in the posterior half of the body of the bird, somewhat to the right of
the posterior aorta, near the anterior lobe of the kidney, by the union
of the right and the left vena iliaca communis. It receives the blood
from all of the posterior half of the body including the posterior
limbs, of the visceral organs, of the abdominal and the pelvic cavity.
The posterior vena cava passes dorsally through the right lobe of the
liver and through the diaphragm and ends in a short, broad trunk on the
posterior dorsal side of the right auricle of the heart. Its opening
into the heart is guarded by two half-moon shaped valves. The basal part
of the trunk reaches from the right auricle of the heart to the upper
anterior rim of the liver where it receives three large trunks, first,
the right and second, the left vena portalis hepatica magna, and third,
smaller vessels from the liver substance.
THE VEINS OF THE POSTERIOR EXTREMITY
In the skin region on the inner sides of the toes near their bases the
small veins collect into five metatarsal veins. The largest vein
collects the blood from the first, the second, and the third toe, passes
up the tarsus and is called the vena metatarsalis interna, or vena magna
(Fig. 65, No. 7). It is located just beneath the skin on the inner
surface of the metatarsal bone. It passes in a circle, around the
condyle of the tibia and becomes the =vena tibialis postica= (Fig. 65,
No. 3 and 8). The vena tibialis postica passes under the tendon Achillis
and the tendon of the flexor digitorum brevis, lies subcutaneously upon
the latter, and reaching the knee-joint crosses over the upper surface
of the ischiadic nerve and becomes the =vena poplitealis=, at which
point it receives the vena tibialis antica.
BRANCHES OF THE VENA CAVA POSTERIOR
( Vena ovariana
( Venæ testiculæ
( Vena proventricularis communis
( Vena suprarenalis revehentis
( Vena portalis magna sinistra
( Vena portalis magna dextra
( Venæ innominatæ
( Venæ hepaticæ
Vena cava ( Vena cardis coronaria magna
posterior ( Vena proventricularis inferior
( ( Vena iliaca interna ( Vena hypogastrica
( ( Vena iliaca externa ( Vena renalis
( ( Vena suprarenalis externa
( Vena iliaca ( Vena ischiadica
( communis ( Vena renalis
( ( Vena intervertebralis lumbalis
( ( Vena renalis magna
( Vena mesenterica communis ( Vena coccygo-mesenterica
Vena ( ( Vena mesenterica anterior
portalis ( Vena pancreatico-duodenalis
dextra ( ( Vena proventricularis
( Vena proventricularis lienalis ( Vena splenica
Vena coccygo-mesenterica ( Vena hemorrhoidalis
On the dorsal side of the metatarsus are two veins. The =vena
metatarsalis dorsalis profunda= (Fig. 65, No. 11), which extends under
the tendon of the extensors of the toes, along with the artery and the
nerve. It collects the blood from the third and the fourth toe and in
the middle of the metatarsus receives the =vena metatarsalis dorsalis
interna= (Fig. 65, No. 4), which connects the vena metatarsalis dorsalis
profunda and the vena magna. The two dorsal veins anastomose with the
vena magna, at the intertarsal joint. They pass transversely under the
ligament and form the main trunk of the vena tibialis antica which lies
close to the anterior surface of the tibia. Near this point there is
formed a plexus of veins which again form a trunk and communicates with
the vena peronealis and enters between the tibia and fibula with the
tibialis antica. It extends along the flexure of the knee and the
posterior part of the lower thigh.
The =vena metatarsalis externa= passes subcutaneously on the outside of
the fourth toe and the metatarsus, and above the intertarsal point joins
the tibialis postica.
The =vena metatarsalis plantaris profunda= (Fig. 65, No. 5) lies on the
ventral side of the foot and forms several anastomosing arches with the
other veins of the toes. Below the intertarsal joint it enters the vena
metatarsalis magna (Fig. 65, No. 9).
The =vena cutanea cruralis= (Fig. 69, No. 7) originates at the height of
the tarsal region and passes subcutaneously on the outer posterior
surface of the lower thigh region to the vena poplitealis.
The =venæ surales= or inferior muscular branches of the vena poplitealis
consist of many veins. One branch comes from the region of the shank and
from the gastrocnemius muscle; another as a main branch from the
posterior surface of the lower thigh; and a third from the outer surface
of the muscles and skin of the upper thigh. The three branches together
with the anterior and posterior tibial (Fig. 69, No. 2) unite at the
flexure of the knee forming the vena poplitealis (Fig. 69, No. 1).
In the region of the upper thigh, between the knee and the abdominal
cavity, the following four veins form the vena cruralis: (Fig. 66, No.
6; Fig. 69, No. 5). First, the =vena cutanea abdominalis femoralis=
(Fig. 69, No. 6) which comes out of the side of the abdominal wall,
draining the skin of the inner surface of the upper portion of the
thigh, the adductor muscles, and the region of the abdominal and the
breast border. It crosses the ischiadic artery in a diagonal direction,
and enters the vena cruralis in the middle of the crural region.
Second, the =vena femoralis interna profunda= (Fig. 69, No. 3) forms a
communication between the end of the suralis near the knee. It lies on
the median portion of the flexor cruris internus muscle.
Third, the =vena femoralis anterior= (Fig. 69, No. 4) is formed from
branches from the sartorius and adjacent structures, and anteriorly
empties into the crural vein near where the latter enters the abdominal
cavity.
Fourth, the =vena epigastrica= (Fig. 70, No. 33) is formed by branches
from the abdominal wall and branches from the walls of the abdominal
air-sacs. It passes along the median surface of the os pubis and ends
into the vena cruralis near the spine of the ilio-pubica or at a point
where these join with the vena hypogastrica.
VEINS OF THE CAUDAL REGION AND OF THE PELVIC CAVITY
The vena iliaca interna or the vena hypogastrica (Fig. 70, No. 22)
collects most of the blood from the tail. The vena iliaca interna
collects most of the blood from the pelvic cavity, and the adjacent
intestines. It unites with the vena iliaca externa (Fig. 70, No. 27) and
receives the vena renalis magna and forms the trunk of the vena iliaca
communis (Fig. 70, No. 26).
The =vena coccygea= originates between the coccygeal vertebræ, and
collects the blood from the region of the tail, including the tail
feathers, the tail muscles, the tail gland, and the skin of the region.
These small collecting vessels form a trunk on each side of the coccyx.
The right and the left pass laterally, each one taking up a vena cutanea
et pudenda, and frequently anastomosing with the vessels on the other
side. These often unite into one vessel. Both trunks are connected by a
transverse, or anastomotic, vessel. At this anastomosis there empty into
it the vena coccygea mesenterica and the vena portalis. There also
communicate at this point the right and the left hypogastrica caudalis.
In its course it is partly imbedded in the kidney and passes anteriorly
to the vena iliaca communis. This circle is called the arcus
hypogastricus. Thus the veins of the abdominal cavity have many
anastomoses forming many arcs, making possible two outlets for the
blood.
The azygos sacralis empties into the arcus at about its middle. From
here it extends forward to the inside and under the kidney and empties
into the vena suprarenalis externa.
The =vena cutanea pubica= originates on the lower portion of the
abdomen, collects the blood from the muscles of the distal part of the
ischium, and enters the pelvic cavity between the ischium and the ilium.
It joins with the vena cutanea caudalis.
The =vena cutanea caudalis= originates from branches which drain the
skin and other parts of the ventral coccygeal region. The vena cutanea
pubica also communicates with the vena caudalis muscularis and with the
vena pudenda, thus forming the caudal trunk of the vena hypogastrica.
The =vena pudenda= originates in the walls of the cloaca in the region
of the generative organs.
A small =vena spermatica= accompanies the lower end of the vas deferens
and the ureter, and empties medially into the vena pudenda.
The pars renalis of the vena hypogastrica extends from the middle of the
arcus to the union of the vena hypogastrica and the vena cruralis.
The =vena hypogastrica= communicates with the pars renalis. The vessels
that empty into the pars renalis are as follows:
The =venæ sacrales= collect blood from the dorsal wall of the abdominal
cavity and enter the pelvis through the foramen sacralis. They pass
between the pelvic wall and kidney, and at times pass through the kidney
tissue. They empty into the pars renalis of the hypogastric arch.
The =venæ intervertebrales sacrales= (Fig. 72, No. 2) originate in the
region of the roots of the plexus of sacral nerves and pass through the
kidney substance or on the dorsal surface and empty into the pars
renalis.
The =venæ renales= (Fig. 72, No. 1) are very numerous and originate in
the kidney substance, forming two main and several minor branches, which
pass posteriorly, and empty partly into the vena hypogastrica, partly
into the vena renalis magna, and also into the vena intervertebralis;
other branches empty into the trunk of the iliaca communis.
The =vena suprarenalis externa= (Fig. 70, No. 30) is located near the
anterior rim of the kidney and is connected with the vena hypogastrica.
It also receives on the medial side, short branches which come out of
the upper kidney surface and sacral vertebræ.
The =vena ischiatica= originates by the union of several venous branches
which come from the muscles of the pelvis and upper thigh region. The
ischiatic vein enters the pelvic cavity along with the ischiatic nerve
and artery, and communicates with the vena hypogastrica at about the
level of the anterior lobe of the kidney. It is always smaller than the
vena cruralis.
The =vena obturatoria= originates mainly from vessels from the obturator
muscles. It enters the pelvic cavity through the obturator foramen.
Another branch is sometimes found which comes out of the inner surface
of the peritoneum which covers the obturator muscles and the walls of
the abdominal air-sacs and empties between the vena ischiatica and the
vena vertebralis into the vena hypogastrica.
VEINS OF THE TRUNCUS VENA ILIACA COMMUNIS
The =vena intervertebralis lumbalis=, which comes out of the lumbar
region, the spinal canal, the lumbo-sacral nerve plexus, and several
small venous branches from the lobes of the kidney. It passes dorsalward
through the kidney and empties into the iliac vein. There are also
communications with the vena intervertebralis thoracica.
The =vena renalis magna= (Fig. 64, No. 47) forms the main descending
vein to the middle and posterior lobes of the kidney. It lies ventrally
and mesially on the middle lobe and partly on the inner part of the
posterior lobe. It sometimes has on each side two main trunks. The vein
receives some small vessels out of the anterior kidney lobe, also other
small veins from that part of the peritoneum which covers the kidney,
from the rectum and finally small veins from the ureter.
VISCERAL VEINS OF THE POSTERIOR VENA CAVA
The =venæ testiculæ=, or the vena ovariana drain the blood from the
testicles of the male and ovary of the female. The size of these veins
change with the enlargement of the testes or of the ovary during
reproductive activity.
The =venæ suprarenales revehentes= are short, thick trunks coming from
the adrenal glands. The left empties into the left side of the posterior
vena cava and the right into the right dorsal side. These receive veins
from the testicles in the male and from the ovary in the female.
The =vena proventricularis inferior= drains the stomach wall. One branch
of this vein enters the left side of the posterior vena cava; the other
enters the vena proventricularis communis, which in turn empties into
the trunk of the anterior vena cava sinistra.
The =venæ hepaticæ= consist of one large and several small veins from
each lobe of the liver, and empty into the posterior vena cava.
Some small vessels come from the pericardium and the peritoneal covering
of the liver, and pass in the mediastinum to the trunk of the posterior
vena cava.
In the region of the vena portalis:
The liver receives almost all the blood from the stomach, the
intestines, the pancreatic gland, the spleen, partly from the liver
itself, and partly from the abdominal air-sacs. This blood enters into
the liver through the vena portalis dextra, the vena portalis sinistra,
and the vena portalis propria.
In both lobes of the liver these veins divide into numerous small
branches and collect again into two large short trunks, the vena
hepatica magna dextra (Fig. 70, No. 23), coming out of the right lobe of
the liver and the vena hepatica magna sinistra (Fig. 70, No. 24) coming
out of the left lobe. These two vessels empty inferiorly into the
posterior vena cava.
The vena portalis dextra receives the blood from the vena mesenterica
communis.
The =vena mesenterica communis= (Fig. 64, No. 36) receives the blood
from the vena coccygo-mesenterica (Fig. 70, No. 28) which comes from the
arcus hypogastricus and receives the vena hemorrhoidalis (Fig. 64, No.
37). This drains the cloaca and the bursa of Fabricius, and it also
receives veins from the rectum and from the base of the cæca.
The =vena mesenterica anterior= (Fig. 71, No. 3) accompanies the
anterior mesenteric artery, and collects the blood from numerous vessels
from the small intestine.
The =vena pancreatico-duodenalis= (Fig. 64, No. 38) comes out of the
duodenum and the pancreas, along the right side of the stomach and along
both cæca.
The =vena proventriculo-lienalis= (Fig. 64, No. 39) comes out of the
dorsal side of the proventriculus on the left side of the gizzard,
passes along the hilus of the spleen, and takes up several splenic
veins.
The =vena portalis dextra= (Fig. 64, No. 40; Fig. 71, No. 4) receives a
vein near the base of the gall-bladder. This branch enters the right
lobe of the liver and unites with the vena portalis sinistra.
The =vena portalis sinistra= (Fig. 71, No. 5) enters the left lobe of
the liver and there forms a sinus. It receives vessels which come from
the muscles of the gizzard, the inferior vena proventricularis, and from
the proventricular wall.
The =vena portalis propria= receives small veins which come out of the
walls of the abdominal air-sacs and from the fat of the abdominal walls.
The =vena umbilicalis= originates in the umbilical region and empties
into the vena hepatica magna sinistra at a point where it comes out of
the liver (Fig. 70, No. 29). This is the remains of an embryonal vein
which collected all the blood of the yolk sac, passed on the left side
of the large intestine to the body, took up the vena mesenterica and
ended as the vena umphalo-mesenterica.
THE LYMPHATIC SYSTEM
The peculiarity of the lymph vessels is that they are associated with
organs in which lymph cells are formed.
The lymphatic system consists of the lymph vessels and the cell-forming
organs. In some instances the cell-producing organs are lymph follicles
and in others lymph glands. For the most part the glands are replaced by
plexuses which in many places surround the blood-vessels.
The lymph of birds is similar to that of mammals. The larger lymph
vessels are similar to the veins, although the walls are always thinner.
Its tunica intima is rich in elastic fibers and has a layer of
endothelial cells on the inner side. The tunica media is formed of rings
of smooth muscle fibers. The adventitia is composed of loose connective
tissue.
The lymph vessels frequently form plexuses. The large lymph trunks
follow the course of the larger blood-vessels, and frequently surround
the arteries. All the lymph vessels of the body, exclusive of the lymph
of the caudal region, form into a large trunk which originates on both
sides of the celiaca communis and passes upward along the side of the
abdominal aorta, reaching a point anterior to the celiaca. By receiving
many vessels in this region it forms a plexus around the aorta, and
finally divides into two vessels, the right and the left, ducti
thoracici.
The lymph vessels of the left side of the head, the neck, and the lung,
and the left wing, and also lymph vessels of the proventriculus and the
throat enter into the left ductus thoracicus. They accompany the jugular
vein and are closely associated with the thyroid gland.
The right thoracic duct receives the lymph veins from the right cervical
lymph vein, and the right side of the head, the neck, the lung, and from
the right wing.
After the right cervical lymph vein has passed through the right thyroid
gland, it divides into two branches, one branch emptying into the right
thoracic duct and the other into the vena cava dextra.
The lymph vessels of the liver, the stomach, the pancreas, and the
duodenum enter near the root of the arteria celiaca into the large lymph
trunk. The lymph vessels of the remainder of the intestines, of the
kidney, and of the generative organs empty farther caudally.
The lymph vessels of the intestines take up the emulsified fat. This
emulsion in birds is colorless. The vessels pass upward along the
mesenteric arteries. There are no mesenteric glands. These vessels form
a plexus around the arteria celiaca. The lymph vessels of the posterior
extremities accompany the artery, especially the anterior iliaca
externa, and empty into the thoracic duct at the point of the anterior
iliaco-communis.
The lymph vessels in birds are numerous. The lymph glands are few. They
are only visibly found in the anterior breast and the neck region, and
sometimes in the wings. Lymph follicles are numerous in the intestines.
The thin walls of the lacteals, of the lymph vessels, and of the
thoracic duct are made up of two tunics, the inner being the thinner and
weaker.
The lymphatics of the foot unite to form the vessels along the sides of
each toe. In palmipedes there are anastomosing branches which pass from
the lateral vessels of one toe to those of the adjoining toe, forming
arches in the uniting web of the foot. These branches form a small
plexus at the anterior part of the digito-metatarsal joint, from which
pass three or four lymph vessels. The anterior and internal branches
accompany and form a network around the blood-vessels. The posterior and
external branches receive the lymphatic vessels from the sole of the
foot. They then ascend along the metatarsus and form, at its proximal
articulation, a close network from which vessels pass along the tibial
region, forming a plexus around it as far as the middle of the leg. From
this there arises two branches. The smaller passes along the anterior
part of the depression between the tibia and the fibula, as far as the
knee-joint, where it joins the other branch, which accompanies the
blood-vessel. The trunk formed by the union of these two vessels
accompanies the femoral vessels. Forming plexuses in its course, it
receives tributary vessels from the adjacent muscles. The iliac trunk
accompanies the femoral vein into the abdominal cavity, entering just in
front of the anterior end of the pubis. At this point it receives
branches from the lateral parts of the pelvis and then separates into
two branches. The posterior vessel receives some lymph from the anterior
lobes of the kidney, and from the ovary, or testis, and communicates
anteriorly with a branch formed by the lymph vessels adjacent to the
anterior mesenteric artery, and posteriorly with a large vesicular
plexus surrounding the aorta and its branches. This plexus receives the
lymph from the renal plexus and from those accompanying the arteria
media.
There are two sacral or pelvic vesicles which are situated at the angle
between the tail and the thigh in the posterior part of the abdominal
cavity. Each vesicle is a trifle more than a half inch long and a
quarter inch wide, and is shaped somewhat like a kidney bean. They have
muscular coats with striated fibers. These sacs are called “lymph
hearts.”
The anterior division of the femoral lymphatic trunk accompanies the
aorta, on which it forms a plexus with the branches of the opposite
side, and with the intestinal lymph vessels. These vessels commence from
a continuous plexiform network located between the mucous and the
muscular coat of the intestine. They are larger at this point than where
they leave the intestine to pass through the mesentery. They accompany
the trunk of the anterior mesenteric artery and form a plexus around it.
Before reaching the region of the aorta, the intestinal lymphatic
vessels communicate with the posterior division of the femoral trunk and
with the lymph vessels of the ovary or of the testis. After passing to
the region of the aorta they receive vessels from the pancreas and the
duodenum, and terminate around the celiac axis with the lymphatics of
the liver, the proventriculus, the gizzard, and the spleen, forming a
rather voluminous plexus (Lauth).
The aortic plexus represents the receptaculum chyli and gives origin to
two thoracic ducts, mentioned above, which passing on each side of the
bodies of the vertebræ, pass one right and one left, over the lungs,
from which they receive lymph vessels, and terminate after receiving the
lymph vessels of the wing, into the jugular vein of their respective
sides. The left thoracic duct, before emptying into the vein, receives
the trunk of the lymphatics of the left side of the neck, and the right
duct that of the right side of the neck, each tributary collecting lymph
from all the structures of its side.
The lymphatics of the wing follow the course of the brachial artery,
forming a plexus around it. These vessels are well developed in the
elbow region. The principal trunk, following the humerus, receives
collateral branches in its upper third. This vessel, when nearing the
chest, receives two or three large lymph vessels from the pectoral
muscles, and a branch which accompanies the brachial plexus.
The lymph vessels of the head accompany the branches of the jugular
vein, collecting the lymph from the structures of the head and the neck.
The lymphatic vessels communicate at the anterior and posterior oblique
anastomosing vessels. At the lower part of the neck each trunk receives
a vessel, which accompanies the carotid arteries. Further on they are
provided with a lymph gland which rests on the jugular vein.
THE BLOOD AND ITS FUNCTIONS
The special function of the blood is to nourish all the tissues of the
body, and in this way to aid growth and repair. It furnishes material
for the purpose of the elaboration of body secretions; it supplies the
organism with oxygen; and it carries away carbon dioxid and other effete
material. Blood is constantly in circulation.
Blood is red, opaque, and is, in the fowl, quite viscid. The exact tint
of the blood depends on whether it is drawn from an artery or from a
vein. Blood from a vein has a purplish tinge while that from an artery
is a bright scarlet. The color of blood is largely due to pigment in the
erythrocyte, called hemoglobin.
The _reaction of the blood_ is alkaline, due to the phosphate and the
bicarbonate of soda. The alkalinity of the blood is reduced by work.
This is due to the formation of sarcolactic acid in the muscle. The odor
of blood is due to volatile fatty acids. Each kind of fowl has its own
peculiar odor. The taste of the blood is saltish, due to a small amount
of sodium chlorid it contains.
The blood consists of the following substances:
First, the unorganized part, or fluid, the liquor _sanguinis_ or
_plasma_. It contains in solution proteids, extractives, mineral matter,
and gases. The gases are held in loose chemical union.
The liquor sanguinis constitutes fully 66 per cent. of the volume of the
blood. It is albuminous in nature and contains a small amount of
coloring matter of a fatty nature. It holds in solution three
proteids—fibrinogen, serum globulin, and serum albumin.
Second, the organized parts, or the cellular structure (Fig. 74, Nos. 1
to 21). The cells float in the plasma and consist of three groups: the
erythrocytes, or red blood cells, the leucocytes, or white blood cells,
and the thrombocytes.
=Erythrocytes.=—The average number of red cells (Fig. 74, No. 21) of the
domestic fowl range between 3,000,000 and 4,000,000 per cubic
millimeter. The red blood cells are flattened and elliptical in shape,
and possess an oval elliptical nucleus. The average length is ¹⁄₂₁₀₀
inch and the diameter ¹⁄₃₈₀₀ inch, or 7 to 8 micra in diameter and 12 to
13 micra in length. However the diameters vary in different kinds of
birds. The cytoplasm is yellow and glassy, and the nucleus takes basic
stains and appears somewhat picnotic.