650 



LECTURE XXVIII. 



anatomical observations apparently indicate that man is adjusted to take 

 care of a diet containing both meat and vegetables. The intestine is 

 neither as short as in the case of the pure carnivora, nor as long as that of 

 the herbivora. It is interesting to find that nations, such as the Chinese 

 and Japanese for example, which are accustomed to a diet in which vege- 

 tables predominate, have a longer intestine than individuals of a nation 

 which is accustomed to a meat diet. As regards the shape of the teeth, 

 it is not possible to draw any definite conclusions; and it is also true as 

 regards the historical development of the human race, that there is no proof 

 that man was originally accustomed to a vegetable diet. Our knowledge 

 of cookery has to a certain extent made us independent of the nature of 

 the raw material. This is particularly so with regard to the products of 

 the vegetable kingdom. Cooking enables us to get at the contents of the 

 plant cells better, which were originally enveloped by cellulose; and 

 important foods, such as the potato, are made more accessible to the action 

 of diastase. If we really wish to make a definite decision with regard to 

 the relative values of vegetables and meats, we must, in the first place, 

 compare the extents to which each is utilized. This may be ascertained 

 by the analysis of the faeces, determining the amount of unabsorbed 

 material. Certain factors come into play here which make it hard for us 

 to decide. A great deal depends upon the nature of the food. A diet rich 

 in starch may have an unfavorable action upon the absorption of the other 

 nutriment, on account of the fermentation processes resulting and the 

 formation of acid (butyric acid), which accelerates the peristalsis of the 

 intestines, thereby causing a prompt evacuation. Food rich in cellulose 

 will have the same effect. Individual peculiarities also undoubtedly come 

 into play here. At the same time it is perfectly possible for us to obtain 

 approximate values for the extent to which the various foodstuffs are 

 utilized in the human organism. Such values are given in the table on 

 the following page. 



The more incomplete utilization of the protein in vegetables as com- 

 pared to that of flesh foods is also shown by the results of experiments by 

 Atwater and Langworth 1 with vegetable, meat, and mixed diets. This is 

 shown in the following summary. 



A Digest of Metabolism Experiments, Washington, 1897. 



