440 



THE AMERICAN NATURALIST [Vol. XLIV 



to careful scrutiny. Wherry 2 first showed in a conclusive man- 

 ner that ground squirrels, obtained from two widely separated 

 sections of California, were infected with the bacillus of bubonic 

 plague. There remained to be ascertained the extent of the 

 infection and appropriate methods for the extermination of the 

 infected animals and the eradication of the disease, which had 

 gained apparently a permanent foothold on the state of Cali- 

 fornia. The records of these investigations form one of the 

 most interesting and important chapters of medical zoology yet 



The splendid work which has been done by the Public Health 

 and Marine Hospital Service on the Pacific coast in connection 

 with the problem of stamping out bubonic plague, has included 

 investigations on the rats and also on native rodents, which have 

 established important points in the relations of these animals 

 to the spread of that disease. While no cases of human plague 

 have been reported for many months, yet plague-infected rodents 

 have been killed at one point or another as recently as February. 

 The disease is not common, since about 2.000 squirrels from one 

 county were examined before an infected individual was found. 

 Nevertheless, one can not doubt its continuance among the wild 

 rodents, or question the advisability of prosecuting the campaign 

 for the total eradication of the infected animals. The service 

 has published • complete siatistics of work to date and a map 

 showing the area studied and the prevalence of plague among 

 ground squirrels. 



The rodents in which plague infection has been demonstrated 

 include both the introduced species, Mus rattus, the black rat, 

 and Mus norvegicus, the brown rat, and also the native species, 

 CI f< II us brrcJiCj/i, the California umund squirrel, and Neotoma 

 fuscipes, the brush rat. The work of McCoy 4 corroborated fully 

 the findings of AVherry, and left no doubt that the disease among 

 ground squirrels is due to the same organism that causes bubonic 

 plague among rats and men. The experimental evidence which 

 the latter reports in a conservative and critical manner includes 

 several typical cases of plague in human beings where the diag- 

 nosis has been verified by bacteriological methods, and where 

 the cases "have been traced to squirrel infection as clearly as 

 one can trace such things." While McCoy states that in his 



'"Public Health Reports," Vol. 25, p. 585. 

 *" Public Health Reports," Vol. 25, pp. 27-33. 



