RATS AND THE PLAGUE 77 



readily goes to man, does not suffer from the plague 

 bacilli which it has gorged, but conveys them to man 

 either by its bite or by its excrement. 



This being so, it becomes important to know all 

 about the fleas of rats. Quite unexpected facts have 

 been discovered in regard to them. In Europe a 

 very large flea is found on the grey and the black 

 rat. This kind has not, I believe, ever been found 

 on human beings or been known to bite them. But 

 in India, in the Philippines, and in the ports of the 

 Mediterranean, this northern rat-flea is rare, and its 

 place is taken by a smaller and more actively vagrant 

 flea, which Mr. Charles Rothschild (who is the great 

 authority on fleas) found upon several different kinds 

 of small animals in Egypt. He named it " Pulex 

 cheopis." This is the flea (and not our big northern 

 rat -flea) which acts as the carrier of plague-germs from 

 rats to man in India. It appears from experiments 

 that the common flea of man (Pulex irritans) and the 

 cat-and-dog flea (Pulex felis), as well as the big northern 

 rat-flea (Ceratophyllus fasciatus), can harbour the 

 plague -bacillus if fed on plague-stricken animals, but 

 there are no observations to show (as there are about 

 the " Cheops flea ") that they pass habitually from man 

 to rats and rats to men. 



It is happily so long (200 years) since we had a real 

 outbreak of plague in Europe that we are still in doubt 

 as to whether the Grey rat or the Black rat is the more 

 susceptible to the disease and what flea, if any, acts, 

 or has acted, as the carrier from rat to man in this part 

 of the world. The suggestion has been made that the 

 Grey Norwegian rat takes plague less easily than the 

 Black rat, or than the Indian Mole-rat (Nesokia), and 

 that the multiplication of the Grey rat in England 

 and France and consequent decrease in Black rats, is, 

 therefore, an advantage, so far as plague is concerned. 

 Possibly with the Grey rat has come the big rat-flea. 



