VACCINATING INJECTION 59 



forty minutes is thereby enabled to tolerate without 

 anaphylactic symptoms an injection one thousand 

 times greater than the lethal dose. 



On November 12, 1910, a series of guinea-pigs was 

 passively sensitised with the serum of a rabbit 

 (1-5 c.c.) which had been given several injections of 

 egg-albumen subcutaneously. On November 13 the 

 lethal dose was established as being 0-002 c.c. of 

 egg-albumen intravenously and 0-005 intracerebrally. 

 In two guinea-pigs of this series we injected in 

 successive doses intravenously, o-ooi c.c, o-oi c.c, 

 0-25 c.c, I c.c, and finally 2 c.c. These injections 

 were made at five minutes' intervals. Two other 

 guinea-pigs, sensitised in the same manner (i.e., 

 passively), were given first o-ooi c.c, then o-oi cc 

 by the jugular vein. Afterwards 0-5 cc was injected 

 intraperitoneally. One hour later 0-25 cc was in- 

 jected into the jugular vein, followed ten minutes 

 after by i c.c Then, three minutes after this, 2 cc 

 of egg-albumen was injected into the jugular vein on 

 the opposite side. These guinea-pigs did not shew 

 the slightest symptoms after the injection of 2 cc. 

 of egg-albumen (diluted with an equal quantity of 

 normal saline solution) whilst the controls succumbed 

 in two or three minutes to an injection of 0-002 cc — 

 that is to say, a dose 1,000 times weaker. 



The guinea-pigs which have been vaccinated in 

 the way we have just indicated straightway resist 

 all tests, however severe they may be. We have 

 injected them with 100 or 1,000 times the lethal dose 

 of serum or egg-albumen intraperitoneally, intracere- 

 brally, intrathecally, or intravenously, but they 

 evince an absolute indifference. 



In the examples quoted the guinea-pigs were 

 vaccinated intravenously or intraperitoneally, but 

 they can be vaccinated just as well, following the 

 same principle, by any of the other routes. Thus, 



