Contributions to the theory of organic form: The intestinal tract

By making some assumptions concerning the symmetry of certain “classes” of vertebrates and other assumptions concerning the mode of absorption of food by the small intestine, an equation is developed which gives a relation between the length of the small intestine and the total mass of an animal. The equation contains parameters which depend upon the category of vertebrates (carnivorous, omnivorous, etc.) with which the animal is to be associated. The paper also contains a brief discussion of the parameters of the equation and some of the implications which stem from assumptions about their relative magnitudes. In particular, it is noted that the constant of proportionality in the equation which relates intestine length to a power of the body mass is found to be inversely proportional to the square of the “energy content” of the food which makes up the animal's diet. Some suggestions are offered which may lead to an experimental evaluation of the parameters.