520 NUTRITION. 



be undertaking a small or large amount of labor. A second feature of such 

 a diet is the marked reduction of the fat and its replacement by carbohy- 

 drates. Although here again we cannot make a distinctly authoritative 

 statement, the evidence which we possess bears clearly in the direction that 

 such a reduction is a marked disadvantage. A third and very characteristic 

 feature of the strictly vegetarian diet is the relatively large amount of un- 

 digested food lost to the body and discharged as feces. Even when the diet 

 is scanty, so that the proteid element is low, the amount of feces relatively 

 to the total food is high ; and when a more normal proteid contribution is 

 secured by ample meals the feces becomes exceedingly voluminous. Indeed 

 when, leaving man, we compare the herbivorous with the carnivorous mam- 

 mal, we find that the former is almost as clearly distinguished from the latter 

 by its frequent and abundant feces as by the anatomical features of its or- 

 ganization. We have already urged that, since the feces serve as a means 

 of excretion of the real waste products of metabolism, a certain amount of 

 vehicle to carry these away is of advantage or even necessary ; but there are 

 no facts at present known to us which show that the larger intestinal cur- 

 rent of the purely vegetable diet effects any such good as can compensate 

 for the obvious waste of labor incurred in the transport and management, 

 to say nothing of the opportunities of mischief offered by a mass of mate- 

 rial more subject to the dominion of foreign organisms than even to that of 

 the body itself, though these opportunities are less than with a correspond- 

 ing mass of animal origin. With respect to these three features, then, the 

 strictly vegetarian diet seems, on physiological grounds, inferior to one of 

 a mixed nature. There are, as we said, other aspects, still of a physiologi- 

 cal kind, to be considered, such as the relative digestibility of vegetable 

 articles of food, the relative metabolic value of the food-stuffs of vegetable 

 origin, and the influence of animal extractives ; but any fuller discussion of 

 these points would be out of place here. 



467. We have treated the diet discussed above as a normal diet, suit- 

 able for man under ordinary or general circumstances. Ought such a diet 

 to be modified for the various exigencies of life, such as labor, age, climate, 

 and the like ? 



We shall discuss the influence of age in the concluding portions of this 

 work. 



We may be inclined, at first sight, to assume that the total amount of 

 the diet should vary with the weight, that is, the size, of the individual; 

 and, indeed, in discussions on nutrition, statements concerning metabolism 

 and amounts of food are often given in terms of per kilo of body weight. 

 In a broad sense, it may be true that a small man needs less food than 

 a large one ; but it must be remembered that, as we saw in speaking of 

 animal heat, the smaller organism, having the relatively larger surface, 

 carries on a more rapid metabolism per unit of body weight, and so needs 

 relatively more food. And, moreover, the influence of size is probably far 

 less than the influence exerted by the inborn individual characters of the 

 organism, giving rise to what we may call the personal equation of metab- 

 olism. The smaller metabolism of woman, leading to the use of scantier diet, 

 as compared with that of man, is to be regarded in this light rather than 

 with reference to the average lesser weight of woman. The relative metab- 

 olism of the two sexes may be illustrated by the case of an active man and 

 his wife, both of about the same age and weight, the man being rather the 

 heavier and the woman rather the older, who in carrying out together an 

 experiment on the relative values of vegetable and animal food, both lived 

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

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



