92 MILK AND ITS HYGIENIC RELATIONS 



On the Presence of Reductases in Human Milk, The amount 

 of work which has been done upon the reducing substances in 

 human milk is small, but enough has been done to obtain reliable 

 information in this direction. It is much easier to obtain human 

 milk free from any great degree of bacterial contamination than 

 cows' milk, although the amount obtained is small. 



Gillet (1902), using Abelous and Girard's method of testing 

 for reduction by the conversion of nitrates to nitrites, obtained 

 negative results. 



Hecht (1904), who worked exclusively with human milk, obtained 

 reduction of methylene blue alone, in from one to two days, but he 

 was not sure that his samples were sterile, and does not appear 

 to have controlled them by plating out. The time of reduction 

 is entirely in accord with the reduction by bacteria, and by no 

 other agency. In one case where special precautions were taken 

 to ensure sterility no reduction was obtained. Reduction was 

 stopped by a temperature of from 6o-8o C. Above this temperature 

 reducing powers again appeared on prolonged heating, presumably 

 due to the lactose. 



Hecht does not appear to have used Schardinger's reagent, 

 and his results were most probably due to bacterial growth. 



Rullmann (2), Smidt (i), Koning and Sassenhagen, using Schar- 

 dinger's reagent, obtained negative results with human milk. 



Hydrogenase in Cows' Milk. There remains one more substance 

 to consider under the heading of reducing bodies, namely hydro- 

 genase, or that ferment which has the property of forming 

 sulphuretted hydrogen from sulphur. 



The literature is not inconsiderable, and the results are quite 

 conclusive. In 1891 Rosing, in the course of his researches into 

 the production of H 2 S from egg-white, found that if sulphur was 

 added to milk it was sometimes possible to obtain the reaction 

 for sulphuretted hydrogen ; the result was, however, sometimes 

 negative. 



Raudnitz (3) (1902) in his excellent resume of the literature deals 

 briefly with the question of hydrogenase, and states that he him- 

 self had not been able to detect H 2 S in milk on the addition of 

 sulphur ; the same was also stated by Schardinger (1902). 



Utz (i) (1903) obtained H 2 S from milk on the addition of sulphur 

 after prolonged boiling. 



Hoeffter (1904), like Rosing, found that fresh milk sometimes 

 gave reduction of sulphur ; the negative samples, however, also 

 reduced after they had been incubated for one or two days. The 

 addition of antiseptics prevented this development, and as a 

 result of these and of other experiments, he concludes that the 

 development of H 2 S in milk upon the addition of sulphur, is bacterial 

 in origin. 



Jensen (1906) also came to the same conclusion. 



Briining (1906) did not detect hydrogenase in fresh milk, but 



