PROBLEMS IN NUTRITION 333 



held that meat is the only active form of food (for muscular activity), 

 and ascribed to it a very high nutritive value. Liebig's theory was 

 disproved 44 years ago by Voit and soon afterward by Fick and Wis- 

 licenius. But even to-day there are physiologists who hold fast to the 

 Liebig doctrine, and indeed the relics of it are still to be found every- 

 where in physiology and medicine. The tenacity of life of this old 

 error would be difficult to explain, were it not apparently supported 

 by the daily experience that the well-to-do eat meat, eggs, etc., while 

 the day laborers satisfy themselves with bread and potatoes. 



From the difference in the diet of those who do severe muscular 

 work and those who do none, there is a further conclusion to be 

 drawn. The only indigestible constituent of human food is cellu- 

 lose. Cellulose, being contained only in vegetable food, forms but 

 a small constituent of the diet of the man doing little physical work. 

 According to von Knieriem cellulose is of great importance in the pro- 

 cess of digestion, for as indigestible, solid substance it stimulates the 

 activity of the intestine. While carnivorous animals, with their short 

 muscular intestine, do not require it, graminivorous animals, with 

 their long, coiled, weak intestine, cannot do without it for any length 

 of time. Man, in the organization of his digestive apparatus, stands 

 midway between these two extremes, and while cellulose is not abso- 

 lutely essential to him, its absence sometimes causes a motoric atrophy 

 of the intestine which results in chronic constipation and its conse- 

 quences. The connection between constipation and sedentary occu- 

 pations has long been recognized, but people Have been too prone to 

 attempt to explain it mechanically, whereas the connecting link in 

 reality is the dietary of the man leading the sedentary life. In his 

 daily life such a man does but little physical work, and consequently 

 in general eats little, and especially little of the vegetable food poor 

 in proteids but rich in cellulose. We hear nothing of digestive troubles 

 of the people living in the country, while city people, especially the 

 well-to-do, suffer severely from them. In England and America, 

 judging from the wide advertisement of purgatives, the trouble is 

 much more common than in Germany; but in both lands the rye 

 bread, which is comparatively rich in cellulose, is replaced by fine 

 wheat bread, which is much poorer in cellulose, and the substitution 

 of animal products for bread is also more common than with us. 



The vegetarians have been agreed on this point for a long time. 

 They observed how many digestive and other troubles are common 

 to the dwellers in cities (i. e. , where few live like the vegetarian pea- 

 sant), and all without knowledge of the physiological grounds held up 

 the peasant as the ideal for the citizen. But what is correct for the 

 peasant, who must produce 4000-5000 calories, is not correct for those 

 who require but 2300 calories or less. He obtains, then, as explained 

 above, too little of proteids, or aids himself by his fondness for the 



