164 THE AMERICAN MONTHLY [May 



Since then it has not appeared in E)urope. In 1894 it oc- 

 curred in Hong- Kong- and Canton; in the latter place 180,- 

 000 people died. 



The credit of discovering this org-anism is due to Yersin 

 and Kitasato, who worked independently in their investi- 

 gations. The organism is known ?^% bacillus pestei bubomc(e. 

 It is found in larg^e numbers in the bubees characteristic 

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

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

 haemorrhagic 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 throug-h 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 g-rows well in blood serum, in the 

 form of white moist, iridescent colonies. It grows slowly 

 in g-elatin but rapidly in glycerin agar, forming a grayish 

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

 teristic way, resembling the growth produced by 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 bacillus soon loses its virulence when grown in 

 artificial media. The virulence of the organism is increas- 

 ed by successive inoculations in certain animal species. 



We are indebted to Yersin, Calmette and Borrell for the 

 antiplague serum. Animals are immunizedagainst the at- 

 tacks of the organism by repeated intravenous or intraper- 

 itoneal iniections of dead cultures or by subcutaneous in- 

 oculation. A horse was immunized in about six weeks. 

 The serum afforded protection to small animals after sub- 

 cutaneous injection of virulent cultures, and even cured 



