258 BARBER AND TEAGUE. 



was boarded up on all sides to keep out the light and to avoid, 

 to a certain extent, currents of air. The gowns, goggles, and 

 head-cloths were removed after the subjects had left the stable 

 and before they entered the laboratory building. One of the 

 authors attended to the spraying and exposure of the subjects, 

 the other endeavored to keep himself and his laboratory room 

 free from B. prodigiosus and made the necessary plate-cultures 

 in order to determine the result of the test. At first the saliva, 

 taken before and after the spraying, was smeared over agar 

 plates, but later it was found that small pieces of moistened 

 cotton, placed in the nostrils and before the mouth (underneath 

 the Mukden mask) , rendered the test much more delicate. 



Agar plates were exposed during the course of the experiment 

 in order to obtain an indication of the living prodigiosus bacilli 

 that were in the air around the mask at that time. 



The following protocols, selected from a long series of such 

 experiments, demonstrate the general mode of procedure and 

 the results obtained. 



PROTOCOL NO. 1. (experiment NOS. 97 AND 98.) 



Two laboratory boys " served as subjects. Control plates were made as 

 follows: A quantity of saliva was expectorated into a plate containing 

 solidified agar, distributed by means of a sterile cotton plug, and a small 



" The first experiment was performed upon ourselves to demonstrate 

 the harmlessness of the procedure. Then several of our colleagues and 

 about 8 different laboratory boys served as subjects in these experiments. 

 Yet, owing to the large number of experiments that were done, it was 

 found necessary to use the same laboratory boys repeatedly as subjects. 

 However, a period of at least a week was allowed to elapse before a boy 

 was again called upon to serve, and then smears were made from nostrils 

 and saliva to determine whether by any chance Bacillus prodigiosus was 

 present. These tests proved to be in every case negative. In order to gain 

 some idea of the length of time that Bacillus prodigiosus can persist in 

 the mouth, one of us rinsed his mouth with a suspension of prodigiosus 

 (one slant in 10 cubic centimeters of salt solution) and gargled some of 

 the same suspension. Plates inoculated with his saliva at intervals gave 

 the following results: 

 Saliva after three-fourths hour Plate No. 1 : Overgrown with prodigiosus. 



Saliva after 3i hours 1^^!^ ?.°- V Overgrown with prodigiosus. 



I Plate No. 1 : Overgrown with prodigiosus. 



Saliva after 5i hours Plate No. 1 : Overgrown with prodigiosus. 



q -i- n, -lay, [Plate No. 1: 20 colonies of prodigiosus. 



jPlate No. 2: 15 colonies of prodigiosus. 



Saliva after 19i hours /Plate No. 1 : No colonies of prodigiosus. 



jPlate No. 2: No colonies of prodigiosus. 

 Two meals were taken during the course of this experiment. 



