558 RESPIRATION AND FERMENTATION 



Various authors, among whom Jorgensen may be mentioned, have attempted 

 to show that Saccharomyces is simply a growth-form of other fungi, but 

 hitherto without success 1 . Hansen has shown that cultural varieties may 

 be produced from several of the species of Saccharomyces. 



Butyric fermentation. Different authors 2 have observed that butyric 

 acid, which commonly appears during putrefaction, forms a main or by- 

 product of the metabolism of many bacteria. Certain of these are obligate 

 aerobcs, but most are obligate or facultative anaerobes, among which the 

 nitrogen-assimilating Clostridinm Pasteurianum is included (Sect. 69). All 

 the species examined ferment dextrose and certain other substances as 

 well, while the anaerobic Clostridinm foetidnm of Liborius and Hiappe's 

 aerobic Bacillus bntylicns energetically decompose proteids with a production 

 of malodorous gases. Hydrogen and carbon dioxide are the only gases 

 which are formed during the butyric fermentation of carbohydrates, but 

 other products may also appear. The relative amounts of the different 

 products vary according to the food-supply and the progress of fermenta- 

 tion, and are also dependent upon the external conditions, as has been 

 shown by Fitz, Perdrix, Grimbert, Bcyerinck, Duclaux, &c. Different 

 species decompose the same food-material in different ways, and although 

 lactic acid may appear as an intermediate product in some cases, the 

 butyric fermentation of sugar certainly does not in all cases follow this 

 course, for Botkin 3 found that a certain butyric bacterium is quite unable to 

 ferment lactates. 



According to Grimbert the anaerobic Bacillus orthobutylicus ferments dextrose, 

 cane-sugar, maltose, milk-sugar, starch, dextrin, inulin, mannite, arabinose, and 

 glycerine, but does not attack gum-arabic, erythrite, glycol, calcium lactate and 

 tartrate. During the fermentation of sugar an abundance of butyric acid is formed 

 as well as large quantities of butyl-alcohol, acetic acid, hydrogen, and carbon 

 dioxide. The hydrogen diminishes in relation to the carbon dioxide evolved as 

 fermentation progresses, while at the same time the amount of butyric and acetic 

 acids produced decreases, but that of butyl-alcohol increases. Apparently the 

 accumulation of free acid exercises a certain inhibitory action, for the addition of 

 chalk causes the production of acid to increase again. The properties of these and 

 other bacteria are subject to transitory or permanent modification, and this makes 



1 Klocker u. Schionning, CentralbL f. Bact., 1896, Abth. ii, Bd. n, p. 185; Meddelelser f. 

 Carlsberg Laboratoriet, 1896, Bd. v, p. 66 ; Hansen, Centralbl. f. Bact., 1895, Abth. ii, Bd. I, p. 859. 



1 Thus : Prazmowski, Unters. ii. Fermentwirk. einiger Bacterien, 1880 ; Fitz, Ber. d. Chem. Ges., 

 1882, p. 867; 1884, p. 188; Hiippe, Mitth. a. d. k. Gesundheitsamt, 1884, Bd. H, p. 319; Perdrix, 

 Ann. d. 1'Inst. Pasteur, 1891, T. v, p. 287; Grimbert, ibid., 1893, Bd. vn, p. 353; Beyerinck, 

 Bntylalkoholgahrung, 1893 (Sep.-abdr. a. d. Verb. d. K. Akad. d. Wetenschappen, Amsterdam); 

 Duclaux, Ann. d. 1'Inst. Pasteur, 1895, T. IX, p. 8n ; v. Klecki, Centralbl. f. Bact., 1896, Abth. ii, 

 Bd. n, p. 288. Summary by E. Baier, Centralbl. f. Bact., 1895, Abth. ii, Bd. i,-p. 17 ; Fliigge, 1. c., 

 p. 236; Lafar, 1. c., p. 164. 



' Botkin, Zeitschr. f. Hygiene, 1892, Bd. XI, p. 432. 



