﻿STUDIES IN PLAGUE IMMUNITY. 291 



however, this series of experiments serves to illustrate particularly well 

 the relations between the duration of the infection and results of the serum 

 treatment. 



For example, in the case of rat number 2797 which succumbed from 

 carbolic acid poisoning one-half hour after the injection of the immune 

 serum, an autopsy performed immediately after death showed that nu- 

 merous pest bacilli already had invaded the spleen. This animal had been 

 infected with pest on November 6 and the serum was inoculated two days 

 later, November 8. Eats numbered 2794 and 2798, which were also 

 infected on September 6, died on September 8 of pest infection before 

 receiving serum. At autopsy the infection likewise was found to be 

 well advanced in both animals and innumerable bacilli were present in 

 each instance in the spleen. 



It therefore seems fair to presume that, in a good proportion of the 

 other rats inoculated on November 6 with the same sized dose, the infec- 

 tion had also already advanced to a somewhat similar stage, and therefore 

 probably in many of these animals the pest bacilli had also already invaded 

 the spleen. Nevertheless, 33.3 per cent of those animals which received 

 the serum forty-eight hours after the time of infection survived. There- 

 fore, these experiments demonstrate not only that animals may be saved 

 by the injection of immune serum at a period subsequent to the incurrence 

 of the pest infection, but that animals in which the disease is fairly 

 well advanced may also be saved by the serum, the percentage of deaths 

 varying directly with the length of the interval between pest infection 

 and serum inoculation. 



Choksy, who has a wide experience with the serum treatment of 

 plague, states : 



Much depends upon the early and free use of the serum. In patients injected 

 on the first day or within a few hours of the onset of the symptoms, one injec- 

 tion of 100 cubic centimeters followed by another after 6 to 8 hours and then 

 if necessary by a third after a similar interval, would cut short the attack if 

 the ease be not pneumonic, malignant or septicemic. 



He also emphasizes the fact that the earlier the serum is used, the 

 more efficacious will it be and that if good results are to be obtained 

 from serum therapy the patient must be treated on the first day of the 

 illness. He admits that the serum can not favorably influence all types 

 of plague, or even the malignant forms of the bubonic type, but he shows 

 that it is the only treatment capable of saving a large proportion in a 

 certain class of patients. Therefore, it seems that in man there is a 

 narrow limit beyond which the antiplague serum will not act, but that 

 within this limit its use in man, as in animals, is efficacious. 



Koux, Yersin, and Dujardin-Beaumetz all emphasize that in the serum 

 treatment of plague, as in that of cholera, the injection of the serum 

 must be given intravenously, on the ground that the absorption from 



