i;8 RELATIONS OF BACTERIA TO DISEASE. 



jected subcutaneously a period of twenty-four hours usually elapses whatever 

 be the dose before symptoms set in. Both tend to produce great inflamma- 

 tion at the seat of inoculation, which in the case of ricin may end in an acute 

 necrosis ; in fatal cases haemorrhagic enteritis and nephritis may be found. 

 Both act as irritants to mucous membranes, abrin especially being capable of 

 setting up most acute conjunctivitis. 



It is also certain that the poisons of scorpions and of poisonous snakes 

 belong to the same group. The poisons derived from the latter are usually 

 called venins, and a very representative group of such venins derived from 

 different species has been studied. To speak generally there is derivable 

 from the natural secretions of the poison glands a series of venins which have 

 all the reactions of the bodies previously considered. Like ricin and abrin, 

 they are not so easily dialysable as bacterial toxins, and therefore have also 

 been classed as toxalbumins. Their properties are also similar ; many of 

 them are destroyed by heat, but the degree necessary here also varies much. 

 There is also evidence that in a crude venin there may be several poisons 

 differently sensitive to heat. All the venins are very powerful poisons, but 

 here there is practically no period of incubation the effects are almost im- 

 mediate. The toxicity of the venins varies much with the animal employed, 

 but chiefly with the species of snake from which it was derived. For instance, 

 .47 milligramme of crude venin from the Indian cobra will kill a rabbit in 

 three or four hours. In the case of the American rattlesnake the dose would 

 be 3.5 milligrammes, and in that of the Australian hoplocephalus variegatus 

 2.5 milligrammes. The general effects of these vary with the dose, and slight 

 variations also exist between the effects of venins of different snakes. Thus 

 cobra poison is said to produce rapid paralysis of the lips, tongue, larynx, and 

 respiratory apparatus, from which death results. On the other hand, the venin 

 of the daboia of Ceylon is said to cause violent general convulsions, succeeded 

 by paralysis, but with very little respiratory affection. In the case of a dose 

 not sufficient to cause immediate death from its general effects, often the most 

 acute and widespread necrosis may occur in a few hours round the site of 

 inoculation. 



The Theory of Toxic Action. While we know little of the 

 chemical nature of any toxins, we may, from our knowledge of 

 their properties, group together the tetanus and diphtheria 

 poisons, ricin, abrin, snake poisons, and scorpion poisons. 

 Besides the points of agreement already noted, all possess the 

 further property that, as will be afterwards described, when 

 introduced into the bodies of susceptible animals they stimulate 

 the production of substances called antitoxins. The nature of 

 the antagonism between toxin and antitoxin will be discussed 

 later. Here, to explain what follows, it may be stated (i) that the 

 molecule of toxin most probably forms a chemical combination 

 with the molecule of antitoxin, and (2) that it has been shown 

 that toxin molecules may lose much of their toxic power and 



