No. 463.] | CORRESPONDENCE. 507 
Fleas and ‚Disease. : : 
Editor of the American Naturalist. 
Sir :— No less epoch-marking than the announcements first made 
of the connection of mosquitoes with malaria and yellow fever, is the 
news which: now comes-through Dr. Ashmead, the leprosy expert of 
New York, that Dr. Carrasquillo of Bogota has found the bacillus of 
Hansen in the intestinal canal of fleas. ‘The rapid progress of 
leprosy after introduction into some of our flea-infested southern 
cities, from local endemicity to alarming epidemicity, is, according 
to Dr. Ashmead, probably to be credited to inoculation by flea 
bites. 
In connection with the -investigation of the relation of fleas to 
bubonic plague, it has alread} been shown by the writer (Proc. U. S. 
Nat. Mus., vol. 27, 1904), that the fleas of rats in the warmer 
regions of the earth are close relatives of the flea specific to human 
beings, and thus, far more likely to bite human beings than are the 
fleas of rats in the colder regions, which are only distantly related to 
Pulex irritans. It is now necessary to know if any of these southern 
rat fleas — of which there are a number of species — voluntarily bite 
human beings. : 
These investigations, and now the new lines brought into striking 
prominence by Dr. Ashmead’s announcement, make it of first impor- 
tance that a complete study be made of all the species of fleas occur- 
ring on rats, mice, dogs, cats, and human beings throughout the 
United States and tropical America, since any well founded medical 
and bacteriological investigations of the subject must be based on a 
thorough scientific knowledge of the fleas themselves, just as in the 
case of the mosquitoes in their relation to yellow fever. The utmost 
gravity of the possibilities involved not only justifies but renders im- 
perative a careful and complete survey. The writer has in progress 
such a work, in continuation of extensive papers on the fleas already 
published. Residence in the tropics and in a leprosy center, together 
with the hearty coöperation of Dr. Howard of Washington, Dr. Lutz 
of Sao Paulo, Brazil, Dr. Carter of the University of Texas at 
Galveston, and others, has made possible a good beginning. It is 
hard to see how anything like a complete survey could be made with- 
out also the active coöperation of college and medical men in every 
part of these regions, the Hawaiian Islands, and the tropical regions 
of the far east. The simplicity of the apparatus needed (tweezers, 
