FERMENTED MILK 505 



identical in them all, or, more properly speaking, may be any 

 one of the several varieties of a distinct and closely related 

 group. On account of its peculiarities, some of which are 

 exceptional and striking, and the importance recently at- 

 tached to it by the discussions both in the scientific and the 

 popular press, a brief resume of its characteristics is given : 



This bacterium was probably first observed by Kern, 

 who incorrectly designated it Dispora caucasicum. His de- 

 scription, however, is so limited that it is impossible to attach 

 the name he proposes to any particular organism. Later 

 Beyerinck, under the name Bacterium caucasicum, and 

 Freudenreich, as Bacillus caucasicus, described organisms 

 isolated from kefir which agree in their essential features with 

 those obtained from yogurt. More recently Bist and Khoury 

 isolated from Egyptian leben two bacilli to which they 

 gave the names Strepto-bacillus lebensis and Bacillus lebenis. 

 Grigoroff and Cohendy isolated similar organisms from 

 Bulgarian fermented milk. These various bacteria are 

 undoubtedly nearly or quite identical and all are included 

 under the name Bacillus bulgaricus, now generally adopted. 

 More strict adherence to the commonly accepted rules of bac- 

 teriological nomenclature would retain the name Bacterium 

 caucasicum proposed by Beyerinck. Recent work by Hastings 

 and by .Heinemann and Hefferan indicates that this bacte- 

 rium is not peculiar to the eastern fermented milks, but 

 is widely distributed, having been isolated from milk, soil, 

 saliva, feces, and various soured foods. White and Avery 

 believe that this bacterium is the representative of a group of 

 closely related bacteria which they divide into two types on 

 the basis of their activity in milk and the nature of the lactic 

 acid formed. The characteristics of the typical culture may 

 be summarized as follows : 



Morphology. — Slender rods 2 microns to 6 or 8 microns in 

 length, breadth usually about 1 micron, flagella and spores 



