60 DB. BASTIATS^ ON THE 



come most notably altered in appearance, it still retains the simple 

 odour of boiled milk. Its reaction, however, has changed, since 

 it is always found to have become more or less acid. 



"When I first examined such a specimen of milk under the mi- 

 croscope, I was puzzled at not being able to discover any distinct 

 or definite organisms amidst the milk-globules. It is true there 

 was a teeming myriad of swarming particles every where, too 

 minute to be individually recognized, and recognizable principally 

 by their aggregate motions. These, however, might be organisms 

 or might not ; and, on the whole, I was inclined to take this latter 

 view. The next specimen of fermented milk was, perhaps, exa- 

 mined with the aid of a better-adjusted light. At all events, I dis- 

 covered therein a sparing number of Micrococci of the figure-of-8 

 type ; and these have since been recognized in every specimen 

 of superheated milk in which I have sought for them — where the 

 fluid has presented the other signs of fermentation. They are 

 to be recognized best in portions of the whey in which the milk- 

 globules are not so abundant. They have a provoking habit of 

 placing themselves vertically beneath the cover-glass, when they 

 look just like small milk-particles ; but as they turn over their 

 proper shape is seen, and we find them composed of a delicate pro- 

 toplasm presenting a much lower refractive index than the milk- 

 particles with which they are intermixed. Once seen, therefore, 

 they need never be confounded with couples of refractive milk- 

 particles of about the same size, which are not unfrequently to be 

 met with. The average length of these organisms is j-jj^jj"; but 

 sometimes they are rather larger, and at others they are distinctly 

 smaller (Fig. 7, 4). Where the fermentation is not vigorous, the 

 organisms are very scarce and mostly small ; where it is better 

 marked, they are not only larger, but sufficiently numerous to be 

 pretty easy of detection. On only a few occasions have I seen a 

 chain of four elements ; the organisms almost invariably exist in 

 the binary form. The same organisms are amongst the first to 

 show themselves when unboiled milk turns sour in open vessels, 

 though under such conditions they are speedily succeeded by 

 several other more or less similar forms*. 



* Micrococci of the same kind have also been found at times in some of my 

 turnip and cheese experiments. I may take this opportunity of saying that I do 

 not accept Prof. Cohn's interpretation of these experiments. Prof.- Huitzinga 

 showed that the small particles of cheese were not indispensable, and that they 

 might be replaced by soluble peptones (' Nature,' 1873, toI. vii. p. 380). 



