"REACTIONS" AND SIMILAR PHENOMENA 309 



more quickly than in the normal person. It leads to an early 

 development of the specific lesion of vaccinia. 



The essential point of this theory is that an infection from which 

 recovery has taken place may lead to an alteration of the facilities 

 with which antibodies may be formed, which alteration persists 

 for a long time. 



It seems desirable here to make a further reference to the 

 subject already mentioned briefly as " hypersensitiveness to 

 toxins," but now more generally termed anaphylaxis i.e., the 

 opposite of prophylaxis. The term was introduced by Richet, 

 who studied especially the poison of the actiniae, which he found 

 to be extremely powerful, the lethal dose being about -009 gramme 

 per kilo of body-weight. He found that a non-lethal dose increased 

 the susceptibility of the animal to a second injection, and that this 

 hypersensitiveness might last as long as six months after the first 

 injection. This, of course, is quite similar to the phenomena we 

 have described in connection with diphtheria and tetanus, which 

 renders it so difficult to immunize small animals to these sub- 

 stances, and which is the cause of much danger in the early stages 

 of antitoxin formation in the higher animals. Richet has also 

 studied the poison formed by the common mussel, which he calls 

 " mytilo-congestine," and finds exactly similar facts; indeed, it is 

 probable that it is a general phenomenon of all the poisons which 

 can act as antigens. In the case of mytilo-congestine the measure 

 of the hypersensitiveness is simple, since one of the most constant 

 symptoms of its action is vomiting, which occur? almost as soon 

 as the injection is made. He finds that in an animal which has 

 previously been injected the emetizing dose is from a tenth to a 

 quarter of the amount originally necessary. Richet has elaborated 

 a theory to account for this phenomenon, and for anaphylaxis in 

 general. He holds that the condition is due to the presence in the 

 blood of a toxogenic substance, which gives rise to a poison after 

 reacting with the mytilo-congestine injected. This toxogenic sub- 

 stance is not formed immediately, for Richet does not find hyper- 

 sensitiveness to come on for five or six days, and it persists for 

 some fifty days, that being the average duration of the state. He 

 holds that the animal produces antitoxin also, but more slowly. 

 When the toxogenic substance has disappeared the antitoxin 

 remains, and the animal is immune. The main evidence in favour 

 of this theory is the fact that the serum of an anaphylactic animal 

 will produce a similar condition in a second animal. Currie has 



