a. H. Chittenden — Papoid-digestion. 307 



as cooked beef, there is a rapid disintegration and falling apart of 

 the proteid into tiny fragments, until at last the undigested matter 

 has the character of a pultaceous residue. Hence, in this respect 

 papoid resembles trypsin. This peculiarity is especially noticeable 

 in the digestion of cooked beef, or boiled tibrin, with papoid in the 

 presence of O'l per cent., and even 0*2 per cent., hydrochloric acid. 

 The natural tendency of the acid under such circumstances, espe- 

 cially at '45° C, is to cause the beef fibres to swell up, but this ten- 

 dency is gradually counteracted by the presence of papoid, and 

 eventually, but more slowly, there comes about the same disintegra- 

 tion of the proteid seen in the neutral or alkaline solution. With a 

 raw or non-coagulated proteid, on the other hand, there is at first, 

 especially in an alkaline solution (sodium bicarbonate), a softening 

 action, which is in great part independent of the alkali ; followed, it 

 may be, by the formation of an almost solid, homogeneous, jelly- 

 like mass, in which the fibres lose their individuality, thus differing 

 from the swelling produced by the alkaline fluid alone. As digestion 

 proceeds, the jelly-like mass gradually becomes thinner from the 

 secondary or solvent action of the ferment. The same softening, 

 though less pronounced, shows itself with a neutral solution of 

 papoid, followed by more or less disintegration, although the residue 

 never takes on the appearance seen in the digestion of a cooked 

 proteid. 



3. Circumstances modifying the proteolytic action of papoid. 



Under this head we have to consider more especially : first, the 

 influence of reaction and temperature on the proteid-digesting power 

 of papoid ; and secondly, the influence of such drugs or therapeutic 

 agents as would most naturally be combined with papoid in medical 

 practice. 



a. Influence of Reaction. 



As regards the influence of the reaction of papoid solutions upon 

 the activity of the ferment, we have already demonstrated that 

 with coagulated proteids the highest digestive power is obtained 

 in the presence of sodium bicarbonate, 2-4 per cent. Furthermore, 

 that while the ferment is extremely active in a neutral solution, its 

 activity is, as a rule, increased slightly by the addition of small 

 amounts of very dilute hydrochloric acid, which increase becomes 

 very marked in the case of raw or non-coagulated proteids. With 

 coagulated proteids, the increased digestive action due to the pre- 

 sence of a small amount of very dilute hj^drochloric acid is not 



