Part 70

_a_, _b_, Brachial artery; _c_, subscapular vessels; _d_, thoracico-dorsal vessels; _e_, deep brachial vessels; _f_, superior collateral ulnar vessels; _g_, brachial vein; _h_, _h″_, cephalic vein; _h′_, mediano-radial vein; _i_, anterior thoracic nerves; _k_, musculo-cutaneous nerve; _l_, median nerve; _m_, ulnar nerve; _n_, radial nerve; _o_, thoracico-dorsal nerve; _1_, subscapularis muscle; _2_, supraspinatus muscle; _3_, teres major; _4_, latissimus dorsi; _5_, deep pectoral muscle; _6_, biceps brachii; _7_, long head of triceps; _8_, tensor fasciæ antibrachii; _9_, internal head of triceps; _10_, pronator teres. (Ellenberger-Baum, Anat. d. Hundes.) ]

[Illustration:

FIG. 488.—ARTERIES OF FOREARM OF DOG, INNER VIEW.

_a_, Brachial; _a′_, median; _c_, common interosseous; _d_, volar antibrachial; _e_, radial; _e′_, _e″_, dorsal and volar branches of _e_; _f_, _f′_, cutaneous branches of _e_; _g_, ulnar; _1_, biceps brachii; _2_, extensor carpi radialis; _3_, pronator teres; _4_, deep digital flexor; _5_, radius; _6_, superficial digital flexor; _7_, flexor carpi radialis; _8_, flexor carpi medius; _9_, humerus. (Ellenberger-Baum, Anat. d. Hundes.) ]

The =ulnar artery= descends on the deep flexor of the digit, and sends a connecting branch to the radial above the carpus. Near the middle of the metacarpus it gives off the =first volar metacarpal artery= and divides into the =second=, =third=, and =fourth superficial volar metacarpal arteries=. The first volar artery unites with the corresponding dorsal artery to form the =first common digital artery=, which supplies proper digital arteries for the opposed surfaces of the first and second digits. The superficial volar arteries descend in the spaces between the other metacarpal bones, unite near the metacarpo-phalangeal joints with the corresponding deep volar and dorsal metacarpal arteries to form three =common digital arteries=. Each of the latter divides after a short course into two =proper digital arteries=, which run along the opposed surfaces of the second to the fifth digits. The external digital artery of the fifth digit comes from the =superficial volar arch= formed by the union of a branch of the volar interosseous with the fourth superficial volar metacarpal artery.

[Illustration:

FIG. 489.—ARTERIES OF DISTAL PART OF RIGHT FORE LIMB OF DOG, ANTERIOR VIEW.

_a_, Branch of volar interosseous artery; _b_, proximal collateral radial artery (external branch); _c_, radial artery (dorsal branch); _d_, rete carpi dorsale; _e_, deep dorsal metacarpal arteries; _f_, superficial dorsal metacarpal arteries; _g_, common digital arteries; _h_, proper digital arteries. ]

[Illustration:

FIG. 490.

_i_, Radial artery; _j_, ulnar artery; _k_, volar interosseous artery; _l_, deep volar arch; _m_, external (fifth) volar metacarpal artery; _n_, deep volar metacarpal arteries; _p_, superficial volar metacarpal arteries; _o_, _q_, common digital arteries; _r_, proper digital arteries. ]

The rete carpi dorsale gives off four =dorsal metacarpal arteries= which descend in the intermetacarpal spaces and unite near the metacarpo-phalangeal joints with the volar arteries to form the common digitals.

The =thoracic aorta= supplies the last nine or ten pairs of intercostal arteries, but no anterior phrenic arteries. It gives off two or more œsophageal branches, in addition to the broncho-œsophageal, which arises close to or with the sixth intercostal and ramifies in the usual manner.

The =abdominal aorta=, after giving off the external iliac arteries, continues about half an inch to an inch (ca. 1 to 3 cm.) under the last lumbar vertebræ, gives off the internal iliacs, and is continued by the middle sacral artery. This small vessel runs backward under the sacrum and coccygeal vertebræ and gives off branches in segmental fashion.

[Illustration:

FIG. 491.—END BRANCHES OF AORTA AND RADICLES OF POSTERIOR VENA CAVA OF DOG.

_a_, Abdominal aorta; _b_, posterior mesenteric artery; _c_, lumbar arteries; _d_, circumflex iliac artery; _e_, external iliac artery; _f_, deep femoral artery; _g_, posterior abdominal artery; _h_, external pudic artery; _a_, femoral artery; _i_, _i_, internal iliac arteries; _k_, visceral branch of _i_; l, parietal branch of _i_; _m_, ilio-lumbar artery; _n_, anterior gluteal artery; _o_, lateral coccygeal artery, _p_, posterior gluteal artery; _q_, umbilical artery; _r_, middle hæmorrhoidal artery; β, posterior hæmorrhoidal artery; _s_, perineal artery; _t_, art. profunda penis; _n_, art. bulbi urethræ, _v_, art. dorsalis penis; _w_, middle sacral artery, _a′_, posterior vena cava; other veins are satellites of arteries and correspondingly named; _1_, ilio-psoas muscle; _2_, tendon of psoas minor; _3_, abdominal muscles; _4_, sartorius; _5_, rectus femoris; _5′_, vastus internus; _6_, pectineus; _6′_, adductor; _7_, gracilis; _8_, symphysis pelvis; _9_, ilium; _10_, pyriformis; _11_, gluteus superficialis; _12_, obturator internus; _13_, penis; _14_, lumbar vertebræ. (After Ellenberger, in Leisering’s Atlas.) ]

The =cœliac artery= gives off the hepatic artery and forms a short =gastro-splenic= trunk. The hepatic artery gives off several hepatic branches, and the pyloric or right gastric artery, which passes along the lesser curvature of the stomach, anastomoses with the (left) =gastric artery=, and is continued by the gastro-duodenal. This divides near the pylorus into right gastro-epiploic and pancreatico-duodenal. The (left) gastric artery passes to the lesser curvature of the stomach and ramifies chiefly on the left part of the stomach, giving off a branch which anastomoses with the pyloric branch of the hepatic. The =splenic artery= gives off pancreatic branches, and reaches the lower part of the spleen. It gives off the left gastro-epiploic, and a branch which passes to the dorsal end of the spleen, which it supplies, besides giving off twigs to the left extremity of the stomach.

The =anterior mesenteric artery= arises close behind the cœliac. It gives off a common trunk for two colic arteries and the ileo-cæco-colic. The former supply the transverse and the anterior part of the left or descending colon, while the latter divides into branches for the ileum, cæcum, and first part of the colon. The trunk is continued as the artery of the small intestine, giving off fourteen to sixteen branches (Aa. jejunales), which form a series of anastomotic arches in the mesentery near the bowel.

Two =phrenico-abdominal arteries= (Aa. phrenicæ caudales) come off from the aorta behind the anterior mesenteric, and divide into phrenic and abdominal branches. Each phrenic artery diverges from its fellow in descending on the abdominal surface of the corresponding crus of the diaphragm to the sternal part. The inner branches anastomose with those of the opposite artery, the outer branches with intercostal arteries chiefly. The abdominal arteries give branches to the lumbar muscles, the renal fat and capsules, and ramify in the oblique abdominal muscles.

The =renal= and =spermatic arteries= offer no special features.

The =utero-ovarian artery= divides near the ovary into three or four branches which supply the ovary and uterus, anastomosing with the uterine artery.

The =posterior mesenteric artery= is small. It divides into two branches which supply the terminal part of the colon and the anterior part of the rectum.

The =circumflex iliac artery= usually arises from the terminal part of the aorta.

The =external iliac artery= usually gives off no collateral branches.

[Illustration:

FIG. 492.—ARTERIES OF PELVIC LIMB OF DOG, INTERNAL VIEW.

_a_, Abdominal aorta; _b_, femoral; _c_, _c′_, deep femoral; _d_, posterior abdominal; _e_, external pudic; _f_, internal circumflex; _g_, anterior femoral (accompanied by anterior branch of femoral nerve); _h_, external circumflex; _i_, _k_, muscular branches; _l_, articular branch; _m_, saphenous; _n_, _o_, plantar and dorsal branches of saphenous; _q_, saphenous nerve; _r_, obturator nerve; _1_, ilio-psoas; _2_, ilium; _3_, gracilis; _4_, semitendinosus; _5_, adductor magnus; _6_, adductor longus; _7_, quadriceps femoris; _8_, sartorius; _9_, semimembranosus; _10_, gastrocnemius; _11_, tibialis anterior; _12_, tibia. (Ellenberger-Baum, Anat. d. Hundes.) ]

[Illustration:

FIG. 493.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF DOG, ANTERIOR VIEW.

_a_, External branch of anterior tibial artery; _b_, anterior tibial artery; _c_, saphenous artery (anterior branch); _d_, perforating metatarsal artery; _e_, dorsal metatarsal arteries; _f_, deep dorsal metatarsal arteries; _g_, superficial dorsal metatarsal arteries; _h_, anastomoses between dorsal and plantar arteries; _i_, common digital arteries; _j_, proper digital arteries. ]

[Illustration:

FIG. 494.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF DOG, POSTERIOR VIEW.

_k_, Saphenous artery (posterior branch); _l_, _l′_, internal and external plantar arteries; _m_, perforating metatarsal artery; _n_, deep plantar metatarsal arteries; _o_, superficial plantar metatarsal arteries; _p_, common digital artery; _q_, proper digital arteries. ]

The =femoral artery= has the usual course. The deep femoral gives off the posterior abdominal and external pudic arteries by a very short common trunk or separately. In the female the external pudic divides into anterior and posterior branches; the former runs forward, supplies branches to the inguinal lymph glands, the mammary glands and skin, and anastomoses with the mammary branch of the internal thoracic artery; the posterior branch pursues a flexuous course between the thighs to the vulva, where its terminal branches anastomose with the internal pudic artery. The anterior femoral may arise by a short common trunk with the external circumflex. The former, accompanied by the anterior branch of the femoral nerve, dips in between the rectus femoris and vastus internus. The external circumflex artery passes forward between the sartorius internally and the rectus femoris and tensor fasciæ latæ externally and supplies branches to these muscles and the glutei. In addition to muscular branches of considerable size, an articular branch (A. genu suprema) arises a little below the middle of the thigh and runs downward and forward to the inner face of the stifle joint. The =saphenous artery= is large. It arises from the inner surface of the femoral a little below the middle of the femur, descends superficially to the upper part of the leg and divides into two branches. The smaller =anterior branch= (Ramus dorsalis) passes obliquely downward and forward across the inner surface of the tibia to the flexion surface of the hock and terminates in three =superficial dorsal metatarsal arteries=. The =posterior branch= (Ramus plantaris) passes down on the inner face of the gastrocnemius and the long digital flexor. It gives off a branch (A. tarsea lateralis) which descends obliquely to the external surface of the tarsus, and at the posterior face of the tarsus detaches the =internal= and =external plantar arteries=; these descend on either side of the deep flexor tendon and unite with the perforating metatarsal artery to form the proximal plantar arch. The artery continues down the middle of the plantar surface of the metatarsus and divides near the metacarpo-phalangeal joints into three =superficial plantar metatarsal arteries=. These vessels unite with three =deep plantar metatarsal arteries= which descend from the proximal plantar arch and with branches from the dorsal metatarsal arteries. From these anastomoses four digital arteries result; of these, the central two have a common digital trunk.

The =popliteal= and =posterior femoral arteries= present nothing of special interest.

The =posterior tibial artery= is small, being replaced largely by the saphenous. It supplies twigs to the flexor muscles at the upper part of the leg.

The =anterior tibial artery= descends on the anterior face of the tibia and tarsus and is continued as the perforating metatarsal artery, which passes through the upper part of the space between the second and third metatarsal bones and concurs with the plantar branches of the saphenous in the formation of the plantar arch. Besides muscular and articular branches, the anterior tibial supplies the external or fifth dorsal metatarsal artery for the outer side of the fifth digit. At the proximal part of the metatarsus it gives off three =deep dorsal metatarsal arteries= which descend in the intervals between the metatarsal bones and concur with the superficial dorsal and the plantar arteries in the formation of the =digital arteries=. The latter resemble in general arrangement the corresponding arteries of the thoracic limb.

The =internal iliac artery= (Fig. 491) runs backward and a little outward across the ilio-psoas, and on reaching the ilium divides into parietal and visceral branches. The =parietal branch= is the larger. It runs backward on the lateral wall of the pelvis, passes out through the lesser sciatic notch, and breaks up into branches which supply the muscles in this region like the posterior gluteal (or ischiatic) artery of the horse. It gives off the following branches: (1) The =ilio-lumbar artery= passes outward between the ilio-psoas and the shaft of the ilium and ramifies in the gluteus medius, giving branches to the ilio-psoas and tensor fasciæ latæ; it may arise from the internal iliac. (2) The =anterior gluteal artery= passes out behind the posterior superior spine of the ilium and supplies branches to the glutei. (3) =Muscular branches= go to the obturator internus, coccygeus, and retractor ani. (4) The =lateral coccygeal artery= (A. caudalis lateralis superficialis) passes back at first on the outer face of the coccygeus and continues beneath the skin along the side of the tail. The =visceral branch= or =internal pudic artery= passes back below the parietal branch on the lateral face of the rectum, retractor ani, and coccygeus. Its chief collateral branches are: (1) The =umbilical artery=, which pursues a flexuous course and supplies twigs to the bladder, ureter, and vas deferens. In the bitch it gives off a large =uterine artery= which ramifies chiefly in the body and neck of the uterus and the vagina and anastomoses with the utero-ovarian. (2) The =middle hæmorrhoidal artery= arises near the ischial arch, passes upward and forward on the lateral surface of the rectum, gains its dorsal surface and anastomoses with the posterior mesenteric; it supplies the rectum and the anus, together with its muscles and glands. (3) A small =perineal artery= is detached to the perineum. In the male the trunk turns around the ischial arch as the =artery of the penis= (A. penis). This vessel, after giving off the =deep artery of the penis= (A. profunda penis), which supplies the =artery of the bulb= (A. bulbi urethræ) and enters the corpus cavernosum, is continued as the =dorsal artery of the penis= (A. dorsalis penis) along the dorsum penis. In the female the terminal branches of the trunk go to the vulva, vestibular bulb, and clitoris.

THE VEINS

The arrangement of the veins is, of course, correlated in general with the arterial system, but a few special features are worthy of mention.

The =anterior vena cava= is formed by the junction of short right and =left brachiocephalic= (or subclavian) =veins=, and each of the latter results from the confluence of =jugular= and =brachial veins=.

The =vena azygos= resembles that of the horse, and receives at the ninth or tenth thoracic vertebra a =vena hemiazygos=.

Two =jugular veins= are present on each side. The =external jugular vein= is formed by the union of external and internal maxillary veins at the posterior border of the submaxillary gland. The two external jugulars are commonly united by a transverse branch below the cricoid cartilage. Each passes along the neck on the sterno-cephalicus, covered only by the skin and panniculus, dips under the cleido-cervicalis, and joins the internal jugular.

The =external maxillary vein= arises on the lateral nasal region by the junction of the dorsal nasal vein with the angularis oculi. Near the infraorbital foramen it receives the lateral nasal vein, and a little lower the superior labial. In its course along the anterior border of the masseter it receives the vena reflexa, which arises in the pterygo-palatine fossa by the junction of infraorbital, sphenopalatine, and palatine radicles, together with a branch from the cavernous sinus. At the lower border of the mandible it is joined by the inferior labial vein, which receives the buccinator vein. The lingual vein is connected with its fellow by a superficial transverse branch at the insertion of the sterno-hyoidei. The sublingual and submental veins terminate in a variable manner, but often form a common trunk which joins the lingual.

The =internal maxillary vein= arises from the pterygoid plexus, formed chiefly by dorsal lingual, inferior alveolar, deep temporal, pterygoid, and meningeal tributaries. It receives the superior cerebral, auricular, superficial temporal, transverse facial, and masseteric veins, and often a trunk formed by the union of the inferior cerebral and occipital veins.

The =internal jugular vein= results usually from the junction of laryngeal and thyroid veins, but in some cases it is formed by the confluence of the inferior cerebral and occipital veins.

The =brachial= and =radial veins= are satellites of the arteries.

The =ulnar vein= is usually double. It unites below the carpus with a branch of the interosseous vein to form the superficial venous arch.

The =cephalic vein= accompanies the ulnar artery in the forearm and joins the superficial venous arch below.

The =accessory cephalic vein= arises from the union of three dorsal metatarsal veins. It joins the cephalic about the middle of the forearm.

There are three short =volar metacarpal veins= which open into the superficial venous arch. They are formed above the metacarpo-phalangeal joints by the junction of the =volar digital veins=, of which there are two for each of the chief digits. The volar vein of the first digit joins the superficial venous arch.

Each of the chief digits has two =dorsal digital veins=, while the first digit has one.

The =posterior vena cava=, its collateral affluents, and common iliac radicles present no special features of importance.

The =internal iliac vein= corresponds in regard to its tributaries with the branches of the artery, except that it is not divided into dorsal and ventral branches.

The =external iliac=, =femoral=, and =popliteal veins= with their collateral tributaries are satellites of the arteries.

The =anterior tibial vein= is usually double, and the =posterior tibial vein= is very small.

The =internal saphenous vein= is the upward continuation of the internal plantar metatarsal vein. It communicates by a large branch with the dorsal metatarsal vein, and ascends the leg as a satellite of the saphenous artery and its plantar (posterior) branch. The =recurrent tarsal= or =external saphenous vein= is larger. It is formed at the lower part of the leg by the union of dorsal and external plantar metatarsal veins, crosses the outer surface of the leg obliquely upward and backward, ascends behind the gastrocnemius and joins the posterior femoral vein.

The =metatarsal= and =digital veins= resemble in general the corresponding vessels of the fore limb.

THE LYMPH VESSELS AND GLANDS

The =cisterna chyli= is large and fusiform. The =thoracic duct= may be single throughout, but often divides anteriorly into two branches, which may then unite and form a dilatation which receives the left tracheal duct and the vessels from the fore limb. The primitive plexiform arrangement persists in varying degree. The duct terminates in the left brachiocephalic vein.

The =tracheal ducts= accompany the internal jugular veins. The right duct opens into the right brachiocephalic vein.

The =submaxillary lymph glands= (Fig. 486) are commonly three in number on each side. They are situated in the angle between the masseter and the submaxillary salivary gland, in relation to the external maxillary vein and covered only by the skin and panniculus. The number may be reduced to two or one with a corresponding increase in size.

A small round =parotid= or =auricular lymph gland= is situated superficially between the upper part of the posterior border of the masseter and the parotid gland.

The =pharyngeal= (or retropharyngeal) =lymph glands=, one or two in number on each side, lie on the pharynx chiefly under cover of the submaxillary salivary gland.

The =prescapular= or =superficial cervical lymph glands= lie on the serratus magnus at the anterior border of the supraspinatus, embedded in a mass of fat. Usually two or three are present on each side, but there may be only one. They are oval and are about an inch long in a dog of medium size when two are present.

The =axillary lymph gland= lies in a mass of fat on the inner face of the lower part of the teres major. It is discoid.

The =cubital lymph gland= is inconstant. It is situated on the deep face of the long head of the triceps or on the latissimus dorsi.

The =mediastinal lymph glands= are small and quite variable in arrangement. Usually one or two glands are found on the course of the internal thoracic vessels at the second segment of the sternum.

The =bronchial lymph glands= are commonly four in number. The largest is situated in the angle of divergence of the chief bronchi, two lie on the origin of the right apical bronchus, and the fourth is between the aortic arch and the anterior face of the left bronchus. They are commonly pigmented.

The =lumbar lymph glands= are small.

The =mesenteric lymph glands= are represented chiefly by a long flattened mass (formerly known as the pancreas Aselli) which lies in the mesentery along the course of the anterior mesenteric artery and vein. It is succeeded by three or four glands which lie along the portal vein and appear to receive vessels from the stomach, spleen, liver, pancreas, and great omentum. A few very small nodes occur along the colon.

The =iliac lymph glands= are relatively large and are situated at the termination of the aorta and the origin of the iliac arteries. Commonly four are present. Of these, the two largest lie on the psoas minor on each side in relation to the aorta and vena cava respectively. The other two are in the angle of divergence of the internal iliac arteries.

The =superficial inguinal lymph glands= are situated in the subcutaneous fat behind the external inguinal ring. They are relatively large, especially when there is only one on each side; two smaller ones may be found instead.

The =popliteal lymph gland=—usually unique, but sometimes double—lies in a pad of fat on the upper part of the gastrocnemius between the biceps femoris and semitendinosus. It may project back so as to be superficial and palpable.

NEUROLOGY

THE NERVOUS SYSTEM

The nervous system is a complex mechanism by which the organism is brought into functional relation with its environment, and its various parts are coördinated. For purposes of gross description it is divided primarily into two parts, central and peripheral.

The =central nervous system= (Systema nervorum centrale) comprises (_a_) the =spinal cord= (Medulla spinalis), and (_b_) the =brain= (Encephalon).

The =peripheral nervous system= (Systema nervorum periphericum) includes (_a_) the =cerebral= and =spinal nerves= with their =ganglia=, and (_b_) the =sympathetic nervous system=.

The division into central and peripheral parts is quite arbitrary and is employed purely as a matter of convenience of description. The fibers of which the nerves are composed either arise or end within the central system, and therefore constitute an integral part of the latter. The structural and functional unit of the nervous system is the =neurone=, which consists of the =cell-body=, usually termed the =nerve-cell=, and all its =processes=. The processes arise as outgrowths from the cell-body and conduct impulses to or from the cell. They vary greatly in length, some being less than a millimeter long, while others extend from a cell in the spinal cord to the distal end of a limb. A nerve is composed of such processes, usually inclosed in a protecting and insulating sheath, and united into bundles by connective tissue. The neurones are embedded in a peculiar supporting tissue termed =neuroglia=. This consists of a very intricate feltwork of glia-fibers, many of which are connected with the small glia-cells or astrocytes. In addition the nervous tissue is invested closely by a vascular layer of connective tissue, the pia mater, from which ingrowths extend into the nervous substance proper.[186]

To the naked eye the central nervous system appears to be composed chiefly of two kinds of substance, white and gray. The =white matter= (Substantia alba) is dead white in color and is soft in the natural state. It consists largely of medullated nerve-fibers, packed closely together and arranged more or less clearly in large or small bundles or tracts (Funiculi, fasciculi). The =gray matter= (Substantia grisea) is usually brownish-gray in color, often with a tinge of pink. It is softer than the white substance and much more vascular. It is composed chiefly of cell-bodies and non-medullated processes. In some situations it is modified to form the =gelatinous substance= (Substantia gelatinosa), which is pale yellowish-gray and jelly-like.