1 66 Arthropods as Direct Inoculators of Disease Germs 



the tsetse-flies are not to be found. It is thought to be spread by- 

 various species of blood-sucking flies belonging to the genera Stomoxys, 

 Hcematobia, and Tabanus. Mitzmain (19 13) demonstrated that in 

 the PhiUppines it is conveyed mechanically by Tabanus striatus. 



The sleeping sickness of man, in Africa, has also been supposed 

 to be directly inoculated by one, or several, species of tsetse-flies. 

 It is now known that the fly may convey the disease for a short 

 time after feeding, but that there is then a latent period of from 

 fourteen to twenty-one days, after which it again becomes infectious. 

 This indicates that in the meantime the parasite has been under- 

 going some phase of its life-cycle and that the fly serves as an inter- 

 mediate host. We shall therefore consider it more fully under that 

 grouping. 



These are a few of the cases of direct inoculation which may be 

 cited as of the simpler type. We shall next consider the r61e of the 

 flea in the dissemination of the bubonic plague, an illustration 

 complicated by the fact that the bacillus multiples within the insect 

 and may be indirectly irioculated. 



The Role of Fleas in the Transmission of the Plague 

 The plague is a specific infectious disease caused by Bacillus pestis. 

 It occurs in several forms, of which the bubonic and the pneumonic 

 are the most common. According to Wyman, 80 per cent ^f the 

 human cases are of the buboijiic type. It is a disease which, under 

 the name of oriental plague, the pest, or the black death, has ravaged 

 almost from time immemorial the countries of Africa, Asia, and 

 Europe. The record of its ravages are almost beyond belief. In 542 

 A. D. it caused in one day ten thousand deaths in Constantinople. 

 In the 14th century it was introduced from the East and prevailed 

 throughout Armenia, Asia Minor, Egypt and Northern Africa and 

 Europe. Hecker estimates that one-fourth of the population of 

 Europe, or twenty-five million persons, died in the epidemic of that 

 century. From then until the 17th century it was almost constantly 

 present in Europe, the great plague of London, in 1665 killing 68,596 

 out of a population of 460,000. Such an epidemic would mean for 

 New York City a proportionate loss of over 600,000 in a single year. 

 It is little wonder that in the face of such an appalling disaster sus- 

 picion and credtdity were rife and the wildest demoralization ensued. 

 During the 14th century the Jews were regarded as responsible 

 for the disease, through poisoning wells, and were subjected to the 



