198 SPECIAL BACTERIOLOGY 



in eight days, and in sterilized bilge water in five days ; also in direct 

 sunlight in three or four hours. (Report of German Plague Commission.) 

 The bacilli are killed by drying at ordinary room temperature in four 

 days. 



Pathogenesis. The most susceptible animal is the rat, a minimum 

 quantity of culture being sufficient, when injected subcutaneously, to 

 cause its death. The same results are obtained when the virus is intro- 

 duced on the mucous membrane of the nose or eye, also by feeding 

 experiments and by gnawing companions dead of the plague. The 

 latter mode of infection is of great importance, as it explains the extra- 

 ordinary and almost inconceivable rapidity with which this rat-pest 

 spreads, and probably also it is the affected rats that carry the plague 

 from house to house. 



Next to the rat the most susceptible animal is the grey monkey. 

 All the ordinary laboratory animals are also susceptible except the 

 pigeon. 



Yersin observed the bacillus in the bodies of dead flies by the 

 inoculation of animals. 



Ogata found the bacillus in fleas on rats dead of the plague. 



Nuttall found that fleas died when fed with plague tissues in seven 

 to eight days at 12 to 14 C., and in about three days at 23 to 31 C. 

 In bed-bugs the bacilli soon died. 



In animals subcutaneously inoculated, the point of the inoculation 

 becomes oedematous, and the lymphatics enlarged in a few hours ; in 

 twenty-four hours the animal is quiet, hair rumpled with excessive 

 lachrymal discharge from the eyes, finally convulsions set in, ending in 

 death. The post-mortem appearances are as follows : Bloody redema 

 at the point of inoculation, reddening and swelling of the lymph-glands ; 

 haemorrhagic extravasation into the abdominal walls ; serous effusion 

 into the thoracic and abdominal cavities ; intestines congested. Spleen en- 

 larged (see Photomicrograph of section of spleen of mouse, Fig. 78), and 

 greyish points resembling miliary tubercles are sometimes present in the 

 spleen. The supra-renal bodies are also enlarged. The characteristic 

 bacilli can be found in large numbers in the local oedema, lymph-glands, 

 blood, and internal organs. 



In cases where the animals do not die quickly, only local evidence 

 of inoculation is present, and the distribution of the organism throughout 

 the body is diminished. 



In man, when the virus gains entrance at the foot, the superficial 

 and deep inguinal glands are the first to become affected, and if the 

 infection be through wounds in the hands, then the buboes appear first 

 in the axillary region. A member of the German Commission was 

 infected while performing an autopsy on a victim of plague ; two days 

 later a small pustule appeared on the right hand, soon followed by 



