182 



BUTYRIC ACID FERMENTATION. 



(L 



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



Bacillus tetani by Mcolaier in 



^^3 1885. The latter is of some- 

 what 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 2 . The remarkable symbiosis of 

 this bacillus with Micrococcus acidi paralactici 

 has already been briefly mentioned in 65. 



114. Methods of Cultivating 1 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 well. Thus R. Koch, in 1884, proposed to 

 cover the gelatin plates with a film of mica, 

 which, however, according to the experience of 

 P. LIBORIUS (I.), is not always sufficient in the 

 case of strictly anaerobic bacteria. On the other 

 hand, a second method (also emanating from the 

 (German) State Board of Health) has proved 

 highly suitable, viz., that of cultures in deep 

 layers, as prescribed by W. Hesse in 1885. For 

 these a puncture culture is made in test-tubes 

 containing nutrient gelatin or agar-agar, the 

 medium being covered, after successful inocula- 

 tion, with a sterile stratum of the same liquefied 

 substance. 



Another method, which has also been vari- 

 ously modified, is that first employed by Pasteur 

 in connection with his studies of the "vibrion 

 septique," which consists in exhausting the air 

 (oxygen) from the vessel containing the nutrient 

 FIG Gruber's medium inoculated with an anaerobic organism, 

 tube for anaerobic The modification made by MAX GRUBER (II.) is 

 foru"e eS Som?what convenient and reliable, and is in general use, 

 reduced in size, especially in the laboratories of Fermentation 

 Physiologists. Strong test-tubes (Fig. 45), about 

 7 inches long, with a much constricted portion in the upper 



