Chapter VIII: Part II: 1, The os occipitale (1, dorsal; 2, two lateral; 3, ventral (7)

=The Common Carotid.=—Near the last cervical vertebra the two carotid arteries occupy the same channel, to which they are attached by fascia, and, lying close to the inferior surface of the bodies of the cervical vertebræ, are covered by the colli muscles. Near the third or the fourth cervical vertebra, the two carotid arteries separate. Near the atlas each carotid divides into the _carotis cerebralis_ and _carotis externa_. Near this division the _superior cervical artery_ branches off. This latter artery extends down the neck in company with the pneumogastric nerve and the jugular vein, supplies the skin and the neck muscles, and anastomoses with the inferior cervical artery and the subcutaneous colli artery.

The _occipital artery_ originates either from the carotis communis or sometimes from the superior cervical.

BRANCHES OF THE CAROTIS CEREBRALIS

The branches of the carotis cerebralis are as follows:

1. The =occipitalis= (Fig. 72, No. 18), which in turn gives off, first, the occipitalis sublimis. The _occipitalis sublimis_ supplies the outer and the middle portion of the digastricus and the posterior mylo-hyoideus muscle. It also gives off, second, the _occipitalis profunda_ which supplies the inner portion of the digastricus muscle and becomes the _meningeal artery_, which passes through the foramen vagi, entering the brain cavity, where it supplies the coverings of the brain as far as the sella turcica. Superficial branches of this artery are distributed to the muscles in the region of the atlas and anastomose with the vertebral artery.

2. The =ophthalmica externa=, which passes below the articulation of the quadrate bone, around the tympanic cavity, enters the canalis caroticus, and passes into the cranial cavity. The ramus occipitalis, passing out of the same foramen, again enters the diploë of the cranium; then after passing dorsally over the upper outer semicircular canal of the ear, passes backward through the occipital bone.

The ophthalmica externa (Fig. 72, No. 9) forms a main trunk and gives off two branches: the _temporal artery_ and the _recurrent ophthalmic_. The recurrent ophthalmic gives off the _rete temporalis_, _rete ethmoidalis_, a branch to the orbital gland, and finally anastomoses with its own branches and with those of the internal ophthalmic at the olfactory foramen and aids in forming the _ethmoidal artery_. These arteries supply blood by giving off branches to the muscles of the eye, sclerotic coat, iris, choroid coat, and the ciliary bodies. It gives off another branch to Harder’s gland, and finally anastomoses with the ethmoidalis.

3. The =plexus temporalis=, rete mirabile ophthalmicum, or wonderful network (Fig. 72, No. 8), is formed between the second and the third trunk of the trigeminus nerve and the rete ophthalmicum.

Inferior to this is the _alveolar plexus_, which plexus accompanies the third branch of the trigeminus into the lower jaw. Two main branches form this plexus, one coming from the carotis facialis, which anastomoses with the alveolar artery.

The _palpebral plexus_ lies between the trunks of the trigeminus, and supplies mainly the lower eyelid.

The _plexus muscularis_ extends to the fifth portion of the temporal muscle.

The _plexus lacrimalis_ forms on the posterior orbital wall on the ramus ethmoidalis and supplies the lacrimal gland and the upper eyelid. It anastomoses with branches from the facial artery.

The _ramus ciliaris posticus_ supplies the inferior rectus and the external rectus muscle of the eyeball. It anastomoses with the ophthalmica externa.

The _median meningeal artery_ passes through the foramen occupied by the second branch of the trigeminal nerve. Passing into the cranial cavity, it supplies the dura mater. Before passing into this foramen, small branches are given off, which supply the skin and the temporal muscle; and some branches anastomose with the superior cervical and the ethmoidal arteries.

=4. The Cerebral Artery.=—Each cerebral artery enters the cranial cavity through the canalis caroticus located in the sphenoid bone, passes forward medially from the cochlea, dorsally from the Eustachian tube, and passes through a small canal which opens on the inner surface of the sella turcica. Originating in this foramen, the _sphenoid artery_ divides into two branches which anastomose with the pterygoidean and the pterygo-pharyngeal artery and which supply the upper jaw and the throat regions.

The _spheno-maxillaris artery_ supplies the gums.

The right and the left cerebral arteries unite at the sella turcica. After this union they divide again immediately and pass to the base of the brain, where they give off twigs to the optic nerve, to the optic chiasm, and where also is given off the arteria retinæ centralis. Passing posteriorly each cerebral artery gives off the _ramus posterior_, and then passes to the side of the cerebellum.

The _basilar artery_, a continuation of the anterior spinal artery, is located ventrally and mesially to the cerebellum. Laterally and inferiorly the basilar artery gives off the inferior cerebellar artery.

The _ramus anterior_ is given off from the cerebralis artery and continues as the _internal ophthalmic artery_. The ramus anterior also gives off the _sylvian artery_, which supplies the sides of the cerebrum and the middle brain. In the fissure between the hemispheres and the optic thalamus is located the _arteria cerebri profunda_. This artery passes along the median surface of the cerebrum and in its course supplies the adjacent parts. It enters into the formation of the choroid plexus of the lateral ventricle.

The _internal ophthalmic artery_ extends out of the cranial cavity, through the optic foramen, into the orbital cavity. It passes upward along the interorbital wall and supplies the optic nerve, the trigeminus nerve trunk, and the eye muscles, and dorsally anastomoses near the olfactory nerve with the rete ethmoidale and the external ophthalmic artery, and continues as the ethmoidal artery.

The _ethmoidal artery_ supplies the supra-orbital gland and the gland of Harder. It gives off twigs to the rete ophthalmicum and other branches to the skin of the frontal region, where it anastomoses with branches of the external facial artery. These branches in the frontal region are rather large. Large branches are given off to the comb.

The _arteria ethmoidalis externa_ originates in the nasal cavity from a division of the ethmoidal artery.

The external ethmoidal artery passes below the lacrimal bone, extends forward, supplies the walls of the nasal cavity, and finally sends a branch anteriorly into the upper median portion of the jaw bone, and other branches to the septum nasi and other parts of the nasal cavity.

There are frequent anastomoses between the ethmoidalis interna, the facialis, and the spheno-maxillary artery.

The _internal ethmoidal_ artery supplies principally the posterior turbinated bones and septum nasi.

BRANCHES OF THE EXTERNAL CAROTID ARTERY

Branches from the external carotid and the facial artery supply the tongue and its muscles, the larynx, the lower jaw bone, the gums, and the upper lateral facial region.

The external carotid (Fig. 62, No. _A_, 8) gives off the following branches:

First, the =hyoid artery= (Fig. 72, No. 12) which supplies the inner portion of the depressor mandibular and also the cornua of the os hyoideum, and extends to the tip of the tongue.

Second, the =superior laryngeal artery= (Fig. 72, No. 16) which supplies the sterno-brachialis and gives off branches which extend downward to the trachea and to the esophagus. The main artery passes along the left side of the esophagus and anastomoses with branches of the inferior esophageal, forming collateral circulation in that region.

FIG. 62.

_A._ Blood-vessels of the head. 1, The cerebellum. 2. The cerebrum. 3,
The semicircular canals. 4, Sinus occipitalis superior. 5, Sinus
temporalis sphenoideus. 6, Sinus transversus dexter. 7, Superior
esophageal artery. 8, Carotis externus. 9, Lingual artery. 10, Sinus
longitudinalis.

_B._ Veins of the antero-inferior part of the head and neck. 1, The
right carotid artery. 2, The left carotid artery. 3, Vena jugularis
dexter. 4, Vena vertebralis dexter. 5, Transverse vein. 6, Vena
cephalica dexter anterior. 7, Vena lingualis. 8, Vena cephalica
posterior. 9, Vena facialis externa dexter. 10, Vena infrapalatina.
11, Posterior nares. 12, Vena facialis interna. 13, Vena facialis
externa sinister.

_C._ The brain. 1, Medulla oblongata. 2, Cerebellum. 3, Optic lobe. 4,
Cerebrum. 5, Longitudinal fissure. 6, Transverse fissure. 7,
Olfactory nerve. 8, Optic nerve. 9, Optic commissure. 10, Motor
oculi. 11, Patheticus. 12, Trigeminal, or trifacialis. 13, Abducens.
14, Facialis. 15, Auditory, or acousticus. 16, Glosso-pharyngeus.
17, Pneumogastric. 18, Spinal accessory. 19, Hypoglossus. 20,
Hypophysis. 21, Crus cerebri. 22, Ganglion on superior nerve trunk.
23, Spinal cord. 24, A pair of spinal nerves.
]

Third, the =lingualis artery= (Fig. 62, No. _A_, 9) which lies between the mylo-hyoideus and the posterior part of the hyoid bone. It supplies the tongue muscles. It passes to the median surface of the lower jaw bone, where are given off small branches which enter the jaw and anastomose with the inferior alveolar artery.

Fourth, the =Facial Artery=.—The facial artery divides into the following branches:

The _auricular artery_ is given off near the articulation of the os quadratum with the os zygomaticum. It is located at the outer auditory canal, and its branches are distributed to the parotid region and to the depressor mandibular, or digastricus, muscle.

The _external facial artery_ is located between the os quadratum and the masseter muscle. It gives off a branch to the lower jaw bone and to the skin of that region, and then passes to the lacrimal bone and supplies branches to the commissure of the mouth, the auditory canal, the masseter muscle, the three eyelids (upper and lower eyelids and the membrana nictitans), the nose cavity, and the skin in the frontal region. It communicates on the other side with the ethmoidal artery.

The _internal facial artery_ passes over and through the os pterygoideum, supplies all the jaw muscles, and is continued as the inferior alveolar artery.

The _inferior alveolar artery_ enters the canal of the lower jaw bone along with the mandibular nerve. It is finally continued as the mental artery, leaving the canal, and passing to the outer jaw surface.

The facialis continues as the _internal maxillary artery_.

The internal maxillary artery (Fig. 72, No. 15) supplies the pterygoid muscle, the upper part of the pharynx, the commissure of the mouth, the salivary gland region, the gums, and finally anastomoses with branches of the spheno-maxillaris artery.

BRANCHES OF THE VERTEBRAL ARTERY

The vertebral artery is given off, dorsally near the thyroid gland, from the carotis communis or from the carotid trunk. The vertebral artery passes horizontally and dorsally into the canals formed in the transverse processes of the cervical vertebræ. After it leaves the carotid, it is divided into anterior and posterior branches.

The =posterior vertebral artery= passes in the canals of the transverse processes of the fifth or sixth dorsal vertebra. It sends branches into the vertebræ, into the spinal canal, and into the intercostal muscles between the ribs and anastomoses with the intercostal arteries.

The =anterior vertebral artery= is larger than the posterior. It extends laterally along the side of the neck in the foramen of the transverse processes of the cervical vertebræ, and lies along the course of the inferior vertebral vein and the deep imbedded trunk of the sympathetic nerve. It continues to the head. In its passage it gives off to each vertebral segment a dorsal and a ventral branch. Twigs from these branches pass into the bodies of the vertebræ and the spinal canal, giving nutriment to the bony structure and to the spinal cord and its coverings. Other twigs are distributed to the muscles of the neck and some finally anastomose with branches of the carotis communis. This artery, reaching the head, gives off a long anastomosing branch which passes between the atlas and posterior part of the occipital bone and joins the ramus profundus and the occipital artery, thus again communicating with the carotid artery. The remainder of the vertebral artery is small and passes through the foramen magnum into the cranial cavity where it anastomoses with terminal branches of the cerebral artery. At the base of the neck and before the vertebral artery enters the canal of the cervical vertebræ, it gives off the _arteria cervicalis ascendens_, superior artery of the crop (Fig. 73, No. 18) which branches out on the upper surface of the crop is also distributed to the neck muscles, and later subdivides into the transverse cervical arteries which supply the skin and the muscles of the base of the neck, and the shoulder region.

On the ventral side of the neck there are given off two subvertebral carotid arterial branches. They lie in a shallow furrow on the ventral side of the cervical vertebræ and close to the median line.

BRANCHES OF THE SUBCLAVIAN ARTERY

The subclavian artery (Fig. 20, No. 13; Fig. 73, No. 11) gives off the following branches:

1. =Sterno-clavicularis= (Fig. 73, No. 9) which originates on the upper part of the subclavia, between the carotid artery and external thoracic (Fig. 73, No. 3), divides into many branches. The sterno-clavicularis gives off the _sternal artery_, which enters by the side of the supra-coracoid muscle and the anterior rim of the sternum. It is distributed to the inner surface and over the air-sac. Another outside branch passes the posterior end of the crista sterna and supplies the large breast muscles.

The _clavicular artery_ (Fig. 73, No. 8) accompanies the clavicle to the shoulder-joint.

The _acromial artery_ is given off from the sterno-clavicularis on the ligament near the shoulder-joint.

2. The =thoracic artery= branches from the subclavian artery (Fig. 70, No. 4). The thoracic artery gives off the following branches:

The _internal mammary_, or _internal thoracic artery_ (Fig. 73, No. 16) arises on the inner side of the sternum and extends downward and backward, giving nutrient branches to the anterior vena cava and to the diaphragm. At the point of the costo-sternal muscle it divides into an inner and an outer branch.

The inner branch supplies the costo-sternal muscle and extends along the ribs and along their juncture with the breast-bone. It finally extends posteriorly, giving numerous branches to the abdominal muscles. The outer branch is distributed in a similar manner, giving off branches to the diaphragm and to the abdominal muscles, and anastomoses, on the surface of the abdominal muscles, with the epigastric artery.

The _external thoracic artery_ (Fig. 73, No. 3), ramus superior, supplies principally the large breast muscles.

The _inferior thoracic artery_, external ramus inferior, passes along the outside of the pectoralis major muscle, extends downward, and gives off the arteria thoracica longa (subcutaneous thoracic). This latter artery supplies the skin of the breast region. Other branches are given off to the muscles of the breast and to the skin of the region, and some finally anastomose with the branches of the sternal artery.

3. The =axillary artery= (Fig. 73, No. 12) extends out of the thoracic cavity along with the brachial nerve plexus. It gives off the _subscapularis_ which supplies the muscles of the scapular region. The axillary artery terminates as the _brachialis_ which passes between the biceps brachii and anconeus muscles downward along the humeral shaft. It gives off the anterior humeral circumflex artery and the brachialis profunda artery (Fig. 68, No. 3). It gives off near the elbow-joint the ulnar and radial arteries.

The _anterior circumflex humeral artery_ passes through the short head of the biceps and gives off a branch to the biceps muscle, supplying the insertional part of the breast muscles.

BRANCHES OF THE BRACHIALIS PROFUNDA

The brachialis profunda artery (Fig. 68, No. 3) continues as the _posterior circumflex humeral artery_. This artery supplies the muscles of the posterior part of the humerus, the skin of the wing, and the muscles of the brachial region. The trunk of the arteria brachii profunda passes downward along the anconeus muscle, supplying that muscle and giving off the collateral ulnar artery. On the ulnar olecranon it anastomoses with the recurrent ulnar, thus establishing, at this region, collateral circulation. The rest of the brachialis sends branches to the biceps muscle and to the skin of the upper arm, and finally gives off the arteria collateralis radialis, which supplies the condylo-ulnaris. It then anastomoses with the end branches of the recurrent radialis artery.

The _radial artery_ (Fig. 67, No. 4) passes downward on the outer rim of the forearm. It continues down to the carpal region, where it supplies the muscles and the skin of the carpal region it gives off the recurrent radial, which passes on the middle finger and finally anastomoses with the collateral radialis artery.

The _ulnar artery_ (Fig. 68, No. 6 and 9) passes downward on the inner surface of the ulna to the carpal region where it gives off a branch to the wing plexus and divides into two branches, the smaller branch supplying the thumb (Fig. 68, No. 7). This branch passes down the radial side of the middle finger to the last joint of the second finger. The larger (Fig. 68, No. 8) lies between the second and the third finger bones, and passes through a slit between these two bones to the flexor side of the hand and extends to the last finger-joint, supplying the structures in the region. The ulnar artery gives off a small arterial twig to the papilla of each large wing feather (Fig. 67, No. 6).

The _recurrent ulnar_ passes backward to the olecranon of the ulna and supplies the muscles, the skin, the feathers, and other structures of the region, and terminates in end collateral ulnar branches (Fig. 67, No. 5).

BRANCHES OF THE POSTERIOR AORTA[7]

( Esophageal
( Intercostales
( Dorsal
( Lumbars
( Spermatics
( Renals
( Ovarian
( Celiac ( Recurrent esophageal
( axis ( Recurrent intestinalis ( Recurrent ilio-colicus
( ( Posterior or recurrent sinister ( Renalis
( ( Anterior or recurrent dexter ( Splenics
( ( ( Hepatic
( ( Hepatica dextra ( Gastric
(
Posterior ( Sacralis media ( Coccygeæ laterales
aorta ( ( Coccygea media ( Coccygeæ laterales
(
( Anterior mesenteric ( Recurrent ilio-celiacus
( ( Recurrent superior hemorrhoidal
( Posterior mesenteric ( Median hemorrhoidal
( ( Recurrent renalis
( ( Tibialis postica
( Ischiadica ( Tibialis antica ( Peroneal ( Anterior tibial
plexus
( ( Arteria ovarialis
( Pudenda communis ( Renalis
( ( Hemorrhoidalis intima
( ( Pudenda externa
(
( Crural ( Internal pelvic (umbilical)
( (External iliac) ( Circumflex femoris
( ( Femoralis

Footnote 7:

Nomenclature used by Bronn.

The posterior aorta (Fig. 63, No. 2) passes backward along the inferior part of the bodies of the dorsal and lumbo-sacral vertebræ. In the thoracic cavity it lies dorsal to the esophagus. It gives branches (_esophageal_) only to the esophagus during its passage as far as the seventh dorsal vertebra. Following this point there are given of several pairs of arteries which divide into a superior and an inferior branch. The superior branch extends upward and anastomoses with branches of the vertebral artery and other twigs coming from the _intercostal arteries_. These latter arteries given off are small dorsal arteries. The inferior branches extend downward between the ribs and supply the intercostal muscles. The intercostal arteries do not take their origin from the aorta in numerous and regular branches as in mammals; they consist originally of but few vessels, which are multiplied by anastomoses with each other and with the arteries which come out of the spinal canal. An arterial plexus is thus formed around the head of each rib, from which a vessel is sent to each of the intercostal muscles and ribs and are continued into the muscles upon the outside of the body and its integuments. The anastomosis of the intercostal arteries round the ribs is similar to the plexus, which is produced by the great sympathetic nerve in the same location. The _lumbar arteries_ are given off farther posteriorly and along the lumbar region. The lumbar, like the dorsal branches are given off in pairs. These arterial branches pass along the thigh and the upper sacral vertebral region, and supply those parts. Ventrally they are covered by the kidneys and pass into the abdominal muscles. The posterior aorta gives off the _spermatic arteries_ and the _ovarian artery_. In the male the former supply the testes. The ovarian artery of the female gives off a twig to each calyx containing an ovum. Each calyx is voluminously supplied with blood. Next the _renal arteries_ are given off to the kidneys.

FIG. 63.—The vascular system injected. 1, The heart. 2, The posterior
aorta. 3, The right brachio-cephalic artery. 4, The left
brachio-cephalic artery. 5, The anterior mesenteric artery showing
its many branches and anastomoses near and on the intestines. It is
accompanied by branches of the mesenteric vein. 6, The rectal branch
of the posterior mesenteric artery. 7, The duodenal loop and
pancreas showing the pancreatic artery. 8, The anus. 9, The cloaca.
10, The liver. 11, The lungs. 12, The right subclavian artery. 13,
The right carotid artery. 14, The right anterior vena cava. 15, The
subclavian vein. 16, The right jugular vein. 17, The carotid trunk.
18, The posterior vena cava.
]

FIG. 64.—The splanchnic arteries, veins and nerves. 1, A portion of
the left testes. 2, Adrenal gland. 3, Anterior lobe of kidney. 4,
Heart. 5, Liver. 6, Second portion of the esophagus. 7,
Proventriculus. 8, Gizzard. 9, Spleen. 10, Duodenal loop. 11,
Pancreas. 12, Blind extremity of cæcum. 13, Floating portion of
small intestine. 14, Rectum. 15, Cloaca. 16, Anus. 17, Celiac axis.
18, Ureter. 19, Vas deferens. 20, Recurrent sinister artery. 21,
Anterior recurrent dexter artery. 22, Arteria hepatica dextra. 23,
Recurrent esophageal artery. 24, Recurrent intestinalis artery. 25,
Ilio-colicus artery. 26, Anterior mesenteric artery. 27, Recurrent
branches of the same. 28, Ilio-cœliacus artery. 29, Recurrent
superior hemorrhoidal artery. 30, Posterior mesenteric artery. 31,
Crural arteries. 32, Sacralis media artery. 33, Recurrent renalis.
34, Middle renal lobe. 35, Posterior renal lobe. 36, Vena
mesentericus communis. 37, Vena hemorrhoidalis. 38, Vena
pancreatico-duodenalis. 39, Vena proventriculo-leinealis. 40, Vena
portalis dextra. 41, Ischiadic nerve. 42, Thoracic sympathetic
trunk. 43, Anterior splanchnic plexus. 44, Spinal nerves. 45,
Posterior splanchnic nerve plexus. 46, Intestinal nerve trunk. 47,
Vena renalis magna.
]

The =celiac axis= (Fig. 64, No. 17) originates near the seventh sternal vertebra and to the right of the esophagus, breaks through the diaphragm, and, near this point, gives off a recurrent esophageal (Fig. 64, No. 23). The celiac axis gives off three main branches: The anterior or recurrent dexter, the posterior or recurrent sinister, the recurrent intestinalis, all of which lie to the right of the spleen, under the left lobe of the liver, and along the left side of the stomach. The _recurrent sinister_ (Fig. 64, No. 20) gives arterial branches to the proventriculus, the gizzard, the pyloris, and the left lobe of the liver. The anterior or recurrent dexter (Fig. 64, No. 21) gives off a renal artery and from four to six splenic arteries.

The _recurrent intestinalis artery_ (Fig. 64, No. 24) arises on the posterior of the stomach within the duodenal loop, and supplies the duodenum and the pancreas (Fig. 63, No. 7). It gives off a branch, called the recurrent ilio-colicus (Fig. 64, No. 25), which supplies the large intestines, including the cæca.

The _arteria hepatica dextra_ (Fig. 64, No. 22) is a branch from the celiac axial trunk. It gives several branches to the right lobe of the liver and to the gall-bladder. The gastric branches pass to the muscles of the stomach. The anterior and posterior recurrent branches often anastomose.

The =anterior mesenteric artery= (Fig. 63, No. 5; Fig. 64, No. 26) originates from the posterior aorta near the generative glands. It is directed downward, and divides into many branches which pass in the mesentery toward the intestines. Recurrent branches (Fig. 64, No. 27) are given off, which anastomose, forming mesenteric arches. From these arches are given off branches which supply the intestinal walls.

The anterior mesenteric artery gives off the _recurrent ilio-celiacus_ (Fig. 64, No. 28) which is distributed to the cæca; other of its branches are distributed to the small intestine.

The anterior mesenteric artery extends along the small intestine and ends in the _recurrent superior hemorrhoidal arteries_ (Fig. 64, No. 29) which anastomoses on the surface of the rectum with a branch of the posterior mesenteric artery.

Branches from the anterior mesenteric artery also anastomose with branches of the celiac axis.

The =posterior mesenteric artery= (Fig. 64, No. 30) is given off from the posterior aorta posterior to the origin of the anterior mesenteric and near the arteries of the thigh and is distributed to the lesser mesentery supplying the large intestine. Branches of the superior hemorrhoidal arteries anastomose with branches of the posterior mesenteric artery. Branches from this source are called the _median hemorrhoidal_ (Fig. 63, No. 6).

The posterior mesenteric artery (Fig. 64, No. 30) also gives off a long branch to the cæca. Branches of the posterior mesenteric artery anastomose with branches of the anterior mesenteric.

The =crural arteries= (Fig. 64, No. 31) are given off in a pair from the posterior aorta. They pass through the mass of the lobes of the kidneys, at about the median region, and extend out of the pelvic cavity in front of the spine and ilio-pubic ligament.

FIG. 65.—Blood-vessels and nerves of the hind extremity. Inside view
of leg. 1, Ischiadic nerve. 2, Ischiadic artery. 3, Posterior tibial
vein. 4, Vena metatarsa dorsalis interna. 5, Vena metatarsalis
plantaris profunda. 6, Vena cruralis. 7, Vena metatarsalis interna,
vena magna. 8, Vena tibialis postica. 9, Vena metatarsa magna. 10,
Nerves of the toes. 11, Vena metatarsalis dorsalis profunda.
]

The crural, or the external iliac artery, is divided into three branches as follows:

First, the _internal pelvic_, or _umbilical artery_, is given off just as the cruralis leaves the pelvic cavity. It passes, as a long vessel, on the inner surface of the lumbo-sacral bones and supplies the obturator internus muscle and extends into the umbilical region. It gives off branches to the abdominal muscles, and, in the female, a branch is distributed to the ligament of the oviduct.

Second, the _arteria circumflex femoris_, which passes between the sartorius and vastus internus and extends dorsalward, supplies the sartorius muscle, the vasti muscles, and the ilio-trochanteric region.

Third, the _femoral artery_, which passes beside the vena cruralis and extends down the posterior surface of the thigh to the knee-joint, supplies the upper thigh muscles with the exception of the adductor muscles.

FIG. 66.—Blood-vessels and nerves of the posterior extremity. Outside
view. 1, Anterior tibial artery. 2, Metatarsal artery. 3, Digital
arteries. 4, Vena cutaneous crurus. 5, Ischiadic artery. 6, Vena
cruralis. 7, Lateral cutaneous branch of the ischiadic nerve.
]

FIG. 67.—Blood-vessels and nerves of the fore limb. Outside view. 1,
Median nerve. 3, Ulnar nerve. 4, Radial artery. 5, Recurrent ulnaris
artery. 6, Twigs of ulnar artery to wing feathers.
]

The =ischiadic artery= (Fig. 69, No. 9) forms the main artery of the posterior extremity. This artery, the largest vessel of that region, is given off from the posterior aorta and passes ventrally over and between two of the main lobes of the kidney. The continuation of the posterior aorta is called the _sacralis media_ (Fig. 64, No. 32). The ischiadic artery gives off a _recurrent renalis_ on the posterior lobe of the kidney (Fig. 64, No. 33). On the left side it gives off a branch to the oviduct and to the ligament of the oviduct. The main trunk leaves the cavity with the ischiadic nerve (Fig. 65, No. 1) through a foramen formed by the os ilium and the os ischium. It sends branches into the adductor muscles of the upper and the lower thigh. It gives off anastomotic branches which unite with those from the femoral artery. At the flexure of the knee-joint it gives off two branches to that region (Fig. 69, No. 10). It gives off another branch to the gastrocnemius muscle and one to the flexor perforans digitorum. It terminates in the anterior and posterior tibial arteries.

FIG. 68.—Blood-vessels and nerves of the fore limb. Inside view. 1,
Vena humeri profunda. 2, Brachialis longus inferior. 3, Brachialis
profunda. 4, Radial artery. 6, Ulnar artery. 7, Ulnar arterial
branch to thumb. 8, Digital branch of ulnar artery. 9, Ulnar artery.
]

The first, the _tibialis postica_ (Fig. 69, No. 12) passes between the gastrocnemius and the deep flexors giving off branches in its course to the skin and to other parts, and disappears shortly below the intertarsal joint.

The second, the _tibialis antica_ (Fig. 66, No. 1; Fig. 69, No. 11), is often the larger of the two arteries. The anterior tibial artery gives off branches to the knee-joint and to adjacent structures. It gives a large branch to the head of the gastrocnemius muscle. It passes to the posterior surface of the tibial head and gives off the peroneal artery, which passes through the membrana interossea located between the tibia and fibula giving branches to the anterior side of the membrane of the patellar region of the knee-joint. It gives branches to the anterior side of the lower thigh and finally terminates subcutaneously in the anterior tibial plexus.

The main portion of the anterior tibial artery passes downward along the posterior surface of the membrane located between the tibia and fibula, and sends branches for the flexor digitorum communis et profundus. It then breaks through the membrane, reaches the anterior side and there communicates with the anterior tibial plexus. It gives off branches to the muscles on the anterior side of the lower thigh and the skin, and passes between the outer and the middle malleolus of the tarsal bones. It passes to the plantar surface and divides between the toes. In addition to the plantar branches there are given off dorsal branches between the third and the fourth toes. These branches form the direct continuation of the dorsal vessels of the anterior tibial plexus.

FIG. 69.—Blood-vessels and nerves of the femoro-tibial region. A
section of the tibia removed.

_A._ Veins, arteries and nerves dissected as in _B_.

_B._ _V_, Vein. _A_, Artery. _N_, Nerve. 1, Vena poplitealis. 2, The
three veins forming the vena poplitealis. 3, Vena femoris interna
profunda. 4, Vena femoris anterior. 5, Vena cruralis. 6, Vena
cutanea abdominalis femoralis. 7, Vena cutaneous cruralis. 8, Deep
vein of the knee-joint. 9, Ischiadic artery. 10, Branches of
ischiadic artery to flexure of knee. 11, Anterior tibial artery. 12,
Posterior tibial artery. 13, Ischiadic nerve. 14, Trunk (a branch of
the ischiadic) which gives off the superficialis peroneus and
peroneus profundus. 15, Median branch of ischiadic nerve. 16,
Superficialis peroneus. 17, Lateral branch of the ischiadic nerve.
]

The =arteria pudenda communis= (Fig. 70, No. 20) passes to the depressor coccygeus muscle, gives off a branch to the caudal part of the kidney, crosses the ureter, provides the ischio-pubic and pubio-coccygeus, or depressor coccygis lateralis, muscles, and on the lateral rim of the latter muscle it gives off the _arteria hemorrhoidalis intima_. This artery passes to the bursa of Fabricius and to the end of the cloaca. It enters into the ischio-coccygeus muscle, and divides into the _arteria pudenda externa_, and in ducks, the _arteria profunda penis_. These branches supply the vas deferens, the ureter, the cloaca, the penile structure, and the muscles of these parts.

FIG. 70.—Blood-vessels of a Cornish cock. 1, The left pulmonary
artery. 2, Right pulmonary artery. 3, Left brachio-cephalic artery.
4, Left subclavian artery. 5, Left carotid artery. 6, Right
brachio-cephalic artery. 7, Posterior aorta. 8, Posterior vena cava.
9, Left pulmonary vein. 10, Right pulmonary vein. 11, Celiac axis.
12, Anterior mesenteric artery. 13, Ischiadic artery. 14, Crop. 15,
Superior artery of the crop and vein of same name. 16, Testicular or
ovarian artery. 17, External iliac artery. 18, Intercostal nerve.
19, Median sacral artery. 20, Arteria pudenda communis. 21, Anus.
22, Vena hypogastrica. 23, Right vena hepatica magna. 24, Left vena
hepatica magna. 25, Vena iliaca interna. 26, Vena iliaca communis.
27, Vena iliaca externa. 28, Vena coccygo-mesenterica. 29, Vena
umbilicalis. 30, Vena suprarenalis. 31, Origin of the pars renalis.
32, Lumbar veins. 33, Vena epigastrica. 34, Lumbales (arteries). 35,
Anterior division of the lumbo-sacral plexus. 36, Posterior division
of the lumbo-sacral plexus. 37, Left anterior vena cava. 38, Right
anterior vena cava.
]

=The Sacralis Media.=—The _median coccygeal artery_ (Fig. 70, No. 19) forms the single extension of the sacralis media. It gives off lateral branches between the caudal vertebræ which supply the dorsal muscles of that region and the skin. The third pair are the largest. These are the _arteriæ coccygeæ laterales_, and are located on the dorsal side of the tail, they supply the tail glands and rudder feathers, the main tail feathers, or rectrices. A small arterial twig is given off to the papilla of each rectrix.

THE VENOUS TRUNKS

The venous blood enters the lungs from the right ventricle through the two pulmonary arteries (Fig. 70, No. 1 and 2).

The two pulmonary veins (Fig. 70, No. 9 and 10) collect the arterial blood from the lungs, and empty it into the left auricle.

There are three venæ cavæ which collect the systemic blood and empty it into the right auricle. These venæ cavæ are two anterior (Fig. 70, No. 37 and 38) and one posterior (Fig. 70, No. 8).

Each anterior vena cava is formed by the union of a vena jugularis, a vena vertebralis, and a vena subclavicularis (Fig. 63, No. 15).

FIG. 71.—Veins of the liver of a fowl. 1, Vena mesenterica communis.
2, Vena portalis propria. 3, Anterior vena mesentericus. 4, Vena
portalis dexter. 5, Vena portalis sinister. 6, Posterior vena cava.
7, Celiac axis. 8, Base of the heart. 9, The liver. 10, Hepatic
veins.
]

The jugular vein is formed by the union of the vena cephalica anterior, and the vena cephalica posterior.

The jugular vein (Fig. 62, No. _B_, 3) passes along the side of the neck and lies near the trachea, the esophagus, and the pneumogastric nerve. Near the base of the skull the two jugular veins, the right and the left, are connected by a transverse vein. By this anastomosis part of the blood from the left jugular vein is sent into the right. Therefore the right jugular vein is larger than the left. The jugular veins collect the blood from the tongue region, the thyroid, the esophagus, the trachea, the crop, and other structures along its course through the cervical region.

The =vertebral veins= are divided into the anterior and the posterior, or the inferior and the superior. The _anterior vertebral vein_ is located in the cervical region and collects the blood from the brain and the inner part of the head. The vertebral vein passes along the dorsal side of the spinal cord.

BRANCHES OF THE VENÆ CAVÆ ANTERIORES

( Venæ linguales
( Vena occipitalis lateralis ( Vena
occipito-collores
( Vena ascendenes lateralis
( Venæ colli cutineæ
( Venæ esophagealeæ
( Venæ tracheales
( Vena ( Vena subscapularis
( jugularis ( Venæ glandularum thyroidearum
( ( ( Vena occipitalis ( Sinus foraminis
( ( ( interna ( occipitalis
( ( Vena (
( ( vertebralis ( Vena vertebralis posterior ( Vena
intercostales
Vena cava ( ( ( Vena vertebralis anterior
anterior ( ( Vena vertebralis
( Vena vertebralis lateralis dorsalis ( Venæ intercostales
(
( Venæ coronariæ
( Vena subclavicularis
( Vena thoracica interna ( Vena intercostales

( Vena pharyngea superior
( Vena muscularis depressoris mandibularis
Vena facialis ( Vena muscularis colli anterior superioris
communis ( Vena lingualis
( Vena sublingualis et sphenoidea

The _posterior vertebral vein_ is located in the dorsal region, passes backward and receives the blood from the dorsal neck region and from the intercostal veins and from the vertebral segments and adjacent regions.

The anterior and the posterior vertebral vein form one trunk, the vertebral vein, and this trunk empties into the vena jugularis just before the subclavian and the jugular unite.

The =subclavian vein= collects the blood from the anterior extremities. It unites with the vena jugularis of the same side.

The left vena cava receives the coronary veins from the heart.

THE VEINS OF THE HEAD

BRANCHES OF THE VENA FACIALIS INTERNA

The =vena facialis interna= (Fig. 62, No. 12) lies dorsal on the pterygoid bone and receives the vena maxillaris, the vena ophthalmica, the vena mandibularis interna, the venæ pharyngeæ superiores, and the vena retis mirabilis temporale.

FIG. 72.—Blood-vessels and nerves of the abdominal cavity and hind
extremity and head. 1, Vena renalis. 2, Vena intervertebrales
sacrales. 3, Posterior aorta. 4, External iliac. 6, Ischiadic nerve.
7, Ischiadic artery. 8, Arterial rete (plexus temporalis). 9,
Ophthalmic artery. 10, Palatine artery. 11, Lingual artery. 12,
Hyoid artery. 13, 14, External carotid artery. 15, Internal
maxillary artery. 16, Superior laryngeal artery. 17, Superior
esophageal artery. 18, Occipital artery. 19, Internal carotid
artery.
]

The =vena maxillaris= comes out of the upper beak with the recurrent trigeminus nerve and then passes backward between the jugular and palatine bones. It lies medio-ventrally to the eyeball and communicates at this point with the ophthalmic vein. It is covered ventrally with the pterygoid bone. The maxillary vein collects the blood from the gland of Harder, the upper beak, and receives blood from the _vena supra-palatina_ and from the lower jaw bone and the external mandibular vein. It also receives blood from the external sublingual vein, and the sublingual gland. It follows the inner rim of the jaw bone. The maxillary vein receives an anastomosing branch from the cutaneous facial vein, at a point near the commissure of the mouth.

FIG. 73.—Photograph of blood-vessels and nerves of the thorax. 1, Vena
sternalis. 2, Vena thoracico-externa. 3, External thoracic artery.
4, Coracoid bone. 5, Sternum. 6, Shoulder-joint. 7, Humerus. 8,
Clavicularis artery. 9, Sterno-clavicularis artery. 10,
Thoracico-humeralis artery. 11, Subclavian artery. 12, Axillary
artery. 13, Brachialis profundus artery. 14, Ulnar artery. 15,
Radial artery. 16, Internal mammary artery. 17, Superior vein of the
crop. 18, Superior artery of the crop. 19, Brachial nerve plexus.
20, Anterior division of brachial nerve plexus. 21, Posterior
division of brachial nerve plexus.
]

The =vena ophthalmica= lies close to the point where the olfactory nerve passes out of the cranial cavity. The largest branch it receives is the recurrent ophthalmo-temporalis, which accompanies the lateral side of the optic nerve. It collects the blood from the base of the brain, from Harder’s gland, from the eye muscles, from the inner eye, the nose, the lacrimal gland, the skin of the frontal region, and the comb.

BRANCHES OF THE VENA JUGULARIS

( Vena
maxillaris
( Vena
ophthalmica
( Vena facialis ( Vena mandibularis
interna
( interna ( Vena retis mirabilis
temporalis
( Vena cephalica ( ( Venæ pharyngeæ superiores
( anterior or (
( facialis ( ( Vena facialis cutinea
( communis ( ( Vena temporalis
( ( Vena facialis ( Vena auricularis
Vena jugularis ( ( externa ( Vena palpebralis
or cephalica ( ( Vena transversus
communis ( ( Vena retis mirabilis temporalis
( Vena subclavia
( Venæ vertebrales
( ( Sinus cranii et cerebri
( ( Vena carotis
( (
( ( Vena auris ( Sinus foveæ cerebelli
( ( ( Vena occipitalis externa
( Vena cephalica ( Vena jugularis prima
( posterior ( Vena occipitalis
( Vena lingualis

( Vena mandibularis externa
Vena maxillaris ( Vena sublingualis externa
( Vena supra-palatina

Vena ophthalmica ( Vena ophthalmo-temporalis, recurrent

Vena facialis communis ( Vena cephalica externa

Vena occipitalis externa ( Vena occipitalis interna

Vena retis mirabilis temporalis ( Vena spheno-temporalis

Sinus foveæ cerebelli ( Sinus occipitalis externa

The trunk of the internal facial vein receives the blood of the =internal mandibular vein=. The internal mandibular vein emerges from the alveolar canal of the inferior jaw bone and receives branches from the muscles of mastication.

The =vena retis mirabilis temporalis= passes out of the eye cavity and lies between the internal facial vein and the external facial vein, and passes around the os quadratum and the os pterygoideum. It receives veins from the outer ear region, lacrimal gland, eyelids, and the spheno-temporalis.

The =venæ pharyngeæ superiores= are the veins on the dorsal surface of the pharynx. These veins form the small plexuses which unite with the two trunks of the facial veins. This forms an anastomosis between the left and the right facial veins.

BRANCHES OF THE EXTERNAL FACIAL VEIN

The vena facialis externa (Fig. 62, No. _B_, 9) lies behind the quadrate bone and is partly covered ventrally by the inner extension of the lower jaw bone. It collects the blood principally from the upper region of the cranium and the face, including the comb.

The =vena facialis cutinea= receives branches from the muscles in the region of the jaw, the lower jaw bone, the muscles of the eyelids, the frontal region, and the anastomotic branches from the vena maxillaris.

The =vena temporalis= is made up of veins from the skin of the temporal region, the masseter and the tongue muscles, and from the sides of the upper throat region.

The =vena palpebralis= is made up from veins from the three eyelids and the temporal region near the eye. Its trunk passes laterally over the temporo-mandibularis ligament. The vena palpebralis collects blood from the lacrimal gland, the eyelids, and the outer ear region.

The following veins empty into the trunk of the =vena facialis communis=: venæ pharyngis superiores, vena muscularis depressoris mandibulæ, vena muscularis colli anterior superioris, vena lingualis et hyoidea. The right terminal branches of the vena lingualis empty into the vena cephalica posterior.

The venæ pharyngis superiores and vena lingualis et hyoidea collect blood from the muscles of the tongue and posterior tongue region.

The _vena lingualis et hyoidea_ (Fig. 62, No. _B_, 7) collects the blood from the muscles of the tongue region, the lower tongue glands, and the upper throat region.

Between the two trunks of the vena facialis communis and anterior to the entrance of the vena cephalica posterior there is an anastomosis, the vena transversus (Fig. 62, No. _B_, 5). Through this anastomosis which lies crosswise the two jugular veins are influenced in different ways. At this point both jugular veins are of the same size. The anastomotic branch lies crosswise. Through this anastomosis the right receives some blood from the left head region indicating that the blood flows from left to right. This, as stated before, makes the left jugular vein the smaller.

BRANCHES OF THE VENA CEPHALICA POSTERIOR

The left vena cephalica posterior (Fig. 62, No. _B_, 8) communicates with the transverse vein (Fig. 62, No. _B_, 5). The left receives the smaller veins of the skin region, the esophagus, and the trachea. These vessels communicate with their fellow of the opposite side and with the vertebral vein of the same side, which causes a gradual reduction of the size of the jugular vein.

BRANCHES OF THE VENA OCCIPITALIS EXTERNUS

( ( Venæ choroideæ
( Sinus ( Venæ cutaneæ et frontales
( longitudinalis ( Venæ nasales
Vena ( ( Venæ ophthalmiæ
occipitalis (
externus ( ( ( Sinus occipitalis
( Sinus ( Sinus ( Sinus temporo-sphenoideus
( semicircularis ( transversus ( Venæ cerebellares
( ( ( Sinus petrosus sphenoideus

Sinus petrosus sphenoideus ( Retis mirabile temporalis
Sinus temporo-sphenoideus ( Sinus annularis venosus
basilaris
Sinus foraminus occipitalis ( Venæ medullares

( Venæ cerebrales
Sinus ( Vena cerebralis basilaris ( Sinus venosus annularis anterior
venosus (
annularis (
basilaris ( Vena ophthalmica
( Vena medullaris mediana longitudinalis

The vena cephalica posterior (Fig. 62, No. _B_, 8) is formed from the veins of the sinuses of the cranium, the brain, the vena auris, the vena jugularis prima, the vena carotis, and the vena occipitalis. It collects most of the blood from the cranium and the posterior part of the head and from the tongue.

THE VENOUS SINUSES OF THE HEAD

The =sinus longitudinalis= (Fig. 62, _A_, 10) extends from the dorsal median line of the internal occipital protuberance to the olfactory nerve. It collects the blood from the choroidea of the brain and from the skin of the frontal region. It receives laterally the veins of the nose, the vena ophthalmica, and the sinus transversus.

The =sinus occipitalis= (Fig. 62, No. _A_, 4) forms the continuation of the transverse sinus. It is located in the posterior cerebral cavity, and is wing-shaped, extending both to the right and to the left.

The =sinus foraminis occipitalis= a continuation of the sinus occipitalis, lies transversely on the ventral side of the cranial cavity and receives the veins from the medulla oblongata. One branch passes through the os occipitalis basilare, and then extends sidewise to the foramen magnum and anastomoses with the vena occipitalis.

The =sinus transversus= (Fig. 62, No. _A_, 6) extends in a pair from the internal occipital protuberance between the cerebrum, cerebellum, and the corpus quadrigeminum. It receives vessels from the upper surface of the cerebellum. The sinus has three branches, all of which empty into the sinus semicircularis.

The =sinus semicircularis= extends along the dorsal petrosal rim, anterior to the inner ear, and from this point backward. Near the foramen magnum it passes through the os occipitale and empties into the external occipital vein.

The =vena occipitalis externus= extends near the foramen magnum, surrounds the basis occipitalis, and receives the semicircular sinus and through the semicircular sinus the blood from the sinus transversus.

The =sinus petrosus sphenoideus=, passing in company with the occipital sinus, extends from the transverse sinus to the cavity near which the trigeminus lies. The sinus dividing into two branches, one of these extends to the hypophysis and unites with the basal veins of the brain; the other passes with the rete out of the cranial cavity along with a branch of the trigeminus, and communicates with the rete mirabile temporale.

The =sinus temporo-sphenoideus= (Fig. 62, No. _A_, 5) extends forward and outward from the transverse sinus, and, between the corpus quadrigeminum and the cerebrum, unites with the sinus venosus annularis basilaris.

The =sinus venosus annularis basilaris= lies in the region of the optic nerve and surrounds the hypophysis, forming a complete circle. It receives small vessels from the cerebrum, the corpora quadrigemina, and anteriorly the longitudinal basilar vein or vena basilaris media, of the cerebrum, which comes out of the anterior annular venous sinus. The anterior annular venous sinus surrounds the base of the olfactory nerves. It communicates with the sinus petrosus sphenoideus, which emerges from behind the optic lobe, the sinus temporo-sphenoideus, which emerges from in front of the optic lobe, and posteriorly the median longitudinal vein of the medulla oblongata or vena basilaris. Laterally and anterior to the optic lobe it receives the vena basilaris lateralis, and also a branch of the vena ophthalmica.

The blood received by the =sinus annularis basilaris= comes from the brain cavity through three pairs of veins, as follows: first, the two ophthalmic veins which pass through the posterior orbital wall between the olfactory and the optic nerve; second, two other branches of the ophthalmica which pass with the optic nerve; third, two veins which pass through a foramen by the side of the sella turcica to the hypophysis together with the carotis cerebralis, and then leave the cerebral cavity ventrally, at which point they are called the venæ carotes. These last accompany the cerebral artery backward, and pass through a foramen in the base of the cranium. Each one then passes through the cranial wall close to the external auditory canal, and empties into another vein in the posterior region of the head.

The =sinus fovæ hemispherii cerebelli= lies in the hollow between the os petrosum and the semicircular canals. It receives blood from the external occipital sinus and from the cerebellum, and empties into the vena auris interna.

VEINS OF THE BRAIN CAVITY

The =vena auris interna= passes through a bony canal along the outer rim of the posterior semicircular canal and then along the external semicircular canal. It receives vessels from the labyrinth, and extends along the posterior rim of the tympanum to the outer ear canal.

The =vena occipitalis interna=, extending from the sinus foraminis occipitalis, passes through the side of the atlas and divides near the condyle into two branches. One of these branches the internal occipital, forms the root of the vena vertebralis, and the other empties into the vena occipitalis externa.

Near the outer and upper part of the condyle it forms two large veins and collects the blood from the vena occipitalis media. These veins collect the blood from the rectus capitis anticus, and communicate with the vena cephalica anterior.

The =vena occipitalis externa=, sometimes called the vena occipitalis collateralis, extends from the vena auris, and receives vessels from the neck region. It receives on the side of the occipitoatloid joint the vena occipitalis interna. The vena occipitalis externa forms a junction with the vena vertebralis emptying into the transverse vein.

THE VEINS OF THE NECK

BRANCHES OF THE VENA JUGULARIS

The trunks of the vena jugularis or vena cephalica communis pass subcutaneously on both sides near the trachea and the esophagus. Near the height of the thyroid gland they almost touch the carotid artery. They then cross, dorsalward, the trunk of the subclavian artery, and in their course receive the vertebral vein and unite with the subclavian vein toward the side of the vena brachiocephalica. The union on the right side lies to the right of the anterior aorta, and the union on the left side lies to the left of the pulmonary artery.

The jugular vein (Fig. 18, No. 4) receives in its course the following veins:

The =venæ linguales= (Fig. 62, No. _B_, 7), which at times empty into the vena cephalica posterior.

The =vena occipito-collares=, which arises on the ventral side from the muscles of the neck and the vertebræ; empties into the vena occipitalis lateralis and also communicates with the vena jugularis by anastomoses.

The =venæ ascendentes laterales=, which collect blood from the lateral sides of the neck.

The =venæ colli cutineæ=, which enter the jugular vein laterally. The upper branches are directed crosswise, and are shorter than the lower ones. The lower branches are located near the thorax, are directed upward, and anastomose by fine terminal twigs. Plexuses are frequently formed in the inner side of the skin of the neck.

BRANCHES OF THE VENA SUBCLAVIA

( Vena profunda
ulnaris
( Vena brachialis ( Vena profunda
radialis
( Truncus venæ ( ( Vena profunda humeri
( axillaris (
( ( Vena basilica or cutinea ulnaris
(
( ( Vena cutinea abdomino-pectoralis
Truncus venæ ( Vena pectoris ( Vena infrascapularis anterior
subclaviæ ( externa ( Vena thoracica externa
( Vena coracoidea
( Vena sternalis

The =venæ esophageæ= are numerous smaller veins formed in closely woven plexuses in the region of the esophagus along the neck. Some pass upward and some downward.

The =venæ tracheales= are located on the supero-lateral side of the trachea and along the edge of the lateral tracheal muscle. They have numerous anastomoses transversely with the longitudinal vein of the cervical region, anteriorly with the vena lingualis, and on the left side with the left jugular vein.

The =vena subscapularis= passes along the median line of the scapula to the side of the jugular vein, and anastomoses with the vertebral vein.

The =venæ glandularum thyroidearum= are several small, short veins coming from the thyroid gland.

The =vena vertebralis=, originating near the atlas, is a continuation of the internal occipital vein. The internal occipital vein receives the bulk of the blood from the brain and communicates with the lateral veins of the cervical region and collects blood from the cervical vertebra. The vertebral vein accompanies the vertebral artery and the deep sympathetic nerve trunk in the vertebral canal. The vein either leaves this canal with the vertebral artery at a point near the last two vertebral nerve trunks of the brachial plexus, or it leaves the canal one vertebra in front of the vertebral artery.

THE VEINS OF THE DORSAL REGION

The =vena vertebralis lateralis dorsalis= collects blood from the cervical vertebræ, from the dorsal vertebræ, and from the intercostal region.

The blood from the neural canal, including the spinal cord, is collected in one long vein extending from the head to the tail on the upper side of the cord. This vein has sinus-like expansions. Between each two vertebræ it anastomoses with the vertebral vein on each side. In the lumbo-sacral region these anastomotic branches empty into the hypogastric veins.

The =vena intercostalis= is formed in the costal region and anastomoses with the vein extending longitudinally between the capitulum and the tuberculum of the rib.

The =vena vertebralis posterior= at the height of the first and the second dorsal vertebræ, empties into the main trunk of the vertebral vein. Its lower roots come out near the side of the kidney, and unite, forming a large ascending trunk uniting with the vena vertebralis anterior forming one large trunk, which extends into the chest cavity.

The posterior vertebral vein also receives a large vein from the skin of the outer tarsal region and a few vessels from the muscles of the outer abdominal and the outer costal region, from the skin, from the pectoralis muscles, and from the shoulder region.

VEINS OF THE THORAX

BRANCHES OF THE VENA SUBCLAVIA

The =vena thoracica externa= (Fig. 73, No. 2) is made up of veins mainly from the pectoral group of muscles. The posterior branch anastomoses with the vena cutinea. Its anterior branch is made up mainly of branches from the furcular region. It empties into the vena pectoralis externa and the vena pectoralis externa empties into the vena subclavia.

The =vena coracoidea= comes out of the region of the shoulder-joint, passes downward along the inner surface of the coracoid, and receives small branches from the walls of the arteria brachia cephalica and from the pericardium.