THE NATUEE OF TOXINS 193 



But apart from the fact that with such bacteria as those of tetanus 

 and diphtheria, toxins may have a digestive origin, analogies have been 

 drawn between ferment and toxic action. The chief facts upon which 

 these have been founded are as follows : Thus the toxic products of these 

 and other bacteria lose their toxicity by exposure to a temperature which 

 puts an end to the activity of such an undoubted ferment as that of the 

 gastric juice. If diphtheria toxin be heated at 65° C. for one hour, it 

 loses much of its toxic effect, and in the case of b. tetani all the toxicity is 

 lost by exposure at this temperature. In regard to both diseases there is 

 a still further fact which is adduced in favour of the toxic substances being 

 of the nature of ferments, namely, the existence of a definite period of 

 incubation between the injection of the toxic bodies and the appearance 

 of symptoms. This may be interpreted as showing that after the in- 

 troduction of, say, a filtered bouillon culture, further chemical substances 

 are formed in the body before the actual toxic effect is produced. Too 

 much reliance must not be placed on such an argument, for in the case 

 of tetanus, at least, the delay may be explained by the fact . that the 

 poison apparently has to travel up the nerve trunks before the real 

 poisonous action is developed. Further, with some poisons presently to 

 be mentioned which are closely allied to the bacterial toxins, an incuba- 

 tion period may not exist. It would not be prudent to dogmatise as to 

 whether the toxins do or do not belong to such an ill-defined group of 

 substances as the ferments. It may be pointed out, however, that the 

 essential concept of a ferment is th it of a body which can originate 

 change without itself being changed, and no evidence has been adduced 

 that toxins fulfil this condition. Another property of ferments is that 

 so long as the products of fermentation are removed, the action of a given 

 amount of ferment is indefinite. Again, in the case of toxins no evidence 

 of such an occnnence has been found. A certain amount of a toxin is 

 always associated with a given amount of disease effect, though a pro- 

 cess of elimination of waste products must be all the time going on in 

 the animal's body. Again, too much importance must not be attached 

 to loss of toxicity by toxins at relatively low temperatures. This is not 

 true of all toxins, and furthermore many proteids show a tendency to 

 change at such temperatures ; for instance, if egg albumin be kept long 

 enough at 55° C. nearly the whole of it will be coagulated. We must 

 therefore maintain an open mind on this subject. 



Similar Vegetable and Animal Poisons. — It has been found that 

 the bacterial poisons belong to a group of toxic bodies all present- 

 ing very similar properties, other members of which occur widely 

 in the vegetable and animal kingdoms. Among plants the best- 

 known examples are the ricin and abrin poisons obtained by making 

 watery emulsions of the seeds of the Ricinus communis and the Airus 

 precatorius (jequiritv) respectively. From the Robinia, psendacacia 

 another poison— robin — belonging to the same group is obtained. The 

 chemical reactions of ricin and abrin correspond to those of the bacterial 

 toxins. They are soluble in water, they are precipitable by alcohol, but 

 being less easily dialysable than the albumoses they have been called 

 toxalbumins. Their toxicity is seriously impaired by boiling, and they 

 also gradually become less toxic, on being kept. Both are among the 

 most active poisons known — ricin being the more powerful. When they 

 are injected subcutaneously a period of twenty- four hours usually elapses 

 —whatever be the dose — before symptoms set in. Both tend to produce 



J 3 



