318 THE 



and, in addition, the drug has been found to be of decided 

 therapeutic value. Hence it appears that a diminished calcium 

 content of the patient's blood at the time of the injection may be 

 of some importance in bringing about the conditions necessary for 

 the development of the disease. If this is the case, it might 

 account for the symptoms in some cases and not in others, 

 although precipitin might be produced in both. And there are 

 probably other factors which are at present unsuspected, or the 

 use of the calcium salt would be efficacious in all cases. 



The alternative theory is, of course, that the patient gradually 

 becomes hypersensitive to the serum, and that the grade of 

 hypersensitiveness necessary for a reaction is reached before the 

 serum is eliminated from the blood, or, in the case of an im- 

 mediate or accelerated reaction, has not passed off before the 

 second injection is given. It would make it a phenomenon 

 analogous to those of Koch or Theobald Smith. 



A good argument in favour of this theory is the long interval 

 which may occur between the first injection and the second in the 

 case of an accelerated reaction. This may be a year or more a 

 very long period for antibodies to persist in the blood after a single 

 injection of antigen. 



