46 BACTERIOLOGY 



precipitates. Their powers of fermentation (enzymes) and 

 of intoxication (toxins) are apparently specific. 



The enzymes of bacterial origin with which we are best 

 acquainted may be defined as amorphous constituents of 

 living protoplasm that are able through catalytic activity 

 to split up complex organic substances into simpler, more 

 soluble and diffusible combinations. They may be classified 

 as proteolytic, diastatic, inverting, coagulating, sugar 

 splitting, fat splitting, etc. It is important to note that 

 such enzymes may and do originate in both the animal 

 and vegetable world. Those obtained from bacteria are, 

 in so far as it is possible to say, identical with those found 

 in the cells of animals. 



The proteolytic or albumin-dissolving enzymes are formed 

 by a great many bacteria. The most familiar indications of 

 the formation of a proteolytic enzyme are seen in the lique- 

 faction of gelatin, in the digestion of coagulated blood-serum, 

 and of casein. Most frequently the proteolytic enzyme is 

 allied to trypsin, since the liquefaction, hydrolysis or 

 digestion induced by it proceeds only under an alkaline reac- 

 tion.' Some bacteria, however, produce a proteolytic enzyme 

 analogous to pepsin, and this enzyme is active under an 

 acid reaction. The proteolytic enzymes of different bacteria 

 vary considerably with regard to their resistance to heat, 

 some being destroyed in a few minutes when heated to 60° 

 or 70° C, while others may be exposed to 100° C. for a short 

 time without suffering marked deterioration.^ The proteo- 

 lytic enzymes also differ in respect to their susceptibility to 

 the action of acids and other chemicals. 



The formation of proteolytic enzymes is one of the func- 



' See Abbott and Gildersleeve, Journ, of Med. Research, 1903, vol. v. 

 2 Loc. cit. 



