CONTACT CEPTORS 75 



methods of adaptation advance, sanitation, drugs, 

 clothing, etc., yet insects still menace man's welfare, 

 even his life ; the mosquito is still the most active agent 

 by which malarial fever and yellow fever are dissemi- 

 nated ; by the bite of the flea, man may be inoculated 

 with bubonic plague ; and sleeping sickness may result 

 from the sting of the tsetse fly. 



A second type of tickle reflex is elicited by heavy 

 penetrating pressure in the region of the ribs, the loins, 

 the base of the neck and the soles of the feet the 

 pressure simulating the penetrating contact of a tooth- 

 shaped body. The reaction in this case is a violent 

 discharge of energy in the form of laughter with cries 

 for mercy and frantic muscular efforts to be free if the 

 stimulus be continued. If one were tied hand and foot 

 and were vigorously tickled for an hour, he would prob- 

 ably be as completely exhausted as if he had run a 

 Marathon race or sustained a crushing injury ; indeed, 

 victims of torture in the Middle Ages were often killed 

 by prolonged tickling. 



The fact that these ticklish areas are found in those 

 parts of the body which are still and must always have 

 been the points most frequently attacked by savage 

 beasts leaves little doubt that this reaction developed 

 at a time when man's progenitors, like the carnivora 

 to-day, fought their enemies face to face with tooth and 

 claw, and that this mechanism was acquired as a means 

 of protection against valiant foes. (Fig. 6.) 



There is abundant evidence to bear out this conclu- 

 sion. Children and young animals at play invariably 

 recapitulate the fight maneuvers of their ancestors by 

 attacks in ticklish spots. Playful puppies in frolic 



