﻿244 STRONG. 



1247, 1286, 1287, 1300, 1301, 1302, 1357, 1358), in which an attempt 

 was made gradually to immunize these animals with the strain "Pest 

 Virulent" up to such a degree that these anti-bodies would be demon- 

 strable in their blood, only two were able to survive the inoculations 

 when the immunization had reached the point in which the agglutinins 

 could be detected even in small amounts, (lumbers 1300 and 1357. 

 See agglutination experiments, p. 246.) The remaining ten animals 

 succumbed either to pest infection or intoxication as a result of the 

 injections, before agglutinins could be shown to exist in their blood. 

 Moreover, notwithstanding the fact that from i to 4 oese of this strain 

 "Pest Virulent" represented a certain lethal dose for normal animals of 

 this species and although these monkeys were immunized to such an 

 extent that in a number of instances they were able to resist and survive 

 the inoculations of such large amounts as 6 to 8 oesen of this organism 

 (over twelve times the maximum fatal dose), agglutinins were still not 

 present in sufficient quantities to be demonstrable in their blood. 



Only small quantities of agglutinins could be detected in the exam- 

 ination of several pest immune sera which were prepared from horses 

 and which were known to possess, in two instances at least, considerable 

 protective (anti-infectious) power. 



A horse which was being immunized against pest and which had 

 acquired a sufficient immunity to withstand the injection of nearly 10 

 agar cultures of a virulent pest strain, gave a serum which at this time 

 showed an agglutinative reaction in dilutions of 1 to 10, but none above 

 this strength. However, at the same time 1 cubic centimeter of this 

 serum protected from fatal pest infection about 60 per cent of the white 

 rats inoculated. (See Series 45), p. 284. A pest immune serum 

 obtained from Asia, which protected about 72 per cent of the inoculated 

 rats against fatal pest infection in doses of from 1 to 2 cubic centimeters 

 (see Series 8, 10, and 20, pp. 274, and 281), when carefully tested 

 with the virulent pest strain showed no agglutinative reaction after three 

 hours. However, it must be stated that at the time its anti-infectious 

 and agglutinative reactions were tested this serum had been bottled 

 for about a year. A second pest serum purchased from Asia which 

 showed a somewhat lower protective power (see Series 27, p. 283) also 

 revealed no agglutination when tested with the strain "Pest A virulent." 

 This serum had been bottled about nine months. "Moreover, a laboratory 

 immune serum which possessed a higher anti-infectious power and which 

 protected about 90 per cent of the inoculated white rats against plague 

 infection (see Series 53, p. 286) in doses of 1 cubic centimeter also 

 showed almost no agglutinative reaction against the virulent strain giving 

 only a weak reaction in a dilution of 1 to 10. 



The following selected experiments justify the preceding remarks upon 

 agglutination. Experiments performed with a number of animals less 



