[HARRISON] VISCOUS FERMENTATION OF MILK AND BEER 89 



Slime Productiox, 



We have at present very little knowledge of the nature of the slimy- 

 substances formed by. the growth of bacteria. It has been supposed 

 that the viscous condition was due to the swelling of the membrane of ' 

 the bacteria, — the so-called capsules, — and that the slimy substance 

 was a body related to cellulose. Storch, Leichmann inter alios believed 

 that the lactose was converted into a mucinous substance, and Weigmann 

 expressed the opinion that the slimy material was produced from albu- 

 minoids, as for example, from the casein of milk. Ee}Tiolds Green ^° 

 in his work on the " Soluble Ferments," wrote as follows : — " It is 

 probable that in most of these cases the viscous matter is nothing more 

 than the extremely diffluent cell-walls of the organisms, and it is there- 

 fore doubtful whether these phenomena should be classed among such 

 fermentations as we are considering. Whether or no enzymes having 

 the properties of cytase or pectase are secreted by the microbes we have 

 no evidence to show, nor whether the changes in the cell-walls are due 

 to cytasic or pectasic powers of the protoplasm.'' 



As the formation of the viscous substance was much the same in 

 all the varieties studied, the slime production of these organisms is 

 here considered together. By referring to the cultural qualities of the 

 various organisms described, it may be noted that viscosity appeared 

 whenever growth became visible, and the more vigorous the growth, 

 the more pronounced was the viscosity, so long as no acids formed, for 

 these acids seemed to disturb, sooner or later, the slime-like condition. 

 In milk, bouillon, agar, potatoes, etc., the viscosity of the culture was 

 more marked than in peptone solution, in which the growth was not 

 so luxuriant, but in peptone solution with the addition of sugar the 

 viscosity corresponded with the more luxuriant growth, and was almost 

 as ^dscous as milk or bouillon cultures. There were exceptions to this 

 rule, because the faculty of slime production was not an altogether 

 constant quality of the bacilli : for example, a culture, which for several 

 generations produced only slight or moderate viscosity, would suddenly, 

 without any visible cause produce on exactly the same medium a very 

 viscous growth and would keep this quality for several generations, only 

 to lose it at a later date. The same diversity of different gelatine or 

 agar colonies of the same l)acillus often occurred, and in the earlier experi- 

 ments this inconsistency was thought to be due to contamination with 

 other bacteria, and many experiments were made to ascertain if tliis 

 surmise was correct, but the cultures were found to be pure and this 

 work only confirmed the correctness of the first experiments, and showed 

 the mutations of the viscous properties of these organisms. 



