270 Professor J. Reynolds Green [Feb. 9, 



pora ; it is a gelatinous bacterium, consisting of much-coiled filaments 

 with strongly marked sheaths, which form what is technically known 

 as a zoogloea. The gelatinous appearance of the grain is mainly due 

 to this. The second is the ordinary bacterium which produces lactic 

 acid from sugar, and the third is a yeast. These are both surrounded 

 by the coiled filaments of the Dispora, in whose meshes they are 

 entangled. 



The Kephir sets up its fermentation in the milk of cows, goats, 

 or sheep. The yeast and the bacterium either jointly or separately 

 split up the lactose or milk sugar into two other sugars, galactose 

 and glucose. The yeast then forms alcohol from the latter, and the 

 bacterium lactic acid from the former. The action of the Dispora 

 seems to be to change the casein of the milk, so that it is not pre- 

 cipitated or curdled by the lactic acid. 



These general outlines only sketch the probabilities of the course 

 of action which has not so far been definitely studied. The mode of 

 development and the full function of the separate factors are not yet 

 known. 



Another organism, or rather association of organisms, constitutes 

 what is known as the ginger-beer plant. It is the agent of fermen- 

 tation in the preparation of the so-called " stone ginger-beer," which 

 is a favourite beverage in the country districts of England, there 

 being a pleasiug delusion that it is non-alcoholic. The origin of this 

 " plant " is obscure ; no one knows exactly where it came from, but 

 it is preserved carefully by the villagers and handed on indeed from 

 one to another. 



This material is composed essentially of two organisms ; one is a 

 yeast known as Saccharomyces pyriformis, from its being somewhat 

 pear-shaped ; the other a bacterium, to which the name Bacterium 

 vermiforme has been given. In their association the bacterium forms 

 long coiled filaments, in the meshes of which the yeast is entangled. 

 As it occurs in use it is seldom pure, but is found to be contaminated 

 by admixture with other yeasts and schizomycetes, which however 

 have nothing to do with the fermentation it sets up, their presence 

 being accidental. As it is met with it forms, like Kephir, translucent 

 lumps of a jelly-like consistency which are slightly heavier than 

 water. 



The yeast appears to differ but little from the ordinary yeast of 

 beer. When it is isolated it sets up a fermentation of cane-sugar and 

 grape-sugar, which exhibits the usual features. 



The bacterium is a very interesting form, and when it is isolated 

 it can be made to grow in two different conditions : — (1) In the form 

 of long rods, varying in number and invested by a common trans- 

 lucent, often wrinkled sheath. This is found to be capable of coiling 

 and twisting in very curious ways, and can form a convoluted thread- 

 like gelatinous body. (2) The constituent microbes can escape from 

 the sheath and live and multiply freely without forming one. In 

 many preparations the empty sheaths can frequently be found, some- 



