815 



THE VARIABILITY OF COWS' MILK. 

 Pakt i. The Afteknoon-Milk. 



By H. S. Halcro Wakdlaw, D.Sc, Linnean Macleay Fellow 

 OF THE Society in Physiology. 



(From the I'hys'ioloyical Lahoratory of the Univertiify of Sydney.) 



(With six Text-figures.) 



Synopsis. 



Page. 



Introduction... ... ... ... ... ... ... 815 



Methods 824 



Results 832 



Discussion of results ... ... ... ... ... 838 



Relations between constituents and properties... ... 852 



Influence of breed ... ... ... ... ... ... 854 



Influence of age of cow ... ... ... ... ... 850 



Intiuence of stage of lactation ... ... ... ... 858 



Summary ... ... ... ... ... ... ... 862 



References ... ... ... ... ... ... ... 863 



Introduction. 



Although cows' milk has been used by man as a food so long, 

 only during the last fifty years have precise methods been devel- 

 oped for the determination of its quality. 



The keeping of herds is one of the most ancient of human indus- 

 tries, and the forerunner of the dairy farmer must soon have 

 noticed that the milk obtained from different cows differed in 

 quality. The differences first observed were, no doubt, merely dif- 

 ferences of taste; their detection arose directly from the evidence 

 of the senses. But later, when the arts of cheese- and butter- 

 making were acquired, arts which are themselves older than any 

 human record, differences in the amounts of these products 

 obtained from different samples of milk must have made them- 

 selves apparent. Rich milk was distinguished from poor; and so 



