DEFINITION OF FOODS. 115 



matters facilitate the transfer of material from the recep- 

 tive organs to the working, and from the working to the 

 excretory. Foods to replace matters which have been oxi- / 

 dized must be themselves oxidizable; they are force gener-f 

 ators, but may be and generally are also tissue formers: they 

 are nearly always complex organic substances derived from 

 other animals or from plants. Foods to replace matters 

 not oxidized in the body, as water and salt, are force regu- 

 lators, and are for the most part tolerably simple inorganic 

 compounds. Among the force regulators we must, how- 

 ever, include certain foods, which, although oxidized in the 

 body and serving as sources of energy, yet produce effects 

 totally disproportionate to the amount of energy which they 

 thus set free. Their influence as stimulants in exciting cer- 

 tain tissues to activity, or as agents checking the activity of 

 parts, is more marked than their direct action as force gener- 

 ators. As examples, we may take condiments: mustard and 

 pepper are not of much use as sources of energy, although 

 they no doubt yield some when oxidized; we take them for 

 their stimulating effect on the mouth and other parts of the 

 alimentary canal, by which they promote a greater flow 

 of the digestive secretions or an increased appetite for food. 

 Thein, again, the active principle of tea and coffee, is taken 

 for its stimulating effect on the nervous system rather than 

 for the amount of energy which is yielded by its own oxi- 

 dation. 



To the above definition of a food should be added the 

 condition that, neither the substance itself nor any of the 



What foods must be oxidizable? What are they called? Do they 

 also make tissue? Are they complex or simple? What is their source? 

 What is meant by force regulators? Examples? Are tLey chem- 

 ically complex or simple? What oxidizable foods are included 

 among the force regulators? How is their influence chiefly exhib- 

 ited? Give examples 



