164 THE AMERICAN MONTHLY [May 



Since llu'ii it has not a])]>earLMl in lOurojic. In 1S"»4 it oc- 

 curred in Honw- Kon*^ and Canton; in the latter place ISO,- 

 UUO people died. 



The credit of discovering- this oi'ijanisni is due to Yersiii 

 and Kitasato, who worked independently in their investi- 

 <^ations. The oriifanism is known w^ bacillus pfstei bubomcif. 

 It is found in lai'i^X' numbers in the l^ulxi's characteristic 

 of this disease, in the lymphatic g-lands and occasionally in 

 the internal org-ans. It occurs in the blood only in acute 

 hecmorrhag"ic types, shortly before death. 



The org"anism has been cultivated inartificial media and 

 disease resembling- it has been produced in lower animals. 

 It is pathogenic to many animals and during epidemics 

 rats, mice and flies die in large numbers, the disease being 

 apparently transmitted through them. 



It is a short and thick bacillus, somewhat motile, with 

 rounded ends, somewhat motile, and stains with aniline 

 dyes, the ends coloring more deeply than the middle. It 

 does not form spore. It grows well in blood serum, in the 

 form of white moist, iridescent colonies. It grows slowly 

 in gelatin but rapidly in glycerin agar, forming a gra^'ish 

 white surface growth. In bouillon it grows in a very charac- 

 teristic way, resembling the growth jiroduced l)y the ery- 

 sipelas organism. The culture medium appears clear, 

 with white granular deposits on the walls and in the bottom 

 of the tube. 



It is pathogenic for rats, mice, guinea pigs and rabbits, 

 which die usually within two or three days after inocula- 

 tion. The l)acillus soon loses its virulence when grown in 

 artificial media. The virulence of the organism is increas- 

 ed by successive inoculations in certain animal s]iecies. 



We are indel»ted to Yersin, Calmette and Horrell for the 

 antiplague serum. Animals are immunizedagainst the at- 

 tacks of the organism by rejieited intravenous or intraper- 

 itoneal injections of dead cultures or by subcutaneous in- 

 oculation. A horse was immunized in about six weeks. 

 The serum afforded |)rotection to small animals after sub- 

 cutaneous injection of \ iruient cultures, and even cured 



