42 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



of physiological necessity. Cooking, however, serves many useful 

 ends : — 



1. It destroys all parasites and danger of infection. This relates 

 not only to bacterial growths, but also to larger parasites, such as 

 tapeworms and trichinas. 



2. In the case of vegetable foods it breaks up the starch grains, 

 bursting the cellulose and allowing the digestive juices to come into 

 contact with the granulose. 



3. In the case of animal foods it converts the insoluble collagen 

 of the universally distributed connective tissues into the soluble 

 gelatin. The loosening of the fibres is assisted by the formation of 

 steam between them. By thus loosening the binding material, the 

 more important elements of the food, such as muscular fibres, are 

 rendered accessible to the gastric and other juices. Meat before it is 

 cooked is generally kept a certain length of time to allow rigor mortis 

 to pass ofif. 



Of the two chief methods of cooking, roasting and boiling, the 

 former is the more economical, as by its means the meat is first 

 surrounded with a coat of coagulated proteid on its exterior, which 

 keeps in the juices to a great extent, letting little else escape than the 

 dripping (fat). Whereas in boiling, unless both bouillon and bouilli 

 are used, there is considerable waste. Cooking, especially boiling, 

 renders the proteids more insoluble than they are in the raw state, but 

 this is counterbalanced by the other advantages that cooking possesses. 



Beef Tea. — In making beef tea and similar extracts of meat it is 

 necessary that the meat should be placed in cold water, and this is 

 gradually and carefully warmed. In cooking a joint it is usual to put 

 the meat 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 

 constituents, next to water, being the salts and extractives (creatine, 

 creatinine, lactic acid, &c.) of flesh. 



Many invalids restricted to a liquid diet get tired of milk, and 

 imagine that they get sufficient nutriment by taking beef tea instead. 

 It is very important that this erroneous idea should be corrected. 

 One of the greatest difficulties that a physician has to deal with in 

 these cases is the distaste which many adults evince for milk. It is 

 essential that this should be obviated as far as possible by preparing 

 the milk in different ways to avoid monotony. Some can take 

 koumiss ; but a less expensive variation may be introduced in the 



