VACCINATING INJECTION 5S 



In other words, the addition of two doses of toxin, 

 of which one is definitely lethal, made at one to two 

 hours* interval, destroys all the harmful action of 

 this toxin. There was here a kind of phenomenon of 

 interference which till then was only recognised by 

 physicians. Setting aside the hidden mechanism of 

 this phenomenon, which appeared very obscure to us 

 at that time, we immediately set to work to utilise 

 the facts with a view to defence against anaphylactic 

 shock. This was the starting-point for our procedure 

 of vaccination by small graduated doses. But before 

 explaining this process it will be useful rapidly to 

 recapitulate the experiments which, historically, have 

 preceded it. 



In the course of researches on the relations between 

 the toxicity and temperature of sera, we have proved 

 that heated sera are so much the less toxic in propor- 

 tion as they are brought to a higher temperature; 

 and, furthermore, that an intimate relation exists 

 between the toxicity of the sera and the duration of 

 the heating. In studying concurrently the action of 

 the temperature on the vaccinating power of sera 

 from the point of view of anaphylaxis, we observed 

 that the sera could be raised to a considerable tem- 

 perature without perceptibly deteriorating the vacci- 

 nating power. Without entering into the detail of 

 these experiments, we may say that the serum, even 

 when heated to 80° C , is yet shown to be endowed with 

 the peculiar quality of protecting against anaphylactic 

 shock. It has the advantage over unheated serum 

 that it possesses a minimum toxicity; even in in- 

 creased doses this heated serum does not give rise to 

 the slightest symptoms in sensitised guinea-pigs. It 

 is sufficient, then, to inject prophylactically, for 

 example, 3 c.c. of horse serum heated to 80° C. into 

 a hypersensitive guinea-pig, subcutaneously or intra- 

 peritoneally, to render it absolutely immune to the 



