156 MODERN DAIRY PRACTICE. 



and under different conditions vary so greatly that the 

 sterilization of milk on a large scale must always remain 

 a difficult problem. In my opinion we ought to begin 

 with reforms in the cow-stable, and better milk, contain- 

 ing fewer bacteria, than that now generally available, 

 should be supplied. Some milk is difficult to sterilize and 

 other milk is easily made germ-free. Sometimes this may 

 be attained by a single heating of three fourths of an 

 hour; sometimes, again, the operation has to be repeated 

 for three or four days. According to my investigations 

 this depends, without doubt, on the treatment which the 

 milk receives on the farm. The milk from the same 

 farms also shows a certain regularity as regards the diffi- 

 culties met with in its sterilization.* 



As long as the question of the sterilization of the milk 

 by heating for practical purposes is at its present stage we 

 ought, however, in my opinion, to receive with great re- 

 serve claims that some experimenters have succeeded in 

 solving the problem. 



[Since the preceding account of the sterilization of 

 milk was written (1891), the question has not received any 

 further light. An excellent exposition of the subject is 

 given by H. Weigmann in his small work, already referred 

 to, on " Methods of Preservation of Milk " (" Die Methoden 

 der Milchconservirung," Bremen, 1893, 176 pp.), to which 

 the reader interested in the subject is referred. The book 

 is especially complete as regards descriptions of different 

 kinds of apparatus and methods proposed for the steriliza- 

 tion and pasteurization of milk.f] 



*The preparation of absolutely germ-free milk is more easily 

 accomplished the purer and fresher the milk used, a fact which 

 is of the greatest importance to milk-condensing factories as well as 

 to physicians and persons using sterilized or even pasteurized milk. 

 See Weigmann, " Milchconservirung," 1893, p. 51. W. 



f Author's addition to American translation. 



