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 
and sends 
off branches to the digits. 
the saphenous, 
THE VENOUS SYSTEM 
The veins are the vessels 
returning the blood to the 
heart. Asa 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 
Fic. 76. 
TERY AND VEIN. 
CRoss-SECTION OF AR- 
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 “ Auman 
Body.’ ) 
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 epithelial, or tunica intima; the middle, or muscular; 
The three coats composing the walls of the veins are 
