FLIES AND FLEAS 41 



fevers and dog-fevers, and probably of some obscure 

 fevers of man, must make us all more anxious than we 

 were about contact with insect life. For ages popular 

 tradition has ascribed diseases of one kind and another 

 in various parts of the world to the bites of flies. But 

 actually it is little more than fifty years ago since it was 

 really shown that deadly germs or parasites existed 

 which could be, and actually are, carried by flies from 

 one animal to another, and introduced into the blood by 

 the flies' stab. This was first shown in regard to the 

 bacterium of splenic fever (or anthrax, or wool-sorters 1 

 disease), a blood-disease of cattle which is transferred 

 by the big, fiercely-biting " horse-flies " (tabanus), from 

 animals to man, and is invariably fatal. Another 

 bacterial disease, " pernicious oedema," is inflicted on 

 man in the same way. These cases were exceptional, and 

 it is only quite recently that the agency of flies and fleas 

 in great epidemics, and in diseases causes thousands 

 of deaths every year in well-known regions, has been 

 discovered. 



1 5. Monkeys and Fleas 



The wingless parasites known as pediculi are not 

 known as active agents in spreading disease germs, prob- 

 ably because they do not readily transfer themselves 

 from one animal to another. It is in this connection a 

 really remarkable fact that monkeys are not infested by 

 fleas, and that only in few cases and not in many kinds 

 have pediculi or acari been observed. In this respect the 

 lower races of men (and even the higher) seem to have 

 fallen away from a grade of excellence attained by their 

 despised quadrumanous cousins. When this fact as to 

 the freedom of monkeys from insect parasites is men- 

 tioned, those who have watched monkeys in captivity 

 will immediately say, " Surely I have seen monkeys 



