INSECTS AND HUMAN DISEASE 155 



by people, if a finger was presented, the bold insect would 

 immediately protrude its sucker, make a charge, and, if 

 allowed, draw blood. No pain was caused by the wound. 

 It was curious to watch its body during the act of sucking, 

 as in less than ten minutes it changed from being as flat as 

 a wafer to globular form. This one feast, for which the 

 Benchuca was indebted to one of the officers, kept it fat 

 during four months; but after the first fortnight it was 

 ready to have another suck." 



FLEAS AND PLAGUE 



The most dread disease that has ever attacked mankind 

 is the bubonic plague, and it is also probably the oldest of 

 all known diseases. It is caused by a bacterium known as 

 Bacillus pestis, which produces an epizootic in rats, and 

 is carried to man by fleas. One of the most curious and 

 interesting facts in connection with plague is that, although 

 the causal agent has only been discovered within the last 

 quarter of a century, its association with rats dates at least 

 from Biblical times, and probably earlier. In the first 

 book of Samuel, the reference to emerods and mice of the 

 field undoubtedly refers to plague; Sennacherib's army 

 was attacked by a disease in the spread of which rats 

 played a part ; whilst in a fragmentary writing of Ruf us 

 of Ephesus, a contemporary of Trajan, in the third century 

 B.C., we find the first mention of the disease, though its 

 association with rats does not appear to have been recog- 

 nised at this early date. In the sixth century, during the 

 reign of Justinian, plague reached Europe; beginning at 

 Pelusium in Egypt, in 542, it reached Constantinople during 

 the next year, and there was responsible for ten thousand 

 deaths in a single day ; in the same year it also spread to 

 Italy, and three years later it reached France, whilst England 

 came under the fatal spell in 664, 672, 679, and 683, and its 

 ravages continued unabated for nearly two hundred years. 



