326 R. H. Chittenden — Papoid-digestion. 



fat was reasonably pure. A series of digestions with papoid was 

 then made in the manner already described ; i. e. each digestive 

 mixture contained 0*5 gram papoid, 8 grams of the moist casein, and 

 25 c. c. of water with the necessary amounts of sodium bicarbonate, 

 etc., to give the indicated percentages. 



The mixtures were warmed at 40-45° C. for 6 hours, and when 

 ready for filtration each was made as near neutral as possible, in 

 order to precipitate any dissolved casein not converted into pro- 

 ducts soluble in water. 



The 8 grams of moist casein contained 2*1377 grams of dry pro- 

 teid (dried at 110° C). Following are the results obtained : 



Weight of 

 Reaction. undigested residue. Casein digested.* 



Neutral 1-5128 grams 29-2 per cent. 



1*0 per cent. Bicarb, soda 1*2205 



2-0 '* " 1-2463 



4-0 *' " 1-3615 



25-0 " Lime water 1-2575 



0-1 " Hydrochloric acid 1-6774 



42-9 

 41-7 

 36-3 

 41-1 



21-0 



It is thus evident that papoid is able to digest precipitated casein 

 under all the above conditions, but that, as with other proteids, 

 digestion proceeds to the best advantage in the presence of 1-2 per 

 cent, sodium bicarbonate. It is also to be noted that lime water 

 constitutes a particularly good medium for the digestive action of 

 the ferment on casein. 



The digestive action of papoid on milk-casein was next tested in 

 a somewhat different manner, milk itself being used instead of the 

 precipitated casein. In this series of experiments, each digestive 

 mixture had a total volume of 100 c. c, composed of 25 c. c. of 

 fresh milkf and 75 c. c. of water,J; the latter containing 0-5 gram of 

 papoid, and in some cases the requisite amount of sodium bicarbon- 

 ate to give the indicated percentages. The solutions were warmed 

 at 45° C. for 6^ hours, when the undissolved casein was filtered off, 

 washed, dried and weighed. In all of these mixtures, the papoid 



* The presence of adherent fat in the casein without doubt introduced some slight 

 errors in the above results, as it was noticed when the mixtures were filtered, that 

 some butyric acid had been developed, thus changing, for example, the reaction of 

 the neutral solution to a distinctly acid one ; but it is safe to assume that the above 

 percentages at least approximately represent the rate of proteolytic action, under the 

 given conditions. 



f In one mixture boiled milk was used, as noted. 



X In one mixture water and lime water, as indicated. 



