﻿XL THE ANTI-INFECTIOUS POWEE OP PLAGUE SERUM. 



Since the report of Yersin, Calmette and Borrel in 1895, 88 practically all 

 observers have recognized what may he termed the anti-infectious action of 

 plague imnrane serum. The disputed point has been rather in regard to 

 the extent of its curative value. As has already been mentioned, it was 

 considered advisable to investigate to what amount these anti-infectious 

 substances became developed in the blood of animals which had been im- 

 munized to plague infection by vaccination, and in others immunized 

 in the same manner and the immunity of which to plague infection had in 

 addition been tested, in order to ascertain whether or not these substances 

 could be demonstrated in the blood of such animals in sufficient quantities 

 for the method of their detection to be used as a test of the degree of 

 immunity obtained in the serum of human beings vaccinated against 

 plague. The method employed in investigating this question was as 

 follows : A rat was inoculated intraperitoneally or subcutaneously with the 

 serum to be tested - while at the same time the animal was infected by 

 thrusting beneath the skin near the tail a syringe needle which had been 

 dipped in a suspension of the virulent pest organism. Numerous control 

 animals were inoculated in all the series. Eats were used rather than 

 mice in these experiments, since a much more accurate determination of 

 the value of plague serum can be made with these animals than with mice. 

 However, even with rats there is considerable individual variation in regard 

 to their reaction to plague immune serum. Sometimes, after infection, 

 one rat will be saved by a dose of serum, whereas another one of the 

 same size and which has received the same amount of it will succumb. 

 For this reason it is difficult and sometimes impossible accurately to 

 determine the dose of serum which is just sufficient to save the animals. 

 The method used in testing the protection obtained by the rats from the 

 serum inoculations was somewhat more severe than that which has been 

 used by other observers, the infecting needle employed in my experiments 

 being larger; however, in spite of this, it is recognized that the values of 

 the immune sera which I have experimented with were not high; a fact 

 which may be seen from a study of the tables. 



The details of the experiments are given in Series 8, 10, 13, 14, 15, 

 19, 20, 22, 27, 45, 53, and 57 (pp. 274 to 288). 



83 Ann. d. I'inst. Pasteur (1895), 9, 589. 

 272 



