28 FEEDS AND FEEDING, ABRIDGED 



down and once more becoming non-living matter, are termed 

 metabolism. 2 



The circulatory canals of the body. — The body of the animal is 

 made up of innumerable cells, which, grouped and modified in myriads 

 of ways, form all its organs and parts. Everywhere among the cells 

 are minute spaces called lymph spaces, which are connected with the 

 lymphatics, a set of vessels which permeate most parts of the body. 

 In some respects the lymphatics resemble the veins, but they are 

 thinner and more transparent and drain in only one direction — toward 

 the heart. Within these vessels is a clear fluid called lymph. These 

 vessels unite with one another, forming a network in many places. 



Fig. 10. — Diagram of the Circulation of the Blood 



1, The heart; 2, artery carrying blood to the head and fore limbs; 3, circula- 

 tion thru the upper portion of the body; 4, vein carrying blood from upper part 

 of body back to the heart; 5, artery carrying venous blood to lungs; 6, circula- 

 tion thru lungs; 7, vein carrying arterial blood back to heart; 8, artery carrying 

 blood to lower portion of body; 9, circulation thru rear extremities; 10, vein 

 carrying blood to heart from rear extremities; 11, artery carrying blood to in- 

 testines; 12, circulation thru intestinal capillaries; 13, portal vein carrying 

 blood to liver; 14, circulation thru liver. (From Smith, "Manual of Veterinary 

 Physiology.") 



Here and there a trunk subdivides into five or six smaller vessels, and 

 the latter enter a nodule-like body called a lymphatic gland. From 

 this gland come several small vessels, which, after a short space, again 

 unite to form a trunk. Gradually these trunks unite, forming larger 

 trunks until a large duet and another smaller one are formed which 

 enter veins in the neck. 



The arteries and the veins are the other set of canals. These perme- 

 ate every portion of the body, the former carrying the blood away from 

 the heart, and the latter carrying it to the heart. At the extremities 

 of the arteries are still more minute tubes, called capillaries, which con- 



2 Constructive metabolism, or the building-up processes, is termed anabolism, 

 while the breaking-down and wasting processes are called catabolism. 



