THE CHEMISTRY OF FOOJ). 50 



and made into cheese, by pressing it sufficiently to drive 

 off the water. 



20. The Fats or Oils. This is the second group of 

 organic foods. Those which are more solid are called fats : 

 the more fluid ones are the oils. Oleaginous substances 

 are supplied in both animal and vegetable food; but, from 

 whatever source derived, they are chemically much alike. 

 They are insoluble in water, and yet they unite readily 

 with the watery fluids of the body, and are by them con- 

 veyed to its various parts for their nourishment. This is 

 due to their property of "emulsifying;" that is, they are 

 held in suspension, in a finely divided state, in water. Or- 

 dinary milk is an example of an emulsion. We know that 

 it contains fat ; for butter is obtained from it, and, under 

 the microscope, the minute oil-globules may be distinctly 

 seen. 



21. In our country and climate, and also in colder 

 climates, fatty articles of food are principally derived from 

 the animal creation, such as meat or flesh, milk and butter. 

 But most of the bread-stuffs contain more or less fat or oil; 

 Indian meal as much as nine parts in a hundred. 



22. Among persons living in cold climates, the appetite 

 for oleaginous food is especially eager ; and they require 

 large quantities of it to enable them to resist the depress- 

 ing influences of cold. Since vegetation is scanty and 

 innutritions, and the waters of the frozen regions abound 

 in animal life, they must rely wholly upon a diet derived 

 from the latter source. The Esquimaux consumes daily 

 from ten to fifteen pounds of meat or blubber, a, large 

 proportion of which is fat. The Laplander will drink 

 train-oil, and regards tallow-candles as a great delicacy. 

 In hot climates, on the contrary, where flourish the olive 



20. What are the fata ? The oils ? How supplied? How alike? Emulsifying? 

 Example * How do we know it? 



21. Whence are fatty articles of food derived? 



22. Appetite of persons in cold climates ? What do they require ? Upon what 

 must they rely ? Why? The Esquimaux? Laplander? Olive and palm ? 



