EFFICACY OF VARIOUS MASKS. 257 



relief on removing it. We shall designate this type of mask 

 in the discussion to follow as the "Mukden mask." ^ 



The following experiments were undertaken with the idea of 

 determining whether this Mukden mask is, in fact, an efficient 

 barrier against the passage of plague bacilli into the lungs and, 

 also, whether or not other types of masks are more efficient. 



At the International Plague Conference held in Mukden in 

 April, 1911, Broquet, the French delegate, demonstrated a mask 

 "copied from those used by doctors in the epidemic of the four- 

 teenth century as shown in old books." ^ It consisted of a hood 

 of light canvas or khaki cloth, covering the entire head and 

 drawn in at the neck. In front was a window of mica. No 

 experiments had been performed to test the efficacy of this mask. 

 We shall refer to this type of mask hereafter as the "Broquet 

 mask." It was not used during the recent epidemic of pneu- 

 monic plague in Manchuria with the exception of a few times 

 by Broquet himself. 



Our preliminary tests indicated that a hood of heavy Canton 

 flannel with a nap was more effective in holding back Bacillus 

 pj-odigiosus than hoods of lighter cloth such as the one demon- 

 strated by Broquet. Instead of mica for the window, we used 

 sheet celloidon such as one sees in the storm curtains of auto- 

 mobiles. The hood was made narrow at the neck so that it 

 would spread out over the shoulders and could be dravni in 

 and tied snugly around the neck. Comparative experiments were 

 made with this mask and the Mukden mask; the subjects wear- 

 ing the two masks were forced to breathe air containing Bacillus 

 prodigiosus simultaneously for the same length of time. 



Bacillus prodigiosus was selected for the experiments as being 

 entirely harmless and easily recognizable on account of its pig- 

 ment production. An ordinary throat atomizer was used for 

 making the spray, but with the idea of getting smaller droplets 

 the rubber bulb was removed and a stronger airblast was 

 obtained by using an automobile pump. 



Special precautions were taken to avoid accidental contami- 

 nation with B. prodigiosus on removing the mask. (See Plate 

 V, fig. 2.) The subject was clothed in an operating gown and, 

 in the case of the Mukden mask, his head was covered with a 

 cloth and the eyes protected by automobile goggles. The spray- 

 ing was generally done in a small, single-roomed stable which 



* We were informed that this mask was extensively used in Harbin 

 before its introduction into Mukden. 



' Report of the International Plague Conference, p. 303. 



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