CHEMICAL FERMENTS. 579 



the ferments of the gastric juice and of the pancreatic 

 secretions which belong to this group, hodies possessing 

 a similar action also occur fairly widely distributed 

 in plants. Thus, from Carica papaya we have papain, 

 which acts like the pancreatic juice in alkaline solutions ; 

 then we have a ferment similar to pepsin, which acts when 

 the reaction is acid, and occurs in those plants which 

 feed on flesh, and in ^Ethalium septicum. Ferments of 

 this class are evidently extremely common in the lower 

 fungi. The large number of species of bacteria now Occurrence in 

 known which cause liquefaction of the nutrient gela- 

 tine, appear to cause this liquefaction only by the pro- 

 duction of a ferment which dissolves albumen and 

 gelatine. As the liquefaction usually occurs when the 

 reaction is alkaline, these bacterial ferments approach 

 the pancreatic ferment, trypsin and papain, rather than 

 pepsin. Attempts at isolating these ferments, and 

 accurate investigations as to the action of the pepton- 

 ising bacterial ferments on various albuminous materials, 

 are as yet wanting. The fact that many bacteria liquefy 

 gelatine, but not solidified blood serum, seems to show 

 that the various albuminous bodies are not all rendered 

 fit for assimilation in the same manner, viz., by means 

 of this production of ferment. Many bacteria do not 

 produce peptonising ferment under all circumstances ; 

 this production seems especially to cease when oxygen 

 is excluded, just as was observed by Wortmann in the 

 case of the diastatic ferment of the bacteria.* 



5. Rennet ferment. This causes an alteration of Ferment 

 the albuminoid materials of milk, which shows itself in 

 the coagulation of the casein. A similar ferment is, as 

 is well known, present in the stomachs of calves ; and 

 we may further assume that it is at times produced by 

 the milk glands, for Meissnerf found that the milk of 

 goats, even when bacteria were completely excluded, 

 became coagulated, evidently from a ferment which had 



* For further details with regard to this subject see the Paper by 

 Liborius (Zeitschrift f. Hygiene, i., Part 1) which has appeared while 

 this book was passing through the press. 



f Meissner, Deutsche Zeitsehr.f. Chir., vol. 13, p. 334. 



