472 
the destruction of rats by buying all which are killed or captured 
by the people. This practice has a twofold purpose—one the prevention 
of an epidemic, and the other the ascertaining whether any infected 
animals, the presence of which usually precedes an epidemic among 
men, are existent. An immense number of rats is bought by the Govern- 
ment and each one of them is examined bacteriologically. (Pls. Nos. 
XIV-XVI picture their examination in the laboratory of the ‘Tokyo 
Metropolitan Police Board.) In this latter place from 3,000 to 4,,000 
rodents are examined daily even in ordinary times, but when an, 
epidemic occurs the number is increased to an enormous figure. As 
plague outbreaks in Japan are usually preceded by rat infection, these 
examinations are to be regarded somewhat in the light of a reconnois- 
sance. The utility of this precaution is illustrated by the fact that in 
1904 an infected rat was discovered in Yokohama before any human 
victim had been found and as a result the source of the infection was 
sought and finally traced to a British steamer, the warning being given. 
in time. During epidemics, the examination of rats is even more 
necessary, for it is only by such a process that the condition and the 
manner of propagation of the pestilence are actually known. 
To judge from the experience of the past, it can be suggested that in 
examining rats particular attention should be paid to their submaxillary 
and cervical glands and to the spleen. ‘These organs in most cases show 
the evidence of infection, if there be any. The inference to be drawn 
is that the rat receives the plague germ through the mucous membrane 
of the mouth and throat. 
An important work during an epidemic is the bacteriological exami- 
nation of specimens obtained from the patients and the dead, for the 
diagnosis must depend upon both clinical and bacteriological observa- 
tion. In suspicious cases, material for investigation is taken from 
the affected parts, such as the glands or skin. The sputum of the 
patient is also frequently subjected to examination. In the dead, the 
heart’s blood and spleen and the contents of the glands or lungs are 
scrutinized. Microscopical examinations are undertaken, cultures are 
made and animal experiments are performed with the specimens which 
are gathered. Agglutination by a pest serum, of the bacteria obtained 
is also studied. Obviously it is often difficult to assure one’s self of 
the discovery of an infection by any of these means, but there are many 
cases on record where suspicious substances such as cotton, filth, and 
rotting grain harbored the Bacillus pestis; as an illustration I will cite 
the fact that in 1899, in Osaka, cotton waste was found to contain the 
plague organism. 
The searching for patients, especially when the first invasion of plague 
is suspected, is also an important portion of the preventive work. Phy- 
sicians are expected by law to report any infectious disease which they 
discover, but such reports are in most cases not reliable; indeed, during 
