STUDY OF FOOD CHARTS. 



31 





edge of the cover-glass. What is the ef- 

 fect of the soda on the oil -globules ? 

 Prepare a second drop of milk for examina- 

 tion as directed above (i). Place a drop 

 of osmic acid solution at the edge of the 

 cover-glass. What is the effect of the 

 osmic acid on the oil-globules ? 

 Reaction of milk when tested with litmus. 



1 . Test some fresh milk with red and blue lit- 



mus paper. Is it acid, alkaline, or neu- 

 tral? 



2. Set the milk aside in a warm place and al- 



low it to sour. Again test it with the 

 red and blue litmus paper. What is the 

 result? (The souring of milk is caused 

 by the action of certain micro-organisms 

 called bacteria. See study of bacteria, 

 49.) 



16. STUDY OF FOOD CHARTS. 



(In "Foods: Nutritive Value and Cost,"* or in " Principles of Nu- 

 trition and Nutritive Value of Food."*) 



A. Composition of food materials. 



(Make estimates from Chart i, p. n, and 

 compare with per cents, given in Table A, p. 

 27, in " Foods: Nutritive Value and Cost.") 

 i. Which kind of food (animal or vegetable) 



* The.se pamphlets will be furnished free by the U. S. Department 

 of Agriculture, Washington, D. C 



