VACCINATING INJECTION 45 



sera, we asked ourselves if the serum poison was not 

 modified by temperature. We were led to this view 

 still more definitely from the fact that in previous 

 experiments we observed that, when tested a short 

 time after the venesection, the sera were quite as 

 toxic as those of other countries. It appeared from 

 that time very probable that the feeble toxicity of 

 our commercial sera was connected with the 

 raising of the temperature to 5S°-S6° C. which they 

 underwent before being put on the market. To settle 

 the question clearly, it only remained to make an 

 experimental control ; that is to say, it was necessary 

 to choose a serum of fixed toxicity, to submit it to 

 different temperatures, and to follow the modifica- 

 tions of its toxicity Mn the course of the experiment. 

 The complete disappearance of the toxicity at boil- 

 ing-point has been already pointed out by Rosenau 

 and Anderson in their first memoir. These scientists 

 have not, however, stated precisely if their serum, 

 when it had become atoxic, was coagulated or not, 

 a detail which is not without importance. In our 

 experiments we have always worked with uncoagu- 

 lated sera, whatever the temperature to which they 

 were raised. To prevent coagulation we added to 

 I part of serum 3 parts of distilled water. The serum 

 thus diluted was kept for twenty minutes at 100° C 

 When injected into the brain of sensitised guinea-pigs 

 in the maximum dose of 0-25 c.c, the serum thus 

 heated appeared almost harmless. The animals ex- 

 perienced a little discomfort, it is true, immediately 

 after the injection, but they did not shew the slightest 

 symptoms of anaphylaxis . 



Another series of sensitised guinea-pigs were in- 

 jected intracerebrally with the same serum, diluted 

 with 3 volumes of distilled water, but not heated; 

 at the end of two to three minutes all these guinea- 

 pigs succumbed with the most marked anaphylactic 



