Preliminary remarks 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 

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

 is borne without any inconvenience by the larvae of the Rhinoceros 

 beetle. They are equally refractory to large doses of the diphtheria 

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

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

 to A. Kovalevsky 1 , crickets contract anthrax very readily even at 

 moderate temperatures (22 23 C.). On the other hand they are, 

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

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

 view, present analogous facts, with which, 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 

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

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

 particularly 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, 

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

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

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

 enteritis 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 

 a 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 

 toxic 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 invertebrSs," Melangeg 

 biol. de VAcad. d. so. de St-Petersb., 1894, t. JHII, p. 458. 



