VARIATIONS IN COW'S MILK 31 



is abundant, the milk is generally a little less rich in 

 solids and especially in fat than it is later when the 

 secretion begins to fall off; with some cows the differ- 

 ence is not very great, but with others it is considerable. 

 In the last month the secretion falls off rapidly and 

 often ceases entirely; at the same time the proportion 

 of solids usually increases and this is especially the case 

 in relation to fat. The milk gradually acquires a decided 

 alkaline reaction to litmus paper and not infrequently 

 develops a salty taste. The changes in composition 

 are shown in the following table, which gives the results 

 of analyses, made by Fleischmann, of the milk of one 

 cow which calved January 28th. 



With this cow, the percentage of fat during the 

 period of lactation rose from 3.033 to 8.300; but this 

 significant increase occurred almost entirely in the last 

 month when the cow had become an old milker. At the 

 same time the quantity of albumin, lactose and salt 

 (i.e., solids not fat) increased only from 8.14 per cent, 

 to 9.00 per cent. 



The chemical composition of milk of some cows does 

 not change noticeably during the whole period of lac- 

 tation, and the percentage of fat as well as the other 

 solids may even fall off a little at the end of the lactation 

 period. Fleischmann gives a table showing analyses of 

 the milk of such a cow for the whole lactation period: 

 the daily quantity of milk in April was 19.84 kg., on the 

 31st of January following it was 3.6 kg. The fat per- 

 centage, which had varied between 2.56 and 2.97, fell in 

 January to 2.42, 2.60, 2.32, and 2.48 upon different 

 analyses. The percentage of solids not fat also fell a 

 little. 



5. The time and method of milking. It is commonly 

 believed that there is always a slight difference between 

 the chemical composition of the morning and the even- 



