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



to digest its meal for 48 hours. The result is, that almost all the blood 

 has been digested and absorbed, and the plague germs remain unaffect- 

 ed, — in fact, they appear to have multiplied, because they are far more 

 numerous, than they could have been when ingested with the blood, 

 and their appearance would indicate multiplication to one who is 

 acquainted with bacilli which have been stained under such circum- 

 stances. 



In the flea's stomach we find the plague germ in surroundings which 

 will daily supply it with the -very pabulum it desires — animal blood. 

 The germ is not destroyed by the digestive juices of the flea. It is 

 protected from light and dessication and the presence of contaminating 

 bacteria, (weeds in other words,) — conditions which would have put an 

 end to its existence if it had remained exposed on earth. We have all 

 the conditions which are fulfilled by the gooty in the case of the plant. 

 The gardener after a certain time cuts off the new plant below the gooty, 

 and transfers it to its natural soil. So, too, the germ within the flea 

 has now to be transferred to more suitable soil, the animal body ; and 

 this is accomplished by the bite of the flea itself. The flea, being animate, 

 fulfils the double function of gooty and mali. 



And now, to understand the last part of my subject, it is necessary to 

 say a few words about fleas. It would be possible to write pages on 

 the subject. My difficulty is to tell you enough in a short space, to 

 fully explain the relation between fleas and the plague. I hope, there- 

 fore, you will bear with me if I detain you a few jmoments longer. 

 There are four species of fleas met with in this country commonly 

 associated with men and rats. Specimens of these are displayed under 

 the microscopes. I can only now mention them by name, and detail 

 a few of the habits of these species. 



The most common flea and the one most universally distributed is the 

 cat flea, Pulex felis, sometimes also called Pulex serratkeps. This flea 

 is, for the most part, found on cats and dogs ; but it is frequently taken 

 on man too. I have also found it on rats, monkeys, sheep, deer, goats f 

 guinea-pigs, the hedge-hog, and the horse. It is a rather small flea, 

 but variable in size ; and is of a dark colour. It is frequently found in 

 light airy places, and it is not so nocturnal in its habits as the other 

 fleas. Then, there is the human flea, Pulex irritans. It is a large 

 fairly light-coloured flea, found almost exclusively in human habitations, 

 and in only those of them which are dark and more or less dirty. I 



