MILKING AND MILKING APPARATUS. 229 



For instance, when the milk falls off in quantity, the 

 first thing to suspect is something" in the feeding or 

 the watering. A cow will often fall ofl; in milk when 

 changed from dry feed in the spring, too suddenly or 

 abruptly, to grass. The grass acts upon the bowels as a 

 laxative and diuretic, and, in stimulating other organs, 

 interferes with the secretion of milk by changing the 

 currents of the circulation. It may not follow that a 

 change from moderately good to more stimulating food 

 will always produce an increase in the milk ; if too sud- 

 denly made, the change may easily reduce the flow of 

 milk for a time. In the same way the increased feeding 

 will often so stimulate the milk organs as to cause them 

 to pass blood into the milk ducts unchanged, instead of 

 elaborating it into glandular cells which produce the milk, 

 and then the milk is mixed with blood. This result may 

 also occur from any undue excitement of the circula- 

 tion of the udder, such as excessive exercise in runnins: ; 

 or from bruising or pressure when a cow lies upon a well- 

 filled udder; or from contact of the udder with damp or 

 wet ground at any time, or with a cold floor in the 

 winter. 



The careful owner of a cow should always consider 

 that the udder is a highly nervous and vascular organ, 

 provided with a very finely diffused circulatory and secre- 

 tive apparatus, and that a slight injury may have a very 

 serious effect upon it. It has been explained that the 

 cell structure of the milk glands is itself the source from 

 which the milk is derived, and that these cells are replen- 

 ished from the arterial blood conveyed to and distributed 

 through the udder. When, therefore, it is considered 

 that in a cow giving thirty pounds of milk in twenty- 

 four hours all this quantity is actually produced by the 

 twofold change of blood into cells and of cells into milk 

 and cream, the activity of the organ which performs this 

 enormous work must indeed be wonderful ; and it should 



