Chapter IX: Part II: 1, The os occipitale (1, dorsal; 2, two lateral; 3, ventral (8)

The =vena sternalis= (Fig. 73, No. 1) is made up of two branches. The outer branch comes from the muscles of the subclavian region passes over the cristi sterni, medially, to the sterno-coracoid joint and into the breast cavity, where it receives the inner branch, which drains the inner surface of the breast-bone.

The =vena thoracica interna= empties into the vena cava anterior. It extends from the abdominal muscles where it communicates with the epigastric vein. It then passes on the inner side of the thoracic cavity close to the breast-bone and receives many intercostal veins.

The =vena cava sinistra= receives first, the _vena proventricularis communis_, which collects the blood from the walls of the proventriculus, and second, the vena coronaria cardis magna. This latter vein originates close to the apex of the heart and collects blood principally from the walls of the left ventricle. It connects in the left sulcus transversus with the vena cardis superior and ends at the base of the left upper vena cava. Its exit is not guarded by a valve. The veins of the right ventricle are partly on the surface. They collect blood along the sulcus transversus dexter and enter directly into the right ventricle. The veins of the front part of the heart are small. They collect behind the sulcus coronalis and end either directly into the right auricle or into the vena cardis magna.

VEINS OF THE FORE LIMB

The =vena radialis profunda= accompanies the radial artery on the dorsal anterior rim of the index-finger and passes, on the dorsal side, over the carpal region. It passes through the interosseous ligament between the ulna and the radius, and reaches the ventral surface of the arm. At this point it passes upward and anastomoses with the vena ulnaris. It collects the blood from the skin of the anterior wing region and the flexor muscles of the anterior arm. It empties into the vena brachialis.

The =vena humeri profunda= (Fig. 68, No. 1) emerges at the height of the elbow, and collects blood from the skin of the dorsal surface of the wing. It also receives veins from the muscles of the posterior side of the upper arm. It passes subcutaneously and dorsally over the dorsal portion of the humerus in company with the external radial muscle and passes with it around the external part of the humerus between the long and short heads of the triceps. It takes a diagonal course to the shoulder cavity and at that point empties into the brachial trunk.

The =profundus ulnaris= originates at the volar surface of the hand, proceeds in company with the ulnar artery, and sends on the base of the hand small anastomotic veins to the vena cutanea ulnaris or basilica. It passes along the anterior arm and between the flexor carpi ulnaris and the pronator profundus muscle to the elbow-joint. On the median surface of the biceps it passes upward and anastomoses with the radial vein. The ulnar vein, in the region of the elbow-joint, receives a large lateral branch which extends around the end tendon of the biceps and anastomoses above with the vena basilica.

The =vena basilica= or cutanea ulnaris is a long vein which originates from the subcutaneous dorsal surface of the index-finger. Near the base of the hand it receives an anastomosing branch from the vena radialis and the vena ulnaris, and then passes upward along the posterior rim of the ulna. It receives numerous branches from the roots of the flight feathers. It crosses below the elbow-joint and reaches the volar surface of the arm. It receives a large branch from the ulnar vein, and then, passing in a diagonal and median direction to the triceps, extends to the shoulder cavity where it empties into the axillary vein.

The outer breast veins unite forming a trunk which crosses ventrally to the subclavian artery, and empties into the subclavian vein.

The vena cutanea abdomino-pectoralis collects the blood from a large skin area of the abdomen, the upper thigh, the breast, and the intercostal region. In the skin of the abdomen it forms a network.

BRANCHES OF THE ILIACS

( Vena metatarsalis ( Vena
metatarsalis
( Vena ( interna or magna ( plantaris profunda
( tibialis ( Vena tibialis antica
( postica ( Vena metatarsalis ( Venæ metatarsales
( ( externa
(
( Vena ( Vena metatarsalis dorsalis profunda
( Vena ( tibialis ( Vena metatarsalis dorsalis interna
( poplitealis ( antica ( Vena peronealis
( ( Vena cutanea cruralis
( ( Venæ surales
Vena (
iliaca ( ( Vena cutanea abdominalis femoralis
externa ( Vena ( Vena femoralis interna profunda
( cruralis ( Vena femoralis anterior
( ( Vena epigastrica

The main trunk passes in the median abdominal line forward and then upward, along the outer edge of the pectoralis major, over the first sternal rib; receives blood from the infrascapular vein, and empties into the pectoralis externa.

The =vena brachialis= is located in the middle of the humerus and the triceps muscle. It is formed by the vena ulnaris, and the vena radialis. It passes with the median nerve and the brachial artery over the inner surface of the humeral joint. Posterior to the humeral head it receives the vena profunda humeri. At the shoulder cavity it receives the vena cutanea ulnaris or vena basilica.

The trunk of the axillary vein is very short and is formed by the veins of the shoulder and the wing. The deeper wing veins accompany the large arterial and the nerve trunks.

BRANCHES OF THE VENA ILIACA INTERNA

( Vena intervertebralis lumbalis
( Pars truncalis ( Vena renalis magna
( (
( ( ( Vena hypogastrica caudalis sinistra
( ( Vena renalis ( Vena hypogastrica caudalis dextra
( ( ( Vena portalis
( ( Vena coccygea ( Vena cutanea et pudenda
Vena iliaca ( ( Vena coccygea mesenterica
interna or ( ( Vena cutanea pubica
vena hypogastrica ( Pars caudalis ( Vena cutanea caudalis
( ( Vena pudenda ( Vena spermatica
( ( Vena caudalis muscularis
( ( Venæ sacrales
( ( Venæ intervertebrales sacralis ( Venæ renales
( ( Venæ renales
( Pars renalis ( Vena ischiadica
( Vena obturatoria
( Vena suprarenalis externa ( Azygos
sacralis

THE POSTERIOR VENA CAVA

The posterior vena cava (Fig. 63, No. 18; Fig. 70, No. 8) has its origin 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.

=Thrombocytes.=—The thrombocyte (Fig. 74, No. 19) is of about the same length as the erythrocyte but somewhat narrower. The nucleus is round, stains purple with the Wright’s stain, and the chromatin material is somewhat diffused. The diameter of the nucleus is nearly equal to that of the cell. The cytoplasm is pale and may show vacuoles near the nucleus. They may contain small circumscribed red structures. They vary somewhat in size and shape. There are in the domestic fowl between 45,000 and 55,000 per cubic millimeter.

=Leucocytes.=—There are, in the blood of the hen, 28,000 to 35,000 leucocytes per cubic millimeter. The leucocytes may be divided into five distinct types. These are as follows:

_Polymorphonuclear leucocytes_ with eosinophilic rods (Fig. 74, No. 2) are round and have a diameter about equal to the length of the erythrocyte. The nucleus is polymorphous; that is, it has two or more lobes. The nucleus stains a pale blue, and the chromatin is diffused. The cytoplasm is colorless with bright red staining spindle-shaped rods. There are 28 to 32 per cent. of this type of cell in the blood of the hen.

FIG. 74.—Blood cells of the fowl. _Wright’s stain._ From a S. C. Rhode
Island Red cockerel. 1, Basophile (mast cell) with lilac staining
spherical granules. 2, Eosinophile with rod-shaped acidophile
bodies. 3 and 4, Eosinophiles with acidophile staining round
granules. 5, Eosinophile ruptured. 6, Mononuclear leucocyte with
vacuoles in the cytoplasm. 7 and 9, Transitional leucocytes (first
stage). 8, Mononuclear leucocyte. 10, 11, and 12, Small lymphocytes.
13 and 14, Large lymphocytes. 15, A lymphocyte. 16, Lymphocyte
(nucleus centrally located). 17 and 18, Transitional leucocyte. 19,
Thrombocyte. 20, Neutrophile (polymorphonuclear). 21, Erythrocytes.
]

Polymorphonuclear leucocytes with eosinophilic granules (Fig. 74, No. 3 and 4) are of about the same shape and size as the preceding. The nucleus is similar to the former except that it may appear slightly picnotic. The cytoplasm stains not at all or faintly blue; it contains round or spherical granules which stain a dull red. There is from 4 to 6 per cent. of this type of eosinophiles found in the domestic fowl.

_Lymphocytes_ are round in shape and of about the diameter of the width of a thrombocyte (Fig. 74, No. 11). The nucleus is round, staining somewhat purple, and contains a diffused chromatin material. The cytoplasm exists in only small amounts; it lies to the side of the nucleus and stains a pale blue. This is the small lymphocyte. A similar cell but much larger also exists. This is the large lymphocyte (Fig. 74, No. 13). There is from 40 to 44 per cent. of the lymphocytes in the blood of the fowl. The small lymphocytes are most abundant.

_Large mononuclear cells_ (Fig. 74, No. 6) either round or oval, in shape, whose diameter may be about that of an erythrocyte and at times much larger. The nucleus may be round, oval, or irregular, and at times rather crescent or U-shaped (Fig. 74, No. 17). The cytoplasm is abundant and completely surrounds the nucleus. The cytoplasm stains a paler blue than the nucleus. Both taking the basic stain as do the lymphocytes. These constitute 18 to 20 per cent. of the cells of the blood.

_Mast cells_ or _basophiles_ (Fig. 74, No. 1) are of about the same size and shape as the eosinophiles. The nucleus is round or oval, and stains a very pale blue. The cytoplasm is colorless, mostly to one side of the nucleus, and contains round or spherical purple staining granules. This type of cell constitutes from 2 to 4 per cent. of the white cells of the blood.

=Structure of the Red Blood Cell.=—The red blood cell is composed of a spongy stroma holding in its meshes the red coloring matter. The stroma, or framework, of the erythrocyte consists principally of nucleo-albumin; it contains lecithin, cholesterin, and salts. The red matter consists of an albuminous crystalline substance called hemoglobin, which forms about 90 per cent. of the total solid matter of the dried corpuscle. Each red cell offers a certain absorbing surface for oxygen. As the blood circulates through the delicate walls of the lungs and the air-sacs, it takes up oxygen; the blood at the same time delivers to the air carbon dioxid which has been brought from the tissues where active cell metabolism has been going on. This oxygen taken up by the erythrocyte forms a loose chemical union and is known as oxy-hemoglobin. In this form it is carried to the tissues of the body where it is given up by the erythrocyte to the tissues where oxidation is going on.

_Hemoglobin_ is a crystallizable proteid substance containing carbon, hydrogen, oxygen, nitrogen, sulphur, and iron.

=Formation of the Cells of the Blood.=—The red blood cells are formed in the red marrow of the bone.

Polymorphonuclear leucocytes are formed in the red marrow of the bones, and the lymphocytes in the lymph glands and lymph follicles.

The bird carries a normal body temperature of 105° to 107° F. The average temperature of 50 mature hens and cocks was 106.8° F. The blood is of a deep red color.

=Composition of the Blood.=—The average composition of the blood of the domestic fowl as given by Owen, is as follows:

Whole shed blood:
Water 780 parts
Clot 157 parts
Albumin and salts 63 parts
—————
1000 parts

Moist blood cells:
Average total weight 456.69
Water 342.52
Solid matter 97.50

Plasma:
Total weight 543.30 parts
Water 495.72 parts
Solid matter 30.72 parts

Blood when drawn and allowed to stand soon coagulates. In the blood of birds this process is very rapid, the blood coagulating, in most instances, in about one-half minute. Blood coagulates only in the presence of calcium salts.

During life, the liquor sanguinis is termed plasma; but after it has been shed from the body and coagulation has taken place, the liquid residue is called serum. Serum is plasma with its modifications as the result of coagulation, and as this latter process is brought about by the production of fibrin, we may say that serum is plasma minus fibrin-forming elements.

The proteids of the serum are serum globulin, serum albumin, and a ferment produced as the result of coagulation. As fibrinogen is used up in the process of coagulation, it is not found in the serum, but there is in the serum a proteid known as fibrino-globulin. This is produced from fibrinogen during the process of fibrin formation. The following tabulation gives a clear idea of the difference between the proteids of plasma and of those of serum:

Proteids of Plasma

Fibrinogen
Serum globulin
Serum albumin

Proteids of Serum

Serum globulin
Serum albumin
Fibrin ferment (nucleoproteid)
Fibrino-globulin

Fibrinogen is the precursor of fibrin.

The fibrin of the blood clot of the bird is soft and very lacerable. The serum is usually yellow.

THE FATE OF THE ERYTHROCYTE OF THE FOWL

The power of vascular endothelium to ingest red blood corpuscles has been studied by Keys.

When bacteria or other minute foreign bodies are injected into the blood stream of pigeons, they are rapidly withdrawn from the circulation into the tissues of the liver and of the spleen. The foreign bodies are noted to be contained within cells of a distinct type, which is found in both liver and spleen. This type of cell contains, in addition to the foreign substances injected, much yellow pigment, and when tested for iron by Pearl’s method gives a positive Prussian-blue reaction.

In such specimens there is a display of contrast to other tissues. There is an extensive content of cells possessing the distinct tone of Prussian-blue iron reaction. These cells are distributed rather evenly throughout both the spleen and the liver, but more numerously in the liver.

In the liver, under low-power magnification, these cells appear as blue patches, sharply differentiated from the red-stained parenchyma. These cells are larger in their greater diameter than the liver cells. They vary much in size and form. They bear a constant relationship to the venous capillaries, and often appear to occupy the lumen of the vessels. Under higher magnification it is noted, however, that each cell is an integral part of the endothelial intima lining of the capillaries. They are therefore fixed tissue cells, engaged by one of its surfaces upon the reticulum of the vessel wall, with a free surface bulging a greater or less degree into the lumen of the vessel. The attached surface of the cell follows exactly the line of the vessel wall. These cells are similar to those described for mammals by Kupffer and are called Kupffer cells or stellate cells. In the fowl Keys proposes the name hemophages. The nucleus of the hemophage stains a deep garnet with the carmine used in the above-given technic, and contains two or three very distinct and intensely stained nucleoli. In the hemophages, which are more nearly flat, the nucleus appears like those of the typical endothelial cells; whereas in the protruding hemophages of greater bulk, the nucleus is more vesicular and is irregularly pyramidal in form. Rarely two nuclei are found in one cell. Within this cell may be seen vacuoles of the cytoplasm which contain red blood corpuscles. These blood corpuscles have been phagocyted from the circulating blood stream. Approximately one-third of the intimal cells are hemophages. Each hemophage displays evidence that it contains, or has recently contained, one or more red blood cells. The cell body of the hemophage has no fixed morphology, but changes from time to time according to its phase of phagocytic activity. In a stage which the hemophage has recently ingested a red blood cell, the cell body bulges out into the lumen of the vessel and the nucleus is crowded to one side. At this time the red blood cell appears as those in the blood stream and possesses the characteristic staining reactions. The nucleus of the red blood cell stains deep reddish brown and the cytoplasm an even yellow bronze. In the next stage the cytoplasm of the hemophage gives a diffuse Prussian-blue reaction. Then in hemophages which represent later stages there are various stages of disintegration and digestion of the red blood cell. The first changes of the phagocyted red blood cell is hemolysis, the hemoglobin escaping into vacuoles of the cytoplasm of the phagocytic cell, leaving the nucleus-containing stroma distinctly outlined. The stroma may retain the original ovoid form or may become spherical; the nucleus in such instances remains ovoid. Gradually, both the stroma and nucleus lose their staining reaction until finally the vacuoles contract about a small indistinct remnant of the nucleus, which in its turn ultimately disappears. During this latter process the size of the hemophage gradually decreases. The hemoglobin, which has escaped into the cytoplasm of the hemophage, is seen to undergo a series of changes. At first the greater part of the pigment does not give the iron reaction but retains its yellow-bronze tone with erythrosin and occupies vacuoles of various sizes. Later the contents of the vacuoles give the iron reaction and with increasing intensity. Later there is a gradual decrease in the staining reaction indicating that the iron gradually disappears from the cells which extracted it from the red blood cells it digests. As a summary we find, that these cells take care of the worn out red blood cells. They devour them; hemolyze them, destroying the stroma and nucleus; split the hemoglobin and free the iron; and then finally return to their normal form.

The spleen contains the same type cells, but they are fewer in number. For the most part they are confined to the pulp cords and have no such evident relation to the vessel wall, or lumen, as in the liver.

The function of the cells of the spleen are essentially the same as those in the liver.

Iron freed from the worn out red blood cells is not retained by the cells freeing it, nor is it found in the bile. It does not occur elsewhere in the tissues of the liver and spleen. It is possibly discharged into the blood stream, and transported to the hemapoietic tissues. Cells which hemolyze red blood cells and liberate the iron are to be seriously thought of in connection with bile formation since bilirubin is approximately, if not identical with, iron-free hematoidon.

NEUROLOGY

=The Nervous System.=—The nervous system is an apparatus by means of which animals appreciate and become influenced by impressions from the outer world. Animals react on these impressions, and thus are enabled to adapt themselves to their environment. This system is the organic substratum of life, sensation, and motion. Broadly stated, the nervous system connects the various parts of the body with each other, and to coördinate the parts into a harmonious whole in order to carry on the bodily functions methodically and to control the physiological division of labor throughout the organism.

The nervous system consists of two parts. The first is the _cerebro-spinal system_, which comprises the central nervous axis, including the brain and the spinal cord, and the peripheral nerves, including the cranial and the spinal nerves. The second is the _sympathetic nervous system_. The two parts of the system are closely linked together, and both terminate in peripheral nerve endings, including those of special sense, of sensation, and of motion.

The cerebro-spinal nerves especially preside over the special senses, motion and sensation; and the sympathetic over the digestive, the pulmonary, and the vascular apparatus.

From a structural standpoint, the nerve system consists of cell elements peculiarly differentiated from all other tissue cells in that their protoplasm is extended in the form of processes, often to great distances from the nuclear region. The cell elements are held in place by supporting tissue and receive an abundant blood supply; they are partly of ectodermal and partly of mesodermal origin.

The cell element of the nerve system, called a _neurone_, is the developmental, structural, and functional unit of the nervous system. It is a single cell presenting unusual structural modifications. It comprises not only the nerve cell body with its numerous protoplasmic processes, or dendrites, but also the axone, which may vary in length from a fraction of a millimeter to fully half the bird’s length. The bulk of the axone is many times the bulk of the cell body.

Certain non-medullated axones are surrounded by a delicate, homogeneous, nucleated sheath, called the neurilemma, or sheath of Schwann.

THE CRANIAL NERVES

The cranial nerves have their origin in the brain and leave the cranial cavity in pairs. They are numbered numerically from before backward, there being twelve pairs in all. The following is a tabulation according to their number, name, and function:

No. Name Functional Nature
I. Olfactory Smell-sense
II. Optic Visual-sense
III. Oculomotor Motor to muscles of eyeball and orbit
IV. Pathetici Motor to superior oblique muscle of eyeball
V. Trifacial Mixed: Sensor to face and tongue. Motor to face
VI. Abducentes Motor to External rectus of eyeball
VII. Facial Motor to muscles of head and face
VIII. Auditory Hearing-sense
IX. Glosso-pharyngeal Mixed: Tongue, pharynx and muscles of throat
X. Vagus Mixed: Sensori-motor to respiratory tract and part of alimentary tract
XI. Spinal accessory Motor to muscles of pharynx, neck and heart
XII. Hypoglossal Motor to muscles of the tongue

=Olfactorius.=—Nervus olfactorius (Fig. 75, _C_, 16). This is the nerve of smell, one of the nerves of special sense. The organ of smell consists of five layers as follows:

First, a layer of olfactory fibers extending in different directions and consisting of a dense plexiform arrangement of the axones of the olfactory cells. From this layer the fibers pass into the layer of olfactory glomeruli where their terminal ramifications mingle with the dendritic terminals of cells lying in the more dorsal layers, to form distinctly outlined spheroidal or oval nerve fiber nests, the _olfactory glomeruli_.

Second, a fine granular layer of basic substance containing round cellular structures, the _stratum granulosum_.

Third, broader granular, or molecular layer, having on its inner surface a row of large pyramidal cells which are both small and large and which send their dendrites into the olfactory glomeruli. Their points are directed outward.

Fourth, a layer of round cells tightly pressed together and measuring about 5 microns in diameter. Between these cells are very fine nerve fibers.

FIG. 75.—The brain of a hen. Photograph.

_A._ Upper surface of the brain. 1, Medulla oblongata. 2, Calamus
scriptorius. 3, Cerebellum. 4, Optic lobes. 5, Transverse fissure.
6, Longitudinal fissure. 7, Upper surface of the left cerebral lobe.
8, Upper surface of the right cerebral lobe. 9, Lateral pillar of
the cerebellum.

_B._ The posterior surface of the eyeball. 10, The sectioned surface
of the optic nerve.

_C._ The inferior surface of the brain. 11, Corneo-scleral juncture.
12, The cornea. 13, The sclera. 14, The optic nerve. 15, The optic
chiasm. 16, The olfactory lobes. 17, The medulla oblongata. 18,
Tuber cinererum et infundibulum.
]

Fifth, a layer of epithelial cells.

The peripheral fibers and the nerve cell layers near the hemispheres disappear so that the basic substance of the trabecula with the hemispheres form the entire lobe mass. On the lower surface of the hemispheres there is a long bundle of nerve fibers which enter into the substance of the olfactory lobes and there disappears. These fibers are medullated. Non-medullated fibers enter into the makeup of the olfactory trunk.

The original center of the olfactory nerve is not in the hemisphere, but in the same location as the optic nerve. This nerve trunk consists of very fine non-medullated fibers. The nerves of smell are therefore not peripheralistic nerves. The nerve fibers are distributed to the mucous surface of the turbinated bones. Toward the front they form an expanded prolongation.

The olfactory nerve, as it emerges from the cone-like anterior tip of the cerebrum, is of considerable thickness and extends along with the median dorsal artery of that region above and to the inside of the orbit, under the thin bony structure. Before its termination into the posterior turbinated bones, it is crossed by the superior maxillary division of the fifth pair of cranial nerves. It extends as far as the pituitary membrane of the turbinate bones upon which its filaments are distributed radially.

=The Opticus.=—The nervus opticus (Fig. 75, No. _C_, 14) the second cranial, is the nerve of sight. The optic lobe, or tuberculum bigeminum lies at the base of the brain on each side of the optic tract.

From the optic lobes the two trunks pass forward along the under surface of the cerebri, forming the optic chiasm at the hypophysis (Fig. 75, No. _C_, 15), at which point the nerve fibers originating from the right side pass to the left, and _vice versǎ_. From the chiasm the true optic nerves pass forward to the posterior surface of the eyeball. They are composed of a bundle of very fine, marrow-like nerves. These fibers enter into the ganglionic cells of the retina. By removal of the finely adherent neurilemma, the optic nerve is seen to be composed of parallel, longitudinal lamellæ, the margins of which are mostly free on one side.

=The Motor Oculi.=—The motor oculi (Fig. 62, No. _C_, 10), the third cranial nerve is a motor nerve. It originates close to the base of the brain behind the position of the hippocampus of mammals on the inner side of the crus cerebri, and also on the inner somatic column close below and somewhat aside from the aqueduct of Sylvius. The nerve leaves the brain cavity through a distinct foramen near the foramen opticum, and supplies the following eye muscles: first, after entering the orbit, it sends a branch upward to the inferior portion of the inferior rectus; then, it gives off the thick ramus ciliaris. The trunk then extends under the optic nerve and passes forward to innervate the inferior rectus, the internal rectus, and the inferior oblique. A ciliary ganglion forms on the trunk.

=The Patheticus.=—(Fig. 62, No. _C_, 11) is a small motor nerve, originating close to the sulcus centralis, in the circle of the center brain over the valve of Vieussens, between the posteriors of the optic lobes. It extends in a dorsal direction between the cerebellum and the lobus opticus, to the posterior of the latter of which it then forms a loop ventrally. Lying close to the optic foramen it passes through a fine opening into the eye cavity and supplies the superior oblique muscle of the eye. During its course it passes dorsally over the optic nerve, and then crosses dorsally over the ophthalmic division of the fifth pair of cranial nerves and the internal rectus muscle.

=The Trifacialis.=—(Fig. 62, No. _C_, 12). This, the fifth cranial, is a mixed nerve and is divided into two parts, portio major and portio minor.

The _portio major_ originates in the ganglion cells of the posterior part of the brain. Commencing near the medulla oblongata it passes through the posterior part of the brain, then upward and outward; and along its route it forms the Gasserian ganglion, which lies partly in the cranial cavity or in its wall.

The _portio minor_ consists of the downward passing fibers containing the motoric elements which are distributed to the muscles of the jaw and of the eye. The roots are found in the ganglion from the center and back brain, close below the pathetic nerve origin, where the pathetic passes between the lobus opticus and the pars peduncularis; it then takes a lateral course between the two.

The fibers of the portio minor do not take part in the formation of the Gasserian ganglion, but are only partly surrounded by it.

There are three nerve trunks given off of the trifacialis: the ophthalmic, the superior maxillary, and the inferior maxillary.