236 



STRONG AND TEAGUE. 



guinea pigs were placed together in a closed glass cage about .75 

 meter square, the nozzle of the spray introduced at one side 

 of the cage, and the suspension sprayed into the cage for about 

 one minute. Thie position of the nozzle was then changed to the 

 opposite side of the cage, and the suspension then sprayed for 

 another minute. The animals remained in the closed cage about 

 ten minutes after the spraying was discontinued. The other 6 

 vaccinated guinea pigs with 6 controls were sprayed in like 

 manner in a similar cage. While performing all of the spraying 

 experiments referred to in this article, we always wore masks^ 

 and goggles, such as we employed when working with pneu- 

 monic-plague patients during the recent epidemic in Manchuria. 

 Rubber gloves were also worn in handling the animals. 

 The result in this first series of animals was as follows : 



Series I. — Infection by inhalation. 



Vaccinated gniinea pigs. » 



Normal guinea pigs, b 



No. 5268 died in 6 days. 



No. 5348 died in 4 days. 



No. 5269 died in 6 days. 



No. 5349 died in 4 days. 



No. 5270 survived. 



No. 5350 died in 4 days. 



No. 5273 survived. 



No. 5351 died in 5 days. 



No. 5274 survived. 



No. 6352 died in 11 days. 



No. 5275 survived. 



No. 5353 died in 13 days. 



No. 5276 survived. 



No. 5354 died in 4 days. 



No. 5277 survived. 



No. 5355 died in 3 days. 



No. 5278 died in 6 days. 



No. B356 died in 4 days. 



No. 5279 survived. 



No. 5357 died in 4 days. 



No. 5280 survived. 



No. 5358 died in 3 days. 





No. 5359 died in 3 days. 



" Total : 8 survived ; 3 died. 

 " Total : survived ; 12 died. 



In this series 72.7 per cent of the vaccinated animals survived, 

 while all of the unvaccinated control ones died of plague in- 

 fection. 



EXPERIMENT NO. 2. 



On August 10, 1911, each of 24 guinea pigs of a second series was 

 vaccinated with one agar slant of a 48-hour culture of avirulent plague 

 and 23 survived the treatment; one died of an injury. Four weeks later, 

 these vaccinated guinea pigs, together with 24 controls, were subjected 

 to infection by inhalation with a virulent strain of plague. The culture 

 used was originally obtained from a pneumonic-plague necropsy at Muk- 



^ The experiments of Barber and Teague, see XII, p. 255 of this report, 

 demonstrate that this mask (the Mukden type) was not a safe protection 

 while carrying on these inhalation experiments. Fortunately, we escaped 

 pneumonic-plague infection, probably because the spray was not directed 

 toward us but into the cage. 



