﻿STUDIES IN PLAGUE IMMUNITY. 313 



Series 60. — Showing the attenuation of the strain "Pest Virulent," etc. — Continued. 



Animal 

 No. 



Inoculated. 



Result. 



Autopsy and remarks. 



3029 



3030 

 3031 



3032 



3033 



3034 

 3139 



3140 

 3141 

 3142 

 3143 

 3144 

 3145 



3146 



3147 



3148 

 3149 



Jan. 29, one agar slant culture "Pest Viru- 

 lent" (attenuated 14 months) subcuta- 

 neousiy. 

 do 



Dead Feb. 5, 

 after 7 days. 



Dead Feb. 4, 

 after 6 days. 



Dead Feb. 11, 

 after 13 days. 



Dead Feb. 9, 



after 11 days. 



Alive and well— 



.do 



Large suppurating 

 bubo in abdominal 

 wall. 



Large cyst like bubo. 



Advanced pest pneu- 

 monia. 



Subacute pest. 



Large bubo. Subacute 

 pest. 



Subacute pest. 



Do. 

 Not of pest infection. 



Acute pest infection. 



Jan. 29, one-half agar slant culture "Pest 

 Virulent" (attenuated 14 months) subcu- 

 taneously. 



do 



Jan. 29, one-fourth agar slant culture "Pest 

 Virulent" (attenuated 14 months) subcu- 

 taneously. 

 do _. 



Apr. 25, one-half agar slant culture "Pest 

 Virulent" (attenuated 17 months) subcu- 

 taneously. 

 do _ 



Dead May 6, 

 after 11 days. 



Alive and well.. 

 do 



do . 



do ... 



.do 



do .. . 



do . . 



do .. .... l. 



do 



do 



Dead May 6, 



after 11 days. 

 Dead May 3, 



after 8 days. 

 Dead Apr. 26, 



after 1 day. 

 Alive and well- 

 Dead Apr. 30, 



after 5 days. 



do 



.... do 



....do 



Apr. 25, one-tenth oese "Pest Virulent" 

 (original) rubbed over abdomen. 



STABILITY OP VIRULENCE OP THE PLAGUE BACILLUS. 



These experiments, relating to the artificial attenuation of the pest 

 bacillus in cultures, as well as those performed on animals with the 

 view of increasing the pathogenicity of this organism all demonstrate its 

 great stability of virulence. 



In respect to this phenomenon, it is interesting to compare the behavior 

 of the cholera organism with that of the pest bacillus, both in its growth 

 on artificial media and in successive passages through the animal body. 

 The cholera organism if left for a few months on culture media such 

 as agar, soon loses its virulence and indeed, frequently dies out, largely 

 owing to the autolytic digestion of the bacteria which takes place. If, 

 instead of allowing the spirillum to remain in the original tube in which 

 it was inoculated, it is transplanted for a number of times on agar, a rapid 

 loss of virulence is also obtained. On the other hand, this virulence 

 can quickly again be increased by successive passages of the culture 

 through a series of a species of animal such as the guinea pig, and in 



