I 



Preliminary remarlis on immunity in animal kingdom 41 



septicaemia — these larvae exhibit a very remarkable natural immunity [44] 



against the bacilli of anthrax and diphtheria. A large dose of bacteria 



>f the second anthrax vaccine, fatal to rabbits, guinea-pigs and mice, 



borne without any inconvenience by the larvae of the Rhinoceros 



>eetle. They are equally refractory to large doses of the diphtheria 



)acillus. And yet, there are not wanting species of insects which 



ire susceptible to these same micro-organisms. Thus, according 



A. Kovalevsky^, crickets contract anthrax very readily even at 



loderate temperatures (22°— 23°C.). On the other hand they are, 



Lccording to the same author, refractory to the bacillus of avian 



ttuberculosis. Many of the Invertebrata, studied from this point of 



view, present analogous facts, with wliich, however, we need not at 



present occupy ourselves. 



In the Vertebrata in general and in Man in particular, natural 

 immunity against many infective diseases and soluble poisons is 

 50 widespread that we are at no loss to find examples for citation. 

 yVe have a whole series of human infections whose study is rendered 

 )articularly difficult simply because of the natural immunity of all 

 [other species of animals from these infections. Such are syphilis, 

 [Scarlatina, leprosy, exanthematous typhus, etc. On the other hand, 

 large number of diseases, very infective for domestic animals, are 

 [uite innocuous to man. In this group we have cattle plague, 

 itrangles, contagious pleuro-pneumonia, fowl cholera, pneumo- 

 mteritis of pigs, and a number of other diseases. 



As in a very large majority of instances pathogenic organisms act 



through the agency of their toxic products, one might believe — and 



this has been assumed repeatedly — that natural immunity against 



[infective diseases is dependent on the insusceptibility of the refractory 



[organism to the specific poisons. 



Such a supposition cannot survive criticism. We have un- 

 ^doubted instances of a species of animal being resistant both to 

 micro-organism and to its toxin. Such instances, however, are 

 [rare and usually an organism that is refractory or only slightly 

 ^susceptible to the micro-organism itself is very susceptible to its 

 >xic products. Even those micro-organisms which come almost 

 [constantly in contact with the human organism without becoming 

 ^pathogenic, may produce toxins capable of gravely affecting health. 



^ " Etude experimentale sur les glandes lymphatiques des invertebres," Melanges 

 ^iol de VAcad. d. sc. de St-Petersb.^ 1894, t. xiii, p. 458. 



