200 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



erages of this type is decidedly conducive to longevity be- 

 cause it induced the development of a lactic acid flora in 

 the large intestine, and there was, in consequence, little or 

 no development and consequent absorption of poisonous 

 putrefactive substances from the colon. Acting upon this 

 suggestion pharmaceutical houses have prepared tablets 

 consisting usually of mixtures of milk sugar and dried 

 cultures of Lactobacillus bulgaricus. More recent work 

 seems to indicate that while soured milk of this type is an 

 excellent food, nevertheless, the unusual health-promoting 

 qualities ascribed to it by Metschnikoff have scarcely been 

 confirmed by the facts as they have developed. Bulgarian 

 soured milk undoubtedly has a place in the dietary of 

 invalids and convalescents. 



Soured milk beverages have been used apparently since 

 ancient times practically all around the shore of the Medi- 

 terranean both in Africa and Europe, about the Black Sea 

 and the Balkan countries, in Greece, in southern Russia, the 

 Caucasus and parts of India. The methods of manufacture 

 differ materially with the locality. In some cases the milk 

 is subjected to a preliminary heating and is then inoculated 

 by introducing a small amount of a previously fermented 

 batch of milk. It is then kept in a comparatively warm 

 place. This encourages the growth of bacteria belonging to 

 the group of lactobacilli, particularly Lactobacittus ~bul- 

 garicus. A soured milk of good flavor and comparatively 

 high acid content is thereby secured. 



In c'ertain districts dried kernels, termed kefir grains, are 

 introduced into the milk which is to be fermented. When 

 examined microscopically these kefir grains are found to be 

 made up of gelatinous masses of bacteria with yeast cells 

 embedded throughout. When introduced into milk a com- 

 bined lactic acid and alcoholic fermentation occurs. The 

 resultant beverage is somewhat acid and effervescent, con- 

 taining a low percentage of alcohol. It should be observed 



