286 KOPINESS IN MILK, ETC. 



first case. Whilst the malady is in progress, the colour of the 

 wort changes to a chicory-brown, and at the same time an odour 

 develops, which cannot be more closely defined, but which of itself 

 suffices to reveal the presence of the complaint. A further char- 

 acteristic affording a means of distinguishing between these two 

 species of bacteria is their behaviour towards a sterilised solution 

 of 3 grams of cane-sugar and i gram of peptone in 100 c.c. of 

 water. This medium is made viscid and ropy by B. v. I. alone, 

 the second species producing nothing more than a persistent tur- 

 bidity, accompanied by the evolution of carbon dioxide. Milk is 

 altered by both species in the same manner as wort. 



The fact that both these organisms also cause ropiness in 

 nutrient solutions, devoid of sugar and containing no organic matter 

 beyond calcium lactate or ammonium tartrate, is also interesting. 

 As a matter of fact, a high content of sugar is even injurious to 

 the organisms. This discovery agrees with the experience gained 

 in practice, that beers with a low attenuation (and therefore a 

 higher sugar content) are comparatively seldom ropy. The proxi- 

 mate cause of this alteration of the medium is a mucus excreted 

 by the bacteria. In the presence of sugar, carbon dioxide is 

 liberated, and presumably a small quantity of another acid is also 

 formed, since the acidity increases with the ropiness. The mucus 

 is not a uniform substance, but consists of at least two constituents, 

 one of which (insoluble in water) is characterised by its content of 

 nitrogen. This fact harmonises with the circumstance that the 

 malady sets in earlier in proportion as the nitrogen content of the 

 nutrient medium is greater. It also explains the fact, noticed in 

 practice, that worts rich in protein, peptones, and the like, are 

 those most readily becoming ropy. A higher content of acid 

 (o. 1 5 per cent, reckoned as lactic acid) restricts the development 

 of both these species of fission fungus ; but alcohol, even in the 

 proportion of 6 per cent, by volume, is powerless to injure them. 

 In both cases growth proceeds at all temperatures between 7 and 

 42 C., and is most vigorous at about 33 C. 



A third viscous ferment, also discovered by Van Laer, differs 

 from the other two in its property of liquefying gelatinised meat- 

 juice. 



L. V AND AM (I.) obtained from ropy English beer pure cultures 

 of a fourth organism (Bacillus viscosus III.) in the form of rods 

 0.7 fM broad and 1.3-2.0 p long, mostly isolated, but frequently 

 also forming bands of two or three cells. So far as can be gathered 

 from the particulars given, ropiness is produced, not by any meta- 

 bolic product excreted by the bacillus, but by the thickened cell 

 membrane of the organism. In other ways, too, this microbe 

 differs from Van Laer's bacilli. For instance, the development of 

 the organism and the gelatinisation of the medium occur only in 

 presence of sugar, and the degree of ropiness is proportional to 

 the amount of sugar eliminated. No evolution of gas could be 



