CH. XXVIII.] ACCESSORIES TO FOOD 469 



into boiling water at once, so that the outer part is coagulated, and 

 the loss of material minimised. 



An extremely important point in this connection is that 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 con- 

 stituents, next to water, being the salts and extractives 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 soup when cold to gelatinise. 



Accessories to Pood. 



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, etc.), which are stomachic 

 stimulants, the abuse of which is followed by dyspeptic 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 theine 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 infusions of tea and coffee, produce over-excitement, loss of diges- 

 tive 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. In manufac- 

 tured cocoa, the amount of fat is reduced to 30 per cent., and the 

 amount of proteid rises proportionately to about 20 per cent. The 

 quantity of cocoa usually consumed is too small for these food 

 materials to count very much in the daily supply. The amount of 

 proteid in solution (mainly albumose) in a breakfast cup of cocoa is 

 under half a gramme ; most of the food stuffs are in suspension, for 

 cocoa is drunk "thick," not as a clear infusion. 



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, 1 to 2 proteid, 2 to 4 carbohydrates, and 1 to 1'5 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. 



