JUDGING DAIRY CATTLE 79 



same destination by a slightly different course. It passes 

 into the lacteals that are contained in the villi mentioned 

 and these join a long tube that runs beneath the spine and 

 finally reaches the thoracic duct, which also receives all 

 the fluid coming from the other lymphatics in the cow. 

 The thoracic duct empties its contents about the region of 

 the first rib into a great vein (the anterior vena cava) 

 which opens into the right side of the heart, so all the 

 digestible constituents of the food are now in the blood 

 and have reached the right side of the heart. From here 

 the blood goes to the lungs to be purified by the air that 

 is breathed in and then it again goes back to the left side 

 of the heart to be pumped through the arteries to the 

 various portions of the body. Several branches run to 

 the various organs of the body but that which goes to the 

 mammary gland is of chief interest in the function of 

 making milk. The aorta runs along under the spinal 

 column and finally reaches the femoral artery which is 

 about parallel with the femur or thigh bone. This throws 

 off a branch (prepubic) which again branches into another 

 (the external pubic) and this again after it passes through 

 the inguinal ring divides into two branches (the anterior 

 or subcutaneous artery, and the posterior abdominal or 

 mammary artery) and from these the mammary gland re- 

 ceives its supply, as they branch into all the regions of the 

 udder. 



Following the blood still further, it passes through the 

 udder and appears outside of it in what are known as the 

 milk veins. They run along the belly, pass into the body, 

 and finally direct the blood to the heart again. In respect 

 to the function and relations of the organs up to this point, 

 we can understand that the stomach and its accessories 

 perform the greatest amount of work in making food into 

 blood, while the lungs purify it, and the heart propels it to 

 those parts that are in most need of it. 



131. Function of the Udder. In the dairy cow the 

 udder is an important organ, for it directly performs the 

 work of making milk, which is the dairy cow's specialty. 



