VACCINATING INJECTION 67 



to achieve our end we have recourse to intravenous 

 injection. In such cases the use of graduated {i.e., 

 " subintrant ") vaccination is certainly indicated. In 

 place of one injection of serum only, two, three, or even 

 four are made. At each fresh injection, which follows 

 the preceding by a few minutes (three to five), the dose 

 of serum is increased, and, as each new injection 

 further strengthens resistance, we succeed in creating 

 very rapidly a state of anti-anaphylaxis of remarkable 

 stability. The following are some examples: 



A sensitised guinea-pig is given, for the pur- 

 poses of vaccine, 0-025 c.c. of serum intravenously, 

 the lethal dose being 0-05 c.c. After this first injec- 

 tion, which gives rise to no trouble, the animal is able 

 to tolerate, five minutes later, o*i c.c. serum, double 

 the lethal dose. This second injection does duty in 

 its turn as vaccine, and enables the animal to tolerate, 

 two minutes later, 0-25 c.c, or five times the lethal 

 dose. If we wait two minutes more we shall see 

 that the animal can tolerate an intravenous injection 

 of I c.c. — that is to say, twenty lethal doses — and that 

 without the least trouble. All these injections can 

 be made one after the other, without even with- 

 drawing the cannula from the vein. Therefore, in less 

 than ten minutes we succeed by this process in 

 vaccinating against twenty times the amount of the 

 lethal dose. We have been able to satisfy ourselves 

 subsequently that we can vaccinate in this manner 

 against as many lethal doses as we desire. 



Another example may also be cited of guinea- 

 pigs passively sensitised — that is, animals injected 

 with serum from a guinea-pig or a rabbit already 

 sensitised. The degrees of hypersensitiveness of the 

 guinea-pigs in the experiments were such that they 

 succumbed to the intravenous injection of 0*0125 to 

 o -02 5 c .c . We gave one of the guinea-pigs thus passively 

 sensitised graduated inoculations at regular intervals 



