390 BACILLI WHICH CAUSE FERMENTATION. 



or spherical shapes, or form long thread-like and irregu- 

 larly swollen cells. After treatment with iodine solu- 

 tion, all these forms take on the same yellow colour. 

 It is not as yet possible to say with certainty whether 

 some of the cells with thicker walls and of rounder 

 shapes are to be looked on as arthrospores, and whether 

 they are, as a matter of fact, much more resistant th.au 

 the other growing cells, or whether all these variations 

 from the ordinary form of the chains are in reality in- 

 volution stages. Nothing trustworthy is as yet known 

 as regards the mode of growth of this organism on 

 solid nutrient substrata. 



Bacillus, Pasteurianus (Hauser). 

 (Mycoderma Pasteurianum.) 



This organism does not differ morphologically from 

 the foregoing one ; it forms similar chains and involu- 

 tion forms, but on treatment with iodine all the cells 

 take on a blue colour. It was first observed by Han sen 

 in sweet Copenhagen double beer, and develops best in 

 beer which contains a large amount of extract, and a 

 small amount of alcohol, and also in beer wort. 



Bacillus urcea (Leube)'. 



Bacilli of the These are plump rods with rounded ends, usually 

 fSmenSti^n 2 /,. in length, and 1 p.. in breadth. On gelatine plates 

 of nrine. a sma ll, almost transparent, patch appears after 2 days, 

 and extends in the course of 10 days to about the size 

 of a farthing ; the colonies have the appearance of a 

 ground- glass plate which has been breathed upon ; the 

 'growth extends from the point of inoculation in the 

 form of circular irregular zones, so that at a later period 

 a number of concentric rings are seen ; the outermost 

 zone shows a dentate outline. Growth occurs exclusively 

 at the surface ; the gelatine is not liquefied. In punc- 

 ture cultivations the track of the needle appears after 

 10 days as a very thin grey prolongation, and it is only 



