THEORY OF FERMENTATION 339 



clusters, the compactness of which impeded tKe movements 

 of those which were in motion. Moreover, it was noticeable 

 that the masses of these latter rested on tartrate not yet 

 dissolved, whilst the granular clusters of the others rested 

 directly on the glass, at the bottom of the flask, as if, having 

 decomposed the tartrate, the only carbonaceous food at their 

 disposal, they had then died on the spot where we oaptured 

 them, from inability to escape, precisely in consequence of 

 that state of entanglement which they combined to form, dur- 

 ing the period of their active development Besides these 

 we observed vibrios of the same diameter, but of much 

 smaller length, whirling round with great rapidity, and 

 darting backwards and forwards; these were probably iden- 

 tical with the longer ones, and possessed greater freedom of 

 movement, no doubt in consequence of their shortness. Not 

 one of these vibrios could be found throughout the mass of 

 the liquid. 



We may remark that as there was a somewhat putrid 

 odour from the deposit in which the vibrios swarmed, the 

 action must have been one of reduction, and no doubt to 

 this fact was due the greyish coloration of the deposit. We 

 suppose that the substances employed, however pure, always 

 contain some trace of iron, which becomes converted into 

 the sulphide, the black colour of which would modify the 

 originally white deposit of insoluble tartrate and phosphate. 



But what is the nature of these vibrios? We have already 

 said that we believe that they are nothing but the ordinary 

 vibrios of putrefaction, reduced to a state of extreme tenuity 

 by the special conditions of nutrition involved in the fer- 

 mentable medium used ; in a word, we think that the fermen- 

 tation in question might be called putrefaction of tartrate 

 of lime. It would be easy enough to determine this point 

 by growing the vibrios of such fermentation in media 

 adapted to the production of the ordinary forms of vibrio; 

 but this is an experiment which we have not ourselves tried. 



One word more on the subject of these curious beings. In 

 a great many of them there appears to be something like a 

 clear spot, a kind of bead, at one of their extremities. This 

 is an illusion arising from the fact that the extremity of 

 these vibrios is curved, hanging downwards, thus causing 



