THEORY OF FERMENTATION 347 



centre of the flask. The movements and fissiparous multi- 

 plication of the vibrios may thus be seen in all their 

 beauty, and it is indeed a most interesting sight. The 

 movements do not immediately cease when the tempera- 

 ture is suddenly lowered, even to a considerable extent, 15 

 C. (59 F.) for example; they are only slackened. Never- 

 theless, it is better to observe them at the temperatures most 

 favourable to fermentation, even in the oven where the 

 vessels employed in the experiment are kept at a tempera- 

 ture between 25 C. and 30 C. (77 F. and 86 F.). 



We may now continue our account of the fermentation 

 which we were studying when we made this last digression. 

 On June i/th that fermentation produced three times as 

 much gas as it did on June nth, when the residue of 

 hydrogen, after absorption by potash, was 72.6 per cent.; 

 whilst on the 1 7th it was only 49.2 per cent Let us again 

 discuss the microscopic aspect of the turbid liquid at this 

 stage. Appended is the sketch we made (FiG. 14) and our 

 notes on it: "A most beautiful object: vibrios all in motion, 

 advancing or undulating. They have grown considerably 

 in bulk and length since the nth; many of them are joined 

 together in long sinuous chains, very 

 mobile at the articulations, visibly less 

 active and more wavering in proportion 

 to the number that go to form the chain, 

 of the length of the individuals." 

 This description is applicable to the 

 majority of the vibrios which occur 

 in cylindrical rods and are homogene- 

 ous in aspect. There are others, of 

 rare occurrence in chains, which have 

 a clear corpuscle, that is to say, a portion more refractive 

 than other parts of the segments, at one of their extremities. 

 Sometimes the foremost segment has the corpuscle at one 

 end, sometimes the other. The long segments of the com- 

 moner kind attain a length of from 10 to 30 and even 45 

 thousandths of a millimetre. Their diameter is from i l /2 to 

 2, very rarely 3, thousandths of a millimetre.* 



i millimetre=o.o39 inch: hence the dimensions indicated will be 

 length, from 0.00039 to 0.00117, or even 0.00176 in.; diameter, from 

 0.000058 to 0.000078, rarely 0.000117 in. D. C. &. 



