202 BACTERIA, YEASTS, AND MOLDS 



completely destroyed. Different kinds of foods differ in this 

 respect. Thus the vitamins of tomato seem especially re- 

 sistant to heat and are present in abundance in the canned 

 product. As explained on page 85, there are several kinds 

 of vitamins, each with its own function in physiology, and 

 their exact chemical nature is not yet wholly understood. 

 More accurate information is gradually accumulating in 

 regard to them ; and it is not impossible that we will soon 

 know more definitely which foods suffer most in this respect 

 on heating, and why their vitamins are more readily de- 

 stroyed than those of other foods. 



For the present one can merely speak a word of caution 

 against making canned food one's only diet; but as this 

 is never done in ordinary civilized life, canned goods can 

 be regarded as very useful and perfectly safe food products. 



