66 INFECTION AND IMMUNITY. 



typhoid and cholera proliferate in the intestines of 

 the fly. It seems not unlikely in the case of ty- 

 phoid, inasmuch as Ficker 2 found them in the fly 

 twenty-three days after a feed on the bacilli. Tsu- 

 zuki 3 cultivated cholera vibrios from flies which 

 were taken in the dwellings of patients. 



It seems probable that flies, in some instances, 

 may distribute plague bacilli after they have them- 

 sejves become infected by feeding on the sputum 

 of pneumonic patients or on the cadavers of rats 

 dead of the disease. Yersin 4 found plague bacilli 

 in flies dying in a laboratory in which plague was 

 being studied, and in Nuttall's 5 experiments they 

 became infected by feeding on diseased organs. 

 Fiea and The flea, on the other hand, appears to act both 

 as a disseminator and as a transmitter of plague. 

 The human flea, at least two species of rat fleas, 

 and the flea of the dog and cat readily become in- 

 fected by feeding on rats during the stage of septi- 

 cemia in the latter, the bacilli multiply for a few 

 days in their stomach and intestines, and are ex- 

 creted in large numbers in their feces. They are 

 able to communicate the disease to other animals 

 by biting for at least three days after their infec- 

 tion, but in a short time the bacilli disappear from 

 their alimentary tract and they lose the power of 

 transmission. The organisms, which are excreted 

 in their feces, are virulent, and are able to produce 

 infection through very small abrasions and 

 through the minute wounds made by the bites of 

 these insects. The deposition of bacilli in the feces 

 of the flea on the skin of a person is a question 



2. Arch. f. Hyg., 1903, xlv, 247. 



3. Arch. f. Schiffs-u. Tropenhygiene, February, 1904, viii 



4. Ann. de 1'Inst, Past, 1904, i, 662. 



5. Centralbl. f. Bakteriol., 1897, Abt. I, xxii, 87. 



