562 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



does not belong to the snakes, than to that of the venom of snakes of the 

 Crotalus family, although the Cobra is phylogenetically far removed from 

 Heloderma. The same lack of parallelism between the effects of the venoms 

 and phylogenetic relationship holds good, also, as far as the susceptibility of 

 different species of animals to these poisons is concerned. Thus in the study 

 of the venom of Heloderma it was found that the rat and toad are relatively 

 little susceptible to this venom ; in this case we meet again with peculiarities 

 which stand outside the system of phylogenetic relationship. Evidently we 

 have to deal with characteristics of production and mode of action which 

 in snake venoms and the venom of Heloderma are intimately connected with 

 the development of certain organs. In amphibia it is the cutaneous glands and 

 also the parotid or sublabial glands, in snakes it is presumably the parotid 

 gland and in Heloderma the sublabial gland which undergo specific changes ; 

 within certain groups of animals the same kinds of organs may show mor- 

 phologically, chemically and functionally more or less related changes. 



It may then be concluded that the various animal venoms are not, in a 

 strict sense, representatives of substances carrying the organismal differen- 

 tials, but that they may have an indirect relationship to the latter in the same 

 way as have the structure of organs and the organ differentials. Furthermore, 

 as already stated, with certain restrictions the various substances poduced in 

 an organism do not exert a toxic action on those cells and organs of its own 

 body with which they normally come in contact, nor do they interact in an 

 injurious manner with other substances normally produced in the same 

 organism; in particular, also, they do not give origin to the formation of 

 antibodies. 



These facts apply to the animal toxins or venoms in general. The organisms 

 in which the venoms or toxins originate are, to a large extent, although not 

 necessarily completely, resistant to the poisonous effects they produce. Thus 

 toads are resistant to the digitalis-like action of the bufagins and bufotoxins, 

 but not to the bufotenins and to substances acting like epinephrin. As to the 

 mechanism which underlies this resistance of toads, it is restricted to that 

 organ which, in susceptible animals, is principally affected by these constit- 

 uents of the venom, namely, the heart; such resistance extends also to the 

 digitalis group of substances derived from plants. These effects must be 

 considered as due to primary mechanisms of adaptation and not to secondary 

 effects of auto-immunization. 



Also, in reptiles the animals which are carriers of the poison glands are, 

 to a large extent, immune against their own poisons ; they possess an autog- 

 enous as well as a homoiogenous immunity. Heloderma is not susceptible 

 to poisoning by its own venom, but it is susceptible to the effects of rattlesnake 

 venom; likewise, certain non-poisonous snakes seem to be susceptible to 

 the effects of Heloderma venom. However, inasmuch as the Heloderma 

 venom is in some essential respects similar in its action to Cobra venom, it 

 might be expected that a mutual relative immunity exists in Heloderma and 

 Cobra for both types of venom. Such tests have not yet been made. But 

 we have found that Calmette's Cobra antivenin exerts a certain antitoxic 

 effect upon Heloderma venom. A species immunity to a toxin produced by 



