PROPERTIES OF BACTERIAL FERMENTS. 177 



period of incubation between the injection of the toxic bodies 

 and the appearance of symptoms. This may be interpreted as 

 showing that after the introduction of say a filtered bouillon 

 culture, further chemical substances are formed in the body be- 

 fore the actual toxic effect is produced. In the case of tetanus 

 at least the delay, however, may be explained by the fact that 

 the poison apparently has to travel up the nerve trunks before 

 the real poisonous action is developed. With some poisons pres- 

 ently to be mentioned which are closely allied to the bacterial 

 toxins an incubation period may not exist. It would not be 

 prudent to dogmatise as to whether the toxins do or do not be- 

 long 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 that 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 occurrence has been found. 

 A certain amount of a toxin is always associated with a given 

 amount of disease effect, though a process 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. Many proteids 

 show a tendency to change at such temperatures ; for instance, 

 if egg albumin be kept long enough at £5° C. nearly the whole 

 of it will be coagulated. Such considerations suggest that the 

 relation of toxic action to fermentation must be left an open 

 question. 



Similar Vegetable and Animal Poisons. — Within recent years 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 vege- 

 table 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 Abftis precatorius (jequirity) respectively. 

 From the Robinia pseudacacia 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 

 powerful poisons known — ricin being the more fatal.. When they are in- 



