366 A TEXTBOOK OF PHYSIOLOGY 



poisonous. When prepared properly that is, when infused for 

 only a few minute* and then poured off tea is free from injurious 

 effects, but the habit of taking strong tea every two or three hours 

 of the day is to be condemned no less strongly than the taking of 

 alcohol. 



Cocoa is more of a foodstuff, particularly if made with milk. It 

 contains fat and a certain amount of theobromine an alkaloid 

 closely related to caffeine. 



Cooking of Food. This is accomplished by means of heat, either 

 moist or dry. Cooking has certain advantages and certain disad- 

 vantages, the former outweighing the latter. The chief disadvantage in 

 cooking is that coagulable proteins are possibly rendered more insoluble 

 in the digestive juices, so that their digestion takes longer, although 

 eventually it is just as complete. On the other hand, cooking kills 

 bacteria and other parasites such as trichinae and tape-worms, which 

 may be present in the food. The connective tissue of meats is 

 rendered more soluble, the fibres disintegrated and made easier for 

 mastication, especially by moist heat. In the cereals, the starch 

 granules swell up and rupture the cellulose envelope, rendering the 

 cell-content more accessible to the digestive juices. In vegetables, 

 the woody fibre is also more or less disintegrated, the tissue rendered 

 more tender, and the cell-contents more or less liberated. Dry heat 

 also converts a certain amount of starch into dextrin e.g., as in the 

 crust of bread. 



The chief forms of cooking are boiling, broiling, and roasting. 

 The main loss ia cooking is water the loss increases with the length of 

 time of cooking in roasting a considerable quantity of fat (the 

 dripping) is lost from the joint. When boiling is employed, the liquor 

 should be used to prepare soup, otherwise a considerable proportion 

 of proteins, extractives, vitamine, and salts, is lost. This is true 

 both for meat and vegetables. The peeling of vegetables greatly 

 increases such loss. The most economical forms of cooking are 

 broiling and by casserole. 



In the preparation of food, various flavours and condiments are 

 often added. When used in moderate quantities, these, by rendering 

 the food " toothsome," have the effect of causing a " psychic " flow 

 of gastric juice, and thereby promoting digestion. On the other hand, 

 the excessive use of condiments tends to upset the digestive apparatus. 

 The appetizing effects of cooking enhance the pleasures of the table, 

 but often lead to overeating, and so to nutritive disorders of sedentary 

 workers. A certain amount of uncooked natural food should be 

 eaten, such as fruits and salads. 



Meals should be restricted to three a day, and no food should 

 be taken between meals. For the preservation of the teeth, it is 

 necessary that the mouth be kept free from food for most hours of the 

 day. 



