142 



ELEMENTS OF MAMMALIAN ANATOMY. 



anastomoses with the dorsal branch of the saphenous, form- 

 ing a superficial arch sending branches to the digitis. The 

 peroneal is so small that it is frequently not injected. In 

 the tarsal region two branches, an external malleolar and 

 an internal malleolar, are given off. A centimeter or two 

 distal to the latter branch, the main artery passes between 



the second and third meta- 

 tarsals to the deep plantar 

 region, where it receives an 

 anastomosing branch from 

 the saphenous, and sends 

 off branches to the digits. 



THE VENOUS SYSTEM 



The veins are the vessels 

 returning the blood to the 

 heart. As a rule, veins carry 

 only impure blood, but the 

 pulmonary veins returning 

 blood from the lungs to 

 the left auricle carry pure 

 blood. After death the 

 veins can readily be distin- 

 guished from the arteries by 

 the fact that they have much 

 thinner walls than the ar- 

 teries and are usually full of 

 blood, while the arteries are 

 empty (Fig. 76). This is 

 due to the fact that the thick 

 muscular coat of the arteries, by its contraction tends to 

 drive the blood into the veins, whose muscular coat is very 

 thin. The three coats composing the walls of the veins are 

 the epithelial, or tunica intima; the middle, or muscular; 



FIG. 76. CROSS-SECTION OF AR- 

 TERY AND VEIN. X 350. 



V ', Vein ; A, artery ; en, inner coat ; 

 ep, epithelium lining the vessels ; 

 et, middle or muscular coat of 

 vein; ex, muscular coat of ar- 

 tery; fb, fibro-areolar coat. 

 (From Martin's "Human 

 Body."} 



