398 BACILLI WHICH DO NOT CAUSE FERMENTATION. 



sugar were used up, and that lactic acid, volatile fatty 

 No fermenta- acids, carbonic acid, and hydrogen, were produced ; hut 

 these substances were formed in such small quantities, 

 and after such a length of time (1 to 2 months) that we 

 cannot speak of a true fermentation ; on the contrary, 

 these products only indicate the result of the assimila- 

 tion and tissue change Of the growing bacilli within 

 ordinary limits. Further, in Vandervelde's experiments 

 the absolute quantity of gases produced was not deter- 

 mined, and there was no certainty as to the -purity 

 of the cultivation, and for this reason the experiments, 

 which are nevertheless interesting as regards the 

 tissue change of bacteria, cannot be regarded as definite 

 proof of the fermentative activity of bacillus subtilis. 

 'eptonising As the only energetic transformation of the substratum 

 caused by the bacillus we have its peptonising power on 

 albumen (also on blood serum) and on gelatine, as indi- 

 cated by the mode of its growth in cultivations. As to 

 the supposed transformation of hay bacilli into anthrax 

 bacilli, seepage 241. . 



Bacillus aerophilus. 



.erobic This organism was found by Liborius in the hygienic 



laboratory at Gottingen as an accidental impurity. It . 



lorphological presents the appearance of thin rods, |rds of the thickness 



haracters. Q f b ac in us subtilis ; these vary in length and frequently 

 hang together, forming straight or zig-zag pseudo-threads. 

 In the unstained preparations we can at times see a 

 delicate sheath around the bacillus. They form on agar 



ultivations. oval, highly refracting spores. On gelatine plates fine 

 punctiform colonies appear after 40 hours, which under 

 a low power show sharply defined borders, are of an 

 oval or pear shape, and have a yellowish green colour. 

 Energetic liquefaction of the gelatine soon commences ; 

 while the colonies have only slightly increased in size, 

 and have otherwise remained unaltered, the surface of 

 the gelatine is liquefied over the whole plate. In 

 puncture cultivations a broad sac-like liquefied area is 

 formed, the upper part of which is greyish -yellow and 



