Section IV., 1905. [ 71 ] Trans. R. S. ^ 



VIII. — The Viscous Fermentation of Milk and Beer. 



F. C. Harrison, Professor of Bacteriology, Ontario Agricultural College. 



(Communicated by Dr. Fletcher, and read May 24th, 1905.) 



Slimy fermentations of various liquids have been kno^vn since the 

 beginning of the century, and several chemists studied them before 1860; 

 thus Girardin ^ in 1847 investigated this infection of milk by chemical 

 analysis and sought the cause in the defective composition of the fodder. 

 But the work that was done Avas of little value, since it was founded 

 upon erroneous conceptions. Pasteur - first turned our thoughts in 

 the right direction by discovering that there was a special '' yeast " 

 which had the power of producing a slimy fermentation in milk sugar, 

 producing a sort of gum and carbon dioxide. These substances were 

 constant products of the fermentation, whilst lactic acid, butyric acid, 

 and hydrogen were frequently by-products. Pasteur was soon able to 

 make practical use of this discovery by suggesting a remedy for the 

 prevention of ropy wine, which has caused considerable trouble to the 

 vintners. This remedy consisted of heating the product to a certain 

 temperature, thus killing the "yeast." Other instances of this fer- 

 mentation were soon found, until a well defined type of fermentation 

 was recognized; usually certain carbo-hydrates, under the influence of 

 micro-organisms, would undergo a change by which slimy matter was 

 produced. Saccharose, glucose, lactose, galactose, mannite, starch, dex- 

 trin, etc., were all subject to such change. The chemical nature of the 

 process is as little known as is that of other fermentations. 



A considerable number of micro-organisms are capable of producing 

 this type of change, more than twenty different species have been de- 

 scribed, although some of them are possibly duplicates. They include 

 bacilli and cocci. They do not act alike, even under similar conditions. 

 For example, B. viscosus sacchari of Kramer ' produces slimmess in 

 vegetable Juices, but under no circumstances can it cause a slimy fer- 

 mentation in milk. B. viscosus vini will produce ropiness in solutions 

 containing glucose but not lactose, and several species will render milk 

 sugar solutions slimy without affecting media containing cane sugar. 



The first scientific notice of slimy milk was by Lister* in 1873. 

 Among other fermentations, all of which he had at first attributed to 

 the same organism, Lister found one which rendered milk slimy. So 

 viscous did the milk become, that after 48 hours the vessel in which it 

 was held could be inverted without the milk spilling, and so ropy was 

 it, that it could be drawn out to fine, slender threads. Lister was able 



^ References on p. 93 et seq. 



