316 BACTERIOLOGY. 



of mixed infection the pest bacilli are said to stain less 

 intensely with alkaline methylene-blue than do the 

 streptococci, and more intensely than do the staphylo- 

 cocci that are present. Also, in this event, the strepto- 

 cocci retain the Gram stain, while the pest bacilli do not 

 and the staphylococci may or may not. It has been 

 suggested that possibly the organisms found by Kitasato 

 in the blood, and which he describes as pest bacilli, 

 that retained the color when treated by the method of 

 Gram, were pairs of micrococci, and not bacilli at all. 



It is the opinion of Aoyama that the suppuration of 

 the glands is not caused by the plague bacillus, but is 

 rather the result of the action of the pyogenic cocci 

 with which it is so often associated. It is also his 

 belief that the most important and frequent mode of 

 infection in man is through wounds of the skin. He 

 does not regard either the air-passages or the alimentary 

 tract as frequent portals of infection. Wilm, on the 

 contrary, is inclined to regard the alimentary tract as a 

 frequent portal of infection ;^ and subsequent investiga- 

 tions leave little doubt that infection occasionally occurs 

 through the respiratory tract. 



The order in which the lymphatics manifest disease 

 appears to depend upon the location of the primary 

 infection. That is to say, if it is upon the feet, as of 

 persons who go barefooted, the superficial and deep 

 inguinal glands are the first to show signs of the dis- 

 ease ; while if infection occurs through wounds of the 

 hand, the buboes appear first in the axillary region. 

 As a rule, the wound through which infection is re- 

 ceived shows little or no inflammatory reaction.^ 



1 Wilm : loc. cit. 



2 The works of Yersin, of Kitasato, and of Aoyama have been ?5- 



