374 BACILLI WHICH CAUSE FERMENTATION. 



parts of phosphate of potash, 5 parts of sulphate of 

 magnesia, '5 parts of chloride of calcium, 9 parts of 

 tartrate of ammonia, 44| parts of milk sugar, and 

 1,000 parts of water ; according to Krannhals they also 

 grow in mixtures containing extract of meat, milk sugar, 

 and gelatine. Investigators have, however, not as yet suc- 

 ceeded in making out any definite culture characteristics. 

 The yeast cells which are also present in the kephyr 

 are round or egg-shaped, 3'2 to 6*4 M- in diameter, and 

 occur singly and in various stages of budding ; spherical 

 and ovoid spores are also seen. We must await further 

 investigations of these organisms, and more especially 

 pure cultivations, in order to obtain a clear understand- 

 ing of the peculiar fermentative process which takes 

 place in the preparation of kephyr. (See under " Fer- 

 mentation.") 



The culture characteristics and the fermentative products 

 of the following bacilli which act on media rich in sugar are 

 imperfectly known. 



Bacillus polymyxa (Clostridium polymyxa), Prazmowski. 

 This organism exactly resembles bacillus butyricus in size, 

 shape, and mode of development, and occurs along with it. 

 The only difference between the two organisms is that in the 

 case of the bacillus polymyxa we find here and there peculiar 

 dilated and wavy threads without any distinct segmentation, 

 and these break up at a later period into shorter segments ; 

 it is probable that these structures are involution forms. 

 Further, these bacilli usually require free oxygen for their 

 growth and spore formation, and do not exert any fermentative 

 action under normal conditions ; but if the access of oxygen is 

 prevented they set up intense fermentation, the exact nature 

 of which is not known, in infusions of potato, lupin-seeds, &c. 

 The bacilli form a scum on the surface of nutrient solutions ; 

 on boiled beet-root they form gelatinous masses of large ex- 

 tent, and of cartilaginous consistence like those of leuconostoc 

 and ascococcus. In nutrient solutions containing starch the 

 bacilli show a faint blue colour when treated with iodine, but 

 this reaction is not found when they are growing in solutions 

 in which starch is not present. 



Bacillus dysodes (Zopf). These are rods forming threads 

 which break up into short rods and cocci, and each of these 

 rods produces an elliptical spore. They cause peculiar f ermen- 



