THE EFFECTS OF BACTEBIA. 117 



through a clay or porcelain cylinder possesses the 

 power of fermentation ; or 



3. That this power inheres in a sterile preparation 

 of the ferment, made in the shape of a powder. 



Of the extremely numerous details which we have 

 learned from Fermi's methodical and thorough inves- 

 tigations, we can here give only the most important. 

 All ferments dialyze as little as ordinary albuminoids 

 through good parchment paper. 



Proteolytic i.e., albumin-dissolving enzymes are 

 widely distributed. The liquefaction of the gelatin, 

 which is chemically allied to albumin, in our nutrient 

 media is sure evidence of the presence of a proteolytic 

 ferment. As the reaction at which the gelatin is dis- 

 solved is always or may be alkaline, the bacteria 

 cultures do not contain pepsin (which is effective only 

 with acid reaction) but trypsin. The different bac- 

 terio-trypsins vary greatly in their resistance to heat 

 (in a moist condition they tolerate a temperature of 

 from 55-70 for one hour), their sensitiveness to dif- 

 ferent acids, etc. Some are efficient even when a con- 

 siderable amount of acid has been added, but they 

 never act better than in an alkaline reaction. 



The action on fibrin is much weaker than that on 

 gelatin, and hence Fermi has recommended the fol- 

 lowing method as the most convenient and certain 

 demonstration of the presence of even a trace of pro- 

 teolytic ferment. A non-neutralized solution is made 

 of about seven per cent gelatin in one per cent car- 

 bolic acid and equal amounts are placed in test tubes 

 of the same size. The solution to be tested for the 

 ferment is then placed on the solid gelatin, after re- 

 ceiving two per cent carbolic acid. We can then read 



