322 MANUAL OF BACTERIOLOGY. 



state that it requires longer than this. KoUe and Wasser- 

 mann quote various authorities, none seem to agree. Abel states 

 that it required two hours in this strength. Gioxa and Gosio, 

 three hours. In solutions of higher strength the discrepancy 

 between authorities varies also; in 5 per cent, solution from 

 one to ten minutes, one hour in i per cent, carbolic acid.* 

 It is pathogenic for rats, mice, guinea-pigs, rabbits and a num- 

 ber of other animals besides flies and other insects. The 

 rat-flea, pulex cheapis, has been shown by the British Commis- 

 sionf to bite human beings ; the inference from this is that the 

 plague bacillus is conveyed from the rat to man in this way. 

 Thompson^ holds that the flea is the intermediary between 

 the plague rat and human beings. 



In man it appears usually to enter through wounds of the 

 skin. Other possible avenues of infection are the air-passages, 

 the mouth and the gastro-intestinal tract. In plague three 

 different clinical forms are to be recognized — the bubonic, 

 the pneumonic and the septicemic. The bubonic form is com- 

 monest. The point in the skin at which the inoculation takes 

 place seems generally to exhibit no inflammatory reaction. 

 The lymph-nodes are generally swollen, especially the deep in- 

 guinal and axillary nodes. The swollen lymph-nodes may 

 suppurate. The suppurating nodes are often infected simul- 

 taneously with micrococci. The bacilli are numerous in the 

 enlarged lymph-nodes, but may be detected in the other organs 

 of the body and in the blood. The organism is furthermore 

 to be found in the fluid aspirated from buboes during life. 

 It may be cultivated from this fluid, and recovered from rats 

 and guinea-pigs inoculated with it. In the pneumonic or pul- 



*Rosenau. ViabiUty of Bacillus pestis. Marine Hospital Service. Hy- 

 gienic Laboratory Bulletin. No. 4. 1901. 



tLondon letter to Journ. Am. Med. Assn. Nov. 16, 1907. See also Ibid. 

 Vol. L., No. 2. Jan, 11, 1908. p. 127. 



tAustralian Medical Gazette. Nov. 20, 1907. Abs. Journ. Am. Med. Assn. 

 Jan. iS, igoS. p. I27. 



