JOGHURT AND LACTOBACILLINE 319 



Much care, however is needed in the preparation of 

 pure cultures on a commercial scale, and many of these 

 products, for which absurdly exaggerated claims have 

 been made, are found on examination to be impure, or to 

 contain few of the right organisms in a living condition. 



The Joghurt bacillus (Bacillus bulgaricus, Heupel), is a long, 

 slender, rod-shaped bacillus, rounded at the end, occurring 

 singly or in chains and threads. Single cells are usually about 

 3 to 10 /a- long, and i to 1.25 fj, broad. It stains by Gram's 

 method, is aerobic or anaerobic, and difficult to cultivate. It 

 grows best at 45 to 50 C., little or no growth at 20 C., slow 

 at 25 C., fair at 30 C. 



Whey gelatine. Stab, filiform, beaded, not liquefied, anol no 

 surface growth. 



Whey agar. Colonies roundish or irregular, greyish, .5 to 

 1.5 in diameter, with filamentous curly margins. 



Potato. No growth. 



Milk is rendered acid and coagulated in eight to eighteen 

 hours at 44 C. There is no gas formation, and the casein is 

 not peptonized. 



This organism is remarkable in being able to produce large 

 amounts of lactic acid in milk, some forms giving rise to over 

 3 per cent, in ten days when incubated at 35 to 36 C. 



The Granular bacillus of Joghurt is a longer organism, which 

 stains irregularly with Loffler's methylene blue. Its surface 

 colonies on sugar agar media are transparent and irregular ; deep 

 colonies, curly or radiate. It grows best at 37 to 45 C. 



On potato no visible growth occurs. 



Milk is coagulated and becomes acid very rapidly at 37 to 

 40 C. ; no gas formation. 



The Streptococcus of Joghurt occurs usually in pairs, which stain 

 readily with Gram's gentian violet. It grows only on milk agar, 

 in small, yellowish-white, round colonies. Milk is made acid 

 and coagulated. 



