106 MAN AN ADAPTIVE MECHANISM 



facts of clinical experience which confirm the parallel 

 evolution of the two. It is noticeable that just as 

 natural selection has established contact ceptors only 

 for those types of physical contact which the species 

 experienced during its phytogeny, it has likewise es- 

 tablished chemical ceptors only for those chemical 

 substances which during phytogeny affected the exist- 

 ence of the organism. In this connection it is inter- 

 esting to compare the physiological response of the 

 organism to a dose of toxins with its response to a dose 

 of a standard drug. There are no well-known drugs 

 except the iodin compounds (analogous in chemical 

 nature to thyroid extract) which cause a febrile response 

 in the system, and there is no drug which causes a 

 chill. On the other hand, all the specific toxins cause 

 febrile responses, and many cause chills. Had man's 

 progenitors been poisoned by a given drug throughout 

 the evolution of the species, natural selection would 

 have eliminated those individuals unable to evolve 

 a specific response to that drug and a self-defensive 

 mechanism against it. The administration of the drug 

 would then cause a nod association with a consequent 

 reaction analogous to the reaction which follows the 

 injection of toxins. 



The inaugural symptoms of most infections repro- 

 duce in miniature all the typical phenomena of the 

 ensuing disease, just as by rapid pulse, increased res- 

 piration, trembling, pallor and muscular weakness the 

 phenomena of fear or of anger recapitulate all the 

 physiological phenomena which accompany the flight 

 from an enemy or the physical combat of which they 

 are the precursors. In the dullness, stupor, headache, 



