“After structure—function!” Having seen in the last chapter that man is constructed throughout for a diet composed entirely of fruits, nuts, grains, and other non-flesh foods, we now turn to a consideration of the functions of the various organs of the body—the chemical composition of the organic tissues, secretions, etc.—in order to see if these will further bear us out in our argument. There can be no question that the most important argument of all, on this subject of diet, is the argument based upon comparative anatomy—since that argument places man in his right class immediately, and in a manner that cannot be evaded by any amount of argument. But other aspects of the question are also of importance, and afford strong proof of the natural character of man’s diet. The next argument we should consider, therefore, is the physiological, and we shall first of all consider the _secretions_. * * * * * _The Saliva._—The differences between the saliva of man and that of any of the carnivora is striking. In man, this secretion is _alkaline_—though only slightly so, in a healthy man. Nevertheless, that is its normal reaction, and to this there is no exception. In the carnivora, on the other hand, the reaction is _acid_, and because of this fact is capable of dissolving the food more or less whole, and without the long process of mastication necessary for the herbivora and frugivora. The saliva in the human being effects many chemical changes in the food—notable among these being the conversion of starch. Were man intended to live on flesh, the saliva would be acid also—instead of alkaline as it is. * * * * * _The Gastric Juice._—Dr Schlickeysen says of this:[10] [10] “Fruit and Bread,” pp. 108-109.