80 MICRO-ORGANISMS AND FERMENTATION. 



potato this species thrives but poorly ; in older cultures of this 

 kind peculiar involution forms appear. In meat-broth 

 gelatine the organism was killed after eight minutes' heating 

 at 60 C., but not at 50 to 55 C. after the lapse of 12 

 minutes. In hopped beer-wort it yields a sediment, and 

 subsequently forms a film. The formation of acid in the 

 liquid after the action of this Pediococcus is very slight, and 

 the author assumes that traces of lactic acid are formed. 

 Lindner states that in no case was he able to produce any 

 real disease in wort or beer by inoculating these liquids with 

 a vigorous growth of this bacterium ; he therefore remarks 

 that the change in the flavour of the beer may not be caused 

 by this species, but by other bacteria co-existing in the 

 infected beer ; on the other hand, he states that Pediococcus 

 cerevisice causes a turbidity. The slime-forming species 

 described by Lindner has been mentioned above. 



A. Petersen observed that an abundant development of a 

 Sarcina could take place in bottom-fermentation lager-beer 

 without causing any disease ; on the contrary, the beer was 

 bright and stable, and had an agreeable taste and odour. 



Thus, Sarcina species exist which are not productive of 

 any disturbance in the brewery. The investigation of this 

 problem has not, however, as yet been carried further. 



8. CRENOTHRIX. 



In microscopical examinations of water we often meet the 

 very typical forms of Crenothrix Kuhniana (Fig. 16). 



This ferment (frequently associated with Beggiatoa alba) 

 occurs in every water which contains organic matter ; some- 

 times it multiplies to such an extent that it may make the 

 water unfit for use. Thus, according to Zopf, great 

 calamities have been caused by this fungus in the water 

 supplies of Berlin, Lille, and certain Russian towns. In 

 consequence of its power of storing iron compounds in its 

 walls, it forms red or brown flocks in water. Its forms are 

 very beatitiful ; it occurs in the form of cocci (a -/), which 



