JR. H. Chittenden — Pap old- digestion. 305 



as are formed in diphtheria, etc., and hence we might fairly draw 

 the deduction that the pseudo-membranes would be attacked by 

 papoid with equal facility. 



As already stated, these two series of experiments show well the 

 effect of dilution on the action of papoid as a proteolytic agent. In 

 the first series of experiments, it is to be noted that the total volume 

 of fluid in each digestive mixture was 50 c. c, while in the second 

 series of experiments, only half that volume of fluid was used, the 

 amount of papoid being the same in both cases. Furthermore, in 

 the first series of experiments, the mixtures were warmed at 40-45° 

 C. for 8 hours, while in the second experiment the digestions were 

 continued for only 3^ hours, yet in the latter case a very great 

 increase in digestive action is to be noted; an increase which is to 

 be attributed mainly to the greater concentration of the papoid 

 solution. This constitutes a very good illustration of what I have 

 found to be charactei'istic of papoid digestion in general, and with 

 all forms of proteid matter. Papoid will act in dilute solutions, 

 but the best and characteristic action is seen only when a small 

 volume of fluid is present. In this respect, it differs verj^ markedl}'' 

 from the animal ferment pepsin, and for this reason any direct 

 comparison of the two ferments is practically impossible, since they 

 act best under such widely different conditions. 



It is well-known that raw blood-fibrin, like raw beef tissue, is 

 more or less attacked by dilute acids and alkalies alone, especially 

 at the body-temperature, but blank experiments, without papoid, 

 show that these reagents have in themselves only a comparatively 

 slight solvent action on raw fibrin ; thus, in one experiment where 

 10 grams of moist, raw blood-fibrin were exposed to the action of 25 

 c. c. of an 8 per cent, solution of sodium bicarbonate at 45° C. for 6 

 hours, only 5-2 per cent, of the dry proteid was dissolved. 



e. Action on Boiled Blood-fibrin. 



The fibrin was simply well washed blood-fibrin, boiled with water 

 until it was thoroughly coagulated, and then pressed as dry as pos- 

 sible. 



Each digestive mixture contained 0*5 gram papoid, 10 grams of 

 the prepared fibrin, and 25 c. c. of water with the respective percent- 

 ages of acid and alkali. 



The 10 grams of boiled fibrin contained 3*092 grams of dry pro- 

 teid (dried at 110° C). 



The mixtures were warmed at 45° C. for 9 hours. 



