26 MANUAL OF MILK PRODUCTS 



conditions which are opposed to the coagulation of fibrin being 

 the ones which give the most efficient creaming. 



The average amount of fibrin in milk is supposed to be about 

 three ten-thousandths of one per cent, which is about one-thou- 

 sandth as much as is found in blood. The amount in differ- 

 ent milks varies considerably, some milks being almost free 

 while others contain a large amount. Colostrum milk always 

 contains more than normal milk from which it is derived, 

 and skim milk contains scarcely any. This results from 

 the fat globules being entangled in the small clots formed. 

 The clots are thus floated and become incorporated with the 

 cream. 



Babcock did not actually demonstrate the presence of fibrin 

 in milk, but Doane found "that where any inflammation of 

 the udder exists, fibrin and white blood cells are given off, and 

 this fibrin can be centrifuged out of the milk and smeared on 

 a coverglass, and stained so that the threads are easily demon- 

 strated by the use of a microscope. When this inflammation 

 existed the fibrin could be seen as a large number or mass of 

 parallel threads, and was associated with a vast number of 

 leucocytes. It was noticed in looking for fibrin, in the sedi- 

 ment of milk, with a particularly small leucocyte count, that 

 an occasional single fibrin thread would be seen. They were 

 very few in number, and it was seldom that more than one 

 thread could be seen in one microscopic field. They were so 

 evidently like the threads found in the pus in all their charac- 

 teristics that there was no reason for doubting that they were 

 fibrin. 



" The presence of the fibrin could not always be demonstrated 

 in the known healthy milk by centrifuging. Two other means 

 of securing it were tried. One was to allow the cream to rise 

 on the milk, on the theory that a large part of the fibrin would 

 be carried into the cream by the fat globules. A small portion 

 of the cream was poured on several layers of filter paper, to 



