GASTRIC DIGESTION. 51 



8. Compare the Reducing Power of Maltose and Dextrose. 



(a.) With Fehling's solution estimate the reducing power 

 of the solution obtained in 7 (/.) (See " Urine.") 



(b.) Boil in a flask for half an hour 50 cc. of the solution 

 of maltose with 5 cc. of hydrochloric acid. Neutralise with 

 caustic soda, and make up the volume, which has been re- 

 duced by the boiling, to 50 cc., and determine by Fehling's 

 solution the reducing power. The acid has converted the 

 maltose into dextrose, and the ratio of the former estimation 

 (a.) to the present one should be 66 to 100. 



(c.) A solution of pure dextrose treated as in (b.) is not 

 affected in its reducing power. 



Saliva has practically the same effect on starch as malt-extract, 

 and may be used instead of the latter. 



LESSON VII. 

 GASTRIC DIGESTION. 



1. Preparation of Artificial Gastric Juice. 



(a.) Take a part of the cardiac end of the pig's stomach 

 provided for you, which has been previously opened and 

 washed rapidly in cold water. Spread it, mucous sur- 

 face upwards, on the convex surface of an inverted capsule. 

 Scrape the mucous surface firmly with the handle of a 

 scalpel, and rub up the scrapings in a mortar with fine sand. 

 Add water, and rub up the whole vigorously for some time, 

 and filter. The filtrate is an artificial gastric juice. 



(b.) From another portion of the cardiac end of a pig's 

 stomach detach the mucous membrane in shreds, dry them 

 between folds of blotting-paper, place them in a bottle, and 

 cover them with strong glycerin, letting them stand for 

 eight days. The glycerin dissolves out the pepsin, and on 

 filtering, a glycerin extract with high digestive properties is 

 obtained (v. Wittich's Method). 



