338 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



finds that hydrochloric acid alone does destroy trypsin, but not so 

 rapidly as when pepsin is also present. 



All possible opinions have been held by various observers as to the 

 reaction with which trypsin acts, and acts best ; * it is now generally 

 accepted that it can act either in an alkaline, neutral, or very faintly 

 acid solution, but that the optimum reaction is that given by about 1 

 per cent, sodium carbonate (Na 2 Co 3 ). 2 



Active proteolysis by trypsin cannot take place in presence of an 

 acid reaction, except the acid be combined with proteid. If the proteid 

 be completely saturated with acid, the rate is greatly slackened even 

 when there is no free acid in the solution; and if much proteid be 

 present, the ferment action may be abolished even before this stage is 

 reached. 3 



Heidenhain 4 states that the concentration of sodium carbonate 

 necessary to ensure maximum activity varies with the richness in 

 ferment of the solution experimented upon ; the richer in ferment, the 

 lower the percentage of sodium carbonate necessary for maximum 

 action. 



Other alkaline carbonates are much less effective than sodium 

 carbonate in increasing the activity of trypsin. The action is also said 

 to be assisted, but to a still less degree, by other salts of the alkalies. 5 



Organic acids have not nearly so destructive an action as hydro- 

 chloric acids, arsenious acid has no hindering effect, and salicylic acid 

 only when in saturated solution. 6 



The nature of the proteid submitted to digestion by trypsin has 

 also a profound effect upon the rapidity of the process. Fresh unboiled 

 fibrin is so quickly dissolved that it cannot be used as a comparative 

 test for trypsin, and fibrin which has been boiled, or discs of hard-boiled 

 white of egg, must be substituted for it. 



Amylopsin. An active amylolytic extract of pancreas can best be 

 prepared by following Eoberts' method of extracting with dilute alcohol. 



Pancreatic juice is much more intensely diastatic than saliva, but 

 it cannot be determined, until some method for isolating the diastases 

 has been discovered, whether this is due to a difference in the amylolytic 

 ferments present or to a mere difference in concentration. It is certain, 

 however, that salivary, pancreatic, and malt diastases are practically 

 identical in the qualitative character of their action on starch. Eoberts 



1 See Corvisart, "Collection de me'moires sur une function peu comme du pancreas, la 

 digestion des aliments azotes," Paris, 1857-8, p. 41 ; Meissner, Ztsclir. /. rat. Med., 1859, 

 3 Reihe, Bd. vii. S. 17 ; Kiihne, Verhandl. d. naturh.-med. Ver. zu Heidelberg, N. F., 

 Bd. i. S. 190 ; Danilewski, Virchow's Archiv, 1862, Bd. xxv. S. 291 ; May, Untersuch. a. d. 

 physiol. Inst. d. Univ. Heidelberg, 1880, Bd. iii. S. 378 ; Lindberger, Jahrcsb. u. d. Fortschr. 

 d. Thier-Chem., Wiesbaden, 1883, Bd. xiii. S. 280 ; Ewald, Ztschr. f. Uin. Med., Berlin, 

 1880, Bd. i. S. 615 ; Langley, Journ. Physiol., Cambridge and London, 1880-2, vol. iii. 

 p. 262. 



2 Weiss, Virchows Archiv, 1876, Bd. Ixviii. S. 413 ; Melzer, Inaug. Diss., Erlangen, 

 1894. According to the latter author, a digestion which is complete in two and a half 

 hours with 1 per cent. Na 2 C0 3 is incomplete in twenty-four hours with either 3 per cent. 

 Na 2 Co 3 or O'OIO per cent, of HC1. 



3 Chittenden and Cummins, Stud. Lab. Physiol. Chem., New Haven, 1885, vol. i. p. 100. 



4 Hermann's "Handbuch," Bd. v. (1), S. 187. 



6 Podolinski, " Beitr. z. Kenntniss des pankreatische Eiweissfermentes, " Breslau, 1876, 

 S. 43. See also Chittenden and Cummins, loc. cit., who found that borax and potassium 

 cyanide augment, while salts of mercury and iron decrease, the activity. 



(! Lindberger, Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1883, Bd. xiii. 

 S. 280 ; Schafer u. Bohm, ibid., 1872, Bd. ii. S. 363 ; Kiihne, Verhandl. d. naturh.-med. 

 Ver. zu Heidelberg, N. F., Bd. i. S. 190. 



