ACTION OF THE PANCREATIC JUICE. 255 



change. Hb-0 2 is split up into albumin and ha^niochromogen. In other respects, trypsin acts 

 on tissues containing albumins just like pepsin (166, III.). 



Trypsin is never absent from the pancreas of new-born children (Zweifel), and it may be 

 extracted by water, which, however, also dissolves the albumin. Kuhne has carefully separated 

 the albumin and obtained the ferment in a pure state. It is soluble in water, insoluble in 

 alcohol. Pepsin and hydrochloric acid together act upon trypsin and destroy it; hence it is 

 not advisable to administer trypsin by the mouth, as it would be destroyed in the stomach. 

 When dried it may be heated to 160 without injury. 



Trypsin is formed within the pancreas by a " mother-substance," or zymogen, 

 taking up oxygen. The zymogen is found in small amount, 6 to 10 hours after 

 a meal, in the inner zone of the secretory cells, but after 1 6 hours it is very abund- 

 ant in the inner zone of the cells. It is soluble in water and glycerine. Trypsin 

 is formed in the watery solution from the zymogen, and the same result occurs when 

 the pancreas is chopped up and treated with strong alcohol [Kuhne). The addition 

 of sodium chloride, carbonate, and glycocholate, favours the activity of the tryptic 

 ferment (Heidenhain). [The following facts show that zymogen (v/xr), ferment), or, 

 as it has been called, trypsinogen, is the precursor of trypsin, that it exists in the 

 gland-cells, and requires to be acted upon before trypsin is formed. If a glycerine 

 extract be made of a pancreas taken from an animal just killed, and if another 

 extract be made from a similar pancreas which has been kept for 24 hours, it will 

 be found that an alkaline solution of the former has practically no effect on fibrin, 

 while the latter is powerfully proteolytic. If a fresh, and still warm, pancreas be 

 rubbed up with an equal volume of a 1 per cent, solution of acetic acid, and then 

 extracted with glycerine, a powerfully proteolytic extract is at once obtained. 

 Trypsin is formed from zymogen by the action of acetic acid. There is reason to 

 believe that trypsin is formed from zymogen by oxidation, and that the former 

 loses its proteolytic power after removal of its oxygen. The amount of zymogen 

 present in the gland-cells seems to depend upon the number and size of the 

 granules present in the inner granular zone of the secretory cells.] 



Further Effects. When trypsin is allowed to act upon the hemi-peptone 

 formed by its own action, the latter is partly changed into the amid-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 ( 252, IV. 3). Hypoxanthin, xanthin, and aspartic or amido-succinic 

 acid (C 4 H r N0 4 ), are also formed during the digestion of fibrin and gluten, and so 

 are glutamic (C 5 H 9 N0 4 ) and amido-valerianic acid (C 5 H n N0 2 ). Gelatin is first 

 changed into a geletin-peptone, and afterwards is decomposed into glycin and 

 ammonia. 



Putrefactive Phenomena. If the action of the pancreatic juice be still further 

 prolonged, especially if the reaction be alkaline, a body with a strong, stinking, 

 disagreeable fsecal odour, indol (C 8 H 7 N), skatol (C 9 H 9 N), and phenol (C 6 H 6 0), and 

 a substance which becomes red on the addition of chlorine- water (Bernard), [or it 

 gives with bromine-water first a pale red and then a violet tint (Kiihne)\ volatile 

 fatty acids are formed, while, at the same time, H, C0 2 , H 2 S, CH 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 

 (Kuhne). 



[Artificial Digestion. From fibrin placed in pancreatic juice, or in a 1 per cent, 

 solution of sodium carbonate containing the ferment trypsin, peptones are rapidly 

 formed at 40 C. "When we compare gastric with pancreatic digestion, we find 

 that the fibrin in pancreatic digestion is eroded, or eaten away, and never swells up. 

 The process takes place in an alkaline medium, and never in an acid one. In fact, 

 a 1 per cent, solution of sodic carbonate seems to play the same part in assisting 

 trypsin, that a '2 per cent, solution of HC1 does for pepsin, in gastric digestion. In 

 gastric digestion acid-albumin or syntonin is formed in addition to the true peptones. 



