552 CARLO TIRABOSCHI 



ques et la grande abondance de Puces dans les localités où la peste 

 estendémique (Garhwai, Yunnan, Beni-Cheir, Agra, Transbaïkalie^ 

 etc.), rapporte un grand nombre de faits, qu'il a observés dans les 

 Indes et qui l'amènent à conclure que la transmission de la peste 

 n'est pas due à l'infection du sol ou des aliments, ni au contact acci- 

 dentel du microbe, ni à la piqûre des Moustiques, mais bien à la 

 piqûre des Puces. D'après lui (p. 79), « tbe true nidusoi tbe plague 

 infection is some species of Flea, in which tbe microbe causes a 

 slowly developing infection, that at length renders tbe Insect capa- 

 ble of transmilting tbe disease, and in wbicb Insect tbe virus can 

 retain or regain its virulence. If Simond's view were true, namely, 

 that tbe Flea merely retains tbe microbe in its intestine and passes 

 it ont witb its dejecta, one would expect Fleas tobe most virulent 

 immediately after, or soon after, ingesting tbe blood of infected 

 Rats. Tbe theory now put forward is that tbe microbe developes (I) 

 in tbe Flea, and only after a lapse of time is in a position to reach 

 tbe proboscis in tbe act of biting. This theory obviously présuppo- 

 ses an interval between tbe time of réception of tbe virus by tbe 

 Flea and tbe development of its capacity to pass tbis virus on to 

 otber animais. As explained above such an interval is usually ob- 

 served in outbreaks of plague. Changes in tbe habits of Fleas as 

 tlie Rat population dies ofï may explain cases in which Ratsappear 

 to play différent parts in tbe spread of tbe disease at différent 

 periods of tbe outbreack. Différences in tbe habits of Fleas in ditïe 

 rent localities may be tbe cause of abnormal outbreacks in which 

 certain susceptible species of animais temporarily or perma- 

 nently escape. The class of facts hère referred to, and which bave 

 been described in earlier paragraphs, are impossible to explain 

 on tbe theory that plague transmission is simply a chance passage 

 of tbe microbe from infected dejecta to accidentai cuts or scratches 

 on tbe bodies of susceptible animais. » 



(1) Pour démontrer que les Bacilles pesteux se multiplient dans le corps de la' 

 Puce, Hankin (p. 81) captura une Puce vivante sur un Rat trouvé mort après le 

 premier cas de peste humaine; il la secoua fortement dans plusieurs tubes de 

 bouillon stérile, et en ayant extrait l'estomac par dissection aseptique, y trouva 

 des Bacilles semblables au BaciUus pestis, a arranged in clusters of about a 

 dozen individuals each, and embedded in the tissues of Ihe stomach wall. NO' 

 Bacilli were observed in the liquid contents of the stomach. The arrangement of 

 the Bacilli in clusters obviously suggests that they were engaged in reproduction, 

 insitu)). Zir.oLiA et Liston avaient déjà observé que les Bacilles de la peste peu- 

 vent se multiplier dans l'estomac des Puces. 



