﻿178 STRONG. 



animals employed in this series was not severe, since in some instances, 

 monkeys which had not been protected at all, survived such a method of 

 infection (for an example of this fact see Series 16, p. 188, animals num- 

 bered 1357 and 1358). However, it is true that the two control animals 

 inoculated in Series 5 died of pest infection. In Series 49 (p. 197), nine 

 other monkeys were inoculated by the same method, from 10 to 15 cubic 

 centimeters being injected in each instance. One month after the 

 inoculation, the immunity of the animals was tested and only two were 

 found to resist the infection (numbers 2699 and 2703). 



Because of the superiority of the killed agar cultures over the killed 

 bouillon ones, the reasons for which have already been j:>ointed out, only 

 the former were employed in the remainder of the experiments of this 

 nature. 



Three monkeys in Series 9 (p. 190) were inoculated, each with two 

 48-hour killed agar cultures of the strain "Pest Virulent." Ten days 

 later, upon the injection of 2 oesen of the living virulent organism, all 

 the animals succumbed to the resulting infection. The amount used in 

 testing the immunity of these animals obviously was excessively large, 

 as was shown by later experiments ; therefore, the series does not repre- 

 sent a fair test of the value of this method of immunization. 



The experiments recorded in Series 23 (p. 191) comprise 18 monkeys 

 besides the control animals. The pest organisms in the suspension were 

 not all killed by heating before inoculation, and hence no accurate con- 

 clusions can be drawn from these experiments in regard to the immunity 

 produced by the killed organism alone. The size of the dose used in 

 testing the immunity of the animals was also not sufficiently large. (See 

 remark under Series 23.) 



In Series 25 (p. 192), twenty monkeys were inoculated with from one 

 to two 48-hour agar cultures of the virulent, killed organism. Three of 

 the animals succumbed from the effects of this inoculation. The immunity 

 of the remaining seventeen was tested eighteen days after the primary 

 inoculation, when but four (23 per cent) resisted the infection and 

 remained alive. 



In Series 48 (p. 195), fifteen monkeys were inoculated with one 

 48-hour agar slant of the killed virulent strain. One of these animals 

 succumbed, its death being apparently caused by this inoculation. The 

 immunity of the remaining fourteen was tested one month after the first 

 injection when but four, or 28 per cent, remained alive. 



B. With guinea pigs. — In Series 50 (p. 197), fifteen guinea pigs were 

 inoculated, each with one 48-hour agar culture of the killed virulent 

 organism. Upon testing the immunity of these animals one month later, 

 but four, or 26 per cent, resisted the infection and remained alive. 



No further attempts to immunize larger series of guinea pigs were 

 made with killed cultures since, reasoning from the experiments of other 

 observers as well as from my own, it appears that it is possible to immunize 



