4:2 LABORATORY EXERCISES. 



and shake them at frequent inter- 

 vals. Examine them at the end 

 of a few hours and at the end of 

 a day or two. 

 2. Results and conclusions. 



a. In which tube has digestion taken 



place? 



b. Does pancreatin, therefore, perform 



its digestive action by the aid of an 

 alkali or of an acid? 



22. DIGESTION OF FATS. 



Materials: Butter, olive-oil, lard, white of egg; sodium carbonate, 

 caustic soda, hydrochloric acid; bile, pancreatin; test-tubes, alcohol- 

 lamp, apparatus-stand; compound microscope, slide, cover-glass. 



A. Effect of heat on fats. 



1. Put a small piece of butter in a spoon and 



hold the spoon over a hot stove. What 

 change takes place ? 



2. How, then, can you distinguish between a 



fat and a proteid? 



3. Hold a piece of butter in your mouth. Does 



it become liquid at the temperature of 

 the body? 



B. Emulsion of fats. 



i . In a test-tube shake up a few drops of olive- 

 oil with some caustic soda solution. 



a. What change takes place in the ap- 



pearance of the mixture after shak- 

 ing? (This mixture is called an 

 emulsion.) 



b. Put a drop of the mixture on a glass 



