266 MAN --AN ADAPTIVE MECHANISM 



of proteins. Lusk has shown that the mass action of a 

 protein injection is greater than could be accounted 

 for by the calories of the protein itself. This is expli- 

 cable on the hypothesis that protein, in excess of the 

 cellular needs, is an adequate stimulus for the kinetic 



A. B. 



Section of normal cerebellum Section of cerebellum of cat after 



of cat. injections of leucin. 



FIG. 62. EFFECT OF LEUCIN ON THE BRAIN-CELLS OF A CAT. 



Note the loss of chromatic material in all and the evidences of disintegra- 

 tion in many of the cells of B. 



(From photomicrographs, X 310.) 



system. (Figs. 65, 66, 67.) We postulate that it is an 

 adequate stimulus because the kinetic system has been 

 evolved to defend the body against the accumulation 



