706 EXPERIMENT STATION RECORD. 



acids, the presence of unknown ferments capable of producing a typical propionic- 

 acetic acid fermentation is considered by no means excluded. The existence of such 

 a ferment has been shown by Fitz. Only in brick cheese prepared in the manner of 

 Limburger cheese was valeric acid detected with certainty, since bacteria, capable 

 of producing this acid, were found in all other kinds of cheese, it is thought probable 

 that valeric acid is invariably present, although in quantities too small to he distin- 

 guished from the other acids. The simultaneous presence of different ferments in 

 cheese, of which now one and now another gains supremacy, would explain in the 

 simplest manner, according to the author, the varying relations between the different 

 volatile acids. 



The absence of any considerable amount of butyric acid in rennet cheese is 

 explained by the low temperature used in cheese ripening which favors the prepon- 

 derance of lactic-acid bacteria over butyric-acid ferments. In the sour-milk cheese, 

 in which the lactic-acid bacteria were destroyed, butyric acid was present in large 

 quantities. Capric and caprylic acids were not determined, as these, as a rule, bear 

 a definite relation to caproic acid. To these 3 acids and valeric and butyric acids are 

 attributed the aroma of cheese. Propionic, acetic, and formic acids, unless present 

 in excessive amounts, play no important role, as these are seldom present in a free 

 condition but usually in the form of neutral salts. 



The formation of ammonia corresponded closely with the rate of cleavage of fat. 

 The quantity of ammonia present was never sufficient to give an alkaline reaction 

 with phenolphthalein, although the soft cheeses, especially the outer layers, reacted 

 often with litmus. The most important constituent of the characteristic aroma of 

 the different kinds of cheese are formic acid for Emmenthal, butyric ester for Roque- 

 fort, certain decomposition products for Limburger, and the odoriferous constituents 

 of the clover, used in its manufacture, for the Glarus sour-milk cheese. 



Appended to the article proper is a report of some experiments in which the 

 influence of pepsin, combined with rennet and paracasein, was studied. Paracasein 

 was strongly attacked by the pepsin and rennet, but this influence was increased to 

 a marked extent by the presence of Bacterium lactis acidi showing that lactic acid is 

 favorable to proteolysis. Bacillus casei limburgensis, although possessing an alkaline 

 reaction, did not hinder the action of pepsin when these 2 were used together. 



The influence of the different organized and unorganized ferments studied in this 

 work is summarized as follows: Bacillus casei limburgensis alone forms only primary 

 albumoses; pepsin, in the presence of lactic-acid ferments, forms also secondary albu- 

 moses and peptones; Micrococcus casei liguefaciens, Paraplectrum fcetidum, and Bacillus 

 nobilis form mainly peptones, formic acid, and ammonia. Their proteolytic action 

 decreases in the order mentioned. Micrococcus casei liquefaciens in common with 

 Bacillus casei limburgensis acts almost the same as Bacillus nobilis. Bacillus casei a and s 

 form apparently only formic acid. 



It is further noted that the author and E. von Freudenreich, while this article was 

 in press, have succeeded in isolating a propionic acid ferment similar in morpho- 

 logical and cultural characteristics to Bacterium lactis acidi. 



VETERINARY SCIENCE AND PRACTICE. 



The alexins and bactericidal substances of normal serum, Y. Pirenne 

 (Centbl. Bakt. u. Par., 1. AM., Orig., 36 (1904), No. 5, pp. 723-731).— The author main- 

 tains that there are 2 bactericidal substances in the normal serum of rats essentially 

 different in nature and exhibiting specific characters. One of the substances destroys 

 the anthrax bacillus and other organisms belonging to this group. The second body 

 described as occurring in the rat serum is capable of destroying the cholera vibrio. 

 These bodies are called by the author bactericidal and vibrionicidal, respectively. 



