54 



ADVANCED PHYSIOLOGY 



FIG. 23. THE CELLS OF A POTATO 



Showing the inclosed starch grains. 



boiling water boiling; sometimes by submerging the ma- 

 terial in hot or melted fat frying. Heat has a variety of 



effects upon food and pro- 

 duces some decided chemical 

 changes. 



Few foods except milk and 

 fruit are palatable in their 

 natural state. Cooking food 

 improves it in three differ- 

 ent ways: (1) in flavor, (2) in 

 digestibility, (3) in safety as 

 food. 



1. The change in flavor is 

 very great, so great indeed, 

 that in some cases our taste 

 hardly recognizes the raw and 



the cooked food as being the same material. The "cul- 

 tivated" tastes of the present day make people fastidioi 

 as to the flavors of foods. They seldom stop to questioi 

 the nutritive value of a particular dish, but select foo( 



with reference to their flavoi 

 eating those that are palatabl 

 whether they are nutritious 

 not. An agreeable flavor 

 important, since it enables 

 more easily to digest our f( 

 2. Exposure to heat and 

 the hot fluids in which foo< 

 are cooked does much towan 

 SHOWING HOW COOKING softening food, "making it ten- 



^M SQ thftt lftter ft 



falls to pieces under the actior 

 of digestive ferments and the mechanical grinding of th( 

 mouth and stomach. Vegetable foods, especially, net 

 cooking. The walls of the plant cells resist digestive agenl 



FIG. 24 

 BURSTS THE STARCH-HOLDING 



CELLS 



