4 o6 THE HUMAN SPECIES 



the smaller the body of the man or animal, and the fuller the 

 poison sac has become through a prolonged period of activity, 

 the sooner does a fatal result take place. 



From the earliest times exceptions have been known to the 

 general rule cases in which men and animals were immune to 

 animal poisons, and in which animals had become immune to 

 vegetable poisons. 1 In the old authors (yElianus, Hist. Anim., 

 lib. i., cap. 57; Celsus, v., 27; Plin., Nat. Hist., vii., 2, etc.; 

 Lucan, ix., v., 95 et sqq^) there is an account of a race, the 

 Psylli, in Lybia, who were absolutely immune to snake bites. 

 Pliny mentions another race, the Ophiogenes on the Helles- 

 pont, who were similarly immune, and moreover had the power 

 of healing those who had been bitten by snakes, by means of 

 their saliva. 



The hedgehog is one of the animals possessing natural 

 immunity to poisons. The naturalist Lenz states he has ob- 

 served that the hedgehog is not affected by the bite of an 

 adder, and can devour Spanish flies with the keenest appetite, 

 and without coming to any harm : Brehm has confirmed this ob- 

 servation, and also mentions the Iltis and Mongoose (Herpestes 

 javanicus) as champions who can receive many bites in their 

 contests with snakes without being poisoned. The wasp buz- 

 zard (Pernis apivorus) is quite insensitive to the stings of wasps 

 and bees, and so is the Edolius paradiseus, and the bee eater, 

 Merops apiaster. The Batrachians react very variously to 

 wasp and bee stings. While the ordinary pond frog avoids 

 both bees and wasps, the grass frog is immune against bees 

 but not against wasps ; the toad, on the other hand, devours 

 both with avidity and without damage to itself. 



(y) Diseases of Special Organs. 



Most of the material available for a comparison between the 

 internal diseases of man and animals is derived from the observa- 

 tions of veterinary suigeons upon domestic animals either during 

 life or after death ; for such diseases in wild animals can only 

 occasionally be observed among the inhabitants of our zoological 

 gardens. In this class of disease also we may note a far-reaching 

 agreement between animals and man, dependent on the general 



1 Hopf, L., Immunitdt und Immniiisiening. Tubingen, 1902, pp. 1-4. 



