220 COMPOSITION OF THE DIGESTIVE JUICES. [CH. VIII. 



H. Amylopsin. 



This amylolytic enzyme is secreted by the pancreas. 

 According to most observers it has an action identical with 

 that of ptyalin. 



J. Mellanby and Wooley* state that pancreatic juice 

 alone converts starch to stable dextrin (25 per cent.) and 

 maltose (75 per cent.), but that after treatment with small 

 amounts of acid it can carry the hydrolysis as far as glucose, 

 owing to the appearance of maltase, the enzyme which 

 converts maltose to glucose. Since the pancreatic juice 

 on entering the small intestine is mixed with the acid chyme 

 it is probable that the observations quoted are of consider- 

 able importance. 



Extracts of the pig's pancreas normally contain maltase 

 as well as amylase. The enzymes are destroyed by acids, 

 and so are not found in the extract described on page 212. 

 According to Mellanby and Wooley the amylopsin is best 

 obtained by extracting the minced pancreas with twice its 

 weight of pure glycerol for 24 hours at 37 C. 



Preparation. The pancreas is extracted with dilute alcohol as described 

 on p. 158. After standing 3 days the mass is filtered. It is not necessary to 

 add a preservative, the alcohol acting as such. The amylase and maltase are 

 somewhat unstable, the best results being obtained with recently prepared 

 extracts. 



264. The action of amylopsin on starch. To 20 cc. of a 3 per 

 cent, solution of soluble starch add I cc. of 5 per cent, sodium 

 chloride, divide into two equal portions, and place them into two 

 test-tubes, labelled A and B. To A add I cc. of the pancreatic extract 

 and a few drops of toluol. Shake, stopper, and incubate for 24 

 hours at 38 to 40 C. To B add about I cc. of saliva, then tolvol, 

 and incubate with A. 



To the digested fluids add phenyl-hydrazine hydrochloride, 

 sodium acetate, and acetic acid, and proceed as directed in Ex. 109. 

 Examine the tubes after they have been in the boiling water bath for 

 30 minutes. A will probably contain a precipitate of phenyl- 

 glucosazone, whilst D will remain clear (see Ex. 122). Examine a 



* Journ. of Physiology, xlix., p. 246. 



