STUDIES ON PNEUMONIC PLAGUE AND PLAGUE 

 IMMUNIZATION. 



VIII. SUSCEPTIBILITY OF ANIMALS TO PNEUMONIC PLAGUE. 



By Richard P. Strong and Oscar Teague. 

 (From the Biological Laboratory, Bureau of Science, Manila, P. I.) 



Many cultures isolated by us during the Manchurian epidemic 

 from the lungs at necropsy have demonstrated the same patho- 

 genicity for animals as virulent bubonic strains of the plague 

 bacillus. The pneumonic cultures have shown themselves to be 

 particularly pathogenic for mice, rats, guinea pigs, and monkeys 

 (Cynomolgus philippinensis Geoff.) , these animals dying from the 

 same doses and succumbing within the same period after inocula- 

 tion as has been observed after infection with bubonic strains. 

 Some evidence was introduced at the Conference held at Mukden 

 that suggested that when the pneumonic strains were injected 

 subcutaneously into the guinea pigs, usually septicaemia was pro- 

 duced very quickly and typical buboes were not obtained. More- 

 over, it was affirmed that the guinea pigs died within a shorter 

 time after inoculation than in the cases in which bubonic strains 

 were employed. However, in these instances it appears that the 

 results were dependent upon the size of the dose inoculated, as 

 much as one-half of an agar-culture having been employed in 

 the infection. We showed in Mukden that the cutaneous or sub- 

 cutaneous inoculation of very small doses of the pneumonic 

 strain into guinea pigs gave rise to the typical lesions observed 

 in these animals after inoculation with virulent bubonic strains, 

 particularly to typical buboes, to miliary abscesses in the spleen, 

 and to secondary septicaemia with haemorrhages in the different 

 organs. Our statements at the Conference in this respect have 

 since been borne out by extensive experiments performed by us 

 in Manila and it has been conclusively sho\vn, in addition, that 

 when guinea pigs are inoculated with the pneumonic cultures by 

 inhalation, they develop primary infection of the glands of the 



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