306 JR. H. Chittenden — Faj^oid-digestion, 



Reaction. 



Weitrht of 

 undigested residue. 



Boiled tibrin digested, 



Neutral 



2-6397 grams 



28-5 per cent. 



0*05 per cent. Hydrochloric acid 



2-5810 " 



30-0 



0-10 



2-7399 " 



25-7 



2-00 " Bicarb, soda 



2-5875 " 



29-9 



From these results, it is evident that there is a far greater differ- 

 ence in digestibility between raw and cooked fibrin, than between 

 raw and cooked beef proteids. With the latter proteids, there is no 

 very pronounced difference in digestibility whether they are cooked 

 or raw^, but with blood-fibrin the difference is very great. Boiled 

 fibrin appears to be quite resistant to the action of papoid, while raw 

 fibrin, on the other hand, is extremely susceptible to the action of 

 the ferment. By long continued digestion, however, boiled fibrin 

 gradually succumbs, and eventually can be almost completely di- 

 gested. 



Casting a backward glance over the foregoing results, it is evident 

 that the statement made at the outset, that papoid has the power of 

 digesting all common forms of proteid matter, both in a neutral, 

 acid and alkaline medium, is well substantiated by the facts. Papoid 

 is peculiar in that it will digest and dissolve proteid matter in a 

 neutral solution, in this respect resembling trypsin, the proteolytic 

 ferment of the pancreatic juice. But trypsin is a ferment associated 

 with an alkaline secretion, and as a proteolytic agent acts to advan- 

 tage only in alkaline fluids. Papoid agrees wath trj^psin in so far 

 that its proteolytic action is increased by the presence of an alkaline 

 medium, in some cases greatl}^ increased by the presence of 2-4 per 

 cent, sodium bicarbonate. On the other hand, the action of papoid 

 in a neutral solution is increased by the addition of very small 

 amounts of hydrochloric acid, and in some cases the increase is 

 very marked. Just here, attention should be called to a state- 

 ment previously made, viz : that an aqueous solution of papoid is 

 not absolutely neutral, but shows, on careful testing, a very faint 

 trace of alkalinity. Consequently, a minute portion of the acid 

 added, may be taken up in bringing about a more complete neutrali- 

 zation of the mixture, although the amount must be too small to 

 have much influence on the final result. 



Another action to be noted as characteristic of papoid digestion is 

 the peculiar phj'sical change it produces in the proteid acted upon. 

 The exact character of this change is dependent upon the condition 

 of the proteid and, in part, upon the character of the medium in 

 which the digestion is carried on. Thus, with a coagulated proteid, 



