626 THE VEINS. 



receives near its origin the median digital vein, rises in front of, and a little to the 

 outsido of, the tarsus, communicating at this point with the anterior tibial veins; it 

 divides above the tibio-tarsal articulation into two branches : a posterior, forming the 

 anterior root of the external sajfhena ; the other anterior, joining the anterior tibial vein 

 of the external side. 



The two posterior veins spring from the sesamoid arch. Situated at first between the 

 suspensory ligament of the fetlock and the posterior face of the metatarsus, and com- 

 municating there by several anastomoses, these two veins are continued along the tarsus, 

 the one within, the other without. The internal follows the corresponding plantar artery, 

 and is prolonged in the tibial region by the posterior tibial and internal saphena veins. 

 The external ascends within the calds, and is united to a branch of the anterior super- 

 ficial metatarsal, to form the external &aphena vein. Before leaving the deep situation 

 it occupies below the suspensory ligament of the fetlock, these two vessels concur, but 

 especially the internal, to form a perforating branch which traverses the cuboido-scaphoid 

 canal to join the anterior tibial veins. 



G. VEINS OF THE ANTERIOR Foor IN THE Ox. Four digital veins escape from the 

 two subungueal plexuses : an anterior, posterior, and two lateral. 



a. The anterior digital vein, which is very slender, is lodged superficially between the 

 two digits, and comports itself at its origin like the analogous vein of the posterior 

 limb, in rising by two roots. In being prolonged above the fetlock, it constitutes a 

 subcutaneous metacarpal branch, which occupies the anterior and internal plane of the 

 cannon, and is united above the knee to the principal cutaneous vein of the fore-arm. 



b. The posterior digital vein, often doubled by a small accessory branch, accompanies 

 the common digital artery, and extends along the collateral artery of the cannon, to 

 constitute one of the posterior radial veins. 



c. The internal digital vein, after passing the digital region, is lodged between the 

 cannon bone and the internal border of the suspensory ligament, proceeds outside the 

 carpal sheath with the radio-palmar artery, and divides above the knee into two 

 branches: an anterior, the origin of the internal subcutaneous vein of the fore-arm; the 

 other posterior, forming one of the posterior radial veins. 



d. The external digital vein occupies, on the outer bide of the external digit and the 

 cannon bone, a position analogous to the internal vein. It gives rise to several deep 

 metacarpal veins which anastomose, and are mixed with the interosseous palm;ir 

 arteries; the principal vein and its accessory branches are joined, below the carpus, to 

 the internal vein. 



It is to be remarked that these four digital veins communicate, in the interdigital 

 space, by anastomoses resembling those of the posterior limb ; and that the last three, 

 or principal veins, anastomose above the fetlock iu forming a complicated and variably- 

 arranged sesamoid arch, on leaving which these digital veins become metacarpal vessels. 



COMPARISON OF THE VEINS IN MAN WITH THOSE OF ANIMALS. 



In Man, as in animals, the veins are grouped into those of the lesser circulation, or 

 pulmonary veins, and those of the greater circulation. The latter open into the heart by 

 three trunks: the cardiac veins, and superior and inferior vena cava. 



The superior vena cava represents the anterior vena cava of animals, and receives the 

 blood from the veins of the head, thoracic limbs, and a portion of the chest. It extends 

 from the first costal cartilage to the heart, and commences after the junction of the two 

 brachio-cephalic trunks (innominate veins). 



The superficial veins of the thoracic limb at first form, on the back of the hand, a 

 plexus of elongated meshes from which the median, radial, and ulnar veins spring. Near 

 the bend of the elbow, the median bifurcates and gives rise to the median cephalic and 

 median basilic. Blood is abstracted from one or other of these branches. At the arm, 

 all the superficial veins constitute but two trunks : the cephalic and basilic veins. The 

 deep vessels join these to form the axillary vein, which becomes the subclavian below the 

 clavicle, then the brachio-cephalic trunk (vena innominata} when it receives the internal 

 jugular 



The venous sinuses of the cranial dura mater are proportionately more developed 

 than in Solipeds, though they have the same disposition. There is constantly present a 

 median or inferior longitudinal sinus. 



The jugulars which carry the blood from the cranium and face to the heart, are four 

 in number. The anterior jugular, the smallest, descends benearh the superficial cervical 

 aponeurosis, in front of the sterno-mastoideus muscle, and enters the subclavian vein. 

 The external jugular commences by the union of the facial and temporal vein; in its 

 disposition it resembles the jugular of the Horse, and would be a complete representative 



