it EXTERNAL DIGESTIVE SECEETIONS 97 



with platinum black, with dilute acetic acid, and according to 

 Klihne with absolute alcohol also. 



According to Heidenhain the amount of trypsinogen in the 

 gland diminishes gradually from the commencement of digestion, 

 reaching its minimum after 6-10 hours. It then begins to 

 increase again, and reaches its maximum 16 hours after the meal, 

 when it remains constant for about 30 hours. 



The other enzymes secreted by the pancreas have not been 

 fully worked out. 



Amylopsin or pancreatic diastase was discovered by Valentin 

 in 1844, and again by Bouchardat and Sandras in 1846. It has 

 an amylolytic or saccharifying action upon starch, similar to that 

 of the ptyalin secreted by the salivary glands, but is more vigorous 

 and rapid, since it is able to act on raw starch. It has been 

 assumed capable of transforming large quantities of maltose into 

 dextrose; other authors (Eohmann) maintain that this effect 

 depends upon another special enzyme, to which the name of 

 glucase has been given. 



According to Korowin, Zweifel, and Sonsino the diastatic 

 power of the pancreas begins to develop in the second month after 

 birth, and is absent in the new-born. 



Little is known in regard to the zymogen of pancreatic diastase, 

 as assumed by Liversedge. According to Griitzner the amount of 

 diastase contained in the pancreas fluctuates during digestion like 

 the trypsin ; it is minimal in the sixth hour of digestion, and reaches 

 its maximum 14 hours after the meal, after which it decreases 

 slowly, though it is still higher than in the first digestive period. 



Steapsin (lipase), the enzyme which emulsifies fats, and splits 

 them into glycerol and fatty acid, was discovered by Cl. Bernard 

 in 1846 ; its hydrolytic power was subsequently confirmed by 

 Nencki, who showed that acetic acid ester and the esters of the 

 aromatic series (salol, benzonaphthol) are decomposed by the same 

 enzyme. It has never been isolated, and is certainly the least 

 known of the pancreatic enzymes. It can be extracted from very 

 fresh glands by a watery solution of sodium carbonate (Paschutin). 

 It does not dissolve in glycerol; is destroyed by alcohol and 

 acids; is not found in glands that are not perfectly fresh. It 

 probably exists in the foetal pancreas because the meconium 

 contains free fatty acids. The optimum of its activity in regard 

 to neutral fats is reached at 38 C. Its action, like that of all 

 other enzymes, is destroyed by boiling. It acts better in a neutral 

 than in an alkaline medium. 



Nothing is known of the zymogen from which lipase arises. 

 According to Griitzner this enzyme increases slowly in the 

 pancreas from the sixth to the fortieth hour after a meal, reaching 

 its minimum (like the other pancreatic enzymes) at the 6th hour 

 of digestion. 



VOL. II H 



