VACCINATING INJECTION 55 



intraperitoneally — ^that is to say, a quantity which 

 is 200 to 500 times below the dangerous dose. 



It is important to note that this vaccination by 

 weak doses is extremely rapid; it can be effected in 

 a few hours or even in a few minutes, according to the 

 case. Let us take an example: Suppose a guinea- 

 pig to have been rendered anaphylactic with horse 

 serum. We inject it subcutaneously with 0-05 c.c. 

 of this same serum, which is an amount at least fifty 

 times less than a toxic dose. Of course, the guinea- 

 pig tolerates the injection without symptoms. The 

 animal immediately begins to be immunised, so 

 effectively that, three-quarters of an hour later, it 

 can be injected with a really lethal dose, or even two 

 lethal doses, in the nerve centres, or in the general 

 circulation without its manifesting the sHghtest 

 symptom. The small dose of serum injected sub- 

 cutaneously (0-05 c.c.) performs, therefore, the func- 

 tion of anti-anaphylactic vaccine. 



After the introduction of this small injection of 

 serum anaphylactic immunity is produced with more 

 or less rapidity. The rate of production depends on 

 whether the serum is introduced subcutaneously, 

 intraperitoneally, intrathecally, intravenously, or 

 intracerebrally. Thus, in the guinea-pig it is ac- 

 quired, on an average, four hours after the sub- 

 cutaneous injection, one or two hours after the intra- 

 peritoneal or intraspinal injection, and is, so to speak, 

 instantaneous after the intravenous or intracerebral 

 injection. The following illustration, drawn from 

 veterinary practice, is an example of this method: 



In 1909, Alexandrescu and A. Ciuca^ had to 

 administer anthrax antiserum to 180 head of cattle 

 (150 milch cows and 30 bull calves). These animals 

 had exhibited, at the time of the previous inoculations, 

 particularly serious anaphylactic symptoms. The 

 1 Comptes rend. Soc. de Biol., Ixviii., p. 687, 1910. 



