VAEIATIOXS IN COW'S MILK 33 



of inilk there is a smaller percentage of fat. Fleisch- 

 inann found l^y continuous investigations of one herd of 

 1:-'() to i;j(l cows during one year, that on the average for 

 the whole year the morning milk contained a little more 

 fat than the evening milk {3:2m per cent, against 3.183 

 per cent.), while the quantity of morning milk was a 

 little less than that of the evening milk (4.143 kg. against 

 4.G16 kg.). 



There is a slight difference dependent upon the sea- 

 sons; it has been shown that in the sunnner the morning 

 milk contains a slight excess of fat while in the winter 

 the evening milk is the richer. It follows that since the 

 (luality of milk is influenced hy e.xternal influences, there 

 can be no general rule to define the difference betwi'cu 

 morning and evening milk but, usually, if no other con- 

 ditions arise, this difference is comjiai-atively small. 



It is commonly believed that three milkings a day 

 cause not only the i)roduction of a greater <juantity 

 of milk, but also a somewhat greater percentage of fat, 

 but it I'an scarcely be said that there is definite jiroof of 

 an increase in the percentage of fat. 



If the milking is done by a strange or inexi)eriencod 

 person, the flow is diminished. This also influences the 

 quality of the milk. The first and the last milk drawn 

 differ greatly in fat content. It is supposed that the fat 

 globules adhere firmly to the walls of the ducts, as a 

 layer of cream, and are freed from these only with dif- 

 ficulty. The following figures show the results of 

 analyses by de Vriezes, who found in the first streams 

 1.2 per cent, fat ; after drawing about one-quarter the 

 quantity of milk, 2.1 per cent, fat ; after drawing about 

 one-half the (|uantity of milk, 3.6 per cent, fat; after 

 drawing about three-quarters the quantity of milk, 5.2 

 per cent, fat; in the last milk, 7.1 per cent, fat; in the 

 very last droi)s of milk drawn, 10.0 per cent. fat. 



3 



