DAIRYING. 127 



practical conditions. For each cow information is obtained of 

 the weight of milk yielded, name of milker, hour of milking, 

 feeding ration, temperature of cow, daily weather conditions. 

 The milk, both morning and evening, is analysed for fat, and 

 solids not fat. This is being done right through the lactation 

 period of 42-43 weeks. From a preliminary series of trials that 

 have recently been concluded it is clear that the fat yield of a 

 cow varies enormously from day to day. Now at the present 

 time, statements as to the fat content of the milk of individual 

 cows are based on an average of four to nine samples per 

 year, but we have no means of knowing whether this sampling 

 is sufficiently frequent. That the question is of considerable 

 practical importance may be shown by a simple illustration. 

 A dairy farmer may purchase a bull out of a cow stated to give 

 milk containing an average of, say, 4% of butter fat. He will 

 expect that bull to get calves which ^will improve the milking 

 qualities of his herd. Actually, however, the percentage may 

 have been based on an average of only half-a-dozen samples 

 taken during the year, and it may be that the true average, 

 based on sufficiently frequent sampling, is lower. If so, his bull 

 will be a disappointment, and he will have unconsciously made 

 a retrograde step instead of an advance. The only way to find 

 out definitely how frequently samples ought to be taken, in 

 order to get a true indication of the milk quality of a cow, is by 

 the method of morning and evening sampling, throughout the 

 whole lactation period, of a number of cows kept under different 

 conditions ; and upon this work — as before indicated — the Insti- 

 tute is now engaged. 



Production of Clean Milk. 

 There are two incentives to the production of clean milk. 

 One is that the dairy farmer is losing, in the aggregate, great sums 

 by adhering to uncleanly methods. The other is that the presence 

 of the disease organisms that are sometimes found in ordinary 

 whole milk constitutes a danger to public health. The loss to 

 the farmer may be emphasised by a simple statement of fact. 

 The whole milk supply to London alone is estimated at about 

 90 million gallons per year. Of this quantity, between i|% and 

 2% is lost through souring; that is, about i\ million gallons have 

 to be thrown away every year through being unfit for human 

 consumption. Assuming a moderate average price of is. a gallon, 

 this means a loss of about ^^75,000 on the milk supplied to London. 

 It may be thought that the wholesaler pays this; but actually 

 the farmer pays, for the price he gets for his milk is based on 



