510 SANGUIFEROUS SYSTEM. 



cular and deep-seated parts around the shoulder joint, and 

 branches to the parts along the humerus, at the lower part 

 of which it divides into the radial and ulnar arteries to sup- 

 ply the fore-arm and hand, as in the inferior classes and in 

 man. The ulnar artery generally sends off, near its 

 origin, a considerable interosseous branch to supply the an- 

 terior and posterior parts of the interosseous space. The 

 radial and ulnar arteries, after giving off several important 

 branches in their course to the wrist, form a deep-seated and 

 a superficial palmar arch, which anastomose with each other, 

 and supply arteries to the hand, and collateral branches to 

 the sides of the fingers according to their number in the 

 different mammalia, like the plantar arches of the posterior 

 extremities. 



The bifurcation of the brachial artery in the short 

 arm of the cetacea, and in the ornithorhynchus, the 

 marsupialia, and several quadrumana, takes place much 

 higher than in man, and in the ruminantia, the solidungula, 

 and some of the rodentia, as the marmot, much lower on the 

 fore-arm. In the walrus, the brachial continues undivided 

 to the metacarpus. In most carnivora, and many rodentia, 

 edentata, monotrema, marsupialia, insectivora, and quadru- 

 mana, animals with free prehensile use of their arms, the 

 brachial artery, sometimes the ulnar, passes palmad through 

 the osseous canal above the inner condyle of the humerus, 

 accompanied by the median nerve, to protect them from pres- 

 sure. But in the tardigrade mammalia with a plexiform 

 humeral artery, the vessel is not protected by an osseous 

 canal, and in the myrmecophagse, where this epitrochlear 

 canal is present, it transmits only the median nerve, while 

 the plexiform brachial artery passes free over the inner mar- 

 gin of the humerus. The radial and ulnar arteries are equally 

 present, where the ulna is only rudimentary or wanting ; but 

 in the seal and walrus the brachial artery continues to the 

 wrist, and supplies their place. The hand of solidungula is 

 supplied with collateral branches as one finger, and that of 

 ruminantia as two ; but the vessels are less regular in the 

 rudimentary fingers. In the tardigrade sloths and loris, the 

 brachial and femoral arteries give off at their origins, several 

 trunks which subdivide into numerous anastomosing plexi- 

 form branches, and which follow them in their course enve- 

 loping the primary trunks and sending twigs to the muscles 



