552 MECHANISM OF SECRETION OF PANCREATIC JUICE. 



Heidenhain established definite characters distinguishing trypsinogen 

 from the actual enzyme, and showed that in some respects their behaviour 

 was similar. The chief relations of the zymogen to the ferment are as 

 follows : 



1. Trypsinogen is soluble in glycerin. Some glycerin extracts of 

 pancreas have no ferment activity, since the ferment is in the condition 

 of zymogen, but if such glycerin extracts, dissolved in 1 per cent, 

 sodium hydrate, be diluted with distilled but not boiled water (this 

 being largely devoid of dissolved air), especially if digested for a time 

 at 40 0., it will become active. 



2. If an inactive glycerin extract of fresh pancreas be dissolved in 

 sodium carbonate, 1 to 2 per cent., the passing through it of oxygen 

 will cause the same to become active. 



3. Platinum black will, according to Podolinski, 1 also render the 

 inert extract proteolytic. 



4. The converse of the change brought about by the influence of 

 oxygen may also occur, for, through the deprivation of oxygen, activity 

 becomes lost. 



5. If fresh pancreas be mixed with the same weight of 1 per cent, 

 acetic acid for ten minutes, and then placed in glycerin, a very active 

 extract will be obtained. The acetic acid converts the trypsinogen into 

 trypsin. According to Kiihne, 2 trypsin is also formed from the zymogen 

 by warming with alcohol. 



The amount of trypsin that can be obtained from an extract varies 

 with the histological condition of the gland. When the luminal zone 

 is of considerable width, a greater amount of proteolytic activity is 

 shown than when it is much reduced. We are justified in associating 

 the ferment with the granules seen in the cells. 



Sodium carbonate may be regarded as an adjuvant to the action of 

 trypsin. Kiihne 3 showed that it worked best in solutions of the strength 

 of 1 per cent. Edkins 4 proved that sodium chloride has a beneficial 

 influence on the digestion of fibrin by pancreatic extracts, and it may be 

 noted that a large amount of the sodium carbonate associated with the 

 pancreatic secretion must be converted into sodium chloride in the 

 duodenum. Ewald 5 states that digestion of fibrin at the instance of 

 trypsin can proceed in the presence of 0*3 per cent, of hydrochloric acid, 

 but, on the other hand, the prolonged action of dilute acids has been 

 shown by Langley 6 to be destructive of trypsin. If a glycerin extract 

 of pancreas be warmed for two and a half hours in 0'05 per cent, hydro- 

 chloric acid, its proteolytic powers are appreciably curtailed. The 

 diastatic ferment has not had the same study bestowed upon it as the 

 proteolytic. It contrasts with this latter in that there is no further 

 enhancement of its activity by treatment with such reagents as convert 

 trypsinogen into trypsin. Liversedge 7 made observations in 1874, 

 which suggested the existence of a diastatic zymogen, but the possi- 

 bility of micro-organic change influencing his experiments was, as 

 pointed out by Gamgee, 8 not eliminated. According to his observations, 



1 Breslau, 1876. 



2 Verhandl. d. naturh.-med. Ver. zu ffeidelberg, 1876, N". F., Bd. i. 



3 Ibid., Bd. i. 4 Journ. PhysioL, Cambridge and London, 1891 Bd. xii. 



5 Ztschr.f. Uin. Med., Berlin, Bd. i. 



6 Journ. PhysioL, Cambridge and London, vol. iii. 



7 Journ. of Anat. and PhysioL, London, 1874, vol. viii. 



8 "Physiological Chemistry," vol. ii. p. 207, 



