400 NAVIN OX THE HORSE. 



changes wliicli take place by the agency of the blood. The 

 oxygen which the blood carries from the lungs unites with car- 

 bon in the system and creates heat, just as the oxygen in the 

 air unites with the carbon in the wood and produces heat in 

 our fireplaces. There are many other interesting things con- 

 nected with the consideration of the blood, but the purpose of 

 this work will not permit their further consideration. 



THE LYMPHATICS. 



1 HAVE already described two sets of vessels distributed 

 through the body, but there' is yet another set of somewhat 

 different character. They are called lymphatics, and contain a 

 fluid called lymph, which they secrete from the parts through 

 which they pass. They present the appearance of a knotted 

 string, or a tube composed of innumerable short joints. They 

 frequently unite with each other, as the cords composing the 

 meshes of the fish-net. There are also places where a great 

 number of these vessels unite in one place, forming a consider- 

 able knot, called a gland, or lymphatic gland. From these 

 glands other vessels depart and continue their way forward. 

 There are main channels of the lymphatics, as of the arteries 

 and veins, and by them the lymphatic fluid is carried on to 

 the great channel which passes forward beneath the spine, to 

 be emptied by it into the left axillary vein, not far from the 

 heart, by which means this fluid is mixed with the blood. 

 • The lymphatics of the fleshy part of the body are arranged 

 principally in two layers — one layer near the skin, the other 

 deep in the muscles. Each of the internal parts is supplied 

 with lymphatic vessels. 



The lymphatic glands are more numerous along the jaws, 

 neck, flanks, and in the folds of the membrane which surround 



