252 PANCREATIC JUICE. [BOOK n. 



of pancreas, prepared in the same method as that of the gastric 

 mucous membrane, is (under appropriate conditions) active on 

 proteids, like the native juice. 



The appearance of fibrin undergoing pancreatic digestion is 

 however different from that undergoing peptic digestion. In the 

 former case the fibrin does not swell up, but remains as opaque as 

 before, and appears to suffer corrosion rather than solution. But 

 there is a still more important distinction between pancreatic and 

 peptic digestion of proteids. Peptic digestion is essentially an 

 acid digestion ; we have seen that the action only takes place in 

 the presence of an acid, and is arrested by neutralisation. Pan- 

 creatic digestion, on the other hand, may be regarded as an alkaline 

 digestion ; the action is most energetic when some alkali is present; 

 and the activity of an alkaline juice is hindered or delayed by 

 neutralisation and arrested by acidification at least with mineral 

 acids. The glycerine extract of pancreas is under all circumstances 

 as inert in the presence of free mineral acid as that of the stomach 

 in the presence of alkalis. If the digestive mixture be supplied 

 with sodium carbonate to the extent of 1 p. c., digestion proceeds 

 rapidly, just as does a peptic mixture when acidulated with hydro-- 

 chloric acid to the extent of '2 p. c. Sodium carbonate of 1 p. c. 

 seems in fact to play in pancreatic digestion a part altogether 

 comparable to that of hydrochloric acid of '2 p.c. in gastric di- 

 gestion. And just as pepsin is rapidly destroyed by being heated 

 to about 40 with a 1 p.c. solution of sodium carbonate, so trypsin 

 is rapidly destroyed by being similarly heated with dilute hydro- 

 chloric acid of '2 p.c. Alkaline bile, which arrests peptic digestion, 

 seems, if anything, favourable to pancreatic digestion. 



Corresponding to this difference in the helpmate of the ferment, 

 there is in the two cases a difference in the nature of the products. 

 In both cases peptone is produced, and such differences as can be 

 detected between pancreatic and gastric peptones are comparatively 

 slight ; but in pancreatic digestion the bye-product is not, as in 

 gastric digestion, a kind of acid-albumin, but a body having more 

 analogy with alkali-albumin. Before solution has actually taken 

 place the fibrin becomes altered in character. It is soluble not 

 only in dilute acids and alkalis, but also in a 10 per cent, solution 

 of sodium chloride, and the solutions obtained by the latter reagent 

 are coagulable on boiling and on the addition of strong nitric acid. 

 The first action of the pancreatic juice therefore seems to be to 

 convert the proteid under digestion into a body intermediate 

 between alkali-albumin and ordinary native albumin. 



But though the general characters of pancreatic and gastric 

 digestion are on the surface similar, it is more than probable 

 that profound differences do exist between them. This is shewn 

 by the appearance, in the pancreatic digestion of proteids, of two 

 remarkable nitrogenous crystalline bodies, leucin and ty rosin. 

 When fibrin (or other proteid) is submitted to the action of 



