SECRETION DIGESTION ABSORPTION. 



strong solution of sodium carbonate. Shake the mixture vigor- 

 ously. Set the emulsion thus formed aside and compare it later 

 with the emulsions made with egg albumin and gum acacia. 



(b) Repeat (a), but do not shake the mixture. Is an emulsion 

 produced ? Place some of this mixture under the microscope and 

 observe the disintegration of the oil-drops into small globules. 

 How does this compare with the emulsification of fats in the intes- 

 tine? 



4. A pancreatic extract may be made in the following way. 

 Take a pig's pancreas or a dog's pancreas which has lain for 

 twenty-four hours at the room temperature. Cut into small 

 pieces or run through a meat grinder. Crush in a mortar with 

 twice its volume of glycerin. Place the mixture in a bottle and 

 allow to stand for several days before using. 



For use, strain the mixture through a fine cloth and dilute as 

 needed with four or five times its volume of water containing so- 

 dium carbonate to make the mixture distinctly alkaline. Prepare 

 a series of test-tubes for digestion experiments as follows : 



A . Place a small quantity of fibrin in a test-tube, adding the 

 alkaline diluted glycerin extract of pancreas until the tube is half 

 full. 



B. To another tube containing fibrin add the glycerin extract 

 diluted with water, alone, and without the addition of the alkali. 



C. To another portion of fibrin add glycerin extract of pan- 

 creas and dilute with o.i-per-cent HC1. 



D. To another portion of fibrin add some glycerin extract 

 which has been boiled, and dilute with o.i-per-cent sodium car- 

 bonate. 



E. To another fibrin portion add o.i-per-cent sodium carbon- 

 ate, alone. 



Prepare a second series of tubes in the same way, substituting 

 commercial pancreatin for the glycerin extract. 



Place all these tubes in a water-bath at a temperature of 38 C. 

 From time to time make an observation of the changes which may 

 be going on in the various tubes. After a half -hour, in which tubes 



