190 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVI. 



in the spread of plague, because the number of susceptible individuals was 

 increased ; and (2) the number of fleas (the transmitters of infection) were 

 also greatly multiplied. If plague was a rat disease, how was it communicated 

 to man ? He then passed on to consider how the flea acted as a transmitter of 

 infection. He classed plague together with certain epizootic diseases which 

 were communicable to man, viz., anthrax, glanders, and hydrophobia. He 

 considered the means by which these diseases were transmitted, and said that 

 plague differed from them all. The microbe of this disease produced no spore 

 or seed like the anthrax bacillus, it multiplied by fission as a plant might be 

 multiplied by cuttings. There were two sorts of cuttings : resistant, 

 which could be kept out of their natural soil for a long time, and non-resistant, 

 which had to be placed shortly after removal from the parent plant into 

 suitable soil. The germ that caused glanders belonged to the former class ; the 

 plague germ and the virus of hydrophobia to the latter class. But in the cases 

 of hydrophobia there was direct transf errence of the poison from the rabid 

 dog to man by a bite. This did not usually occur in plague. There was a 

 third method of reproducing plants, viz., by using a gooty. It was by this 

 method that plague was propagated in men and animals. The flea acts as the 

 gooty. The plague germ found in the flea's stomach a daily supply of the 

 very food it required, viz., animal blood ; it was not acted on by the digestive 

 juices of the flea, and here it was securely protected from light, dessication, 

 and contaminating bacteria, which acted on the plague germ as weeds do on a 

 delicate plant. The flea, however, being animate acted both as gooty andraali, 

 and transferred the plague germ by its bite to suitable soil, the animal body. 

 He then considered the various species of fleas, and some of their habits. He 

 pointed out that flea-ridden animals often had their own characteristic flea. 

 The rat flea was seldom found on man ; how, then, could plague be conveyed 

 from rat to man or from man to rat by means of fleas ? He detailed how the 

 question had been solved. It depended on the migration of rats in the pre- 

 sence of an unusual mortality among them. They left their fleas behind and 

 these latter in sheer hunger attacked men and other animals. He recorded 

 experimental proof of this fact in the case of a certain epidemic among 

 guineapigs and in the case of an outbreak of plague in a chawl in Bombay. 

 While normally rat fleas were never found on guineapigs, in the above case they 

 swarmed on them. 18 aloue were taken on one sick guineapig. Man seldom 

 harbours the rat flea ; he had found one rat flea in 246 fleas caught on man 

 under normal conditions. In the case of the chawl above recorded, of 30 fleas 

 caught on man no less than 14 were rat fleas. He then briefly referred to 

 experimental methods of plague infection in animals, and stated that one or 

 two germs were able to kill an animal when introduced under the skin by a 

 needle, while millions of germs were necessary by any other method. Which, 

 then, was likely to be the most common method of infection ? Granted that 

 infection generally occurred through the skin, he showed that there wa3 a 

 mass of evidence against the introduction of the bacillus through accidental 



