VI GELATIN AS A FOOD-STUFF 279 



consists almost entirely of rice, but if the rice be devoid 

 of its natural husks they incur the risk of suffering from a 

 condition of mal-nutrition known as beri-beri. The 

 particular all impjortant constituent of the husks has been 

 isolated and estimated though the amount necessary to 

 the body daily is almost inconceivably small. 



The salts which leave the body are largely the salts 

 which were introduced in the food. It might therefore 

 at first sight appear that they are merely unavoidable 

 constituents of food which are largely passed without 

 change through the body. But this Is not the case. In 

 some way or other the salts of food play an essential 

 part in directing the metabolism taking place in the 

 tissues. Thus animals fed with an abundance of food, 

 which has however been freed as far as possible from 

 salts, soon die with symptoms of defective nutrition, 

 accompanied by paralysis and convulsions. 



When an animal is deprived of all food whatsoever, it 

 begins to feed on its own tissues. Thus up to the day of 

 its death from starvation there is an output of urea and 

 of carbonic acid, though in amounts less than when food 

 is being taken. The loss of tissue substance thus pro- 

 duced affects the several tissues to different extents ; but 

 without entering into details we may simply point out 

 that the master-tissues suffer least, in the obvious effort 

 to prolong life to the utmost. Thus the brain and spinal 

 cord are almost unaltered at death, and the blood and 

 the muscular tissue of the heart also lose but little as 

 compared with the fat and the skeletal muscles on which 

 the body is now chiefly living. 



5. The Erroneous Division of Food stuffs into 

 Heat-producers and Tissue-formers. —Food-stuffs have 

 been divided into heat- producers and tissue-formers— the 

 carbohydrates and fats constituting the former division, 

 the proteins the latter. But this is a very misleading, and 

 indeed erroneous classification, inasmuch as it implies, on 

 the one hand, that the oxidation of the proteins does not 



