826 PATHOGENIC MICROORGANISMS 



could be secured, the indications are that the vaccine has been of 

 great value. In. one town in India, 794 individuals were inoculated, 

 and 286 uninoculated, and among the inoculated there were only 

 twelve cases and three deaths, while among the smaller number 

 of the untreated, thirty cases developed and twenty-five died. In 

 one house there were four vaccinated and three unvaccinated. All 

 of the unvaccinated died, and only one of the vaccinated contracted 

 the disease and he recovered. A number of similar studies are cited 

 by Major Liston. There seems, therefore, to be very little doubt 

 as to the protective value of some form of plague vaccination. 

 Whether or not the Haffkine virus is the most useful and final 

 method, cannot of course be stated at the present time. 



THE PLAGUE-LIKE DISEASE OF RODENTS (McCOY) 32 



Bacterium Tularense (McCoy and Chapin) 33 



McCoy has described a disease occurring in Californian ground 

 squirrels (Citellus beechyi) which presents lesions very similar to 

 those of plague in these animals. In fact the disease was noticed 

 in the course of the systematic examination of rodents by McCoy 

 at the Federal Laboratory in San Francisco. Although McCoy was 

 able to transmit the disease to guinea-pigs, mice, rabbits, monkeys, 

 and gophers, and plague-like lesions could be produced in most of 

 the animals, he was at first entirely unable to cultivate any organism 

 from these lesions. In 1912 McCoy and Chapin finally succeeded 

 in growing the specific bacterium on an egg medium made entirely 

 of the yolk. Morphologically it is a very small rod, 0.3 to 0.7 micron 

 in length and often capsulated. The rods stain poorly with 

 methylene blue, better with carbol fuchsin or gentian violet. They 

 are found in large numbers in the spleen of animals dead of the 

 disease. 



THE BACILLI OF THE HEMORRHAGIC SEPTICEMIA GROUP 



In many of the lower animals there occur violently acute bacterial 

 infections characterized by general septicemia, usually with petechial 

 hemorrhages throughout the organs and serous membranes and 

 severe intestinal inflammations. These diseases, spoken of as the 

 "hemorrhagic septicemias, " are caused by a group of closely allied 



82 McCoy, U. S. Public Health, Bull. 43, 1911. 



83 McCoy and Chapin, Jour, of Inf. Dis., x, 1912. 



