300 STUDIES ON FERMENTATIOX. 



We may now continue our account of the fermentation which, 

 we were studying when we made this last digression. On June 

 17th that fermentation produced three times as much gas as it 

 did on June 11th, when the residue of hydrogen, after absorption 

 by potash, was 72'6 per cent. ; whilst on the 17th it Avas 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. 72) 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 11th ; many of 

 them are joined together into long sinuous chains, very mobile 

 at the articulations, visibly less active and more wavering in pro- 

 portion to the number that go to form the chain, or the length of 

 the individuals." This description is applicable to the majority of 

 the vibrios which occur in cylindrical rods and are homogeneous 

 in aspect. There are others, of rare occurrence in chains, which 

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

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





Fig. 72. 



Sometimes the foremost segment has the corpuscle at one end, 

 sometimes at the other. The long segments of the commoner 

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

 of a millimetre. Their diameter is from 1} to 2, very rarely 3, 

 thousandths of a millimetre.* 



* [1 millimetre = 0'039 inch : hence the dimensions indicated will be — 

 length, from 0-00039 to 0-00117, or even 0-00176 in.; diameter, from 

 O-0UU0j8 to 0-000078, rarely 0'000117 in.] 



