Ferments in Milk. 45 



The experiments of Weigner and Yakuwa are of interest since 

 they demonstrate that the refraction and specific gravity of the 

 chloride of calcium serum are theoretically of equal value. Mai 

 and Rothenfusser, on the other hand, emphasize the fact that of 

 two theoretical methods of equal value the man in practice has to 

 prefer the method which offers, with the same certainty of the 

 results, greater advantages in regard to rapidity, convenience, 

 and saving of material, advantages which the method of refrac- 

 tion possesses. 



The investigations of Mai and Rothenfusser prove that the 

 variations in the results of continued tests, from day to day may 

 reach in mixed milk of one stable 0.1 to 0.55, and in longer periods 

 ( 22 days ) , up to 1 . 0. Changes of feeding have no marked influence. 

 The milk of individual cows failed to show any important fluctua- 

 tion during the time in which the tests of the entire stable were 

 made (0.2 to 0.6). 



More considerable may be the fluctuation between the find- 

 ings of normal milk and the secretion from cows with an affected 

 udder, and the variation between the findings of milk from the 

 same animal while healthy, and within 24 hours after the udder 

 becomes diseased. 



The milk of individual animals with affected udders shows, 

 not infrequently, values which are considerably below the values 

 of normal milk. This has been proved by the work of Metzger, 

 Fuchs, Jesser and Henkel, and from the experience of the official 

 milk control station. 



These abnormal values, however, do not affect the worth of 

 this method, if the results are compared through the use of satis- 

 factory control tests, and confirmed by other methods. 



Ferments in Milk. Immune Bodies. 

 Milk as Antigen. 



For the testing of milk special characteristics which it pos- 

 sesses, which may be collected under the name of reaction manifes- 

 tation of ferment action, and for which at present there is still 

 no satisfactory explanation, are of importance. 



Under the term ferments (enzymes) those substances are 

 included which hasten chemical changes with an explosion-like 

 rapidity (Uexkuell), and without using themselves up they act in 

 relatively minimal quantities. Their activity is inhibited by the 

 products of the reaction. Higher degress of heat and certain 

 toxins (ferment toxins, as for instance hydrocyanic acid) inhibit 

 their activity, the ferments being thermolabile. The author desig- 

 nates as ferments all of those bodies with ferment-like action, with- 

 out consideration as to whether the nature of the ferment is known 

 or not. 



A careful distinction must be made between original fermen- 



