108 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



ical struggle with an adversary there is a strong 

 impulse to do more injury than is necessary for mere 

 self-protection and preservation. The same tend- 

 ency to overaction is recognized in the vulgar 

 inclination to "hit a man when he is down.'' As 

 might be expected, these self-preservative exaggera- 

 tions are seen with especial distinctness among the 

 lower animals, where contests commonly lead to the 

 death of the weaker organism. This is, of course, 

 true of primitive man and, in general, of man en- 

 gaged in war, but intelligence the expression of 

 memory and imagination powerfully mitigates 

 this overaction. And it will continue to do so, 

 increasingly, as the human animal grows in expe- 

 rience. 



From a biological standpoint, these overactions 

 of the nervous system in the interest of self-preser- 

 vation have a deep interest. For, if we revert once 

 again to the defensive or self-preservative reactions 

 of the cells, we find in them a tendency to overact 

 on stimulation a tendency which strongly suggests 

 a basis analogous to that which is so markedly ex- 

 hibited by the nervous system as a whole. If, with a 

 sharp, thin knife, we make a clean cut into the liver 

 of a living animal, we find that the wound is promptly 

 repaired. But it is a notable thing that the cells 

 which react to repair this wound are not merely those 

 which have been injured by the knife. The reaction 

 of repair is discernible at a measurable distance 

 from the damaged cells in structures apparently not 



