Bacteria in Cheese. 175 



lactic-acid bacteria are not the true cause of the peptoniz- 

 ing process, but that their development prepares the soil, 

 as it were, for those forms that are more directly concerned 

 in the peptonizing process. This they do by developing 

 an acid substratum that renders possible the more luxuriant 

 growth of the aroma-producing species. According to 

 Goriiii, 1 certain of the Tyrothrix forms function at high 

 temperatures as lactic acid producing bacteria, while at 

 lower temperatures they act as peptonizers. On this basis 

 he seeks to reconcile the discrepancies that appear in the 

 experiments of other investigators. 



Milk enzym (galactase) theory. In 1897 B ibcock and 

 the writer 2 showed experimentally that milk is digested 

 spontaneously when treated with various anaesthetics like 

 ether, chloroform and benzol. Under these conditions it w.is 

 demonstrated that bacterial activity was entirely suppressed. 

 Furthermore the3 r showed that the nature of the by-prod- 

 ucts produced in such cases was identical with those found 

 in a maturing cheese, albumoses, peptones, arnido-acids and 

 ammonia being present in varying amounts. When milk 

 or curd was heated to 175 F. or above, or treated with 

 strong chemicals, this digestive process was stopped. 



Under these conditions the only agents capable of pro- 

 ducing such changes were enzyms, and they found that it 

 was possible to concentrate this milk enzyin in centrifuge 

 slime. The addition of these slime extracts to boiled milk 

 started anew the digestive process, and produced by-prod- 

 ucts identical with those occurring in normal cheese. This 

 enzym, called by them galactase, on account of its origin 

 in milk, is somewhat closely related to the tryptic type 



1 Grorini, Abs. in Expt. Stat. Rec.. 11:388. 



a Babcock and Cussell, 14 Kept. Wis. Expt. Stat., 1897, p. 161. 



