466 FOOD. [CH. xxvin. 



beef tea and similar meat extracts should not be regarded 

 as foods. They are valuable as pleasant stimulating drinks 

 for invalids, but they contain very little of the nutritive 

 material of the meat, their chief constituents, next to water, 

 being the salts and extractives (creatine, creatinine, lactic acid, 

 <fec.) of flesh. 



Soup contains the extractives of meat, a small proportion of 

 the proteids, and the principal part of the gelatin. The gelatin 

 is usually increased by adding bones and fibrous tissue to the 

 stock. It is the presence of this substance which causes the soup 

 when cold to gelatinise. 



Accessories to Food. 



Among these must be placed alcohol, the value of which within 

 moderate limits is not as a food but as a stimulant ; condiments 

 (mustard, pepper, ginger, curry powder, Ac.) which arc 

 stomachic stimulants, the abuse of which is followed by dyspep- 

 tic troubles ; and tea, coffee, cocoa, and similar drinks. These 

 are stimulants chiefly to the nervous system ; tea, coffee, 

 mate (Paraguay), guarana (Brazil), cola nut (Central Africa), 

 bush tea (South Africa) and a" few other plants used in various 

 countries all owe their chief property to an alkaloid called thane 

 or caffeine (C 8 H 10 N 4 2 ) ; cocoa to the closely related alkaloid, 

 theobromine (C 7 H 8 N 4 2 ) ; coca to cocaine. These alkaloids 

 are all poisonous, and used in excess, even in the form of in- 

 fusions of tea and coffee, produce over-excitement, loss of digestive 

 power, and other disorders well known to physicians. Coffee 

 differs from tea in being rich in aromatic matters ; tea contains a 

 bitter principle, tannin ; to avoid the injurious solution of too 

 much tannin, tea should only be allowed to infuse (draw) for a 

 few minutes. Cocoa is not only a stimulant, but a food in 

 addition ; it contains about 50 per cent, of fat, and 12 per cent, 

 of proteid. Still, as ordinarily prepared as an infusion, the 

 quantity taken does not contain much of these food materials. 



Green vegetables are taken as a palatable adjunct to other foods, 

 rather than for their nutritive properties. Their potassium salts 

 are, however, abundant. Cabbage, turnips, and asparagus contain 

 80 to 92 water, i to 2 proteid, 2 to 4 carbohydrates, and i to 

 i '5 cellulose per cent. The small amount of nutriment in most 

 green foods accounts for the large meals made by, and the vast 

 capacity of the alimentary canal of, herbivorous animals. 



