PROTECTIVE INOCULATION. 



235 



inoculation in order to retest the value for immunization against cutaneous 

 infection of the culture used for the vaccination in the experiments re- 

 corded in this paper. The 12 remaining vaccinated guinea pigs were 

 subjected to infection by inhalation on the same day. The virulent culture 

 used was isolated from our human case (No. 9) of pneumonic plague at 

 Mukden. The culture was passed through a guinea pig and a monkey, and 

 fresh cultures on agar from the monkey's blood were employed in the 

 experiment. 



The 11 vaccinated guinea pigs, together with 12 normal guinea pigs 

 as controls, were subjected to cutaneous inoculation in the following 

 manner: The growth of one agar slant of the virulent culture just described 

 was suspended in 5 cubic centimeters of peptone solution and 5 oesen of this 

 suspension were rubbed over the shaved and scarified abdomen of each 

 of the guinea pigs. The result was as follows: 



Cutaneous infection. 



Vaccinated gruinea pigrs. ■ 



Normal gruinea pigrs. >> 



No. 6281 survived. 



No. 5360 died in 5 days. 



No. 5282 died in 13 days. 



No. 5361 died in 10 days. 



No. 5283 survived. 



No. 5362 died in 3 days. 



No. 5284 survived. 



No. 5363 died in 10 days. 



No. 5285 died in 14 days. 



No. 5364 died in 8 days. 



No. 5286 died in 7 days. 



No. 5365 died in 6 days. 



No. 5287 died in 6 days. 



No. 5366 died in 9 days. 



No. 5288 survived. 



No. 5367 died in 4 days. 



No. 5289 died in 7 days. 



No. 5368 died in 6 days. 



No. 5290 survived. 



No. 5369 died in 5 days. 



No. 5291 survived. 



No. 5370 died in 3 days. 





No. 6371 died in 6 days. 



» Total : 6 survived ; 5 died, 

 b Total : survived ; 12 died. 



Fifty-five per cent of the vaccinated guinea pigs and none of 

 the controls survived. This experiment merely demonstrated 

 the immunizing value of the culture against cutaneous or bubonic 

 infection. It is desired to emphasize again the fact that guinea 

 pigs can usually only be successfully immunized against cuta- 

 neous or • bubonic infection by means of a living attenuated 

 culture. Only a very few of the animals inoculated with killed 

 cultures, when exposed to infection, survive. 



For the purpose of testing the immunity of the remaining 12 

 vaccinated guinea pigs against pneumonic infection, the growth 

 of two agar slants of the virulent culture described above was sus- 

 pended in 30 cubic centimeters of normal saline solution. This 

 was placed in a glass receiver of an ordinary nasal spray. Air 

 was supplied by a hand-force-pump and rubber tubing connection. 

 The suspension could, in this manner, be sprayed in a fine vapor 

 for a distance of several feet. Six vaccinated and six normal 



