38 THE PRINCIPLES OF IMMUNOLOGY 



General Nature of Toxins. Toxins are soluble poisonous prod- 

 ucts of life processes, which on injection into animals lead to the 

 formation of antitoxins. A corollary of this definition sometimes in- 

 sisted upon is that the injurious effect of these toxic bodies must be 

 preceded by an incubation period, but in certain instances this in- 

 cubation time is a matter of minutes or hours, as is the case with 

 certain snake poisons. The toxins are divided according to their 

 origin into phytotoxins, produced by vegetable life, and zootoxins, 

 produced by animal life. The most important of the phytotoxins 

 are the bacterial toxins, but the group includes also ricin, abrin, 

 crotin, robin, and curcin. Certain of the higher plant poisons which pro- 

 duce the varieties of " hay fever " in susceptible individuals were 

 formerly considered as toxins, but this view has now been discarded. 

 The poison of rhus toxicodendron (poison ivy) and of rhus diversiloba 

 (poison oak) might be considered a phytotoxin, but is chemically a glu- 

 coside and does not produce antitoxin. The poisoning of non-edible 

 mushrooms is due, in the case of amanita muscaris and helvella escul- 

 enta, to definite chemical compounds, muscarine and helvellic acid, 

 which do not produce antibodies. In the case of amanita phalloides 

 there are two substances of toxic nature, a thermolabile hemolytic 

 glucoside capable of producing an anti-hemolysin, and a thermo- 

 stabile toxin of unknown composition and incapable of producing a 

 definite immune body. The most important of the zootoxins are the 

 snake venoms, but this group also includes the poisons of spiders, 

 scorpions, centipedes, bees, wasps, hornets, dermal glands of toads 

 and salamanders, various sera, notably that of the eel, and certain 

 poisonous fish. 



Nicolle, Cesari, and Jouan divide the toxins into those that ap- 

 pear in the form of definite secretions, as snake venoms, those which 

 are determined by logical inference, as the toxins in microbial fil- 

 trates, and those which are obtained by simple maceration, expres- 

 sion, grinding, or autolysis, the endotoxins. Experiments with the 

 end6toxins are performed in large part with the microbial bodies, 

 and therefore these workers refer to the endotoxins as solid toxins. 



The bacterial toxins are synthetic products of the life of the organ- 

 isms themselves. It was thought for years that the bacteria could 

 synthesize the protein toxin from simple nitrogen-containing com- 

 pounds. More modern studies oppose this view and state that more 

 complex substances, such as proteoses and polypeptids, are essen- 

 tial. It seems certain that nothing less complex than the amino- 

 acids can be synthesized, and recent studies indicate that diphtheria 

 toxin is not a synthetic product, but rather a catabolic substance 

 elaborated by the bacteria only in the presence of amino-acids and 

 certain additional substances, probably of the nature of vitamines. 

 They are thus to be distinguished from the ptomains, which al- 

 though products of bacterial growth, are in reality formed from the 

 culture medium and vary according to the medium rather than 

 according to the organism. The chemical nature of the bacterial 



