306 MILK AND ITS HYGIENIC RELATIONS 



field. There is no doubt as to the presence of tubercle bacilli in 

 butter which has been made from tuberculous milk, and much 

 work has been done upon this subject. 



A list of the authors who have investigated the presence of 

 tubercle bacilli in butter is given by Newman and Swithinbank, 

 and the matter has been carefully investigated by Schroeder and 

 Schroeder and Cotton. 



Schroeder and Cotton state that since bacteria, and especially 

 tubercle bacilli, are present in greater quantity in butter than milk, 

 milk should be pasteurised before being used for butter-making 

 Complete references are given by these authors. 



Objections have been raised to the pasteurisation of milk for 

 the making of butter, it being stated that such milk will not 

 work up satisfactorily. Babcock and Russell investigated this 

 and believe that the difficulty arises from loss of viscosity of 

 the cream. They found that this viscosity is much reduced by 

 pasteurisation at a temperature of 140 F. or more for ten minutes. 

 These observers found that the viscosity lost by the heating can 

 be restored by the addition of a small amount of sucrate of lime 

 (four parts to a litre). 



Roger, Berg, and Brook I. Davis investigated the temperature 

 at which pasteurisation should take place in order to obtain the 

 best effects for butter-making. They found that if a temperature 

 below 170 F. was used, some factor appeared to remain which 

 tended to cause deterioration in the quality of the butter. They 

 considered that no disadvantage was incurred by raising the 

 temperature above 170 F., though above 180 F. there was a slight 

 alteration in the flavour. 



Investigations have also been carried out to determine the 

 length of time during which tubercle bacilli will live in butter. 

 Mohler, Washburn and Rogers found that cold storage does not 

 kill the bacillus when present in butter, and they showed that 

 this organism when present is usually unequally distributed in the 

 same piece of butter. They considered that cream should be 

 pasteurised either by heating at 140 F. for twenty minutes or at 

 176 F. for a moment. 



Rosenow investigated two samples of butter for streptococci- 

 one of the samples was found to contain a virulent strain. 



Cheese. The presence of pathogenic micro-organisms in 

 cheese has also been demonstrated, and a number of observa- 

 tions have been made showing that tubercle bacilli occur in this 

 food. 



Thus Horman and Morgenroth, in 1898, found that in fifteen 

 samples of cottage cheese, tubercle bacilli were present in three. 

 Rabinowitch obtained tubercle bacilli in three out of five similar 

 samples. Harrison, who investigated this question, endeavoured 

 to ascertain the length of time during which tubercle bacilli will 

 remain alive in cheese. He found that at the end of ten days they 



