40 THE AMERICAN MONTHLY [Feb 
that they remained alive when kept dry upon woolen 
threads at 20 °C. for twenty-three days and Yersin found 
that although it could be secured from the soil beneath an 
infected house, at a depth of 4-5 cm., the virulence of such 
bacilli was lost. Kitasato found that the bacilli was killed 
by two hours exposure to 0. 5 per cent. carbolic acid, and 
also by exposure to a temperature of 80 °C. for five min- 
utes. Ogata found that the bacillus was instantly killed 
by 5 percent carbolic acid, and in fifteen minutes by 0.5 
per cent carbolic acid. In 0.1 per cent sublimate solu- 
tion it is killed in five minutes. According to Wyman, 
the bacillus is killed by exposure to 55° C. for ten min- 
utes. The German Plague Commission found that the ba- 
cilli were killed by exposure to direct sunlight for three 
or four hours ; and Bowhill found that they were killed 
by drying at ordinary room temperatures in about four 
days. It seems possible to make a diagnosis of the dis- 
ease in doubtful cases by examining the blood, but it is 
admitted that a good deal of bacteriologic practice is 
necessary for the purpose. Abel finds that the blood may 
yield fallacious results because of the rather variable ap- 
pearance of the bacilli, which are sometimes long,and easi- 
ly mistaken for other bacteria. He deems the best tests 
to be the inoculation of broth cultures and subsequent in- 
oculation into animals, which he advises should have been 
previously vaccinated against the streptococcus. _ 
Plague bacilli persist in the urine a week after conva- 
lescence. Wilson, of the Hoagland Laboratory, found the 
thermal death-point of the organism was one or two de- 
grees higher than that of the majority of pathogenic bac- 
teria of the non-sporulating variety, and that, unlike chol- 
era, the influence of sunlight and desiccation cannot be 
relied upon to limit its viability. Dr. Kitasato’s experi- 
ments first showed that it is possible to bring about im- 
munity to the disease, and Yersin, working in India, and 
Fitzpatrick in New York, have successfully immunized 
