138 STRONG AND TEAGUE. 



In the course of the experiments, on a number of occasions 

 during coughing, small droplets or larger particles of sputum, 

 visible to the eye, were expelled, and touched the surface of 

 the media in the Petri dishes which were exposed before the 

 plague patient. The study of these cultures obviously is not 

 included in this investigation. The Petri dishes containing agar 

 were invariably exposed before cases of pneumonic plague with 

 bloody sputum, in which enormous numbers of plague bacilli 

 had been showm to be present. All of the cases before which 

 the plates were exposed died of plague infection within twenty- 

 four to forty-eight hours from the time of the exposure. Twelve 

 series of experiments have been performed in which 82 plates 

 containing agar were exposed and in 78 the microorganisms 

 which have developed upon them studied as far as was prac- 

 ticable. 



The experiments were performed in the following manner: 

 The plates were sterilized in the hot-air sterilizer within a metal 

 plate-holder. They were then removed, the agar-cultures melted 

 and poured in the usual way, and, as soon as the medium was 

 sufficiently hard, were replaced within the plate-holder and taken 

 to the bedside of the patient in whose sputum plague bacilli 

 had previously been found. All of the attendants were asked 

 to retire from the ward in order that as little dust as possible 

 might be present in the air. The condition of the patient before 

 whom the plates were exposed was noted, and during the ex- 

 posure of the plate the character of the respirations was par- 

 ticularly observed and notes made of whether coughing or talking 

 occurred. The time of the exposure of the plate and the distance 

 from the patient were also recorded in each instance. After the 

 exposure, the plate was returned to the holder and placed in the 

 incubator. Twenty-four hours later the plates containing the 

 culture-media were examined for the appearance of colonies and 

 the number of colonies counted, but the plates were not usually 

 opened until after forty-eight or seventy-two hours. The colonies 

 were then again counted and carefully studied. Any of the colo- 

 nies which in any way resembled colonies of the plague bacillus 

 were transplanted to slants of agar. The morphology and stain- 

 ing properties of the organisms on the plate- and agar-slant- 

 cultures were then studied. In every instance in which the 

 morphology was at all similar to that of the plague bacillus or the 

 organism decolorized by Gram's stain, it was inoculated either 

 into mice or guinea pigs. In a number of cases the colonies were 

 so thick on the plate, or surface growths from contamination 



