76 PHYSIOLOGY FOR THE LABORATORY. 



4. Melt the butter and add it to the white of an 

 egg. Beat them together. Add the water 

 and beat again. Does the butter and water 

 mix? Why? This is an emulsion. Of what 

 advantage is it in digestion ? 



II. THE EMULSION OF FAT IN MILK. 



Materials. 1-2 c.c. of milk. 



Apparatus. A glass slide. A cover-glass. Compound microscope. 



Mount a drop of milk and examine under the microscope. 

 Notice : 



a. The fat globules. 



b. The liquid. 



c. Sketch. 



d. In what form is the fatty portion of the milk? Is 

 this an advantage or a disadvantage in digestion ? Why ? 

 Compare the results obtained from C. II, and infer what 

 it is that renders milk so valuable as a food. 



III. THE EXTRACTION OF FAT FROM FOODS. 



Materials. Indian meal. Whole wheat flour. Common flour. Benzine. 

 Apparatus. Evaporating dish. Filter-paper. Funnel. 



Extract the fat from the Indian meal, whole wheat 

 flour, and common flour. 

 Experiment : 



1. Mix the Indian meal with benzine or ether. 



2. Filter and allow a drop of the filtrate to evapo- 



rate on a piece of clean glass. What is left ? 

 Prove that this contains fat. What, then, is 

 one of the food constituents of Indian meal ? 



3. Test in the same way the whole wheat and com- 



mon flour. Which contains the most fat ? 



