476 A MANUAL OF PHYSIOLOGY 



representing about 21 grammes nitrogen and 340 grammes 

 carbon. But the diet of certain miners (Steinheil) and 

 lumberers (Liebig) contained respectively 133 and 112 

 grammes proteid, 113 and 309 (!) grammes fat, and 634 

 and 69 1 grammes carbo-hydrates. The diet of prize-fighters 

 and of athletes in training is richer in proteid than any of 

 these. So that a definite and typical diet for severe labour 

 does not exist. And although perhaps the hardest work ever 

 done in the world is to break athletic records, to cut and 

 handle timber, to mine coal and to make war, the diet on 

 which these things are accomplished is very variable. 



Nevertheless, we may conclude that, for a man of 70 kilos, 

 doing fairly hard, but not excessive work, 20 grammes 

 nitrogen and 300 grammes carbon are a sufficient, and indeed 

 a liberal, allowance, while many men are sufficiently fed 

 with 15 grammes of nitrogen. The 20 grammes nitrogen 

 will be contained in 140 grammes dry proteid, which will 

 also yield 70 grammes of the required carbon. The balance 

 of 230 grammes carbon could theoretically be supplied either 

 in 517 grammes starch or in 300 grammes fat. But it has 

 been found by experiment and by experience (which is 

 indeed a very complex and proverbially expensive form of 

 experiment) that for civilized man a mixture of these is 

 necessary for health, although the nomads of the Asian 

 steppes, and the herdsmen of the Pampas, are said to 

 subsist for long periods on flesh alone, and a dog can live 

 very well on proteids and fat. The proportion of fat and 

 carbo-hydrates in a diet may, however, be varied within 

 wide limits. Probably no ' work ' diet should contain much 

 less than 50 grammes of fat, but twice this amount would 

 be better; 100 grammes fat give about 75 grammes carbon, 

 so that from proteids and fat we have now got 145 grammes 

 of the necessary 300, leaving 155 grammes carbon to be 

 taken in 350 grammes starch, or an equivalent amount of 

 cane-sugar or glucose. Adding 30 grammes inorganic salts, 

 we can put down as the solid portion of a good normal diet 

 for a man of 70 kilos : 



140 grammes proteids = - of body- weight. 



100 fat = 7 foj 



350 carbo-hydrates = 5 J 



30 salt*. 



620 



