560 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



lism, injurious effects may become noticeable and abnormal changes may take 

 place within the economy of the organism. 



But if these special substances are introduced into a strange individual they 

 may here call forth toxic effects. In the preceding chapters we have discussed 

 already the agglutinating and hemolytic properties of heterogenous blood 

 sera, which seem to be conditioned by factors other than organismal differ- 

 entials. We have also discussed states of hypersusceptibility in which otherwise 

 innocuous substances become strongly toxic. 



In a wider sense we may include also the strange organismal differentials 

 among the toxins. But in a restricted sense we understand by toxins, special 

 substances produced by certain micro-organisms or by more complex higher 

 organisms, which are injurious for various species apparently without regard 

 to relationship. Such toxins are substances which may be formed in special 

 organs and they may therefore be regarded as belonging to the class of 

 organ- or tissue-specific substances, without however representing the real 

 organ or tissue differentials; they represent mosaic characters which have 

 developed in addition to the typical organ differentials. 



In the case of injurious substances derived from bacteria, we have to 

 distinguish from real toxins, non-specific so-called ptomaines, which pre- 

 sumably are mainly split products of the medium on which the bacteria grow ; 

 the latter furnish essentially the proteolytic or lipid-splitting enzymes. The 

 ptomaines do not therefore contain the organismal differentials. As to the 

 exotoxins, against which antitoxins can be obtained, these are substances which 

 are specific for certain types of bacteria ; thus the tetanus toxin differs in its 

 character and effects from the diphtheria toxin. These exotoxins apparently 

 do not possess organismal differentials; a gradation in the character of the 

 exotoxins produced by various bacteria, corresponding to the relationship of 

 these microorganisms, has not so far been demonstrated. The so-called 

 endotoxins seem to represent diverse kinds of substances, among which are 

 nucleoproteins which may be distinctive of different species, as for instance, 

 those obtained from pneumococci and streptococci. However, nucleoproteins 

 obtained from various streptococci are less specific than certain other anti- 

 genic substances present in these microorganisms, and moreover, some 

 endotoxins appear to be non-proteins and are, perhaps, glyco-lipids. 



Among animal toxins it is especially the poisons found in amphibia and 

 in reptiles which have been studied more intensively. In various species of 

 urodeles, as well as of anuran amphibia, poisons are produced in the glands of 

 the skin and also in the parotid gland. The distribution of these substances does 

 not show a complete parallelism to the relationship of the various species and 

 their pharmacological effects differ. Some apparently are identical in their 

 action with digitalis, a plant glucoside. Thus in the European toad, Bufo 

 vulgaris, several specific substances have been obtained from the skin and 

 parotid gland; although in different species of Bufo such substances show 

 some differences, essentially they are of a related nature, acting similarly to 

 digitalis. Twitty and Johnson recently observed in embryos of Triturus 

 torosus a substance paralyzing larvae of Amblystoma tigrinum ; this substance 

 is apparently different from the toxic substances present in the glands of the 



