﻿180 STRONG. 



ANIMAL EXPERIMENTS. 



As with the killed pest organism, monkeys and guinea pigs were 

 employed in my experiments on animals with attenuated cultures of the 

 pest bacillus. 



Experiments on the immunization of monkeys with the strain "Pest 

 Avirulent." — Six monkeys in Series 4 (p. 199) were inoculated subcuta- 

 neously, each with one 24-hour agar culture of the strain "Pest Avirulent." 

 The immunity of the animals was tested ten days later, four being inocu- 

 lated by thrusting beneath the skin a needle infected with virulent pest 

 bacilli and two (numbers 1232 and 1233) by lightly scarifying the ab- 

 domen with a scalpel infected with this same organism. Since two control 

 animals (numbers 1286 and 1287) also inoculated at this time in the 

 latter way did not die, the monkeys numbers 1232 and 1233 can not 

 necessarily be considered immune. Three of the four vaccinated animals 

 wounded with the infected needle survived, while but one of four controls 

 inoculated in the same manner recovered. The conditions encountered 

 in this series are somewhat analogous to those met with in Series 5 

 (p. 189), where the killed organisms were employed. 



Five monkeys in Series 11 (p. 200) were vaccinated, each with one 24- 

 hour agar culture of "Pest Avirulent" and eleven days later their immu- 

 nity was tested by the inoculation of 2 oesen of "Pest Virulent." Four of 

 the animals died and one survived. The course of the disease in three 

 of those which died was prolonged to twice the length of that in the 

 control animals. In two (numbers 1277 and 1280) the blood serum 

 had evidently acquired considerable anti-infectious power against the 

 pest bacillus; this was presumed to be the case from the distribution of 

 the bacteria at autopsy and from the fact that in one instance the heart's 

 blood was sterile and in the other but six colonies of this organism 

 developed in cultures from the heart's blood. Hence, these animals 

 probably died rather from pest toxsemia than of septicaemia. Their blood 

 may have acquired considerable anti-infectious power with but little anti- 

 toxic action. Obviously, the dose (2 oesen) employed in testing the 

 immunity was exceedingly large. This series of experiments may be 

 compared with Series 9 (p. 190), in which the animals immunized with 

 dead bacilli all succumbed upon reinoculation with 2 oesen of the virulent 

 strain. 



In Series 12 (p. 201), nine monkeys were inoculated subcutaneously 

 with from one to two 24-hour agar cultures of the strain "Pest Avirulent." 

 One of the animals (number 1299) died twelve hours after the vaccination, 

 of a streptococcus and staphylococcus infection which had existed prior 

 to the vaccination. The immunity of the remaining eight was tested ten 

 days after the vaccination, either by the inoculation of 4 or of 1 oese of 

 the strain "Pest Virulent." Four of the animals remained alive and 

 well, and four died. In those which died, the course of the infection 

 was greatly prolonged beyond that in the control monkeys and the pest 



