EFFICACY OF VARIOUS MASKS. 



261 



perhaps, only imperfectly plugged with cotton." In this experi- 

 ment the masks are subjected to a much more severe test than 

 would occur in practice; nevertheless, it presents conclusive evi- 

 dence, we believe, that these masks do not offer absolute protec- 

 tion against infection with pneumonic plague. 



PROTOCOL NO. :;. (EXPERIMENTS NOS. C.'J AND 70.) 



February 3. A fresh culture of /?. prodigiosns upon slanted ajirar was 

 suspended in 0.5 per cent sodium chloride solution and about one-half of this 

 suspension was sprayed throuph an atomizer by means of an automobile 

 pump. The spray was directed toward all parts of a small single-roomed 

 stable with the walls boarded up to keep out the light and, to a certain 

 extent, the currents of air. Three minutes after the spraying had been 

 discontinued, two subjects, one wearing our Canton flannel Broquet mask 

 and the other a "Mukden mask" were taken into the room and allowed to 

 remain for ten minutes. The temperature of the stable measured 28° 5 C. 

 The weather was overcast and there had been a drizzling rain of short 

 duration about one hour before the experiment began. 



Number of living B. prodigiosus in the air. 



Time after spraying. 



i to 3 minutes 

 „ , . f3 to 6J minutes 

 , J6J to 9 minutes 

 ■ 19 to 12 minutes 



Number of 



prodigiosus 



colonies. 



Innumerable. 



11,400 



1,416 



472 



63 



12 to 23 minutes 

 Subject No. 1. Canton fiannel Broquet mask 



Saliva taken before exposure 

 Cotton from nostrils before exposure 

 Cotton from nostrils after exposure 

 Cotton before mouth after exposure 



J PI ate No. 

 [Plate No. 

 I Plate No. 

 I Plate No. 

 j Plate No. 

 [Plate No. 

 I Plate No. 

 [Plate No. 



1 : Prodigiosus absent. 

 1 : Prodigiosus absent. 

 1 : Prodigiosus absent. 

 2: Prodigiosus absent. 

 1 : Prodigiosus absent. 

 2: Prodigiosus absent. 

 1 : Prodigiosus absent. 

 2: Prodigiosus absent. 



' In another experiment we obtained further evidence that bacteria may 

 pass directly through the cotton pad of the Mukden mask. Layers of 

 cotton as thick as the Mukden mask, sufficiently wide to cover the entire 

 face and overlapping at the back of the head, were held in place by a 

 many-tailed bandage, no openings in the cotton or bandage being made for 

 the eyes. The remaining portion of the subject's head and his neck were 

 then bandaged with layers of cotton of the same thickness and a suspen- 

 sion of prodigiosus bacilli was sprayed about his head for a period of 

 seven minutes. The bacilli were recovered from the cotton immediately 

 before his mouth and from his saliva. 



