Henry Stewart.

The shepherd's manual. A practical treatise on the sheep online

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body derive materials for their nutrition, growth, or repair, and
for their secretions. The blood is replenished with new matter
from the digestive organs, which dissolve and prepare the food
for this purpose. To carry on circulation, an apparatus is pro-
vided which consists of the heart, the arteries, the capillaries which
form the connecting link between the extremities of the smallest
branches of the arteries and those of the veins; the veins; the ar-
teries of the lungs ; the lungs with their capillaries, and the veins of
the lungs. There is thus a double circulation as it were, which
may be readily understood by a reference to the diagram, fig. 69,

in which C I) represents
the left auricle of the
heart, which forces the
blood through the arteries
E, in the direction of the
arrows to the fine net-
work of the capillaries;
then to the veins F, and
Fig. 69. DIAGRAM OF THE oiEOULATioN. thence to the right auricle

of the heart, A B. From

this it is forced through the right ventricle which opens from the
right auricle into the pulmonary artery G, still following the course
indicated by the arrows, into the net-work of the capillaries of the
lungs, from which it is conveyed by the pulmonary vein H t into
the left ventricle, whence it passes to the left auricle, on the same
course over again. The heart is a mass of very strong muscular
fiber, having the four cavities just mentioned, and being supplied
with valves which regulate the flow of the blood. The muscles of
the heart contract and expand with regularity, performing what
we usually term its " beats," four times or thereabouts for every
inspiration of the lungs. In a young sheep the heart beats 80 to
90 times in a minute ; a full grown one, 70 to 80 times, and in a
very old one, 55 to 60 times. At each contraction the blood is
forced through the arteries and their branches to the capillaries.
These capillaries are exceedingly small, being from y 20 oo to Yseooth
part of an inch hi diameter, and inosculate or join together again
and again, forming a net-work of the closest character, so close
that the finest needle cannot penetrate the skin or membranes any-
where without wounding one or more of them, and causing an
escape of blood. While circulating in this net- work of capillaries,
the blood gives up to the tissues amongst which it circulates, the
materials needed for their growth and increase, and also to sup-



178 THE SHEPHERD'S MANUAL.

ply the waste of matter caused by every mechanical movement of
the animal; for every contraction of the fibers of the muscles
causes a decomposition and destruction of some portion of their
substance. Hence is explained the waste of matter or loss of
weight caused by excessive exertion or insufficient food. Here
the blood also absorbs the dead, used up matter created by this de-
composition and destruction of tissue, and carries it off from the
system. This it does by means of the skin, the kidneys, and the
lungs, through which the blood is filtered as it were of matters
useless to the system by means of these capillaries ; and the excre-
tions of perspiration both sensible and insensible, that of the urine,
with some others, are thus thrown off. In this manner the blood
becomes depleted of its nutritive properties, and absorbs the wastes
of the system in its intricate course through these infinitely small
capillaries. It enters them from the arteries a bright red, and
leaves them a dark, blackish purple fluid. It courses onwards
through the veins loaded with impurities, to the lungs, which it
enters still a dark fluid ; here it passes through a second set of
capillaries much finer than the former, in which it is exposed to
pure air contained in the cells of the lungs ; the carbonaceous mat-
ters it contains come in contact with the oxygen of the air, and are
decomposed, burned in fact, giving forth the heat needed for the
continuance of life ; when the blood thus rendered pure, leaves
the lungs a bright red once more, again fitted to fulfill its func-
tions. Before entering into the lungs, the blood receives a new
supply of matter from the lymphatic vessels, called lymph, which
is derived from the digested food. The vessel which conveys the
lymph or chyle, is called the thoracic duct, and passes upwards
into the cavity of the chest in close contact with the vertebrae or
spine. The temperature of the blood of the healthy sheep is 100.
The blood is now believed to possess vitality ; while its circulation
exists it is fluid, and when it is dead it coagulates. The cause of the
coagulation of the blood is not known, and there is a difference
between its coagulation in and out of the body. If a part of the
body be wounded, the blood which escapes from the divided ves-
sels, coagulates between the edges of the wound, forms a clot of
organized material, throws out new vessels, and gradually restores
the wounded parts. It is this coagulating property which saves
the life of a wounded animal and directly leads to recovery ; if
the blood remained fluid, the least wound would cause a flow
which would not stop until the vessels were empty and the animal
dead. The constituents of the blood are exactly those of flesh.
Digestion is the process by which food is taken into the body,



DIGESTION. 179

masticated, dissolved by the stomach and intestines, and rendered
fit for absorption by the lacteals and lymphatics, and assimilation
by the blood. The parts concerned in digestion are the lips, teeth,
and tongue, the salivary glands, the gullet, the stomach, the intes-
tines, the liver, the lacteals, and the thoracic duct which connects
the digestive process with the direct function of circulation and
nutrition. The lips are used by the sheep in gathering its food,
very much as they are used by the horse, and to a much greater ex-
tent than by the ox. The sheep's lips are thin, and very active in
their movement. The upper lip is divided by a groove, or fissure,
so that each half can be moved independently of the other. The
sheep possesses no muffle or broad space between the nostrils on
the upper lip, which in health secretes a liquid which appears in
small drops upon its surface, as in the ox. The teeth have been
already described. Their office is well known. The tongue serves
to convey the food to the teeth, and from the teeth to the gullet,
and also the cud from the gullet to the teeth. The salivary glands
secrete a fluid which moistens the food during mastication, and
which also possesses some of the character of a solvent, or a pre-
paratory digestive agent, in being able to convert starch into solu-
ble dextrine and sugar, and thus prepare it for digestion by the
stomach. The glands are three in number, and are named the
parotid, the submaxillary, and the sublingual. The first is situated
at the outside of the angle of the lower jaw ; the second is placed
on the inside of the lower jaw, near the angle ; and the third is
beneath the tongue. Ducts from these glands give out the saliva
naturally whenever the membranes of the mouth are excited by
the presence of food ; or unduly, as in some diseases which cause
an excessive secretion of the fluid. The gullet conveys food or
drink from the mouth to the stomach. The pharynx is the upper
part of the gullet, by which it is connected with the mouth. It is
separated from the larynx, the entrance into the windpipe or air
passage, by a cartilaginous lid called the epiglottis, which, when
food is swallowed, closes the larynx and allows the food to slide
over it. The pharynx, gullet, stomach and intestines, together
form what is termed the alimentary canal. The gullet, also called
the oesophagus, is a very strong, muscular tube, lined with insensi-
ble white membrane. The fibers of the muscles run spirally
around the tube, in opposite directions, and thus cross each other.
By the contraction of these muscles, gradually extending down-
wards, food is carried into the stomach ; while by their contrac-
tion in an upward direction, the food is brought back to the
mouth to be masticated the second time in the process of rumina-



180



THE SHEPHERD'S MANUAL.




Fig. 70. RIGHT SIDE OF THE
STOMACH.



tion. The food taken up by the lips and ^eeth is ground and
mixed with saliva in the mouth, passed backwards by the action
of the tongue to the gullet, and then forced into the stomach.

The stomach of the sheep consists of a large irregular sac or pouch,
divided into four compartments, generally referred to as distinct
stomachs, or the first, second, third,
and fourth stomachs, (see figs. 70, 71,
and 72), or the rumen or paunch,
seen at 6; the reticulurn or honey-
comb, c ; the omasum or manyplies,
d-, and the abomasum, or rennet, or
true digestive stomach, e. The gul-
let is seen at a, and the duodenum at
/. The functions of the stomachs
of the ruminating animals are known
only somewhat obscurely. Anatomy
only teaches their form and charac-
ter, and leaves all the rest hi doubt,
or to be decided by experiment and
observation. From the structure of
the stomachs we are able to form a generally complete idea of the
process of digestion which goes on within them ; of some of the
details there is nothing certain as yet to offer. The first two
stomachs are placed parallel to each other, and the gullet ends
almost equally in each, as seen at a
in fig. 72, which shows the inside
formation of the stomachs. The
second stomach, c, communicates
with the third by the oesophagean
canal, g, which opens into the third
stomach, (not seen in figs. 70 and 71),
and ends there. The fourth stomach
is connected with the third by a
distinct opening. The paunch, &, is
the largest compartment, being four
times the capacity of the other three
together. It is divided into four in-
complete compartments by muscular
walls, and is lined with a membrane covered by a multitude of soft
pillars compressed closely together, which make an uneven surface.
The second stomach, c, is lined with cells having five or six sides
from which it takes the common name, the honeycomb. These
two compartments, or stomachs, are in reality one, the latter being




Fig. 71. LEFT SIDE OF THE
STOMACH.




THE STOMACH. 181

simply an appendage of the former. The cesophagean canal which
leads from the second stomach to the third, performs a very im-
portant function in the act of rumi-
nation, or it is supposed -with reason
so to do, as will be explained further on.
The third stomach or " manyplies,"
in the sheep the smallest of the stom-
achs, is lined with a number of leaves
or folds, placed lengthwise, by which
the surface is greatly increased. The
fourth stomach joins the third, and
communicates with it by an opening
immediately opposite to the O3sopha-
gean orifice. The fourth stomach is
lined with a membrane which secretes Fig. 72. INTEKIOR OF THE
the gastric juice, the true digestive STOMACH.

solvent. It opens directly into the duodenum or small intestine.

Rumination, or chewing the cud, is a process which distinguishes
a class of animals, known as ruminants, from all others. For the
performance of this process the complicated stomach above de-
scribed is provided. To understand this important alimentary
process, it is necessary to ascertain first, into which of the stom-
achs the food passes after its first mastication ; second, in what
manner and by what process the food is rejected by these stom-
achs and returned to the mouth for a second mastication ; third,
to which of the stomachs is the food finally transmitted for com-
plete digestion.

Some careful experiments, by the French physiologist, Flourens,
have to a great extent determined these questions ; and the com-
parative anatomist, Chauveau, has summed up the functions of the
stomachs of ruminants as ascertained from every modern source
of information as follows :

1st. The rumen is a sac in which the food swallowed during
feeding time is held in reserve, and is softened, and whence it is
ed to the mouth during rumination.

The reticulum partakes of the functions of the rumen, to
which it\)lays the part of an accessory or reservoir ; the food con-
tained hi it being always diluted by a larger quantitjr of water.

3rd. The czsophagean canal carries into the omasum the food
swallowed the second time, or after rumination, or even those por-
tions of food which the animal swallows in wry small quantity and
in a finely divided or softened condition the first time.



182 THE SHEPHERD'S MANUAL.

4th. The omasum completes the maceration or reduction of the
food to a sufficiently fine condition for digestion, by pressing it
between its leaves.

5th. The abomasum is the true digestive stomach, and finally
dissolves the food by its gastric secretion.

In these processes the cesophagean canal performs a peculiar func-
tion. The ordinary food of the ruminating animal is coarse in
texture, aud when swallowed is bulky. When it enters into the
stomach and meets the opening of the oesophagean canal, it forces
open, by its bulk, the muscular lips of which the opening is com-
posed, and drops partly into the first, and partly into the second
stomach. M. Flourens has satisfied himself, by careful experi-
ments upon a living sheep, that when the animal ruminates, a por-
tion of the food swallowed previously and now contained in the
first and second stomachs which are really one is forced by a
contraction of the stomach into the oesophagean canal, and this then
contracting, closes all the other openings except that of the gullet,
and at the same time compresses the morsel of food into a pellet or
ball, which is immediately forced by the upward muscular con-
traction of the gullet into the mouth. When it has been chewed
and mingled with the copious secretion of saliva which takes place
during rumination, it is again swallowed. Being now softened
and in a semi-liquid condition, it passes over the lips of the open-
ing of the canal, without forcing them apart, into the second
stomach, and enters the third stomach ; a small portion of it only
escaping into the first and second stomachs. When fine or semi-
liquid food is first swallowed, it follows exactly the same course,
the same being true of water when drank. From the third stom-
ach the food passes on to the fourth stomach to be finally disposed
of. It has been found that the pellets of food, returned to the
mouth for rumination, are of the precise size, shape, and form of
the portion of the oesophagean canal between the first and third
stomachs. Sheep have been dissected with these pellets ready
formed in the canal for transmission to the mouth.

The intestines of the sheep are of great length, being twenty-
eight times longer than its body. In the duodenum, which is the
upper portion of the intestines that directly communicates with
the lower orifice of the stomach, the partially digested mass of
food undergoes still further changes. As it passes from the stom-
ach it is termed chyme. In the duodenum the chyme is mingled
with the bile, which comes from the liver, and the pancreatic juice,
a secretion of the pancreas, or " sweet-bread," and becomes fitted



THE LIVER. 183

for absorption by the lacteals which communicate with the intes-
tines. It is now termed chyle, and is a white milky fluid which
enters the thoracic duct and mingles with the blood as previously
described. The refuse and insoluble portion of the food, with un-
used portions of the bile pass on through the lower intestines, and
is discharged by the rectum as dung.

The liver is a large organ with the appearance of which almost
every person is familiar. It is called a gland, because its office is
to secrete a fluid which is peculiar to it, and it is the largest gland
in the body. Its secretion is called the bile. Its position in the
body is below the diaphragm and adjacent to the stomachs, with
the third of which it is in direct contact. It is enveloped in the
peritoneum or membrane which covers and also encloses the whole
of the contents of the abdomen, and forms as it were a sac or bag,
one-half of which is doubled into the other half. The liver hi sub-
stance is granular, consisting of grains, or lobules, from one-tenth
to one-twentieth of an inch in diameter. Its color is reddish
brown. The lobules of which it is composed are closely packed,
and are held together by fine tissue and a net-work of minute
veins and ducts. Each lobule is connected with a blood vessel at
its base, and another vessel comes from the center of the lobule
and joins the former one at its base. Between these two is an
exceedingly fine net-work of capillary vessels similar to those pre-
viously described. By means of arteries and veins called portal
canals, which enter and ramify through the substance of the liver,
the blood is carried into and through the substance of each lobule
in streams of exceeding fineness. From the blood thus passing
through the lobules, the gall or bile is secreted by small cells not ex-
ceeding Vioooth of an inch in diameter, and is collected into minute
vessels called biliary ducts, from which it is gathered into larger
ducts, which pour their contents into the great bile ducts. There is
a receptacle in the liver of the sheep known as the gall-bladder, to
which the gall is carried from the hepatic duct by another duct
named the cystic duct. When the gall contained in the gall-blad-
der is required for use, it returns by the same duct into the hepatic
duct, and thence into the great bile duct which ends in the duo-
denum, below the stomach.

The gall is an alkaline fluid of composite character, containing
soda, two peculiar acids, (glycocholic and taurocholic, the latter of
which contains sulphur) ; mucus ; cholesterine ; stearic, oleic, and
lactic acids, with potash and ammonia, and a peculiar coloring
matter. It is in fact a sort of liquid soap. The bile is poured
into the duodenum by the great bile duct. Near this duct is



18-4 THE SHEPHERD'S MANUAL.

another from which flows the secretion of the pancreas or
sweet-bread. This fluid is slightly alkaline and very similar to
the saliva. Its office is supposed to be to change the un dissolved
starch in the chyme into sugar, and to form an emulsion with the
oil or fat of the food, and prepare it for absorption directly into
the blood or into the lacteals. The office of the gall is to neutral-
ize the acidity of the chyme derived from the gastric juice, which
is an acid fluid, to assist in the transformation of starch into su-
gar, and the absorption of oil or fat. It is the chief agent in
changing the chyme of the stomach into the chyle, which is the
perfected source of nutrition of the blood. The perfect action of
the liver is therefore absolutely necessary to the sustenance and
the life of the animal. The quantity of gall secreted by the liver
of the sheep every twenty-four hours is from 3 to 5 pounds. The
whole of this, however, is not destroyed in the performance of its
office, but a large portion is taken into the system in the circula-
tion, the surplus being regained from the blood by the secreting
cells of the liver and again returned for duty to the intestines.
Another office of the liver is to prepare crude albuminous matter
of the blood for final absorption into it. It is also able to form
sugar from other carbonaceous matters conveyed to it in the chyle
absorbed by the lacteal vessels. Thus the liver acts as a filter, in
separating detrimental matters from the blood, besides supplying
a necessary agent in digestion, as well as for respiration. Its im-
portance in the animal functions cannot be over-estimated.

The lacteals are a series of small absorbent vessels which form a
net-work in connection with the coats of the intestines, and pro-
ceed to the thoracic duct, where they terminate. They exist much
more numerously in connection with the small intestines than
with the lower ones. Their chief seat is the mesentery, which is
the thin membrane which supports the small intestines. The lac-
teals enter the numerous glands of the mesentery, and pass
through them, uniting to form larger vessels and becoming fewer
and fewer in number, being finally reduced to two or three ducts
which end in the thoracic duct. The lacteals absorb the chyle,
which is presented to them in the intestines, convey it to the glands
In which it is enriched and perfected, and thence convey it to
the vessels which terminate in the duct from which the new nutri-
tive matter is poured into the large vein near its junction with the
heart, to enter into the circulation.

The chyle is very similar in its composition to the blood, differ-
ing from it chiefly in the absence of coloring matter, or the red
globules which give the color to the blood. It coagulates on



THE EXCBETORY ORGAN'S. 185

being allowed to rest, although the clot is softer than that of the
blood.

The thoracic duct extends from the loins to the neck, and its
course is along the spine. It is the principal trunk of the absorb-
ent system, and, as has been explained, is the connecting link be-
tween the digestive organs and the circulatory system, as the pul-
monary artery and vein is the connecting link between the circu-
latory and respiratory system.

2Jie spleenis another organ which is very important, as being the
seat of a rather obscurely understood disease, known as splenic
apoplexy. It consists of a spongy mass of tissue of a mottled blue
or purplish gray color. It is suspended near the great curvature
of the stomach, but of its functions nothing is precisely known.
It is supposed to act as a reservoir of blood for the portal vein ; it
is also supposed to destroy the red globules of the blood, as it
has been discovered to contain blood globules in a state of decom-
position. It is, however, known that, in the course of researches
to discover the uses of this gland, animals from which it has been
removed have recovered from the operation, and have continued
to live in apparent good health. The fact of its engorgement
with blood in the disease of ruminants known as splenic fever or
apoplexy, and its increase of volume in certain bilious disorders,
would tend to show that its functions are in some way closely
connected with the circulation, and perhaps with the digestive
processes and nutrition.

The Urinary or Excretory Organs. The urine is separated from
the arterial blood by the kidneys. These organs, with the liver
and the lungs, are employed in the purification of the blood. The
liver separates compounds abounding in hydrogen, the lungs those
which abound in carbon, and the kidneys those abounding in ni-
trogen. The nitrogen eliminated through the kidneys exists in
the form of urea, a crystalline substance which readily decomposes
and gives off its nitrogen in the form of ammonia. There are two
kidneys, one each side of the spinal column. The kidneys are
attached firmly to the loins ; in the sheep they are shaped like a
bean, and are imbedded in fat. They perform a double office, or
two separate functions, one being to discharge from the blood any
excess of water that may accumulate in it ; the other being to rid
the blood of excess of saline matter and the products that result
from the waste of the tissues. The blood enters the kidneys by
arteries, and the urine, separated as by a filter, through a very com-
plex system of capillaries, flows into two white ducts termed ure-
ters, which pass it onwards to the bladder. The urine of the



186 THE SHEPHERD'S HAKUAL.

sheep is not so copious as that of the cow in proportion to its size,
but possesses a larger proportion of salts. The following is an
analysis of sheep's urine :

Water 96.0 per cent.

Urea with some albuminoids and coloring matter 2.8 " "
Salts of potash, soda, lime, magnesia, silica, iron,
alumina, and manganese T . . 1.2 " "

100.00 "

In fig. 73 is shown a section of the substance of the kidney
highly magnified, in which appear the uriniferous, (urine carrying)
ducts or tubes, (a, a), surrounded by the secreting glandular sub-
stance, (&, &), which is enclosed in the net-work of the arteries,
(c, c), and the fibrous tissue, (tf, d).

The bladder is situated hi the pelvic cavity, or the lower part of
the abdomen. It is composed of two coats, the outer one being
muscular, and capable of contracting so as to expel its contents.
One half is enveloped in a third coat, and the other half in the
/, tissue of the pelvic

. n '-

region, and masses of
fatty matter. The mus-
cular coat consists of
fibers Placed in various
directions, lengthwise,
crosswise, oblique, and
spiral, so that in the act
of contraction the blad-


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Online LibraryHenry StewartThe shepherd's manual. A practical treatise on the sheep → online text (page 16 of 23)