CHAP, v.] NUTRITION. 843 



some time on the same kind of diet, and found that nutritive 

 equilibrium was, in the one case and in the other, maintained when 



Proteids. Fats. Carbohydrates. 



The man consumed daily about 100 70 400 



The wife 60 67 340 



The most striking difference is in the proteids. 



555. With regard to climate the chief considerations 

 attach to temperature. When the body is exposed to a low 

 temperature the general metabolism of the body is increased 

 owing to a regulative action of the nervous system, 534. We 

 might infer from this that more food is necessary in cold climates ; 

 and, since the increase in the metabolism appears to manifest 

 itself chiefly in a greater discharge of carbonic acid and therefore 

 to be especially a carbon metabolism, we might infer that the 

 carbon elements of food should be especially increased. When 

 the body is exposed to high temperatures the same reflex 

 mechanism tends to lower the metabolism ; but the effects in 

 this direction are much less clear than those of cold, and soon 

 reach their limits ; the bodily temperature is maintained constant 

 under the influence of surrounding warmth not so much by 

 diminished production as by increased loss. We may infer from 

 this that in warm climates not less but if anything rather more 

 food than in temperate climates is necessary in order to supply 

 the perspiration needed for the greater evaporation and discharge 

 of heat by the skin. 



In both cold and warm climates however man trusts much 

 more to variations in his clothings and immediate surroundings to 

 protect him against cold or to guard him from heat than to any 

 marked variations in his normal diet. In the former he may 

 perhaps be expected to eat somewhat more, since, in spite of 

 wrappings, his skin still feels in part the cold, and thus the 

 nervous mechanism for the increase of metabolism is to a certain 

 extent set to work. And since the metabolism thus increased 

 appears to affect especially the carbon of the body, he may further 

 be expected to increase the fats rather than the carbohydrates of 

 his food seeing that the former supply him with the most energy 

 for their weight. But it is very doubtful whether what he might 

 thus be expected to gain over a corresponding increase in carbo- 

 hydrates is not more than counterbalanced by the increased labour 

 of digestion; and the habits of the dwellers in arctic climates 

 cannot safely be taken as guides in this matter, for their reputed 

 love of fat is probably the result of that being their most available 

 form of carbon. Indeed the evidence that the increase of meta- 

 bolism provoked by cold bears exclusively on carbon constituents 

 is so uncertain that it may be doubted whether any change in 

 the normal diet, beyond some increase in the whole, should be 

 made to meet a cold climate. Similar reasons would lead one 



