STUDIES ON PNEUMONIC PLAGUE AND PLAGUE 

 IMMUNIZATION. 



XII. SOME EXPERIMENTS TO DETERAIINE THE EFFICACY OF 



VARIOUS MASKS FOR PROTECTION AGAINST 



PNEUMONIC PLAGUE. 



By M. A. Barber and Oscar Teague. 

 {From the Biological Laboratory, Bureau of Science, Manila, P. I.) 



During the epidemic of pneumonic plague which raged in 

 Manchuria during the winter of 1910 to 1911, it was believed 

 and, toward the close of the epidemic, was experimentally de- 

 monstrated, by Strong and Teague, that sputum in the form of 

 invisible droplets containing viable plague bacilli was frequently 

 suspended in the air near the coughing pneumonic-plague pa- 

 tients. A Petri dish, containing solidified agar-culture-medium, 

 held for a minute or two before the mouth of a patient 

 and closed after a single cough did in some instances on in- 

 cubation show numerous colonies of plague bacilli, although no 

 visible particles of sputum had been thrown against it.^ There 

 was every reason to believe that even the smallest number of 

 these bacilli inhaled into the lung would lead to infection and 

 that this was, in fact, the common mode of infection in pneu- 

 monic plague. The obvious method to protect against such infec- 

 tion was to interpose a barrier to the passage of these droplets 

 into the mouth and nostrils. With this object in view, masks 

 were worn quite generally by physicians and attendants when 

 in the presence of plague patients or suspected cases. That 

 protection was afforded by the masks apparently went unques- 

 tioned and, without the sense of security that their use gave, the 

 mental strain in connection with the work would have been 

 almost unbearable. 



The total number of deaths that occurred among physicians, 



' Report of the International Plague Conference held at Mukden, April, 

 1911. Manila (1912), 83. See also II, p. 137 of this report. 



255 



