2394 Journal of Applied Microscopy 



CURRENT BACTERIOLOGICAL LITERATURE. 



H. W. CONN, Wesleyan University. 



Separates of Papers and Books on Bacteriology should be Sent for Review to H. W. Conn, 

 Wesleyan University, Middletown, Conn. 



Jensen. Studien iiber das Ranzigwerden der Many bacteriologists in the last 15 



Butter. Tahr. d. Sch., igoi. , ^ i- j ^i 11 r ^, 



^ years have studied the problem of the 



rancidity of butter, and a variety of conclusions have been reached. Whether 

 the phenomenon is purely chemical, is due to an enzyme or to the growth of 

 bacteria has never been satisfactorily settled. Jensen has undertaken an inves- 

 tigation of the subject in the light of the facts hitherto obtained, and has carried 

 on a series of exceptionally careful experiments. His evidence is obtained from 

 a chemical study of the product and not, as has been the case with most previous 

 experiments, from physical properties of the butter alone. The chief results 

 which he reaches are as follows : 



1. The air plays a part in the process of rancidity, but is not the cause of 

 the change in question. It acts rather as a stimulant for bacteria growth. 



2. The rancidity of butter is due to the action of micro-organisms. 



3. The chief causes of rancidity are the well known Oidhim lacfis, B. 

 fluorescens laquifaciens, and a form found by him universally present in butter, 



Cladosporium butyri. 



4. These organisms grow in the presence of oxygen and not in its absence. 

 To protect butter from rancidity, therefore, it is desirable to keep it in large 

 masses, under which conditions the inner parts of the butter will remain without 

 rancidity though the surface may change. 



5. The presence of salt checks the growth of the bacteria and thus delays 

 the rancidity. h. w. c. 



Gorini. Ueber die saure-labbildenden Bakte- This author has previously shown that 

 rien der Milch. Cent. f. Bac. ii, viii, p. 137, B. prodigiosHS produces not only a cer- 



IQO2. . r • 1 1 



tain amount of acid but an enzyme 

 with a power of curdling milk similar to rennet. His method of demonstrating 

 this was to cultivate the bacteria in question in milk and then to filter the cul- 

 ture through porcelain ; the filtration was found to possess the power of curd- 

 ling milk in a few minutes, indicating the presence of an enzyme. It occurred 

 to the author to determine if possible whether among the normal bacteria in milk 

 there might be some that had this same power. An examination of a number 

 of samples of milk has shown him the presence of organisms with these two 

 properties. These are cocci of apparently four or five different types. He is 

 therefore inclined to recognize three classes of milk bacteria ; one producing 

 acid, a second a rennet like enzyme, and a third class producing both acid and 

 rennet. The latter he believes may have an important bearing upon the problem 

 of the ripening of cheese. h. w. c. 



