306 A MANUAL OF PHYSIOLOGY 



Pancreatic juice contains four ferments : (i) A proteolytic 

 or proteid-digesting ferment, trypsin ; (2) an amylolytic fer- 

 ment, amylopsin ; (3) a fat-splitting or lipolytic ferment, 

 steapsin, also called pialyn ; (4) a milk-curdling ferment. 



The last cannot be considered as taking any practical 

 share in digestion, since it can hardly ever happen that 

 milk passes through the stomach without being curdled. 



Trypsin, to a certain extent, corresponds with pepsin in its 

 action on proteids. But it acts energetically in an alkaline 

 as well as in a not too acid medium (a very slight amount of 

 digestion may go on in distilled water) ; and its action does 

 not stop at the peptone stage it can split up peptones into 

 leucin, tyrosin, arginine, aspartic acid, and other nitrogenous 

 substances simpler than proteids. 



If fibrin is digested at a temperature of 40 C. with a 

 i per cent, solution of sodium carbonate, to which a little 

 pancreatic extract or juice has been added, along with a 

 trace of thymol to prevent putrefaction, it is gradually eaten 

 away without swelling up and becoming transparent as it 

 does in peptic digestion ; but some granular debris is always 

 left (p. 380). This undigested residue is soluble in i per 

 cent, sodium hydrate, but it is never entirely dissolved in 

 any artificial digestion. In natural digestion, on the con- 

 trary, it is never found ; just as some dextrin always remains 

 when ptyalin has done its utmost upon starch outside the 

 body, while in the intestine little or no dextrin can be 

 detected. When the undigested residue is filtered off, the 

 solution may still contain : (i) a substance resembling alkali- 

 albumin, which is present only in small amount, as it is 

 rapidly changed into (2) albumoses, (3) peptone, (4) leucin, 

 tyrosin, and similar products. It will depend on how far the 

 digestion has been carried whether, and in what quantity, any 

 one of these bodies is present. 



The order in which they appear and their relative amount 

 at different stages of the digestion show that the alkali- 

 albumin and albumoses are, like the acid-albumin and 

 albumoses of peptic digestion, mainly, at any rate, inter- 

 mediate substances through which proteid passes on its 

 way to peptone ; and there is no reason to believe that up to 



