242 MODERN DAIRY PRACTICE. 



for the weight lost in the working, but to continue the 

 work which this process could not finish. The salting can, 

 of course, also be done too late when the butter is too dry 

 or has already been overworked. The salt may increase the 

 keeping quality of the butter to some extent.* 



* Some writers argue that the keeping quality of the butter is due 

 entirely to the salt which it contains. This assertion is not justified, 

 however. While it is well known that salt has strong preserving 

 properties it does not generally check the growth of the pathogenic 

 (disease-producing) bacteria. The only one of these organisms which 

 according to Foster's experiments was influenced by the salt was the 

 cholera bacillus. The typhus bacterium was not at all incommoded 

 by common salt, and tubercle bacilli only after having been exposed 

 to the action of salt for a long time. As regards the non-pathogenic 

 bacteria found in milk I have ascertained that they are generally but 

 slightly influenced by salt that may be present in the substratum. 

 If the conditions are otherwise favorable for these organisms even a 

 high salt content in the nutritive solution will not check their devel- 

 opment. In the experiments mentioned I grew lactic-acid bacteria, 

 among other mediums, in sterilized brine which had previously been 

 a preserving fluid for butter. They developed vigorously in it and 

 fully retained their ability to produce lactic fermentation, although 

 they went through a long series of inoculations from one sample 

 tube with sterilized brine to another. If, on the other hand, salt 

 was added to this brine so that the solution became saturated, the 

 lactic-acid bacteria developed only slowly and feebly and after hav- 

 ing been grown in 3 to 4 such solutions, they died out entirely. As 

 regards the influence of salt on other bacteria found in milk, I have 

 only ascertained that certain putrefactive bacteria are very sensitive 

 to the action of salt, while e.g., the butyric-acid bacillus, i.e., the form 

 of the same with which I have experimented, is only slightly dis- 

 turbed by a high salt content in the substratum. Salt therefore in- 

 fluences as a rule only slightly the growth of bacteria. It may be 

 noted in this connection that the preserving influence of salt, e.g. in 

 butter-making, is largely due to the fact that it indirectly counteracts 



