EFFICACY OF VARIOUS MASKS. 259 



portion spread thinly over a second auar plate. Both plates were preserved 

 for ji:ro\vth and examination. At the same time the nostrils were swabbed 

 with a small pledj;-et of sterile cotton moistened with salt solution and this 

 rubbed over solidified apfar. (In no case was B. prodigioaus obtained from 

 the nostrils or saliva in these controls taken before spraying.) 



The boys were clothed with operating gowns. 



Boy No. 1 wore a Mukden mask consisting of two and one-half layers 

 of Johnson and Johnson absorbent cotton. Thin layers of this cotton 

 in Petri dishes were steamed in an Arnold sterilizer and then placed 

 in the ice box so that water would condense upon the cotton and inside 

 of the Petri dishes. A portion of the cotton thus moistened was placed 

 in approximately the center of the mask between the layers of the 

 cotton, so that when the mask was in place it lay before the mouth 

 and nostrils. Small bits of the moist cotton were placed within the nos- 

 trils and a larger piece before the mouth and nostrils. This latter piece 

 was held -in place by the mask. Small pieces of dry absorbent cotton 

 were placed on each side of the nose and then the Mukden mask was 

 tied in place. Automobile goggles were worn over the eyes. The ex- 

 posed portion of the head above the mask was covered with a cloth. 



Boy No. 2 wore a Broquet mask of heavy Canton flannel cloth. This 

 hood had been used in a number of previous experiments after each of 

 which it had been disinfected in lysol solution and placed in the sun to 

 dry. Small bits of the steamed moist cotton were placed loosely within 

 the nostrils, and as in the preceding instance a larger piece of the same 

 cotton was placed over the mouth and nostrils. This was held in place 

 by a strip of gauze which was tied at the back of the head. A straw 

 hat was placed on the boy's head, and the mask was then put on and tied 

 in snugly around the neck. (See Plate V, fig. 2.) 



The two boys, thus masked, were taken into a stable with the walls 

 boarded up to keep out the light and to prevent currents of air. A sus- 

 pension of prodigiosus bacilli in 0..5 per cent sodium chloride solution 

 (1 agar slant in about 40 cubic centimeters) was sprayed by means of 

 a throat atomizer connected with an automobile pump. The spray was 

 directed alternately toward one mask and then the other for a period of 

 three minutes. The boys were then brought back to the laboratory. But 

 the gowns, goggles, and head-cloths were removed before they entered 

 the laboratory building which was only a few meters away. This was 

 done in order to prevent a possible contamination of the test culture 

 plates with prodigiosus bacilli which might have become scattered in 

 the air while the masks were being removed. (The gowns and cloths 

 were sterilized in an autoclave at 120 °C. before they were used in the 

 next experiment.) 



The subjects then proceeded to the door of the laboratory room where 

 the masks were removed and cultures made as follows: 



The cotton taken from before the mouth, that from the nostrils, and, 

 in case of the Mukden mask, that from the interior of the mask were 

 transferred by sterile forceps to separate Petri dishes containing solidified 

 agar, and rubbed over the surface of the agar. Each mass of cotton 

 was then transferred to a second Petri dish well wet with salt solution 

 and rubbed over the second plate and left on the surface of the media. 



