) , data boos 
et a a a 
478 
In Japan, the insular territory of Formosa which has been invaded by 
plague is now being surveyed by the sanitary officials, and the buildings 
in the central part of Tainan City have already been reconstructed so as 
to keep the rodents out. As a consequence, the ravages of the pestilence 
are now practically confined to the villages or to groups of unsanitary 
habitations of the natives, who live with the rats and permit these animals 
to flourish. 
The following table demonstrates that during a plague epidemic the 
number of infected rats runs parallel with that of the patients dis- 
covered : 
OSAKA, KOBE, 
Patients. Infected rats. Patients. Infected rats, 
May 1 i 0 2 
June 0 0 0 0 
July 0 0 0 0 
August 0 0 2 3 
September 0 5 8 11 
October 6 39 4 17 
November 45 119 36 151 
December 82 634 40 405 
The number of rats examined during the past year in Osaka amounted 
to 1,195,116. Of these, 19 infected animals were found previous to 
May, making a total of 817 in all. In Kobe 553,616 rats Were examined ; 
the number of infected ones can be ascertained from the table. From 
this it may be inferred that the prevalence of the human infection bears 
a direct proportion to the number of infected rats found, and that the 
extent of the epidemic may be known approximately by the area of the 
localities in which infected rats are encountered. 
Our attention is particularly directed to the fact that the fiercest rav- 
ages in every epidemic are evidenced in winter rather than in summer. 
This may be due to the resistance which the pest bacillus has to cold, 
although it appears that this point needs further consideration. A par- 
ticularly interesting fact is that in both Osaka and Kobe the number of 
infected rodents found during the last two months of 1905 was very large 
as compared with the number of plague patients, and also the statistics 
up to the middle of January of this year show a remarkable feature in 
that there were 240 infected rats against three patients in Kobe, and 179 
against nine patients in Osaka. 
During the present epidemic I have had opportunity to make éloge 
observations as to the prevailing conditions, and have discovered an in- 
teresting fact concerning the habits of the rodent. Rats generally live 
on the ceiling below the roof, but in winter they change their abode by 
removing to the ground just below the floor. Therefore, in order to 
discover the openings which harbor the rodents, the ground should be dug 
to a depth of 1 or 2 feet, the rat-holes are thus exposed and the animals 
can be exterminated. This method, owing to the subterranean habit of 
rats in winter, invariably secures a great number. These animals are 
