DIGESTIVE ACTION OF THE PANCREATIC JUICE. 341 



changed into dextrose (Brown and Heron), but cane-sugar i not changed into 

 invertin. 



The ferment is precipitated by alcohol, while it is extracted by glycerine without 

 undergoing any essential change. All conditions which destroy the diastatic 

 action of saliva (p. 296) similarly affect its action, but the admixture with acid 

 gastric juice (its acid being neutralised) or bile does not seem to have any injurious 

 influence. This ferment is absent from the pancreas of new-born children 

 (Korowin). The ferment is isolated by the same methods as obtain for the saliva- 

 ptyalin (p. 295); but the tryptic ferment is precipitated at the same time. The 

 addition of neutral salts (4 p.c. solution) e.g., potassium nitrate, common salt, 

 ammonium chloride, increases the diastatic action. 



II. The Tryptic Action (01. Bernard, 1855), or the action on pro- 

 teids, depends upon the presence of a hydrolytic ferment which 

 Corvisart (1858) called pancreatin, and W. Kiihne (1876) termed 

 trypsin. Trypsin acts upon proteids at the temperature of the body, 

 when the reaction is alkaline, and changes them first into a 

 globulin-like body, propeptone (p. 331), and then into a true peptone, 

 sometimes called tryptone. The proteids do not swell up before they 

 are changed into peptone. When the proteid has been previously 

 swollen up by the action of an acid, or when the reaction of the 

 medium is acid, the transformation is interfered with. Gelatin is 

 peptonised by it; but nuclein (Bokay) and haemoglobin withstand 

 solution (Hoppe-Seyler). Trypsin acts upon the connective-tissues 

 just like pepsin ( 166, III). 



When the trypsin is allowed to act upon the peptone formed by its 

 own action, the peptone is partly changed into the amido-acid, leucin, 

 or amido-caproic acid (C 6 H 13 N0 2 ), and tyrosin (C 9 H n N0 3 ), which 

 belongs to the aromatic series (Kiihne). Hypoxanthin, xanthin (Salo- 

 mon) and asparaginic acid (C 4 H 7 N0 4 ), are also formed during the 

 digestion of fibrin and gluten, and so are glutaminic acid (C 5 H 9 N0 4 ), 

 amido-valerianic acid (C 5 H n N0 2 ). Gelatin is first, changed into a 

 gelatin-peptone, and afterwards is decomposed into glijcin and ammonia. 



If the action of the pancreatic juice be still further prolonged, especi- 

 ally if the reaction be alkaline, a body with a strong, stinking, disagree- 

 able faecal odour, indol (C 8 H 7 N), volatile fatty acids, skatol (C 9 H 9 N), and 

 phenol (C 6 H 6 0) are formed, while, at the same time, HC0 2 H 2 SCH 4 

 and N are given off. The formation of indol and the other substances just 

 mentioned depends upon putrefaction ( 184, III.) Their formation is 

 prevented by the addition of salicylic acid or thymol, which kills the 

 organisms upon which putrefaction depends (Hiifner, Kiihne). 



[If some fibrin be placed in pancreatic juice, or in a 1 per cent, 

 solution of sodium carbonate containing the ferment trypsin, peptones 

 are rapidly formed. When we compare gastric with pancreatic digestion, 

 we find that there are marked differences. The fibrin in pancreatic 

 digestion is eroded, or eaten away, and never swells up. The process 



