62 EXrERIMENTAL PHYSIOLOGY 



XXIX.) This form of crystalloidal proteid is called 

 peptone. 



Add a little alcohol to some of the peptone solution re- 

 maining inside the dialyzer. Filter off the precipitate. 

 Does it resemble coagulated albumin? Add water to 

 some. Does it dissolve? Does coagulated albumin dis- 

 solve? 



Prepare two tubes in the same way as Tube 3, but sub- 

 stitute starch paste in one, and olive oil in the other, for 

 the white of egg. Examine after twenty-four hours. Are 

 they dissolved? 



B. Action of the Enzyme Rennin. Add a little of the 

 rennet ferment (which contains rennin) dissolved in water, 

 to a Uttle milk in a test tube. What happens to the milk? 

 Filter off the precipitate. Test it for proteid. (Rennin 

 coagulates the proteid in milk.) 



Now add a little of the glycerine solution of gastric juice 

 to some milk. Does the action resemble that of the rennin 

 solution? (Gastric juice contains rennin. Pepsin will not 

 convert milk proteid into peptone unless the milk proteid is 

 previously coagulated; hence the necessity of the rennin 

 action.) 



XXXVIII. — Digestion of the Intestine — Pancreatin 

 AND Bile (Optional). 



Apparatus. — Prepared solution of pancreatin (see Ex. XXXV), 

 1.5% sodium carbonate solution, solution of ox gall, hydrochloric 

 acid, caustic soda, materials for food tests, constant temperature 

 apparatus. 



Directions. — A. Action of the Proteid Enzyme of Pan- 

 creatin {Trypsin), Prepare five tubes as follows: Into each 



