BY R. GREIG-SMITH. Ill 



On the other hand, air does not appear to be an absolute 

 necessity. This was shown in an experiment in which the 

 influence of air was tested. A series of portions of Nestle's 

 condensed milk was put into wide tubes, covered with vaseline, 

 and heated for an hour at 60°. These were infected through the 

 small central hole that formed on cooling the tubes. Tlien a 

 thicker layer of melted vaseline was superposed. The tubes 

 were incubated at 37*^ for two months. Upon removing the 

 vaseline and examining the contents, it was found that the milks 

 were thicker than when they were put into the tubes. Control 

 tests with and without chalk were similar, while others sown 

 with the coccus with and without chalk showed swollen masses 

 near the vaseline where the milk had been infected. The coccus 

 in the tube with the chalk produced the larger mass of coagu- 

 lated milk. This experiment makes it appear that the presence 

 of air is not a necessary condition for the coagulation of the 

 milk, and that the addition of lime-salt, such as the carbonate, 

 undoubtedly accelerates the thickening. 



With regard to the nature of the substance that forms the 

 jelly, it may be a slime or gum derived from the saccharose or 

 lactose through the biochemical activity of the microbe. On the 

 other hand it may be altered casein. To elucidate this question, 

 many experiments were made in an endeavour to induce the 

 coccus to form slime on artificial media, but all were fruitless, 

 and I was driven to the alternative that the microbe simply alters 

 the casein. There is some reason for the belief that the coagu- 

 lation is an alteration of the casein. The microbe produces a 

 considerable amount of acid in media containing lactose such as 

 milk or lactose nutrient agar. Milk is coagulated and the acidity 

 of the whey is so pronounced as to make it appear evident that 

 the coagulation is brought about by the acid and not by a pio- 

 duction of bacterial rennin-like bodies. Experimental plates of 

 milk-agar and litmus-milk-agar, when seeded with a giant colony 

 of the coccus, showed an amoeboid growth upon the surface of 

 the agar; but underneath and for some distance around the 

 amoeboid processes the milky medium was opaque while the 

 other parts of the medium were translucent. 



