ON DIET. 521 



Proteids. Fats. Carbohydrates. 



The man consumed daily about . . . 100 70 400 



The wife ' k tk . . . 60 67 340 



The most striking difference is in the proteids. 



468. With regard to climate, the chief considerations attach to tem- 

 perature. When the body is exposed to a low temperature the general metab- 

 olism of the body is increased owing to a regulative action of the nervous 

 system ( 448). 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 espe- 

 cially a carbon metabolism, we might infer that the carbon elements of 

 food should be especially increased. When the body is exposed to high tem- 

 peratures, 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 dis- 

 charge of heat by the skin. 



In both cold and warm climates, however, man trusts much more to vari- 

 ations in his clothing 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, the 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 espe- 

 cially 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 

 carbohydrates is not more than counterbalanced by the increased labor 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 evi- 

 dence that the increase of metabolism 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 to infer that man 

 in the warmer climate would maintain, on the whole, the same normal diet, 

 the only change being, perhaps, to increase it slightly, possibly throwing 

 the increase chiefly on the carbohydrates with the special view of further- 

 ing perspiration. 



469. A special diet for the purpose of fattening that is to say, for the 

 accumulation of adipose tissue out of proportion to the rest of the body is 

 not needed in the case of man. The power to store up fat in adipose tissue 

 is much more dependent on certain inborn qualities of the organism which 

 we cannot at present define than on the kind of food ; of two bodies living 

 on the same diet, and under the same circumstances, one will become fat 

 while the other will remain lean ; and it is an object of the agriculturist to 

 develop by breeding and selection a " constitution " which will store up the 

 most fat on the cheapest diet. In fattening animals the chief care, when the 

 selection of the kind of animal has been made, is to provide adequate carbo- 

 hydrate food, which, as we have seen, is the chief fattener ; and the object of 

 the farmer in rearing stock for the butcher is mainly to convert cheap vege- 



