598 VITAL ACTIONS OF THE LOWER FUNGI. 



to Deherain* and Maquetme the exciting agents of the 

 butyric acid fermentation are found in large numbers in 

 the earth of fields and gardens ; hence it is best to infect 

 the fermentescible mixture with this, or with old cheese, 

 or with cow dung. The vessels are then kept at 40 C. 

 Fermentatire While formerly it was only supposed that one species 

 of bacterium had the power of exciting the butyric fer- 

 mentation, it has been recently demonstrated that several 

 species of bacteria are capable of this act, and that the 

 fermentation with one or with some forms of bacteria 

 can occur in the presence of air, while for the activity 

 of others the exclusion of air is a necessary condition. 

 Besides the species mentioned on page 367, it seems, 

 according to Fitz,t that a short cylindrical bacillus, 

 described by him, is capable of setting up butyric fer- 

 mentation, this bacillus possessing a moderate amount 

 of spontaneous movement, not forming spores, and not 

 becoming blue on the addition of iodine. It belongs to 

 the class of aerobes, and causes fermentation of all carbo- 

 Nature of the hydrates except starch and cellulose. The formula for 

 tion mP S ^e decomposition is probably different for the various 

 different species; in any case, carbonic acid and hydrogen 

 seem to be constantly formed in large quantities. Fitz 

 has also found on analysis of the products obtained from 

 a hundred grammes of starch, 34'7 grammes of butyric 

 acid, 5'1 grammes of acetic acid, and 1 gramme of 

 sethylic alcohol. As, however, it has, as yet, been 

 scarcely possible to cultivate the butyric acid bacilli 

 perfectly pure, no experiment with absolutely pure 

 cultivations has been subjected to accurate analysis, 

 and therefore we must not lay too great weight on 

 these numbers. See page 369. 



Viscous or Mannite Fci mentation. 

 Viscous for- T^ materials which furnish this fermentation are 



mentation ot 



wine. dextrose and invert sugar ; as regards the ferment, the 



micrococcus viscosus, see p. 216. The fermentation 



* Deherain et Maquenne, Bull. soc. chem. (2) vol. 29 Compt. rend 

 vol. 97- 



t Fitz, Chem. Ber., vol. xvii., P. 1188. 



