134 THE BOOK OF BUTTER 



beginning of the milking period, then the relative size 

 declines sharply during the first six weeks, remains fairly 

 constant for five or six months, after which the decline is 

 much more rapid to the end of the lactation period. . . . 

 The Reichert-Meissl number is the only physical con- 

 stant of the fat that can be correlated in any way with 

 the relative size of the fat globules. The data indicate 

 that the small fat globules are accompanied by a low 

 Reichert-Meissl number." If the size of the fat globules 

 should remain constant throughout the period of lacta- 

 tion, the cream of " strippers' " milk should churn more 

 readily than when the cow is fresh, for the olein content 

 of the fat increases during lactation, which means that the 

 fat is softer toward the latter end of the period of lactation. 

 However, it is generally known that the milk-fat at the 

 end of lactation is collected with difficulty in churning. 

 Therefore, this difficult churning must be caused by small 

 milk-fat globules. Eckles and Shaw ^ found that the 

 churning of the cream became more difficult toward the 

 end of the lactation period ; and with some cows samples 

 were found that could not be churned under any condi- 

 tions. These authors do not state what they consider to 

 be the exact cause of the difficult churning. 



100. Amount of cream in churn. — The churn should 

 be one-third to one-half full. There should be enough 

 cream to fall readily, and yet not so much that concussion 

 does not take place. It is usually necessary to raise the 

 temperature a few degrees if the churn is too full, for the 

 agitation is not so great as when the normal amount of 

 cream is in the churn. When the quantity in the churn 



1 Eckles, C. H., and Shaw, R. H., The Influence of the Stage 

 of Lactation on tho Composition and Properties of Milk, U. S. 

 Dept. Agri., B. A. I., Bui. 155, p. 77, 1913. 



