R. H. Chittenden — Papoid-digestion. 311 



nary circumstances, as in the peptonization of milk, the presence of 

 this weak alkali would offer any hindrance to the digestive action 

 of papoid. The results show that when lime water is present 

 to the extent of even 50 per cent, of the total volume, digestion is 

 not materially interfered with. Indeed, in another experiment, 

 where papoid was dissolved directly in 25 c. c. of lime water 

 and no other fluid added, 53-7 per cent, of the raw beef proteid 

 was converted into soluble products, while in the control digestion 

 (papoid in water) 66-5 per cent, of the proteid matter was dis- 

 solved ; thus showing that lime water, even when present in large 

 amount, has little power to hinder the proteolytic action of papoid. 



h. Influence of Temperature. 



Animal ferments, especially those concerned in the ordinary pro- 

 cesses of digestion, act most energetically^ as is well-known, at 

 approximately the body temperature. Raising the temperature to 

 near 60** C. quickly brings about a diminution in digestive action, 

 followed by a gradual destruction of the ferment. Lowering the 

 temperature below that of the body is likewise accompanied by a 

 diminution in digestive action, although ordinarily less marked 

 than the inhibition caused by a rise of temperature. With the 

 animal proteolytic ferments, pepsin and trypsin, digestion is very 

 slow at, say 20° C. With diastase, the vegetable amylolytic fer- 

 ment, the most rapid conversion of starch into sugar takes place at 

 about 55° C. 



A study of papoid digestion, with reference to this point, has 

 revealed a very interesting peculiarity of this ferment, viz: a great 

 resistance towards inhibition of digestive action by high tempera- 

 tures. Thus, in an acid solution (boracic acid), a larger amount of 

 cooked beef proteids is dissolved at 70° C. than at any lower tem- 

 perature, while even boiling the ferment solution fails to destroy 

 entirely the action of the ferment ; a fact which is especially true 

 of an alkaline (sodium bicarbonate) solution of papoid. Further- 

 more, at a comparatively low temperature, 20° C, digestion is very 

 pronounced in both a neutral and acid solution of the ferment, while 

 in an alkaline fluid, digestive action is almost as great at 20° C. as 

 at 45° C. 



The three following series of experiments, illustrative of these 

 points, were made at the same time and under exactly the same 

 conditions, excepting the specified variations in temperature and 

 reaction. Each digestive mixture contained 0*5 gram papoid, 10 



