BINUCLEATA 49 



cell parasites of mammals and birds. Of these, Anopheles are the 

 most important, as they are the agents by which malarial infection 

 is conveyed to man ; while Culex is the host of those varieties of 

 H&moproteus , Proteosoma and Leucocytozoon, which are parasitic in 

 birds. Stegomyia fasciata carries, probably as the true host, the 

 virus of yellow fever, and different varieties of Culex transmit the 

 Filaria of man, the dog, and probably also those of birds. 



Stinging -flies convey pathogenic Trypanosomes both mechanically 

 and in the character of the true host. Such are Glossina palpalis and 

 G. fusca, which transmit the sleeping sickness of man ; and other 

 varieties of tsetse-fly, as well as probably Stomoxys and the 

 Tabanides, all of which convey the Trypanosomes of the domestic 

 animals. 



Louse-flies (Pupipara) probably carry the blood parasites of certain 

 mammals and birds. Varieties of Lynchia transmit the Hcemoproteus 

 of pigeons; the parasites peculiar to the bat are probably all con- 

 veyed by Nycteribia ; while Hippobosca rufipes is believed to be 

 the carrier of the Trypanosoma theileri of cattle. 



Fleas, as far as our present scanty knowledge goes, can be 

 regarded only as occasional mechanical agents of infection. As such, 

 however, they have a considerable experimental interest, especially 

 since the recent discovery that fleas which infest rats convey, not 

 only the Trypanosomes of rats, but other species of Trypanosomes 

 with which the rat has been artificially infected. 



Lice may convey different serum parasites. According to Pro- 

 wazek, the rat-louse, Hcematopinus spinulosus, is not only the true 

 host of the rat but, owing to its voracious habits, it may also transmit 

 the Trypanosome mechanically. It frequently sucks more blood 

 than it is able to digest; consequently, the next time it feeds, the 

 slight contraction of the muscular structure of the body necessary 

 to start the act of sucking, is sufficient to expel the undigested 

 blood into the fresh wound. Advantage has been taken of this fact 

 to perform experiments which have led to interesting discoveries. 

 For instance, Manteuffel has recently proved that Spiroschaudinnia 

 recMrrentis, after being transmitted by inoculation to rats, may be 

 mechanically conveyed by rat-lice, without the louse being in any 

 sense the actual host of the parasite. It is interesting to note in this 

 connection that the Indian Spirochseta fever of man, which resembles 

 but is not identical with relapsing fever, is conveyed by lice. 



Bugs appear to play but a small part in the transmission of blood 

 parasites. They may, by mechanical means, convey the organism 

 of relapsing fever, but after a prolonged sojourn in the stomach of 

 the bug the Spirochsetae become digested (Nuttall). According to 



