( ¢cxv ) 
There are other members of the present section of Prervs, 
but those that I have mentioned are the only ones that I have 
been able to submit to microscopic examination. Pvreris 
limona, recently described by Schaus from Costa Rica (Proc. 
Zool. Soc. Lond., 1913, p. 356, Plate LII, fig. 5) appears to be 
a Central American representative of P. bumae or P. diana. 
Tue METHOD BY WHICH FLEAS INFECT WITH PLAGUE.— 
Mr. A. Bacot exhibited slides showing the development of 
Plague bacilli in the alimentary canal of the Flea, and the 
method of infection through the mouth, and read the following 
paper :— 
The conclusion that fleas are the responsible agents in the 
transmission of Bubonic Plague from animal to animal, first 
arrived at on epidemiological grounds by Ogata (1897), Simond 
(1898), Ashburton Thompson (1900), and Liston (1905), has 
received abundant proof at the hands of later workers, among 
whom may be named Gauthier and Raybaud (1902-3), 
Verbitzki (1904), and the Commission for the Investigation 
of Plague in India (1906-7). Simond’s initiatory experiments 
in flea infection have been confirmed by an overwhelming 
weight of testimony. | 
It was found that the bacilli multiplied freely in the stomach 
of the flea, but the exact method of infection was left in some 
doubt. In the absence of any definite proof of transmission 
through the mouth, the general consensus of opinion tended 
to the view that plague bacilli, voided by the flea with its 
faeces, came in contact with punctures made by fleas, or found 
entrance through abrasions in the skin caused by the animal 
scratching itself. 
Experiments undertaken by Dr. Martin and myself, with a 
view to testing the possibility of mouth infection, were per- 
formed with specimens of Ceratophyllus fasciatus and Xeno- 
psylla cheopis under conditions that precluded the possibility 
of infection by the fleas’ dejecta. The results satisfactorily 
establish the fact that mouth infection does occur, and suggest 
the conclusion that it is not only a possible, but perhaps the 
general, method by which the disease is spread. 
It is not necessary for me to describe our experiments and 
methods in detail, as an account will shortly be available in 
