CONDITIONS FA.VOFRINO FEEMENTATION. 



59 



cealing the original Bacillus-tufts with Torula corpuscles (i). Ano- 

 ther of these tubes was then examined ; and its contents were found 

 to be altogether similar. The vessels were made of combustion- 

 tubing ; and having been sealed when cold, the ends were very 

 strong and thick ; they were thoroughly sound, as are others of 

 them still in my possession *. 



Superheated hay-infusion, when it ferments, invariably retains 

 its characteristic odour, whether it has been heated in its natural 

 acid state t, or when neutralized or made slightly alkaline by 

 potash. In the process of fermentation an acid of some kind is 

 generated, since even the slightly alkaline fluid may be found di- 

 stinctly acid when we come to examine its contents microscopi- 

 cally. With regard to the organisms which are to be found in 

 these fermenting hay-infusions, I have occasionally encountered, 

 in addition to Bacilli of all lengths and Torulse; of various kinds, 

 Micrococci in the form of figure-of-8 organisms or of short chap- 

 lets (fig. 7, 4). In the fluids previously referred to in which the 

 Torulae had developed into well-grown mycelia, I also met with a 

 few organisms (fig. 7, 3) which seemed exactly to correspond 

 with Vibrio Bugula of Cohn. These I have never seen in such 

 fluids on other occasions. 



MilJc.—l^ heated to 230° F. (110° C.) for three quarters of an 

 hour or more, milk is found to be distinctly discoloured by the pro- 

 cess. It is then of a light fawn-colour. A briefer exposure, how- 

 ever, to this temperature does not appreciably affect its colour. 



After it has stood in the incubator for twenty-four hours or 

 so, a cream-like layer is found at the surface, the upper stratum 

 of which is yellow and dry, though it is dotted here and there 

 with globules of fluid oil. At this stage the fluid below is still 

 white and opaque ; but where fermentation ensues, it gradually 

 becomes more and more whey-like, and at last it may assume the 

 appearance of mere dirty water. If left for a long time, the fluid 

 may undergo other changes, and after a time become much disco- 

 loured. If the milk has been heated to 230° F. for as long as 30 

 minutes or more, it may remain many days in the incubator at 

 122° F. before it shows any sign of change. 



"When a specimen of superheated milk has fermented and be- 



* The supervention of a more vigorous fermentation, as shown by the turbi- 

 dity, made the fluid more acid ; and this change in the medium seems to have 

 brought about the development of the previously existing Torula corpuscles. 



t The acidity is always low, mostly equivalent to 1-2 minims of liquor 

 potassae per ounce. 



