TOXINS AND ORGANISMAL DIFFERENTIALS 561 



skin of Triturus. Embryos of related species of Triturus also produce this 

 paralyzing toxin, but either in smaller quantities than Triturus torosus or in 

 a weaker form. Furthermore, other types of Amblystoma are also susceptible 

 to its action, though not to the same extent as Amblystoma tigrinum. The 

 Triturus toxin is not poisonous for various species of Triturus. In some 

 respects there is noticeable a relation between the amphibian organismal 

 differentials, on the one hand, and these toxins and also the structure and 

 metabolism of the poison-producing glands of the skin and parotid, on the 

 other. However, in other respects these organ-specificities do not parallel the 

 organismal differentials. Also, Bytinski-Salz has described, in the embryos 

 of certain anuran amphibia, toxic substances somewhat similar to those which 

 are produced in the adult cutaneous glands, but the order of toxicity in the 

 embryonal material and in the adult skin in different species is not the same. 

 The adult Bufo produces very toxic substances in the skin, while it is 

 especially the embryos of Pelobates which contain poisonous material. 



If we omit from consideration these specific poisons, which do not respect 

 phylogenetic relationship as far as their orgin and their action on different 

 organisms is concerned, there still remain substances, formed in the embryo, 

 having toxic effects, which on the whole run parallel to the distance in relation- 

 ship between the species producing the toxins and the species serving as a 

 test object. We have, therefore, to distinguish between two kinds of toxic 

 substances in these amphibian larvae : (1) Those which are due to peculiarities 

 of certain organs and which apparently act more or less independently of 

 their respective organismal differentials, and (2) those more closely related 

 to organismal differentials, which become more severe in their effects with in- 

 creasing distance in relationship of the donor and host species. But the 

 distinction between these types is apparently not very sharp, being one more 

 or less of degree. 



In the case of snakes we find only to a limited extent, that the phylogenetic 

 position of the respective animals bears a relationship to the character of their 

 poison glands, the mechanism by means of which the poisons are ejected, 

 the nature and effects of the venoms, or even to the behavior of these animals. 

 Important distinctions which can be made between various types of snakes, 

 as, for instance, those between poisonous and non-poisonous snakes, depend 

 at least partly on quantitative differences in the size of the poison glands, in 

 the amount of venom produced, and in the length of the teeth along which 

 the venom is ejected. The Elapinae show certain characteristic features which 

 differentiate them from the Crotalus type; thus the Cobra venoms are prin- 

 cipally neurotoxic, while the venoms of the Viperidae exert a very strong 

 local action. Different types of Ancistrodon show much similarity in their 

 effects. While, however, certain characteristics are thus common to related 

 groups of these animals, there is no definite gradation in the morphological, 

 chemical and physiological factors which are concerned in the production and 

 effects of the various snake venoms, corresponding to the phylogenetic 

 relationship, and the poisons of very distant classes of animals may show 

 marked similarities in their action. For example, the mode of action of Cobra 

 venom is more nearly related to that of the venom of Heloderma, which 



