VARIATIONS IX COWS MILK 39 



decrease in the quantity of milk, while, on the other 

 hand, a lessening of the percentage of fat is often accom- 

 panied l)y an increase in the volume of the milk. 



Although recent experiments have thrown much 

 light upon the influence of food on the milk secretion, yet 

 there is need for further information on many points. 

 For instance, it is not known with certainty if it is pos- 

 sible liy long continued, particularly unfavorable, one- 

 sided composition of food, to produce lasting changes 

 in the fat content of milk and in the solids not fat. 



Lactose occurs in milk in ))ut one form and the char- 

 acter of proteids is not alTected by the nature nf the 

 foods. On the other hand, the milk fats vary, sometimes 

 there is more and sometimes less olein, which affects the 

 consistency of the butterfat, and the percentages of vola- 

 tile fatty acids may vai'y considerably. It has often been 

 said that the fats taken with the food do not pass un- 

 changed into the milk. Only when a great quantity of 

 food, ricli in a kind of fat tliat can be distinguished 

 chemically, is fed, is it possible to find small quantities 

 of that fat in the butterfat of the milk. 



But little is known positively concerning the causes 

 of the variations in the composition of the butter- 

 fat and es])ecially concerning the influence of the food 

 upon it. The milk fat may originate in the fatty tissue 

 of the animal, from the fat stuff's taken with the food 

 and, apparently, also, directly from the carbohydrates 

 consumed. There are a number of other conditions, 

 as the composition of the ration, excessive feeding 

 with fatty foods, starvation, etc., that have some in- 

 fluence in this direction but, as they are of no sanitary 

 importance, it is unnecessary to discuss them here in 

 detail. 



It is generally believed that odors and tastes pass 

 from the food that is consumetl into the milk. The 



