DIAGNOSIS OF PLAGUE 403 



surmised that if the epizootic be allowed to proceed, the 

 susceptible rats will be exterminated and a race of rats 

 relatively insusceptible to plague will ultimately be 

 established. 



On Plague, see Simpson, Treatise on Plague (Cambridge Univer- 

 sity Press) ; Klein, Bacteriology of Oriental Plague ; " Reports on 

 Plague Investigations in India," Journ. of Hygiene (extra numbers), 

 vols. vi-xiv. 



Clinical Examination 



If it cannot be examined immediately, plague material may be 

 placed in a solution containing glycerin 20 c.c., distilled water 

 80 c.c., calcium carbonate 2 grm. The bacilli retain their vitality 

 and virulence in this for thirteen days (Albrecht-Ghon method). 



(1) Withdraw a little of the fluid from the bubo by means of an 

 antitoxin syringe. Make smears and stain with methylene or 

 thionine blue. Search for short plump bacilli, often in pairs, with 

 polar staining and unstained centres. They are not stained by 

 Gram's method. 



N.B. There may be a mixture of organisms in the buboes. 



(2) Make agar plates and broth cultures. Incubate the cultures 

 at 25-27 C., not at 37 C. From colonies on the agar plates the 

 organism may be isolated and its cultural and pathogenic characters 

 ascertained. The appearance of the broth cultures, if charac- 

 teristic, would be very suggestive of plague, but if uniform turbidity 

 develops this may be due to contaminating organisms, e.g. micrococci. 



(3) Inoculate mice, rats, or guinea-pigs subcutaneously with the 

 fluid or with the culture. Some of the animals should be inoculated 

 by the cutaneous method rubbing a little of the material on the 

 shaved abdomen, and also as in (4). Inoculation of rats serves to 

 distinguish the B. pseudo-tuberculosis from the B. pestis. If the 

 animals die, investigate for the Bacillus pestis by staining and 

 culture methods. 



(4) In the pneumonic form, dilute the sputum with a little 

 boiled water, inoculate several agar tubes, and incubate at 

 25-27 C. Examine in two to three days. Also daub the 

 nostrils of a guinea-pig or rat with a brush or pledget of wool 

 dipped in the diluted sputum, avoiding wounding the mucous 

 membrane. Smears of the sputum may also be made, stained, and 

 examined. Gram's method will distinguish the B. pestis from the 

 Streptococcus pneumonice ; the latter stains well by Gra.m, 



