TOXINS AND ORGANISMAL DIFFERENTIALS 563 



a certain species has been observed also in plants. Blakeslee noted that 

 colchicine, an alkaloid which has specific effects on mitotic cell division, and 

 which may induce polyploidy in plant and animal tissues treated with this 

 substance, does not affect the mitotic divisions in Colchicum, the plant from 

 which this alkaloid is derived; this is the only higher plan examined so far 

 which has been found immune to it. However, Cornman has recently shown 

 that if very large doses of colchicine are used mitoses may show the specific 

 effect of this substance also in Colchicum ; it is very probable that the relative 

 immunity of Colchicum is due to the partial inactivation of the alkaloid 

 produced by this plant and not to a lessened sensitiveness of the mitotic 

 process to colchicine. 



As to the mechanism on which depends the immunity of the various species 

 against their own poisons, certain data are of interest. According to Phisalix, 

 snakes which in general are immune to their own venom if it is administered 

 in the usual way, are found susceptible if the venom is injected into the 

 brain substance, thus showing that the tissue immunity does not extend to 

 all the tissues of the animal. In this case the natural immunity of a species 

 against its own venom is therefore not dependent upon a real lack of suscep- 

 tibility to the poison on the part of those qells upon which the toxic substance 

 principally acts. But some mechanisms presumably exist which prevent the 

 poison from reaching the sensitive cells. In this connection it may be men- 

 tioned that Fleisher and the writer found that the liver and kidney of Helo- 

 derma, and of species related to the latter, such as the turtle, have the ability 

 to absorb Heloderma venom more effectively than the organs of species not 

 as nearly related to Heloderma. This suggests that these organs of Heloderma 

 may perhaps be concerned in the natural immunity of this animal against its 

 own venom, and that possibly proteins bearing organismal differentials may 

 play a role in the process of absorption. 



We have to distinguish from the condition of relative immunity of an 

 organism against autogenous and homoiogenous poisons, a nonspecific in- 

 crease or lessening of resistance of some species to certain poisons, irrespec- 

 tive of the phylogenetic relation between the species tested and the species 

 which produces the poison. Various types of mechanisms may come into play 

 in such species differences and they differ in different cases. 



The differences in the effects which the poisons of amphibia and reptiles 

 exert in various classes and species of animals are similar to those noted in 

 various species of parasites and symbionts in general, and in particular, 

 bacteria and protozoa. In neither instance are the effects determined primarily 

 by the genetic relations between the organismal differentials of the host and 

 of the bearer of the injurious agent, whether the latter is an animal or 

 bacterial toxin ; if the organismal differentials play a part at all under such 

 conditions, it is only an indirect one, in the same sense in which also the 

 effectiveness of an organ differential may be affected by its connection with 

 an organismal differential. Thus it is evident that the virulence of certain 

 bacteria for one vertebrate species and their lack of virulence for another 

 does not run parallel to the relationships of the respective microorganisms 

 and hosts. 



