140 BUTYRIC ACID FERMENTATION 



environment devoid of oxygen, and for which this gas is therefore a poison ; and 

 facultatively anaerobic organisms, i.e. those to which oxygen is neither 



injurious nor essential, and which can con- 

 j sequently thrive either in presence or absence 

 of air. Thus, for example, the acetic acid 

 bacteria are strictly aerobic, certain lactic acid bacteria 

 facultatively anaerobic, and the majority of the butyric acid 

 bacteria strictly anaerobic. 



At the present time numerous species of anaerobic fission 

 fungi are known. PASTEUR (IX.) himself, in 1863, associated 

 with the " vibrion butyrique " a second anaerobic species, viz., 

 the microbe which sets up fermentation in calcium tartrate. 

 This process of decomposition, already observed by Noellner, 

 but which requires more careful investigation, often occurs 

 spontaneously in tartaric acid works, destroying the tartaric 

 acid and occasioning great loss. The different species of 

 butyric acid bacteria will be thoroughly discussed later on. At 

 present, by reason of their general interest, the known patho- 

 genic anaerobic species, three in number, will be considered. 

 The first of these, as regards priority of discovery, is the 

 " vibrion septique" found by PASTEUR, JOUBERT, and CHAMBER- 

 LAND (I.), and subsequently examined more closely by R. Koch 

 and Gaffky, and now generally known to bacteriologists as 

 Bacillus ozdematis maligni. According to an opinion expressed 

 by Pasteur, this bacillus is identical with the one effecting the 

 fermentation of calcium tartrate. The decompositions set up 

 by the bacillus of malignant oedema in nutrient media con- 

 taining carbohydrates were studied by R. KERRY and S. 

 FRAENKEL (I.). Grape-sugar yielded ethyl alcohol, ethylidene 

 lactic acid, and butyric acid. From calcium lactate were pro- 

 duced butyric acid, a little formic acid, and propyl alcohol. 

 Milk-sugar and also cane-sugar were gradually fermented to 

 ethyl alcohol, formic acid, butyric acid, and ethylidene lactic 

 acid. Starch was also attacked, and yielded the three last- 

 named acids. With Bacillus cedematis maligni have been 

 associated two other pathogenic anaerobic species of fission 

 fungi, namely, the bacillus of symptomatic anthrax, by Feser 

 and Bellinger in 1876-1878, and that which causes tetanus 

 Bacillus tetani by Nicolaier in 1885. The latter is of 

 somewhat frequent occurrence in arable soil, and was also 

 discovered by S. A. SEVERIN (I.) in horse-dung. The bacillus 

 of symptomatic anthrax, according to the researches of M. 

 NENCKI (I.), when cultivated in media containing grape- 

 sugar, produces chiefly normal butyric acid, along with acetic 

 acid and optically inactive lactic acid, accompanied by the 

 evolution of C0 2 and H,. The remarkable symbiosis of this 

 bacillus with Micrococcus acidi paralactici has already been 

 briefly mentioned in 65. 



FIG. 45. Gruber's 

 tube for anaerobic 

 cultures. Ready for 

 use. Somewhat re- 

 duced in size. (After 



Oruber.) 



114. Methods of Cultivating* Anaerobic Bacteria. 



Pasteur covered the nutrient liquid with a layer of oil in order to prevent 

 access of air. This method of covering up the medium with a protective stratum 

 has been variously modified in order to render it applicable to solid media as 



