separated from the 
blood appear to pass through the liver cells to 
another set of capillaries, called bile capillaries. 
These unite to form small biliary ducts which by 
further union form two larger ducts. Of these, 
one conveys the bile from the right lobe, the other 
from the left lobe; both uniting to form the 
hepatic duct. The gall bladder is connected with THE SECRETORY ORGANS 
77 
this tube by a duct of its own called the cystic duct, 
and these two unite into the common duct which 
passes directly into the duodenum. 
Eig. 14.—Cells of the Liver. One large mass shows the 
shape they assume by mutual pressure. 
a. The same free, when they become spheroid. 
b. More magnified. 
c. During active digestion containing refracting globules 
like fat. (Carpenter.) 
The gall bladder or reservoir of the bile is a 
pear-shaped bag lying on the under surface of the 
liver, and kept in place by peritoneum, which 
loosely invests the whole of the liver. Secretion 
of the bile is continuous, but it is retarded during 
fasting and increased on taking food, the quantity 
secreted in twenty-four hours being about if pint. 
Sometimes this is reabsorbed into the blood, owing 
to obstruction in the hepatic duct, and the result 78 
ELEMENTARY PHYSIOLOGY 
is a symptom called jaundice or icterus, character- 
ised by the yellow colour of the skin. 
The bile has three functions : 
(x) It works upon the fatty portions of the 
food. 
(2) It acts as an antiseptic, and prevents the 
decomposition of the food pulp. 
(3) It promotes the peristaltic movement of 
The liver also forms a substance, called glycogen, 
resembling starch and sugar in composition. This 
is carried off from the liver by the hepatic vein to 
the inferior vena cava, and thence to the lungs, 
where it is oxidised (converted into CO2 and H,O), 
thus helping to maintain the temperature of the 
body. 
the intestines. 
Bile is composed of biliary acids, fat, cholesterin, 
colouring matter, and salts. 
The pancreas, another large secretory organ, is 
situated behind the stomach, and is about 7 inches 
long and 4 inches wide in the widest part. 
The pancreas secretes a juice which passes by a 
duct into the duodenum, 12 to 16 ounces daily. 
Pancreatic juice resembles saliva, and also acts 
on starchy portions of the food which have escaped 
the influence of ptyalin in the mouth ; it has also 
a peculiar action over fatty matters and albumens, 
it aids digestion, and gives the chyle its milky 
appearance (see p. 63). 
The salivary glands are arranged in three pairs THE SECRETORY ORGANS 
79 
2 Parotid, in front of the ear. 
2 Submaxillary, beneath the jaw. 
2 Sublingual, under the tongue. 
The secretion of the saliva is continuous, about 
2 lbs. in 24 hours, and is excited on taking food 
or by the introduction of anything into the mouth, 
and by mental impressions. 
The active principle of the saliva is called 
ptyalin, and possesses the property of changing the 
starchy portions of food into sugar. 
Fig. 15.—Portion of the Mucous Surface of the end of the 
Human Ileum, moderately magnified, showing the 
Peyerian Glands, the orifices of the follicles, and the 
villi. 
Saliva serves to keep the mouth moist, helps the 
movements of the tongue and mastication of the ELEMENTARY PHYSIOLOGY 
food, and softens the food pulp, so that it may be 
easily swallowed. 
The salivary glands are not active until the fourth 
or fifth month of infantile life. 
Mucous glands separate from the blood a watery 
fluid called mucus, which serves to keep the mucous 
membranes moist. 
By its lubrication of the alimentary canal, it 
aids digestion and promotes peristaltic action. 
There are certain other glands in the body which 
have no duct, as the spleen and thyroid gland. Such 
organs are termed ductless glands, and are probably 
engaged in the formation of the blood. 
We know that atrophy of such glands causes 
disease, although their special function is not yet 
fully determined. 
Gland forms may be classed as tubulated or 
lohulated; tubulated when the secretion is con- 
veyed from the gland by minute tubes, and lohulated 
if composed of a group of sacs or lobules, commu- 
nicating with a common outlet. Although glands 
vary considerably in form, yet they are all con- 
structed on one general principle. All consist of 
a secreting membrane which is closely surrounded 
by a network of minute blood-vessels. CHAPTER X 
THE MUSCULAR SYSTEM 
The muscular system occupies little less than half 
the weight of the body and 75 per cent, of muscle 
consists of water. 
Muscle may therefore be said to consist of two 
parts, the fibrous or solid part, which is nutritious ; 
and the serous or watery portion. 
Muscles form the fleshy covering to the frame- 
work of the body; they are divided into two 
classes, according to their structure and function. 
The actions of muscles are either voluntary or 
involuntary; the former are governed by nerves 
from the cerebrospinal system. 
Those muscles not under the power of the will 
are termed involuntary and are unstriped in struc- 
ture ; while those under the power of the will are 
voluntary and striped in structure. (The heart is 
an exception to this rule, for its muscles are in- 
voluntary and yet striped, and of a peculiarly fine 
grain). 
Striped or voluntary muscles are formed of reddish 82 
ELEMENTARY PHYSIOLOGY 
fibres called fasciculi, enclosed in a delicate mem- 
brane, each fasciculus consisting of a bundle of fibres 
running parallel with each other, while the fibres 
are made up of a number of filaments or fibrillte, 
Fig. 16.—Striated Muscle Tissue of Ihe Heart, showing 
the trellis-work formed by the short branching cells, 
with central nuclei. (Carpenter.) 
enclosed in a sheath of tubular, transparent, elastic 
membrane called sarcolemma. The fibres are cy- 
lindrical in shape and marked with very fine lines 
or striae ; the primitive fibrillae contain the con- 
tractile tissue of the muscle. 
Involuntary or unstriped muscles are made up of 
spindle-shaped or fusiform cells, collected into fas- 
ciculi, lying side by side, and held together by con- THE MUSCULAR SYSTEM 
83 
nective tissue; each fibre in unstriped muscle having 
a longitudinal appearance. Every muscle consists 
of two extremities and a body. The attachment of 
a muscle to a stationary bone is called its origin and 
the attachment to a movable bone its insertion ; 
some muscles have a flat termination called apo- 
neurosis, such as the muscles of the abdomen. In- 
voluntary muscles are not attached to bones, and 
are found in the intestines, blood-vessels, glands, &c. 
They have a peculiar movement called 'peristalsis 
or vermicular contraction. Each muscle must 
be looked upon as a complete organism in itself, 
with its own supply of blood, nerves, and lym- 
phatics. 
The special function of muscle is its contractility, 
and this power of contraction is described as its tone. 
If a muscle has practically lost its power of con- 
traction it may be worked up again by some stimu- 
lus such as electricity, irritation, or massage. 
Muscles are either in a state of rest, activity, or 
rigor. Rigor mortis is the stiffening of the muscles 
after death; it comes on, as a rule, shortly after 
death and passes off some hours later. Over-taxa- 
tion of the muscles produces tremor. In fits and 
convulsions we see spasmodic contractions of the 
muscles 3 a persistent contraction is termed a tonic 
spasm, whilst an intermittent contraction is known 
as a clonic spasm. Chorea (St. Titus’ Dance) is 
spasmodic contraction of certain muscles. 
Tetanus (lockjaw), a disease following certain 84 
ELEMENTARY PHYSIOLOGY 
wounds, is spasmodic contraction of all the muscles. 
It may also arise idiopathically. Tendons are ter- 
minations of muscles by which they hold on to 
bones ; when tendons pass over hard surfaces, as at 
the elbow and the knee, sacs of fluid called bursce 
are interposed between tendon and bone to diminish 
friction. 
THE NERVOUS SYSTEM. 
The nervous system may be divided into two 
portions, the sympathetic and the cerebrospinal. 
These differ in structure, mode of action, and range 
of influence. 
The sympathetic nervous system is a chain of 
ganglia [ganglion—a small nervous centre, some- 
times called a diminutive brain) extending from 
brain to pelvis, communicating freely with the 
cerebro-spinal system and forming masses or 
plexuses (networks of interlacing nerves). 
The nervous system is composed of two struc- 
tures, cells and fibres; by the cells nerve force is 
generated, by the fibres nerve force is conducted. 
Most nerves have two kinds of fibres mingled. 
Nerves form plexuses, by which these secure a 
larger connection with the spinal cord. 
The nerves of the spinal column are thirty-one 
pairs; each nerve having two roots, an anterior and 
posterior roots. The functions of the spinal cord 
are conduction, transference, and reflex action. 
The spinal cord is covered by three membranes THE NERVOUS SYSTEM 
85 
called the dura mater, arachnoid, and pia mater ; 
these are continuous with the membranes of the 
brain. The brain is part of the cerebro-spinal 
Pig. 17.—Transverse section of nerve fibres, showing the 
axis cylinders cut across, and looking like dots sur- 
rounded by a clear zone, which is the medullary sheath. 
system and consists of (i) The cerebrum, or brain 
proper, which occupies the whole of the upper 
part of the skull or cranium. 
(2) The cerebellum, or little brain, lying beneath 
the hinder part of the cerebrum. 
(3) The medulla oblongata, or oblong marrow, 
which may be regarded as a continuation of the 
spinal cord within the cavity of the cranium, and as 
forming the connection between the brain and the 
cord. 
The cerebrum and cerebellum are partially 
divided into two lateral halves or hemispheres by 
a deep longitudinal fissure. The surface of the 
hemispheres is divided by a considerable number of 86 
ELEMENTARY PHYSIOLOGY 
tortuous furrows called convolutions, the divisions 
between the convolutions being termed sulci ; the 
use of these convolutions is to extend the surface 
of the grey matter. 
The brain is composed of grey and white matter ; 
both in the cerebrum and cerebellum the grey is 
on the outside and the white inside ; in the spinal 
cord the white is outside and the grey inside. The 
grey matter consists of cells and is considered the 
dynamic part, wdierein resides all intellectual power; 
the white matter consists of nerve fibres, efferent 
and afferent, which cross and re-cross each other in 
various directions. 
At the base of the cerebrum and connected with 
it are two large ganglionic masses of grey and white 
matter called the corpora striata ; behind them are 
two bodies of a similar nature, the optic thalami, 
and still further back are four other bodies, a 
pair on each side, called the corpora quadrigemina. 
All these parts of the brain are connected with 
each other by numerous nerve fibres ; the fibres 
from the spinal cord pass upward to the medulla 
oblongata, those from the posterior columns of the 
cord going chiefly to the optic thalami, while those 
from the anterior columns pass to the corpora 
striata. In the cerebrum and cerebellum and 
ganglia we find fibres running from their anterior 
to the posterior ends, while other fibres run trans- 
versely and unite corresponding parts on the oppo- 
site sides of the brain. THE NERVOUS SYSTEM 
87 
Functions of the different parts of the Brain. 
(1) The cerebrum is the seat of sensation, volition, 
emotion, and all those powers which constitute the 
mind—viz., the will, the intellect and the feelings. 
(2) The cerebellum is probably the regulator of 
muscular movements, or in other words, in the 
cerebellum resides the power of co-ordinate action. 
(3) The ccnpora striata are great centres of volun- 
tary movement; not of volition, but of the nervous 
mechanism by which, when we will with the cere- 
brum, the influences are sent along the spinal 
cord to the various muscles. 
(4) The optic thalami transmit sensory impres- 
sions from the spinal cord to the surface of the brain. 
(5) The corpora quadrigemina receive impressions 
from the optic nerve and transmit these to the 
cerebrum, where the sense of vision is then de- 
veloped. 
(6) The medulla oblongata and the adjoining part, 
or pons Varolii, are the seat of the nervous influ- 
ences which regulate swallowing, breathing, and 
other important involuntary movements. There- 
fore the medulla oblongata and the pons Varolii 
are absolutely essential to life. 
Other parts of the brain may be cut or mutilated 
without instant death, but death immediately fol- 
lows injury to the medulla. 
The spinal cord, or marrow, is a cylindrical 
column of soft nervous tissue extending from the 
base of the skull, where it is continuous with the 88 
ELEMENTARY PHYSIOLOGY 
medulla oblongata, to the region of the loins, on a 
level with the lower border of the first lumbar ver- 
tebra, where it tapers off in threads in the lowest 
part of the vertebral canal. Its average length 
is about eighteen inches, and it is divided by an 
anterior and posterior fissure into two hemispheres, 
each having a semilunar mass of grey matter, con- 
nected by commissural fibres. 
From the anterior horns of grey matter efferent 
nerves pass out; by the posterior, afferent nerves 
pass in. By means of the grey matter each hemi- 
sphere is subdivided into three parts, 
(i) Anterior columns. 
(3) Posterior columns. 
(2) Lateral columns. 
The weight of the brain is about fifty-two 
ounces, whilst the spinal cord weighs about one 
ounce. 
Efferent nerve fibres are the channels by which 
impulses are conveyed from nerve-centres; these 
impulses result in 
(ct) Motion (motor nerve ). 
(h) Secretion (secretory nerves), 
(c) Nutrition (trophic nerves). 
Afferent nerve fibres convey impressions to nerve- 
centres—viz.: 
(ct) Contact. 
(c) Temperature. 
In reflex action both sets of fibres are concerned ; 
the afferent fibres conveying the intelligence, and 
the efferent producing the effect. 
(h) Pressure. 
(cZ) Pain. CHAPTER XI 
THE ORGANS OF SIGHT, SMELLING, 
HEARING, AND TASTE 
The eye is constructed for the purposes of vision, 
for which are required a special arrangement of 
nerves to receive the impressions, certain convex 
transparent lenses to refract the rays or bend them 
out of the perpendicular to a focal point, and a 
protecting envelope to keep the whole in proper 
condition. 
The eyeball lies in the orbit, a conical cavity in 
the skull by which it is afforded bony protection ; 
in front it is further protected by an upper and 
lower eyelid, movable cartilaginous plates covered 
externally with skin, internally with mucous mem- 
brane (conjunctiva) and provided with hairs to 
secure a nicer apposition of the lid edges. 
Under the upper eyelid on its outer side lies the 
lachrymal gland, the function of which is to secrete 
sufficient fluid to keep the eyeball moist. This 
fluid is collected by a little canal which is formed 
in the substance of each lid at its inner part. 90 
ELEMENTARY PHYSIOLOGY 
The upper and lower canals at their point of union 
are distended into the lachrymal sac and the duct 
formed by them runs into the inferior meatus of 
the nose; when the lachrymal gland pours out its 
Fig. 18.—Ophthalmoscopic view of fundus of eye, in which 
the central artery (g and c) and the corresponding veins 
(h and d) are seen coursing through the retina from the 
optic disc ( A). 
secretions so rapidly that the ducts cannot take it 
up, it overflows on the cheek in the form of tears. 
Each eyeball lies embedded in fat, and is supplied 
with six muscles, four straight and two oblique, by 
which rotatory movements are effected. 
The globe of the eye is nearly spherical and is THE ORGANS OF SIGHT, SMELLING, ETC. 
91 
covered on its posterior five-sixths by a fibrous 
membrane (the sclerotic coat). This is pierced 
behind by the optic nerve and ophthalmic artery 
and vein ; its use is protective. 
Inside the sclerotic is found a coat also occupy- 
ing five-sixths of the circumference, and containing 
pigment and blood-vessels. This is called the 
choroid coat, and at its anterior margin it is folded 
upon itself into what are called the ciliary pro- 
cesses; its use is threefold : 
(1) To act as a dark screen. 
(2) To serve for the blood-vessels to break 
up in. 
(3) To protect. 
The anterior sixth of the globe is filled up by 
the cornea, a convex transparent membrane, the 
edges of which are tucked in under the sclerotic. 
Through the cornea can be seen the iris, a musculo- 
membranous pigmented curtain with a central 
aperture, which latter, owing to some of the 
muscles being arranged in a vertical and others in 
a circular direction, is capable of dilatation and 
contraction according as more or fewer rays of 
light are required to be admitted behind it. 
Behind the iris, with a slight space intervening, 
lies the crystalline lens; a hard bi-convex fibrous 
body enveloped in a capsule. The lens is sus- 
pended in its position by a ligament to which is 
attached a muscle (ciliary muscle) and the arrange- 
ment is such that by contraction of the ciliary 92 
ELEMENTARY PHYSIOLOGY 
muscle the tension of the suspensory ligament of 
the lens is relaxed and the lens is allowed to become 
more convex, and consequently capable of bending 
the rays of light more out of their perpendicular 
course. The space between cornea and iris (an- 
terior chamber') is filled with limpid fluid (aqueous 
humour) and this also extends into the space between 
the iris and the crystalline lens (posterior chamber). 
The remaining portion of the globe—i.e., behind 
the crystalline lens—is filled with a gelatinous mass 
[vitreous humour). 
Every ray of light in passing through a trans- 
parent medium remains in an unbroken straight 
line if the surface of that medium is plane. But 
if the surface is otherwise than plane—i.e., if it is 
convex or concave—the ray is bent out of the per- 
pendicular, inwards (if it is convex;) or outwards 
(if it is concave). This is called refraction, and the 
use of these convex lenses in the eye is to bend 
the rays of light inwards so that they meet at a 
point on the retina (focus). If the rays of light 
require to be more than usually refracted, as for 
instance in viewing a near object, the ciliary muscle 
comes into play, acting in such a way as to allow 
the crystalline to increase its natural convexity. 
This is the explanation of the effort which we 
become conscious of when looking closely at any- 
thing. But in people whose eyes are congenitally 
too short from front to back, the ciliary muscle 
is in a constant state of contraction in order THE ORGANS OF SIGHT, SMELLING, ETC. 
93 
that images may be correctly focussed on the 
retina, and as there is an intimate connection be- 
tween that branch of the third nerve which supplies 
this muscle, and that which supplies the internal 
rectus, it is found that many children are first 
discovered to have this congenital peculiarity 
{hypermetropia) by developing an internal squint: 
and moreover in most cases these squints can be 
cured by a convex spectacle lens which corrects 
the error of refraction. The headache which a 
less degree of hypermetropia induces may also be 
similarly cured. 
All rays of light, therefore, striking a convex lens 
are bent inwards, or refracted, more and more by 
each lens they pass through, until they meet at a 
point called a focus. It is clear that rays entering 
the eye are successively refracted by the cornea, 
aqueous (passing through the pupil), crystalline, 
and vitreous until they reach a point of focus, as 
might be gathered from the foregoing description, 
on the choroid. Yet it is not so; for the optic 
nerve, after piercing the sclerotic, has the choroid 
coat reflected upon its trunk, and spreads itself out 
all over the inner surface of the choroid in a thin 
coat called the retina. This retina is made up par- 
tially of nervous elements, especially suited for 
the reception of light-stimuli, and partially of con- 
nective-tissue elements, which hold the nervous 
parts together. The most superficial of the nervous 
elements are arranged in the form of rods and 94 
ELEMENTARY PHYSIOLOGY 
cones lying parallel with one another, and in the 
proportion of four or five rods to one cone. They 
are the terminal portions of the fibres of the optic 
nerve, and the vibrations set up in these by the 
stimuli of rays of light are alone capable of produc- 
ing, when transmitted to the corpora quadrigemina, 
the phenomena of sight. Obviously, therefore, the 
following are conditions which may interfere with 
vision ; 
(i) Any state of the optic nerve (neuritis or 
atrophy) which prevents images being received, or 
damage to retina, such as detachment, retinitis, 
pigmentation, and haemorrhages. 
(2) Any condition of the lenses which may 
obstruct the rays in their passage, or otherwise 
interfere with their proper focussing on the 
retina. 
Such conditions may be caused by inflammatory 
states of cornea, iris, aqueous, or vitreous, or by 
undue hardening of the crystalline from deposits in 
its substance {cataract). But they may also be 
caused by an eye, which is otherwise healthy, being 
of improper shape. In an eye too short from before 
backwards, rays will not be focussed on the retina, 
but behind it (hypermctropia); whilst in an eye too 
long from before backwards, the rays will be 
focussed in front of the retina [myopia). 
It is to meet these two difficulties that extra 
lenses are put on in the shape of spectacles, so as 
to cause either greater refraction (hypermetroptia, THE ORGANS OF SIGHT, SMELLING, ETC. 
95 
convex glass), or lesser refraction of rays [myopia, 
concave glass). 
It has been stated that the muscular fibres of 
the iris are arranged in two sets, an outer longi- 
tudinal and an inner circular. The circular fibres 
are made to contract by a branch of the third 
nerve [motor oculi), and the ciliary muscle has its 
supply from the same source. Atropine (the active 
principle of belladonna) has the peculiar property, 
amongst others, of paralysing only those fibres of 
the third nerve which are within the globe of the 
eye. Therefore, atropine drops (j to jv grs. to §j) 
are used when it is desired to dilate the pupil and 
at the same time paralyse accommodation [ the 
change produced in the lens by the action of the 
ciliary muscle). The effect of atropine lasts some 
days, but a substance known as homatropine is much 
more transient in its action, as well as more rapid. 
Eseriiie (derived from Calabar bean) has the 
opposite property—viz., of causing pupillary con- 
traction. 
Cocain causes slight dilatation, but is used really 
on account of its ansesthetic effect. 
The nose, or organ of smell, has three chambers, 
called 
Superior meatus, or upper passage. 
Middle meatus, or middle passage. 
Inferior meatus, or lower passage. 
The vertical plate of the ethmoid bone with the 
vomer separates the naves or nostrils. The ethmoid, 96 
ELEMENTARY PHYSIOLOGY 
sphenoid, superior maxillae, and two turbinated 
bones help to form the nose, together with several 
pieces of cartilage. These chambers are lined by a 
mucous membrane, called the Schneiderian mem- 
brane, and over the upper third of this mucous mem- 
brane of the nose are spread the olfactory nerves. 
The Schneiderian membrane is highly vascular, 
and if inflamed produces pain, headache, and run- 
ning of the eyes, because it is prolonged from the 
nares into the antrum, frontal sinuses, and con 
junctivae. 
In disease there is frequently discharge from the 
nose ; adenoids are thickening at the back of the 
nose or throat, which occur chiefly in childhood; 
polypus is a growth in the nose. 
The same substance exciting nerves of smell may 
cause peculiar sensations through the nerves of 
taste. 
The action of external matter produces certain 
changes on the nerves which are susceptible to an 
infinite variety of external stimuli. 
Although man is inferior to many animals in 
acuteness of smell, his delicacy of smell is most 
remarkable. 
The ear, or organ of hearing, consists of a visible 
part attached to the head, and an invisible part 
which is fixed in the petrous portion of the temporal 
bone. It comprises three divisions, called— 
(i) External ear. 
(2) Middle ear. THE ORGANS OF SIGHT, SMELLING, ETC. 
97 
The external ear is formed largely by a piece of 
elastic fibre-cartilage called the lobe, over which 
the skin is stretched with very little areolar tissue. 
This lobe is elevated and depressed at various parts, 
in order to facilitate the passage of the vibrations 
of air, known as sounds. The elevations are 
(3) Internal ear. 
named 
(1) Helix 
(2) Antihelix. 
(3) Tragus. 
(4) Antitragus 
The depressions are termed fossce, while the little 
attachment at the bottom is known as the lobule ; all 
the fossce converge to one opening, the external audi- 
tory meatus, which is a passage 1} inch in length, 
| inch being cartilaginous, and \ inch osseous. Its 
direction is inwards throughout, but also, at first 
running backwards and upwards, it finally is 
directed downwards and forwards. The effect of 
this curve is to protect the more delicate parts 
within from deleterious injuries from without. The 
skin of the meatus secretes an oily substance, 
“cerumenand this mixed up into a ball with 
hairs, dirt, and epithelial scales is apt to form 
“ wax.” The cerumen and the peculiarly long hairs 
of the skin in this passage are a natural protection 
against the invasion of foreign matters. 
At the inner end of the meatus lies the middle 
ear, drum, or tympanum. 
The drum is a six-sided chamber of about I inch 
in diameter. Its roof shows one or two fissures 98 
ELEMENTARY PHYSIOLOGY 
into which the dura mater of the brain dips down, 
and this roof is situated just below the lateral 
sinus of the dura mater • to these facts is attributed 
the occurrence of meningitis, the result, in some 
cases, of inflammation of the tympanum. Its floor 
shows nothing of importance ; its anterior wall 
presents an opening, the upper orifice of the Eus- 
tachian tube, through which air is admitted from 
the pharynx. Its posterior wall presents openings 
of communication with the mastoid cells in the 
temporal bone, and into these cells pus is apt to 
burrow when its exit in other directions is ob- 
structed. Its external wall is formed by a thin 
membrane known as the drumhead. 
On its internal wall are various eminences and 
depressions over which the facial nerve takes its 
course and here gives off that branch to the 
tongue and submaxillary gland called the chorda 
tympani. Other small nerves also assist in forming 
a plexus here. Still more important on its inner 
wall are two openings, one the fenestra rotunda, 
circular, lower down and behind ; the other the 
fenestra ovalis, egg-shaped, higher up and in front. 
Over each of these is stretched a thin membrane. 
The membrane of the fenestra rotunda is free, 
but into that of the fenestra ovalis is fitted a small 
bone, stapes (stirrup). With the outer end of this 
bone another articulates, incus (anvil), and again 
with the incus a third bone, malleus (hammer), 
forms a joint. The malleus is continued downward THE ORGANS OF SIGHT, SMELLING, ETC. 
99 
in a bony process which lies against the tympanic 
membrane ; thus a complete chain of bones runs 
across the tympanum, and these, owing to their 
solidity, are powerful conductors of sound. The 
whole of the drum is lined by mucous membrane, 
which is continuous, behind with that of the mas- 
toid cells, and in front,through the Eustachian tube, 
with that of the pharynx. 
The internal ear or labyrinth is composed of two 
cases, an outer of bone, and an inner of membrane, 
fitting exactly into one another. Each of these 
cases has three parts : 
(i) Vestibule. 
(ii) Cochlea. 
(hi) Semi-circular canals. 
The two cases are separated from immediate 
contact by a layer of fluid (perilymph) while a 
further layer of fluid lies inside the membranous 
case (endolymph). The auditory nerve, together 
with the facial nerve, passes through the internal 
auditory meatus into the membranous labyrinth, 
and there gives off its terminal branches. Each of 
these ends in a pyriform cell, which is provided 
with cilia. The vestibule is in communication with 
the middle ear by the media of the membranes 
lying over the fenestras ovalis and rotunda. Thus, 
when vibrations of air impinge upon the external 
ear, they are made to converge by the fossae into 
the external meatus; passing along this they 
stimulate the membrana tympani and throw it ELEMENTARY PHYSIOLOGY 
into vibration. These vibrations are conducted 
across the tympanum in part by the small bones, 
and in other part without their agency. Having 
crossed the tympanum, they throw the membranes 
over the fenestra ovalis and fenestra rotunda into 
vibration. These vibrations are communicated to 
the perilymph which passes them on to the walls 
of the membranous labyrinth and thence to the 
endolymph. 
The movements of the endolymph thus produced 
stimulate the cilia of the auditory cells and thence 
impressions are conveyed by the filaments of the 
auditory nerve to its larger branches, and by these 
to the brain. 
Therefore it follows that any imperfection of 
the auditory nerve itself, of its branches, or of any 
of the labyrinthine structures will prevent these 
vibrations being conveyed to the brain, and it is 
defect in one or other of these parts that produces 
nerve deafness. 
But it equally follows that imperfections in the 
conducting apparatus (external or middle ear) will 
also prevent the endolymph being duly thrown into 
commotion. Thus, a foreign body or a plug of 
wax in the external meatus, blockage of the pharyn- 
geal end of the Eustachian tube (by which air is 
prevented entering the drum, and so the drum-head 
falls inwards) inflammation of the tympanic mucous 
membrane, adhesions and ankylosis of the small 
bones, perforation of the drumhead, &c., will all THE ORGANS OF SIGHT, SMELLING, ETC. 
101 
have their share in producing imperfection in a 
delicate organ in which every part must be in a 
state of perfect working order to ensure its work 
being properly done. 
The tongue, or organ of taste, is situated in the 
floor of the mouth and is composed of muscle, fat, 
the hyoid bone, and the lingual vessels and nerves. 
The tongue is connected with the symphysis of 
the lower jaw, also with the epiglottis; also with 
the soft palate (a fold of mucous membrane and 
muscles situated at the posterior part of the mouth); 
it lies in front of the fauces, which are mucous 
folds connecting the soft palate above with the 
tongue below. There is on each side an anterior 
and a posterior pillar, and between these lies a 
tonsil. 
Each tonsil consists of a number of follicular 
glands or minute secreting crypts, liable to septic 
inflammation (hospital sore throat). Over the 
upper surface of the tongue are distributed papillae, 
of three kinds : 
(i) Gircum vallate 
(ii) Fungiform. 
(iii) Filiform. 
These are small conical eminences, which become 
enlarged and inflamed during illness. 
The tongue is considered to be typical of the 
state of the alimentary canal, and is therefore a 
helpful symptom in disease. CHAPTER XII 
INFLAMMATION 
As a rule, inflammation accompanies all disease. 
Inflammation is produced by some irritant which 
acts like a poison. 
The essence of inflammation is interference with 
the circulation ; there is dilatation of all the blood- 
vessels, with first a quickening and then a slowing 
of the blood stream. 
Blood consists of an albuminous fluid, contain- 
ing solid elements (red and white corpuscles) 
salts, the elements of fibrin, water, and refuse. 
The red corpuscles are circular with a hollowed 
centre, in fact are bi-concave discs ; they occupy 
the centre of the vessels and stick together on 
end in rouleaux; they contain haemoglobin, 
which again contains iron and has an affinity 
for oxygen; red corpuscles do not change in 
shape. 
White corpuscles exist in the blood and also in 
the tissues of the body; in the blood there is one 
white corpuscle to 300 or 400 red. INFLAMMATION 
White corpuscles are larger than red and are 
constantly changing in shape, which is due to their 
amoeboid movements—they have a tendency to 
travel along the sides of vessels and collect at 
any point of inflammation ; they are sometimes 
called leucocytes. 
Blood taken from the body coagulates, the 
coagulum consisting of fibrin and corpuscles; the 
upper layer white, as the white corpuscles are 
lighter than the red. 
In inflammation, fibrin forms a network of fine 
threads, in which the blood corpuscles become 
entangled and so form a coagulum or clot. 
In inflammation there is also effusion of coagu- 
lable fluid and abnormal multiplication of cells. 
The visible symptoms of inflammation are— 
(i) Redness. 
(3) Heat. 
(2) Swelling. 
(4) Fain. 
Redness is due to the increased flow of blood to 
the part. 
Swelling is due partly to the dilatation of the 
blood-vessels, partly to the exudation of the fluid 
contents of the blood-vessels, and partly to the 
multiplication of cells. 
Heat is due partly to the increased amount of 
blood in the part, partly to the extra amount of 
tissue destruction going on (functional activity). 
Pain is due to the pressure on the nerves. 
Alteration of function almost always accompanies 
inflammation and is owing chiefly to the abnormal 104 
ELEMENTARY PHYSIOLOGY 
multiplication of the cells of the part. If an 
inflamed part be examined under a microscope, 
the cells of the part will be seen to multiply and 
degenerate to embryonic form, and then to replace 
the solid tissue, which softens and liquefies and 
finally breaks down, the white corpuscles exude 
and migrate; they also multiply, degenerate, and 
help to destroy the solid material. In the blood- 
vessels, first the small arteries dilate, then the 
Fig. 19.—Diagram of the minute changes in inflammation 
capillary vessels, then the veins. At first the 
blood circulates rapidly, next in the centre of the 
inflammation it oscillates and finally stagnates; 
all this gives rise to redness, swelling, heat, and 
pain. INFLAMMATION 
105 
Round the area of inflammation the arteries 
dilate and blood flows rapidly, and as the vessels 
become full of blood, the fluid material exudes 
into the extra vascular tissues; the white corpus- 
cles exude through the walls and the red corpuscles 
stick together in a solid mass in the vessels. This 
exudation or plasma exudes through the walls of 
the blood-vessels into the extra-vascular tissues; 
it consists of water, albumen, salts, and fibrin in 
solution. 
The chemical nature of the plasma depends on 
the tissue inflamed; in a serous membrane, such 
as the pleura, the exudation contains serum and 
lymph. 
In inflammation of a mucous membrane there 
will not be so much exudation, and its chief 
chemical result will be mucine. 
Suppuration, or the formation of pus, marks an 
intense degree of inflammation. 
Pus is a thickish yellow fluid of alkaline re- 
action ; it consists of albuminous fluid, holding in 
suspension a large number of granular cells or 
pus corpuscles, which closely resemble the white 
corpuscles of the blood and which render the fluid 
opaque. 
The liquid is formed from plasma which has 
exuded from the blood, while the pus corpuscles 
are derived mainly from migrated leucocytes. 
Suppuration also implies destruction and degen- 
eration of tissue. 106 
ELEMENTARY PHYSIOLOGY 
Causes of inflammation. 
(i) Traumatic or mechanical injury, as in a 
compound fracture. 
(2) Physical injury, as cold, causing internal 
inflammation, as in pleurisy. 
(3) Micro-organisms, which if introduced into 
the body produce certain chemical poisons which 
irritate the tissues and set up inflammation. 
(4) Inorganic p>oisons, which if introduced into 
the body in excess, cause inflammation and 
especially affect the liver. 
Constitutional Symptoms of Inflammation. 
(1) Rise of temperature. 
(2) Headache. 
(3) Thirst. 
(4) Diminished secretions of alimentary canal. 
(5) Urine highly coloured and laden with effete 
matter. 
If it were possible to examine the blood, that 
also would be found to be laden with effete matter 
which tends to affect the functions of the liver 
and kidneys. 
Inflammation maybe acute,sub-acute, or chronic; 
its degree depends on the amount of poison in the 
system : if there is a large quantity of poison the 
inflammation will be acute, if small less acute. 
Chronic inflammation may follow acute inflam- 
mation, or may arise quite independently of it. 
Ulceration always occurs on the surface and is inflammation 
107 
destruction of the tissues from inflammation, 
particle by particle. 
Gangrene, Mortification, or death of the part, is 
generally owing to interference with the blood 
supply to the part which leads to its death. The 
skin becomes black and has blebs upon it (bullse). 
Repair is brought about by a process similar to 
inflammation. 
In this process ulceration and suppuration cease, 
while the embryonic corpuscles, entangled in the 
coagulated fibrin, throw out delicate processes which 
unite with one another to form a network, in the 
meshes of which the fibrin is then contained ; new 
vessels and new nerves start from the normal 
vessels and nerves and permeate the newly formed 
tissue, or by degrees some of the leucocytes amalga- 
mate and form what are called granulations which, 
in process of time, unite with other granulations. 
Complex tissue never grows again ; granulations 
are changed into hard connective tissue and the 
scar (cicatrix) is covered by an elongation of skin ; 
the cicatricial substance has no power of forming 
true epidermis. 
Repair is generally described as healing, (1) by 
immediate union; (2) by primary intention; 
(3) secondary intention, or by granulation; 
(4) by tertiary intention or union of two granu- 
lating surfaces. 
Healing by first intention is shown in a clean 
cut, where the sides being brought closely together ELEMENTARY PHYSIOLOGY 
are united by means of coagulable fluid. Granu- 
lations form in the lowest part of a wound and 
also on the edges of a wound, thus a wound heals 
from the centre and is closed in by two granulating 
surfaces, which gradually grow together. 
The internal method of repair is similar to the 
external method, the repairing tissue being as a 
rule similar to the normal tissue of the organ; for 
instance, a fractured bone is united by callus and 
that in time ossifies. 
A fractured patella differs from other bones in 
being united by a layer of fibrous tissue. 
Repair of arteries is brought about by the for- 
mation of a thrombus or clot. 
The thrombus may be absorbed from the injured 
vessels; then the leucocytes, aided by sprouts from the 
vessels, form a fibrous tissue which becomes adherent 
to the walls of the vessel and so strengthens them. 
The terminations of inflammation are : 
(x) Resolution. 
(2) New formation. 
(3) Suppuration. 
(By abscess we understand the formation of pus 
in a solid part; pus can never be absorbed and 
must be let out; it therefore should be treated 
surgically.) 
(4) Ulceration—destruction of tissue particle by 
particle. 
(5) Gangrene—(mortification, death of a part, 
slough) a destruction of the tissues en masse. CHAPTER XIII 
FOOD AND ITS USES 
Food is that which supplies us with energy, by 
means of which we are able to work ; it repairs the 
tissues by supplying Protoplasm. 
The ultimate structure of all the tissues of the 
body consists of cells derived from protoplasm. 
And protoplasm is formed by a chemical combi- 
nation of: 
(t) Carbon. 
(4) Nitrogen. 
(2) Hydrogen. 
(3) Oxygen. 
(5) Phosphorus. 
(6) Sulphur. 
Foods may be divided into two classes : 
Organic foods are further divided into ; 
(1) Organic. 
(2) Inorganic. 
(1) Nitrogenous. 
(2) Non-nitrogenous. 
Nitrogenous foods consist of Carbon, Hydrogen, 
Oxygen, Nitrogen, and comprise all vegetables and 
the flesh of birds, fish, and mammals. 
Non-nitrogenous foods consist of three elements: 
(1) Carbon. 
(2) Hydrogen. 
(3) Oxygen. ELEMENTARY PHYSIOLOGY 
Under this head come sugar, starches, and fats. 
Another plan of division is ; 
(1) Carbohydrates (sugars and starches). 
(2) Fats. 
(3) Proteids (nitrogenous compounds). 
(4) Mineral salts. 
A proper diet should consist of one part nitro- 
genous to three and a half or four and a half non- 
nitrogenous material. 
Or, as it may be expressed, the ratio of carbon 
and nitrogen in a perfect diet should be thirteen 
parts of carbon to one part of nitrogen. 
In bread, for example, we have twenty parts of 
carbon to one part of nitrogen ; therefore bread is 
rich in carbohydrates, but deficient in proteid. 
A somewhat fanciful classification of food is ; 
4 (1) Proteids (flesh-formers). 
(2) Carbohydrates and fats (body-warmers). 
(3) Salts, principally phosphates (bone- 
formers). 
Now, food to be conveyed to the tissues in a suit- 
able form for absorption must pass through the 
process of digestion. 
By digestion (Lat., digerere, to carry in various 
directions) we understand the various chemical pro- 
cesses by means of which the nourishing part of 
our food is separated from that which is not nourish- 
ing, and the mode by which the nourishment thus 
gained is carried to the tissues. 
It is the function, therefore, of the digestive FOOD AND ITS USES 
organs to act upon our food, and by means of 
certain chemical agencies, in the saliva, in the 
Water. 
Carbohydrates. 
Fats. 
Proteids. 
Human milk 
Cow’s milk 
Meat 
Fish 
Leguminous 
fruits 
Potatoes 
Green 
vegetables. 
Bread 
Fig. 20.—Diagram showing the proportion of the principle 
food-stuffs in a few typical comestibles. The numbers 
indicate percentages. Salts and indigestible materials 
omitted. 
gastric juice, and in the pancreatic and hepatic 
juices, either to dissolve the food, or to break it up ELEMENTARY PHYSIOLOGY 
into the smallest possible globules suitable for 
assimilation. 
A carbohydrate consists of the element carbon (C) 
united with water (H2O). 
Starch is a carbohydrate. The chemical formula 
for starch is C 6H10O5 or C 65( 
Starch is a white, amorphous powder, not soluble 
in cold water; when pure, tasteless; if boiled, 
forming a mucilage, or jelly; it is also very easily 
dissolved. 
In the mouth starchy foods are dissolved and 
converted into sugar by a substance in the saliva, 
called ptyalin. When starch is heated, a chemical 
change takes place, and the starch is converted into 
dextrine (a gummy substance formed by the action 
of heat and acids upon starch.) 
This change takes place in flour. 
Bread is made by mixing flour and water into a 
paste, called dough, which is very tenacious and 
close. Flour contains, besides starch, a proteid 
(gluten), which gives the toughness to the 
dough. 
For the separation and breaking-up of this gluten 
in the making of bread, yeast is used. 
Yeast is a living plant, which will grow in a solu- 
tion of sugar. 
Yeast causes fermentation, a chemical operation 
by means of which starch is converted into sugar. 
The dough is kept for a time in a warm place, and 
by the yeast, starch is converted into dextrine, and breaks up again into carbonic acid gas (CO2) and 
water (H2O). 
It is really the action of the C02 which separates 
the gluten and aerates the bread. 
For this purpose also baking powders, containing 
carbonate or bicarbonate of soda and tartaric acid, 
are used, as by the action of the acids on the car 
bonates C02 is formed, and the gluten is thus sepa- 
rated and the bread aerated. 
FOOD AND ITS USES 
113 
Chemical Constituents of Bread. 
Carbohydrates . . . 49^4 
Fats ..... x' 3 
Proteid . . . . B'o 
Mineral salt . . . . I*3 
Water . ... 40-0 
Per cent. 
All proteids (often also termed albuminoids) con- 
tain carbon, hydrogen, oxygen, and nearly always 
15 per cent, of nitrogen. There are both animal 
and vegetable proteids. The amount of nitrogen in 
most plants is 15 per cent. Animal proteid is more 
easily digested than vegetable by the ferments of 
the various digestive juices. A principal proteid 
is albumen, found in its simplest form in white of 
egg ; this may be considered an albuminoid, or type 
of soluble proteid. Some idea of the amount of 
proteid in different foods may be formed from the 
following scale : ELEMENTARY PHYSIOLOGY 
Proteid in Food. 
Per cent. 
Meat . . . . .20 
Fish . . . . .18 
Eggs 14 
Bread . . . .8 
Milk 4 
Potatoes : . . . . i|- 
The only food prepared for us naturally in exact 
chemical proportions to sustain life is milk. 
Chemical Constituents of Milk. 
Per cent. 
Carbohydrates . . . 4‘B 
Fats . . . . . 37 
Proteid ..... 4-o 
Salts ..... 7 
Water ..... 86-8 
Milk may be defined as an emulsion of fat in a 
watery solution of soluble proteids and salts. If 
milk is allowed to stand, cream rises to the top, 
which is a partial separation of the fat. 
Good milk should give 10 to 12 per cent, cream. 
The total amount of solids in milk should be 13 
per cent.; with fats removed, 97 per cent. 
When milk is boiled a scum is given off, a soluble 
proteid—viz., albumen. 
The chief proteid in milk is called casein; and FOOD AND ITS USES 
skim-milk and buttermilk, although deprived of 
fat, are still very nourishing. 
Inorganic foods comprise mainly water, salts, 
and phosphates. 
Water is a most useful ingredient in our 
systems ; it serves to dilute the more solid portions 
of our food, to carry them to the various tissues of 
the body, and to wash away waste material. 
It appears, then, that the use of food to the 
body is to repair the waste of all tissues and to 
produce heat, muscular power, brain power, and 
power to form secretions and excretions. The 
origin of our bodily powers is now said to be owing 
to the transformation of force brought about by 
the influence of the sun’s rays. The sun’s rays are 
a means of chemical force. We give off from the 
body carbonic acid gas; the green leaves of plants, 
under the influence of the sun’s rays, have the 
power of decomposing C02, by taking up the carbon 
and setting free the oxygen. 
One fifth of the atmosphere consists of oxygen, 
which we draw in as we breathe, and without 
which we cannot live, Four-fifths of the atmo- 
sphere consist of nitrogen, which we require but 
cannot take from the air; but plants, under the 
influence of the sun’s rays, combine carbon and 
nitrogen in their structure, taking the carbon 
from the air and the nitrogen from the soil. 
Therefore when we eat plants, digestion de- 
composes these elements, and the force which 116 
ELEMENTARY PHYSIOLOGY 
bound them together imparts to us heat and vital 
power. 
Thus, also, animals feed on plants, digest them, 
and store up chemical force, which again is imparted 
to us when we feed on them. 
It is proved, also, that the different elements of 
which our food is composed are given off in various 
forms from the body. 
Oxygen, drawn into the lungs, combines with 
the carbon in the blood derived from food, and is 
given off by the breath and the skin, in the form 
of carbonic acid gas (CO2). 
Hydrogen combined with oxygen is given off as 
water (H2O) by the breath, in perspiration, and in 
the urine. 
Nitrogen is eliminated from the system in urea, 
salts, and phosphates. 
Food taken into the body may be considered as 
fuel, giving rise to the body’s heat by the setting 
free of chemical force. 
The heat of the body is called its temperature; 
and in health a certain amount of heat is used 
up in tissue-construction. In disease, however, 
tissue-construction is at a standstill; consequently 
the heat naturally used up in tissue construction 
is set free and the temperature of the body rises. 
This fact will also explain the wasting which takes 
place in prolonged fevers. CHAPTER XIV 
VENTILATION 
By ventilation we understand the removal of 
impure air, so that an access of pure air from the 
outside atmosphere may take its place. Air is 
made up of gases and is invisible, without colour, 
taste, or smell. The air we inhale is composed of 
oxygen 21 per cent., or about one-fifth of the 
whole, and nitrogen 79 per cent., or about four- 
fifths, with a trace of carbonic acid gas and a 
variable proportion of watery vapour; whilst the 
air we exhale contains about 5 per cent, less oxygen 
and 5 per cent, more carbonic acid gas, with an 
increased proportion of watery vapour, the nitrogen 
remaining about the same. Oxygen is the life- 
giving principle of the air, whilst nitrogen extin- 
guishes life, but serves to dilute oxygen as water 
does wine. 
We cannot live without oxygen; if a person 
were to shut himself in a room without any means 
of ventilation, the air he breathed would gradually 
be deprived of oxygen and its place taken by C02, ELEMENTARY PHYSIOLOGY 
which would be inhaled and by degrees saturate 
the blood, and would in time cause death from 
asphyxia (cessation of pulse caused by suffocation), 
more due to the deprivation of oxygen than to the 
effects of C02, which in small quantities is only 
slightly poisonous and produces no immediate 
effect on the animal system if the supply of oxygen 
is increased in proportion. It is very questionable 
if it is the C02 {per se) which is poisonous. In 
expired air organic matter is in exact and per- 
petual ratio with the COa, and it is the organic 
matter which mainly does the damage if not 
exhaled. 
In cases of drowning, choking, &c., no oxygen 
can enter the blood, whilst C02 is rapidly accumu- 
mulating and rendering the blood venous; death 
occurs in a few minutes partly from C02 poisoning, 
but chiefly from starvation for want of oxygen, 
and to excess of organic matter. 
Proper ventilation for a sick-room is best de- 
scribed as clean air displacing foul air constantly 
and steadily, without chilling the patient. 
The air outside our room is colder as a rule than 
that inside, and what we wish to do is to let out 
the used-up air, at the same time introducing ex- 
ternal air and warming it as it enters the room. 
It is proved by experience that a very satisfac- 
tory manner of ventilating a sick-room is to keep 
a fire burning, and to have the windows open a 
few inches at the top. By this means the warm VENTILATION 
foul air, which being lighter has a tendency to 
ascend, will pass up the chimney, and its place 
will be supplied by external air coming in at the 
top by the window; and as cold air being heavier 
has a tendency to descend, it will come down into 
the room and be gradually warmed as it mixes with 
the internal air in its descent. 
Ventilation, to be thorough, must be systematic 
and not supplied in jerks. It is frequent changes 
of temperature that do harm. An inrush of cold 
air makes a draught and causes discomfort and 
frequently gives cold, particularly to those suffer- 
ing from illness, whose vital power is lowered for 
the time. An excellent method of ventilation is 
to have perforated openings in the upper part of 
the wall, connected with a shaft leading to the 
outside, by which warm air may escape, and to 
have a piece of wood the exact width of the 
window frame inserted underneath the lower sash 
which would close down upon it. In this way air 
must enter by the space between the sashes, which 
of necessity are open when the lower sash is raised. 
A patient cannot then see that the window is 
open and will probably not complain, also very 
little draught is felt in this way. 
Careful ventilation is an important point of 
skilful nursing, and requires judgment and common 
sense. In order, therefore, to ventilate thoroughly 
we must have an inlet for fresh air, and an outlet 
for foul air. ELEMENTARY PHYSIOLOGY 
Those who think to ventilate by one opening 
deceive themselves ; for the warm, foul air going 
out interferes with the entrance of the fresh air. 
In the ventilation of rooms, wards, &c., it is better 
that the outlet for foul air should be near the 
ceiling, because hot air is warm and heat expands, 
and therefore makes things light, and they ascend. 
The inlet for fresh air should be lower down, 
and arranged to avoid draughts, because fresh air 
is cold, and being heavy has a tendency to descend. 
Door and window of a sick-room should never be 
open at the same time; that always causes a 
draught. Nurses should remember that “win- 
dows are made to open, and doors are made to 
shut.” 
Night air is often the freshest in the twenty- 
four hours, particularly in London and big towns; 
it is therefore a good plan to keep the windows 
open at night a couple of inches at the top. 
There should always be a fire in a sick room, as 
in this manner air is warmed and also carried up 
the chimney. 
Combustion also is supported by oxygen ; there- 
fore a fire burning brightly proves the presence of 
plenty of oxygen. 
The temperature of a room is easily told by the 
thermometer, which, though it does not show the 
freshness of the air, is a very useful guide. 
Temperature of an ordinary dwelling-room 
should be about 570. VENTILATION 
Temperature of a surgical ward or sick-room 
should be about 58°. 
Temperature of a medical ward or sick-room 
should be about 63°. 
Temperature of theatre for ordinary operations 
should be about 65°. 
Temperature of theatre for abdominal operations 
should be about 70°. 
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