EFFICACY OF VARIOUS MASKS. 263 



Subject No. 2. Canton flannel Broquet viaak. 



„ ,. , , , , [Plate No. 1: Prodigiosus absent. 



Saliva taken before exposure ioii.Mor.j-- l 



[Plate No. 2: Prodigiosus absent. 



^ ^^ . ^ ■, , ~ fPlate No. 1: Proditfiosus absent. 



Cotton from nostrils before e.xposure -li^i ^ xt « r. i- • ■ 



[Plate No. 2: Prodijjiosus ab.sent. 



_, ^^ , , XL r.. I Plate No. 1: Prodigiosus absent. 



Cotton before mouth after exposure ir.! . xt o r» i- • ■ 



[Plate No. 2: Prodijjiosus absent. 



„ . . - i. -I ri. I Plate No. 1: Prodijyiosus absent. 



Cotton from nostrils after exposure {t^, ^ -^r ^ t^ ,■■ 



[Plate No. 2: Prodigiosus absent. 



DISCUSSION OF PROTOCOL NO. .'J. 



This test was an extremely light one. A Petri dish exposed 

 during the first three minutes that the masked subjects were 

 in the room developed only 280 prodigiosus colonies and an- 

 other, during the last three minutes, only 29 colonies. In spite 

 of the small number of living prodigiosus bacilli that were in 

 the air, the Mukden mask failed to hold back all of them. We 

 are inclined to believe that this test is even a less severe one 

 than that to which the masks were subjected during the recent 

 plague epidemic in Manchuria, as the coughing patients in the 

 crowded wards must have been throwing out hundreds of fine 

 droplets almost continuously and, on account of the low temper- 

 ature, the plague bacilli in these droplets must have remained 

 suspended in the air in a viable condition for a considerable 

 period of time. Since we have found repeatedly in tests which 

 were not severe that the Mukden mask allowed bacilli to pass, 

 we are forced to the conclusion that the sense of security felt 

 by those who wore this mask in the Manchurian epidemic was not 

 justified. 



PROTOCOL NO. 4. 



This experiment was carried out in a cold-storage room measuring about 

 2.5 by 3 meters at a temperature of 12 °C. A 24-hour agar-culture of pro- 

 digiosus was suspended in about 40 cubic centimeters of 0.5 per cent sodium 

 chloride solution and filtered twice through cotton. A portion of this sus- 

 pension was sprayed by means of a throat atomizer connected by rubber 

 tubing with a two-cylinder force-pump such as is used in filling automobile 

 tires. The spraying was continued for a period of two minutes, the spray 

 being directed toward all portions of the room. The pump was then re- 

 moved and the door of the cold room quickly closed. A period of two hours 

 was allowed to elapse, and then the three masked boys were hurried 

 into the room and the door was closed behind them. They remained ten 

 minutes in the room. During this time each held in his hand an open 

 Petri dish containing solidified agar and closed it immediately after leaving 

 the cold room. 



Boy No. 1 wore a Mukden mask, boy No. 2 our Canton flannel Broquet 

 mask. The usual measures against accidental contamination with B. pro- 

 digiosus were adopted. Boy No. 3 wore a mask of wet gauze. Strips of 



