Chapter V: Muscles of the Leg and Foot (16)

There are three chief metatarsal veins. The great =dorsal metatarsal vein= arises at the distal part of the metatarsus by the union of the dorsal digital vein and a large branch from the venous arch above the sesamoids. It ascends superficially between the long and lateral extensor tendons and becomes the chief radicle of the anterior tibial vein. The =internal plantar metatarsal vein= arises from the venous arch above the fetlock, ascends along the inner border of the suspensory ligament, passes through the vascular canal of the metatarsus and centro-tarsal (as the perforating tarsal) and joins the anterior tibial vein. The =external plantar metatarsal vein= is larger than the preceding. It passes superficially over the outer face of the hock and is continued by the recurrent tarsal vein.

The =digital veins= differ from those of the fore limb chiefly in that the dorsal vein is large and the plantar absent or small.

The =portal vein= is formed usually by the confluence of two radicles, gastric and mesenteric. It receives the right gastro-epiploic vein and veins of the pancreas. The gastric vein is the largest affluent. It is formed by the junction of three veins, the left of which receives the splenic vein. The anterior mesenteric vein is also formed by the confluence of three radicles; it usually receives the small posterior mesenteric vein. The portal tributaries are in general satellites of the corresponding arteries.

THE LYMPH VESSELS AND GLANDS

The =thoracic duct= arises from a small cisterna chyli and is very variable. It is exceptional to find a single trunk throughout, as is often the case in the horse. The duct is largely covered by fat and small lymph glands. There are often two ducts, one on either side of the aorta, which may join at a variable point or terminate close together at the junctions of the jugular and brachial veins. In other cases the duct is single for a variable distance, then bifurcates or divides into three or four branches, which are often connected by plexiform anastomoses.

The efferent vessels from the intestine converge to a large trunk which accompanies the anterior mesenteric artery and vein. It passes below the pancreas and receives usually a large duct which is formed by efferent vessels from the stomach, liver, and spleen; this duct sometimes opens directly into the cisterna. The gastro-intestinal trunk receives the collecting duct (truncus lumbalis) of the lumbar lymph vessels, forms a bend around the right renal vessels, and joins the cisterna.

The =lymph glands= in the ox are in general less numerous but larger than those of the horse, and in some situations a single large gland occurs instead of a group of smaller ones, as found in the latter animal.

The =submaxillary lymph glands= are usually two in number, right and left; each is situated under the external maxillary vein between the submaxillary salivary gland and the sterno-cephalicus muscle. Usually one or two hæmolymph glands are near it. There is generally a small gland on the deep face of the anterior part of the submaxillary salivary gland, and small nodes may be found further forward in the submaxillary space.

A large =subparotid lymph gland= lies on the postero-superior part of the masseter muscle, partly under cover of the upper end of the parotid gland. Several hæmolymph glands lie on its deep face.

The =pharyngeal lymph glands= number two or three on each side. Of these, two large =suprapharyngeal glands= (Lg. retropharyngeales) are situated about an inch apart between the dorsal wall of the pharynx and the ventral straight muscles (Figs. 281, 365). These are two to three inches long. Enlargement of them is likely to cause difficulty in swallowing and in respiration. Behind these are several hæmolymph glands. An =atlantal gland= is situated below the wing of the atlas on the spinal accessory nerve. It is discoid, oval in outline, and may be an inch and a half or more in length. It is partly covered by the upper end of the submaxillary salivary gland.

A smaller lymph gland (parapharyngeal) is usually found along the lower border of the carotid artery (_i. e._, ventral to the atlantal gland) on the lateral wall of the pharynx and under cover of the submaxillary salivary gland or at its posterior border.

Two or three small =anterior cervical lymph glands= commonly lie along the carotid artery a little further back.

The =middle cervical lymph glands= comprise a series of small nodes along the dorsal face of the trachea.

In the sheep and goat there is a lymph gland at the middle of the
neck, in the angle between the spinalis and complexus, covered by the
splenius. It receives vessels from the atlantal gland and sends
efferents to the prescapular gland.

The =prescapular= or =superficial cervical lymph gland= is situated at the anterior border of the supraspinatus under cover of the mastoido-humeralis and omo-transversarius. It is elongated and may be an inch or more in width and four or five inches long. Two occur in exceptional cases.

A chain of hæmolymph glands lies along the front of the shoulder,
covered above by the trapezius. Others are frequently found (in the
calf especially) on the surface of the omo-transversarius at the point
where it passes under the mastoido-humeralis (Forgeot).

FIG. 478.—SUPERFICIAL LYMPH GLANDS OF COW PROJECTED ON SURFACE OF
BODY.

_1_, Submaxillary; _2_, subparotid; _3_, atlantal; _4_,
parapharyngeal; _5_, anterior cervical; _6_, middle cervical; _7_,
prescapular; _8_, precrural. (With use of fig. in Ellenberger-Baum,
Anat. f. Künstler.)
]

The =posterior cervical= or =prepectoral lymph glands= number commonly three or four on each side. One or two are placed on the brachial vessels, one below the brachial vein at the first rib, and one at the junction of the common trunk of the external and subcutaneous thoracic veins with the brachial.

The =intercostal lymph glands= are situated, as in the horse, at the upper parts of the intercostal spaces. Associated with them are hæmolymph glands.

The =sternal lymph glands= are situated along the course of the internal thoracic artery at the lower part of the intercostal spaces. The largest is close to the thoracic inlet. Several glands occur in the fat about the apex of the pericardium.

4. Several =anterior mediastinal lymph glands= are placed along the œsophagus and the trachea.[183] Hæmolymph glands occur here also.

Usually three large =bronchial lymph glands= are present (Fig. 289). One is situated at the origin of each chief bronchus and the third is under the trachea at the origin of the special bronchus of the apical lobe of the right lung. Another may lie between the aorta and the left branch of the pulmonary artery. These glands are often pigmented. Other small nodes are situated on the bronchi within the lungs.

The =posterior mediastinal lymph glands= comprise two or three of large size placed along the dorsal wall of the œsophagus. There may be a single gland about eight inches (ca. 20 cm.) long, the anterior half of which lies on the œsophagus (Fig. 289).[184] A small gland is situated in the acute angle formed by the posterior vena cava and the diaphragm.

A single =axillary lymph gland= is situated on the distal part of the teres major on the course of the vein from the latissimus dorsi.

The =lumbar lymph glands= form an irregular series scattered along the abdominal aorta and posterior vena. A bean-shaped =renal lymph gland= occurs at the hilus of each kidney. Hæmolymph glands occur along the course of the aorta.

FIG. 479.—INTESTINE OF OX, SPREAD OUT.

_Ca_, Cæcum; _C_, colon; _D_, duodenum; _H_, ileum; _J_, jejunum; _R_,
rectum; _m_, mesenteric lymph glands. (After Edelmann.)
]

The =internal iliac lymph glands= comprise a group of five or six at the termination of the aorta and the origin of the vena cava. A discoid gland, two inches or more in diameter, occurs near the side of the pelvic inlet at the angle of divergence of the circumflex iliac artery from the external iliac. A small gland is sometimes found at the origin of the prepubic artery.

The =external iliac lymph glands= number commonly two on either side, and are situated near the point of the hip in front of the anterior branch of the circumflex iliac artery.

The =superficial inguinal lymph glands= are situated centrally below the prepubic tendon and in the narrow space between the origins of the graciles. In the male there are usually two or three on either side of the penis behind the sigmoid flexure. In the cow they are =supramammary=, _i. e._, are situated above the posterior margin of the base of the udder; two large glands which are in apposition with each other medially are constant, and above these there are often two smaller glands.

An =ischiatic lymph gland=, which is discoid and usually about an inch in diameter, is situated on the lower part of the sacro-sciatic ligament near the lesser sciatic notch under cover of the biceps femoris.

An =anal lymph gland= is situated on the retractor ani on either side.

The =gastric lymph glands= are numerous and comprise: (1) a chain along the course of the right ruminal artery and two or three in the left groove of the rumen; (2) several on the reticulum above and below the junction with the omasum; (3) a series along the course of the superior omasal vessels and the lesser curvature of the abomasum; (4) an extensive chain along the ventral face of the omasum and the great curvature of the abomasum at the attachment of the great omentum.

Two or three large =hepatic= or =portal lymph glands= are found at the upper part of the portal fissure of the liver.

No lymph glands occur at the hilus of the spleen. The efferent vessels from the spleen appear to go to glands along the course of the cœliac artery.

A large discoid =cœliac lymph gland= lies on the pancreas and the cœliac artery, covering the latter as it gives off its primary branches.

The =mesenteric lymph glands= are large and numerous. They form a chain in the lower part of the mesentery along the course of the great mesenteric artery. They are chiefly elongated and narrow, and some have a length of six to eight inches (15 to 20 cm.) or more. Sometimes several unite and form a narrow band about two feet in length. A large gland occurs at the origin of the spiral part of the colon, a group is found near the anterior mesenteric trunk, and others are scattered along the coils of the colon, which are best seen on the right side. A chain of small lymph glands extends along the terminal part of the colon and the dorsal face of the rectum.

The =precrural lymph gland= is situated on the aponeurosis of the external oblique at the anterior border of the tensor fasciæ latæ a short distance above the stifle. It is elongated like the prescapular gland and may be six inches (ca. 15 cm.) long. Several subcutaneous hæmolymph glands occur in this vicinity; others are situated further forward on the flank not far from the last rib. There is usually a round, flattened lymph gland about an inch in diameter on the upper part of the quadriceps femoris under cover of the tensor fasciæ latæ, and one or more small ones occur on the surface of the latter muscle.

No =deep inguinal lymph glands= are present.

A single =popliteal lymph gland= an inch or more in length is situated somewhat lower down on the gastrocnemius than in the horse, behind the tibial and peroneal nerves.

CIRCULATORY SYSTEM OF THE PIG

THE HEART

The =pericardium= is attached to the sternum from a point opposite to the third rib as far as the xiphoid cartilage, and also to the sternal part of the diaphragm.

The =heart= is small in proportion to the body-weight, especially in fat animals. It is relatively short and wide. The apex is blunt and is marked by a notch (Incisura apicis). Its long axis is more oblique, but it is less asymmetrical with regard to the median plane, than in the horse or ox. The lower border of the left auricle (appendix) is marked by several notches and is situated at a lower level than the right one. The right longitudinal groove is placed far back and there is no posterior sulcus.

THE ARTERIES

The =pulmonary vessels= present no remarkable features.

The =aorta= resembles that of the horse and ox in its course and relations, but the arch is more strongly curved. There is no common brachiocephalic trunk (anterior aorta).

The =brachiocephalic artery= arises first from the aortic arch and passes forward below the trachea to the first rib. Here it gives off the =common carotid arteries=, and is continued around the first rib as the right brachial.

The =superior cervical=, =vertebral=, and =dorsal arteries= usually arise by a common trunk.

The =inferior cervical artery= is large; its ascending branch gives off the =posterior thyroid artery= and =parotid branches=.

The =internal= and =external thoracic arteries= give branches to the pectoral mammary glands; the external may be absent.

The =left brachial artery= arises from the aortic arch just above the brachiocephalic. It curves forward and downward and turns around the anterior border of the first rib. Its superior cervical, vertebral, and dorsal branches usually arise separately.

The =carotid arteries= arise from the brachiocephalic close together or by a very short common trunk. They terminate in occipital and internal and external carotid divisions.

The =occipital artery= resembles that of the horse.

The =internal carotid artery= usually arises by a common trunk with the occipital. After giving off a large meningeal branch it passes through the foramen lacerum and forms with the opposite artery a rete mirabile which resembles that of the ox, but is smaller and is not connected with the vertebral and condyloid arteries.

The =external carotid artery= has the same course and termination as in the horse. Its branches present the following special features: (1) The =lingual artery= is relatively large and supplies the pharyngeal artery, the sublingual, muscular branches, and branches to the soft palate, submaxillary gland, and larynx. (2) The =external maxillary artery= is small and is distributed chiefly to the submaxillary gland, the pharyngeal lymph glands, the masseter and the panniculus. It does not extend upon the lateral surface of the face. (3) The =posterior auricular artery= is long and relatively large; it gives off the posterior meningeal.

The =internal maxillary artery= pursues a flexuous course between the ramus of the mandible and the pterygoid muscles. Its branches offer the following special features: (1) The =inferior alveolar= (or dental) is large; branches from it emerge through four or five mental foramina and take the place of the inferior labial. (2) The =buccinator artery= is also large and extends to the lips. (3) The =infraorbital artery= extends to the snout and replaces the superior labial largely and the lateral nasal in part. The malar branch compensates largely for the absence of the lateral and dorsal nasal. (4) The =palatine artery= is small.

The =intercostal arteries= number fourteen to sixteen in either side; of these ten to twelve arise from the aorta, usually by short common trunks. Frequently an intercostal artery is given off from that of an adjacent space.

The =bronchial= and =œsophageal arteries= usually arise separately.

The =cœliac artery= is half an inch to an inch long. It supplies a branch to the left crus of the diaphragm and divides into two primary branches, gastro-hepatic and splenic. The =gastro-hepatic artery= is the larger. It gives off pancreatic branches, the anterior gastric artery, branches to the lesser curvature of the stomach, pyloric and gastro-duodenal arteries. The latter divides into pancreatico-duodenal and right gastro-epiploic. The anterior gastric usually supplies the œsophageal artery. The continuing trunk (A. hepatica propria) gives off a cystic branch and divides in the portal fissure into four branches which supply the liver. The =splenic artery= gives off the posterior gastric (usually), branches to the stomach above the cardia, twigs to the pancreas, short gastric arteries to the left part of the great curvature, and splenic branches, and is continued as the left gastro-epiploic artery.

The posterior gastric may arise from the gastro-hepatic or in the
angle of divergence of the two primary divisions of the cœliac. The
œsophageal branch may come from the splenic.

FIG. 480.—ARTERIES OF DISTAL PART OF RIGHT FORE LIMB OF PIG, ANTERIOR
VIEW.

_a_, Terminal part of volar interosseous artery; _b_, dorsal
interosseous artery; _c_, rete carpi dorsale; _d_, dorsal metacarpal
arteries; _e_, dorsal common digital arteries; _f_, dorsal proper
digital arteries.
]

FIG. 481.—ARTERIES OF DISTAL PART OF RIGHT FORE LIMB OF PIG, POSTERIOR
VIEW.

_g_, Ulnar artery; _h_, superficial branch of radial artery; _i_,
collateral ulnar artery; _j_, volar interosseous artery; _h_, deep
branch of radial artery; _k_, deep volar metacarpal arteries; _l_,
superficial volar metacarpal arteries; _m_, volar common digital
artery; _n_, volar proper digital arteries.
]

The =anterior mesenteric artery= is long like that of the ox. It gives twigs to the pancreas, the ilio-cæcal and two colic arteries, and is continued in the mesentery as the artery of the small intestine. This gives off numerous branches which form a series of arches along the mesenteric lymph glands. From these is formed a rich network which gives off innumerable fine branches placed close together. The colic arteries enter the axis of the spiral coil of the colon and anastomose at its apex. Their branches also form rich networks.

A =phrenico-abdominal artery= arises on either side a little in front of the renals. It divides into branches which go to the costal part of the diaphragm and the abdominal muscles.

The =renal= and =spermatic arteries= present no special characters.

The =posterior mesenteric artery= arises near the termination of the aorta. It is small and is distributed like that of the ox.

Six pairs of =lumbar arteries= arise from the aorta. The seventh comes from the middle sacral.

The terminal branches of the aorta resemble those of the ox.

The arteries of the shoulder, arm, and forearm resemble in general those of the ox.

FIG. 482.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF PIG, ANTERIOR
VIEW.

_a_, Anterior tibial artery, continued on tarsus as the dorsalis
pedis; _b_, perforating tarsal artery; _c_, dorsal metatarsal
arteries; _d_, common digital arteries; _e_, proper digital
arteries.
]

FIG. 483.—ARTERIES OF DISTAL PART OF RIGHT HIND LIMB OF PIG, POSTERIOR
VIEW.

_f_, Saphenous artery, continued as internal tarsal artery; _g_,
external tarsal artery; _h_, internal plantar artery; _h′_, external
plantar artery; _i_, perforating tarsal artery; _j_, deep plantar
metatarsal arteries; _k_, common digital artery; _l_, proper digital
arteries.
]

The main facts as to the =metacarpal= and =digital arteries= are as follows: The rete carpi dorsale is formed essentially by the terminals of the interosseous artery of the forearm. It gives rise to three =dorsal metacarpal arteries= which descend in the corresponding interosseous spaces and unite with branches of the volar metacarpals to form three =common digital arteries=. Each of these divides into two =proper digital arteries=, which descend along the interdigital surfaces of the digits. On the volar surface are two =volar arches=, superficial and deep, from which three =superficial= and three =deep volar metacarpal arteries= arise. The deep arteries unite near the distal end of the space between the principal metacarpal bones to form a stem which unites with the middle (third) superficial artery. The superficial arteries unite to form an arch from which =proper digital arteries= are given off to the axial aspect of the small digits, and a common digital which supplies two =volar proper digital arteries= to each of the chief digits.

The arteries of the hip, thigh, and leg are arranged much as in the ox. A few special features may be noted.

The =ilio-lumbar artery= gives off a branch to the quadriceps femoris. It may also supply the posterior abdominal artery, which otherwise arises from the deep femoral.

The =deep femoral artery= is given off above the level of the pubis. The posterior abdominal and external pudic arteries may arise from it by a short common trunk or separately. The =external pudic= gives branches to the prepuce but not to the penis. The =popliteal artery= gives off the peroneal.

The =femoral artery= gives off a short trunk which divides into anterior femoral and external circumflex arteries, the latter being much the larger.

The =saphenous artery= is large. It descends on the inner surface of the leg and hock and concurs with the perforating tarsal artery in forming the proximal plantar arch.

The =posterior tibial artery= is small, being replaced distally by the saphenous. It gives branches to the muscles on the posterior face of the tibia and supplies the nutrient artery of that bone.

The =anterior tibial artery= is continued as the dorsalis pedis on the flexion surface of the tarsus. This gives off the =perforating tarsal artery=, which passes back through the vascular canal of the tarsus and unites with the terminal branches of the saphenous to form the proximal plantar arch.

The =metatarsal= and =digital arteries= resemble in arrangement the corresponding vessels of the fore limb.

THE VEINS

The veins resemble in general those of the ox. Thus there is a hemiazygos vein and two jugular veins, the internal one being relatively larger than in the ox. A few differential features may be noted.

The =buccinator vein= resembles that of the horse, and unites with the =vena reflexa= to form a short common trunk which joins the facial.

The =facial vein= resembles in general that of the horse. The =dorsal nasal vein= is large, receives the veins from the snout, runs backward in the groove of the nasal bone and joins the frontal vein; it is connected with its fellow by a transverse branch, and anastomoses freely with the malar and facial.

The veins of the distal parts of the limbs naturally present differences which are correlated with those of the arteries.

THE LYMPH VESSELS AND GLANDS

The =thoracic duct= often divides near its termination into two branches which unite to form an ampulla. The latter suddenly contracts and opens into the terminal part of the left jugular vein.

The =submaxillary lymph glands= are situated in the space between the omo-hyoid and internal pterygoid muscles in relation to the lower part of the anterior border of the submaxillary salivary gland. There are commonly two on each side, one large, the other small.

The =parotid lymph glands= (Fig. 309) are reddish-brown in color. There are usually four of considerable size on either side. One is situated at the upper part of the posterior border of the masseter, partly covered by the parotid gland. Another large subparotid gland lies below the base of the ear. Ventral to this are two smaller glands, one above and one below the external jugular vein.

The =pharyngeal= (or retropharyngeal) =lymph glands= (Fig. 310) are situated on the dorsal wall of the pharynx above the external carotid artery and below and behind the paramastoid process. There are usually two of considerable size on either side.

The =middle cervical lymph glands= form a group on the mastoido-humeralis on the course of the external jugular vein.

The =prescapular lymph glands= are situated at the anterior border of the anterior deep pectoral muscle undercover of the trapezius and omo-transversarius.

The =prepectoral lymph glands= are reddish in color and usually three in number. The largest is placed centrally under the trachea; the others are situated on the brachial vessels as they turn around the first rib.

The =axillary lymph glands= are usually absent, but very small nodes may be found near the insertion of the latissimus dorsi. Cubital glands are not present.

FIG. 484.—STOMACH AND PART OF INTESTINE OF PIG, SPREAD OUT.

_a_, Pyloric portion of stomach; _b_, duodenum; _c_, jejunum; _d_,
cæcum; _e_, _f_, colon; _g_, pancreas; _h_, epiploic foramen (of
Winslow); _i_, portal vein; _k_, hepatic lymph glands; _l_, gastric
lymph glands; _m_, œsophagus. (After Edelmann.)
]

The =thoracic lymph glands= comprise: (1) a gland of considerable size on the first segment of the sternum; (2) about half a dozen reddish glands along the upper face of the thoracic aorta; (3) several glands along the lower face of the trachea; (4) the =bronchial lymph glands=; one of these lies on the bifurcation of the trachea and another at the apical bronchus of the right lung (Fig. 371).

The =lumbar lymph glands= are scattered along the abdominal aorta and the vena cava. Those placed near the hilus of the kidney are often designated =renal=.

The =internal iliac lymph glands= are rounded and relatively large. They comprise: (1) three or four glands situated on and between the origin of the circumflex iliac and the external and internal iliac arteries; (2) a gland in the angle of divergence of the internal iliac arteries.

The =external iliac lymph glands= are small, two or three in number, and lie in front of the circumflex iliac vessels near the point of the hip.

The visceral lymph glands of the abdomen comprise:

1. =Gastric lymph glands= on the lesser curvature of the stomach.

2. Several small =hepatic lymph glands= along the portal vein.

3. An elongated =splenic lymph gland= on the splenic vessels near the dorsal end of the spleen.

4. A series of =mesenteric lymph glands= situated along the anastomotic arches formed by the vessels of the small intestine.

5. Several =cæcal lymph glands= situated along the first part of the cæcal vessels.

6. Two series of =colic lymph glands= which accompany the arteries of the spiral part of the colon, and are exposed by separating the coils of the bowel. Small glands are placed in the colic mesentery and above the rectum.

7. The =anal lymph glands= are situated on either side on the retractor ani.

A small =ischiatic lymph gland= is found on the sacro-sciatic ligament near the lesser sciatic notch.

The =precrural lymph glands= are situated on the aponeurosis of the external oblique below the external angle of the ilium.

The =superficial inguinal lymph glands= are situated behind the external inguinal ring. No deep inguinal lymph glands are present.

The =popliteal lymph glands= are small normally and may escape notice.

A few nodules occur in front of the distal part of the tendo Achillis.

CIRCULATORY SYSTEM OF THE DOG

THE PERICARDIUM AND HEART

The =pericardium= is attached to the sternal part of the diaphragm by a fibrous band, and is connected with the sternum only by the mediastinal pleura.

The =heart= is almost globular in form, the apex being much blunter than in the other animals, and marked by a notch. Its long axis is almost parallel with the sternum and the apex (covered by the pericardium) is directed against the sternal part of the diaphragm. Its weight averages about 0.8 to 1 per cent. of the body-weight.[185]

The base extends forward to a transverse plane through the lower ends
of the third pair of ribs. The apex lies opposite the sixth costal
cartilage in expiration. On the right side the pericardium is in
direct contact with the chest-wall over a narrow triangular area (base
anterior) from the fourth to the sixth intercostal space inclusive. On
the left side the area of contact is smaller and is at the fourth,
fifth, and sixth cartilages.

The two coronary arteries may arise by a common trunk. Each divides into circumflex and descending branches. The left artery is twice as large as the right one.

The great coronary vein ascends in the left longitudinal groove to the coronary groove, in which it winds around the posterior face of the heart to the right side and opens into the right atrium below the posterior vena cava. Near its termination it receives one or two veins which ascend along the right longitudinal furrow. Several small veins from the wall of the right ventricle open into the right atrium separately or by a common trunk.

THE ARTERIES

There is no common brachiocephalic trunk (anterior aorta). Two large vessels arise from the convexity of the aortic arch; these are the =brachiocephalic= and =left brachial arteries=. The =brachiocephalic= gives off the two =carotid arteries=, no common trunk being present. It frequently also supplies the posterior thyroid artery. The intrathoracic branches of the brachial arteries are as follows:

A common trunk gives off the =dorsal=, =subcostal=, and =superior cervical arteries=. The dorsal artery passes out in front of the first rib, and the superior cervical through the first intercostal space. The latter is relatively small.

FIG. 485.—ARTERIES OF THORACIC CAVITY AND PART OF NECK OF DOG.

_a_, Aortic arch; _a′_, thoracic aorta; _b_, brachiocephalic artery;
_c_, left brachial artery; _d_, _d_, common carotid arteries; _e_,
vertebral artery; _f_, dorsal artery; _g_, deep or superior cervical
artery (usually given off from a common trunk with _f_); _h_,
extrathoracic part of _f_; _i_, subcostal artery; _k_, inferior
cervical artery; _l_, descending branch of _k_; _m_, ascending
branch of _k_; _n_, internal scapular; _o_, acromial; _p_,
superficial cervical; _q_, _s_, extrathoracic part of left brachial;
_r_, external thoracic; _t_, internal thoracic; _t′_, asternal;
_t″_, anterior abdominal; _u_, perforating branch of _t_; _v_,
anterior mediastinal (thymic); _w_, ventral intercostals; _x_,
bronchial; _y_, œsophageal; _y′_, dorsal intercostals; _z_,
descending branch of left coronary artery; _z′_, circumflex branch
of same; _1_, œsophagus; _2_, trachea; _2′_, bronchi; _3_, first rib
(sawn off); _4_, right ventricle; _5_, left ventricle; _5′_, left
auricle; _5″_, pulmonary artery (cut off); _6_, diaphragm; _7_, _8_,
_9_, last three cervical vertebræ; _10_, thymus. (After Ellenberger,
in Leisering’s Atlas.)
]

The =vertebral artery= may arise either in front of or behind the trunk above mentioned; in the latter case it crosses the inner face of the trunk. It passes along the neck in typical fashion to the third cervical vertebra and divides into three branches. The largest of these supplies the muscles in this region, compensating for the absence of branches of the superior cervical artery. The second passes between the second and third cervical vertebræ into the vertebral canal and unites with the opposite artery and a branch of the occipital artery to form the basilar. The third branch is the small continuation of the parent trunk; it passes to the wing of the atlas and anastomoses with the occipital.

The =inferior cervical artery= gives off the superficial cervical which ascends in front of the supraspinatus.

The =internal thoracic artery= is large and sends perforating branches to the pectoral mammary glands.

The =external thoracic artery= arises outside of the thorax and sends branches to the mammary glands.

The =common carotid arteries=, left and right, arise in that order from the brachiocephalic. In the neck the right one lies on the trachea, the left on the œsophagus. Collateral branches are the posterior thyroid (which may, however, arise from the right or left brachial or the inferior cervical), pharyngeal, thyro-laryngeal muscular, tracheal, and glandular (to the submaxillary gland). Each carotid divides under the wing of the atlas into occipital and internal and external carotid branches.

FIG. 486.—SUPERFICIAL VESSELS OF HEAD OF DOG.

_1_, Facial artery; _2_, inferior labial artery; _3_, artery of angle
of mouth; _4_, superior labial artery; _5_, lateral nasal artery;
_6_, dorsal nasal artery; _7_, superficial temporal artery; _8_,
transverse facial artery; _9_, anterior auricular artery; _10_,
zygomatico-orbital artery; _11_, satellite vein of _10_; _12_, ant.
auricular vein; _13_, superficial temporal vein; _14_, internal
maxillary vein; _15_, post. auricular vein; _16_, _17_, external
jugular vein; _18_, external maxillary vein; _19_, _23_, facial
vein; _20_, inf. labial vein; _21_, buccinator vein; _22_, vena
reflexa; _24_, superior labial vein; _25_, vena angularis oculi;
_26_, dorsal nasal vein; _a_, concha; _b_, parotid gland; _c_,
submaxillary gland; _d_, submaxillary lymph glands; _e_,
mylo-hyoideus; _f_, digastricus; _g_, masseter; _h_, zygomaticus;
_i_, scutularis; _k_, temporalis; _l_, orbicularis oculi; _m_,
zygomatic arch; _n_, retractor anguli oris; _o_, buccinator.
(Ellenberger-Baum, Anat. d. Hundes.)
]

The =occipital artery= is small. It gives off =condyloid= and =posterior meningeal= branches, passes up through the notch on the anterior margin of the wing of the atlas, and is distributed to the muscles of this region. Its =cerebrospinal= branch passes through the intervertebral foramen, and unites in the vertebral canal with its fellow and a branch from the vertebral artery to form the basilar. A retrograde branch anastomoses with the vertebral as in the horse.

The =internal carotid artery=, also small, passes to the foramen lacerum posterius, enters the carotid canal and forms a bend before entering the cranium through the carotid foramen. It forms a plexus which is connected by branches with the middle meningeal and ophthalmic arteries. It then perforates the dura mater and enters into the formation of the arterial circle (of Willis).

The =external carotid artery= is the direct continuation of the common carotid. It passes along the lateral wall of the pharynx, emerges from beneath the digastricus, and divides into superficial temporal and internal maxillary arteries. It gives off the large flexuous =lingual artery= which has a course similar to that of the horse. The =external maxillary=, smaller than the lingual, passes along the upper border of the digastricus, gives off the sublingual, gains the anterior border of the masseter, and divides into superior and inferior labial and the angularis oris. The last-named vessel passes forward on the cheek between the labials to the angle of the mouth. The =sublingual artery= passes at first along the upper border of the digastricus and continues between the mylo-hyoideus and the ramus of the mandible. The =posterior auricular artery= arises at the anterior border of the digastricus, gives branches to the salivary glands and the adjacent muscles, and ascends on the convex face of the concha. It divides into two branches which return along the borders of the external ear.

The =superficial temporal artery=, after giving off the =anterior auricular artery= and a small =transverse facial artery=, turns forward under the temporal fascia toward the eye, and divides into upper and lower branches which supply the frontal region and the eyelids. It also supplies branches to the parotid gland and the masseter and temporalis muscles.

The =internal maxillary artery= pursues a course similar to that of the horse. The mental branches of the =inferior alveolar= (or dental) =artery= are of considerable size and are distributed in the lower lip and gums. Two or three =deep temporal arteries= are present. The anterior one may arise from the buccinator; it gives off the middle meningeal, which sends a branch to the carotid plexus. The =ophthalmic artery= gives off a branch which enters the cranium through the foramen lacerum orbitale and connects with the internal carotid; this is termed the internal ophthalmic and gives off the arteria centralis retinæ. The superficial branches of the =infraorbital artery= replace the dorsal and lateral nasal arteries, and compensate for the small size of the superior labial.

The =brachial artery= in its course in the arm presents no special features. At the elbow it passes between the biceps and the pronator teres, descends (as the median) under the flexor carpi radialis about a third of the way down the forearm, and divides into radial and ulnar arteries. Among its collateral branches are: (1) The =subscapular artery=, which passes up between the subscapularis and teres major, turns around the posterior angle of the scapula and terminates in the supraspinatus, deltoid, trapezius, and mastoido-humeralis. In about half the cases it gives off the =anterior circumflex=, which often arises with the =posterior circumflex=. Its other branches resemble those of the horse. (2) The =anterior circumflex artery= (in about half the cases). (3) The =deep brachial= arises about a third of the way down the arm. (4) The =bicipital artery= (for the biceps) is given off at the lower part of the arm. (5) The =proximal collateral radial artery= (not present in the horse) arises at the lower fourth of the arm, crosses over the terminal part of the biceps, descends on the extensor carpi radialis, and concurs with a branch of the volar interosseous in forming the rete carpi dorsale. It often supplies the bicipital artery. (6) The =anterior radial artery= (A. collateralis radialis distalis) is very small. (7) The =common interosseous artery= is given off a little below the elbow. It supplies branches to the flexor muscles and the =dorsal interosseous artery=, which passes through the interosseous space, gives branches to the extensor muscles, and by its terminal twigs concurs in the formation of the rete carpi dorsale. The direct continuation of the trunk is the =volar interosseous artery=, which descends under cover of the pronator quadratus, gives off a branch to the rete carpi dorsale and the =fifth volar metacarpal artery=, and terminates by joining the volar branch of the radial artery to form the deep volar arch. (8) The =volar antibrachial artery= (Ramus volaris antibrachii) arises below the interosseous and descends at first under the flexor carpi radialis, then between the heads of the deep flexor, and divides into ascending and descending branches.

The =radial artery=, the smaller terminal of the brachial, descends along the inner border of the radius, and divides near the carpus into dorsal and volar branches. The =dorsal branch= assists in forming the rete carpi dorsale. The larger =volar branch= descends behind the inner border of the carpus and joins the end of the volar interosseous in forming the =deep volar arch=. From this arch three =deep volar metacarpal arteries= descend in the second, third, and fourth intermetacarpal spaces and concur with the corresponding superficial volar and the dorsal arteries to form the common digitals.

FIG. 487.—VESSELS AND NERVES OF INNER SURFACE OF SHOULDER AND ARM OF
DOG.

_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.)
]

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.

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.
]

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.

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.

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.)
]

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.
]

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.