ACCESSORY FOOD BODIES 97 



ished the chemists and physicists, there really were 

 people in plenty who believed that all the patient 

 endeavours of 150 years had gone by the board. 

 In the same way in medicine, while we say with 

 justice that the knowledge gained of bacteria has 

 revolutionized the science and art of medicine, 

 many of us are inclined to forget that the solid 

 foundations on which the art rested in the fifties still 

 remain established, even though the successful 

 nature of modern achievement has to some extent 

 hidden them from view. 



For many long years it was an established 

 principle among animal physiologists that the perfect 

 physiological diet consisted of so many grammes of 

 carbohydrate, so many grammes of fat, and so many 

 grammes of protein, with a few necessary salts in 

 addition. It was believed that by increased per- 

 fection in the art of measurement the whole of an 

 animal's activities could be expressed in the form 

 of an energy equation, reduced for purposes of con- 

 venience to terms of heat. On the one side were 

 placed the heat units or calories contained in the 

 food; the other side of the equation showed how 

 this energy had been spent, and consisted of such 

 items as the residual energy value of the waste pro- 

 ducts of the body, the heat dissipated to the air 

 through the lungs and skin, the heat absorbed to 

 turn liquids into gases, the energy spent in work 

 and locomotion, and so forth. The work so done 

 was, and remains, valuable, but all the time physiolo- 

 gists had a feeling that everything could not be 

 explained by a consideration of energy factors. 



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