130 DAIRY CATTLE AND MILK PRODUCTION 



as much milk as the other. Physiologists have made many 

 researches with the object of determining what governs the 

 secretion of milk. The matter is far from being understood 

 at present. It is probable, however, that a substance is se- 

 creted in the body somewhere, possibly by some part of the 

 reproductive organs, that circulates with the blood. This 

 substance, whatever it may be, stimulates the udder gland to 

 produce milk. The amount of this substance that a certain 

 animal will secrete is hereditary, although influenced to some 

 extent by the feed and other conditions. A good dairy cow is 

 one that has inherited the power to form a large amount of 

 this substance. An inferior dairy cow, like No. 62 in the ex- 

 periment reported, is one that does not produce a sufficient 

 amount of this stimulating principle. From this viewpoint 

 the selection of the cow is choosing the one that has a strong 

 stimulation to produce milk. 



Another experiment made by the writer illustrates how 

 strong this stimulation to produce milk is with a highly de- 

 veloped dairy cow. A mature Jersey cow was fed a liberal 

 ration while dry ; she calved in more than moderate flesh. Her 

 ration was then adjusted to supply only nutrients sufficient 

 to support the body, leaving nothing for producing milk. 

 She was compelled either to cease producing milk or to make 

 it from the reserve on her body. This was continued for 30 

 days. At the end of this time she was producing only one 

 pound of milk per day less than in the beginning, but was so 

 weak she could hardly get up without assistance. During 

 this time she lost 115 pounds in her weight, and produced over 

 90 pounds of solids in the milk from her own body. 



According to the view expressed the high-producing cow 

 secretes milk on account of the strong stimulation she has in 



