MAKUAL OF CATTLE-FEEBIl^G. 79 



taken up in tlie lungs unites witli some of the wom-ont 

 matters and bm^ns them, producing the Mnimal heat This 

 point will be spoken of h 



more fully in the next 

 section. In Fig. 4, n 

 1 epresents the capillaries 

 of the posterior part of 

 the body, o those of the 

 stomach and intestines, 

 t those of the kidneys, 

 jj those of the liver, 

 and m those of the an- 

 terior part of the body. 

 The capillaries gradually 

 unite together into larger Fic^.5.~(settegEst) capiuan^. 



vessels, the veins, v^hieh convey the blood, no longer suited 

 to notuish the body, back to the heart and limgs. 



The Veins are tubular vessels somewhat similar to the 

 arteries, but with weaker and non-elastic walls, the pres- 

 sure of the blood on them being less, owing to the inter- 

 position of the capillaries between them and the arteries 

 and to the fact that they are larger than the latter. 



To prevent any possible flowing back of the blood, the 

 veins are provided at intervals with valves which permit 

 the blood to pass toward the heart but not in the opposite 

 direction. The smaller veins unite to larger ones, and 

 finally, as already described, empty their contents through 

 two branches into the right auricle of the heart. From 

 the capillaries of the intestines the blood carrying the re- 

 sorbed nutrients passes through the portal vein, Sj to the 

 ]iver,j9, there passes through another system of capillaries, 

 and then rejoins the blood from the extremities through the 

 hepatic vem^ u. Into the branch, Jc^ coming from the head 



