120 ATLAS OF BACTERIOLOGY. 



products of disassimilation of the micro-organism, 

 but we are unable to give any positive data. 



Concerning the influence of the nutrient media upon 

 the formation of trypsin in a culture or the liquefac- 

 tion of the gelatin, the following facts are known : 



1. The majority of circumstances which impair the 

 growth of a variety of bacteria upon a nutrient 

 medium also interfere with liquefaction for exam- 

 ple, the addition of phenol, or a large percentage of 

 glycerin. Wood found that the impaired power of 

 liquefying gelatin, which was produced by phenol, 

 was transmitted during several generations upon a 

 good nutrient medium (C. B., YIIL, 266). 



2. The liquefying facultative anaerobics do not 

 liquefy gelatin* in hydrogen and nitrogen, but they 

 do in carbonic acid, if they are able to grow in the 

 latter medium. As the gases, according to Fermi, 

 have no effect upon the action of the ferment, they 

 must influence the formation of the ferment. Strict 

 anaerobics, on the other hand, produce the most pro- 

 nounced liquefaction of gelatin. 



3. In many bacteria the addition of sugar inter- 

 feres not with their growth, but with the liquefaction 

 of gelatin for example, in bacterium vulgare (proteus 

 vulgaris) but not in bacillus subtilis (Kuhn: A. H., 

 XIII. , 70) . This is explained, perhaps, by the fact 

 that bacterium vulgare produces an acid from sugar, 

 and the vulgare trypsin is very sensitive to acids. 

 Upon 10 c.c. of a one-per-cent grape-sugar gelatin, in 

 five days bacterium vulgare produced 3.7 c.c. of one- 

 tenth normal acid, vibrio proteus 2.1 c.c., bacillus 



*With the single exception of bacterium prodigiosum, but 

 this also ceases to liquefy on the addition of grape sugar. 



