Mosquitoes considered as Transmitters 

 of Yellow Fever and Malaria 1) 



The despised mosquito, denounced by me since 1881 as the agent of 

 transmission of yellow fever, is now attracting considerable attention 

 among distinguished and sagacious observers who attribute to that insect 

 an important role in the etiology and propagation of malaria infection. To 

 those who are familiar with the biological conditions and the habits of the 

 mosquito this will not be a matter for surprise; rather should we wonder 

 how, considering the special aptitudes of the insect, other inoculable disea- 

 ses are not transmitted by it. specially such as are due to germs in the blood 

 or in the tissues that lie within reach of its sting. Much light, however, has 

 been thrown upon this singular eclecticism by modern ideas concerning 

 the process by which some blood-sucking insects convey certain diseases 

 to warm blooded animals. We are induced by them to regard as one of the 

 essential conditions that the transmitting insect should itself experience a 

 true infection, which may not endanger its life or greatly disturb its 

 physiological functions, but must always require, on the part of the 

 insect, pathogenous susceptibility for the specific germs which it is called 

 upon to transmit. It will thus be readilly understood why the same insect 

 may transmit only certain germs and not others, as also that, among 

 insects of the same kind, some species may possess that faculty while other 

 do not. 



Among the publications that have appeared concerning the transmis- 

 sion of malaria by mosquitoes, the most important one, and that which 

 has caused most sensation, has been the lecture delivered, a few months 

 ago, by Robert Koch, in which he declared himself decidedly in favor of 

 the mosquito theory as the one which most plausibly accounts for the 

 propagation of the said disease. In support of his idea he cites a 



1) New York Medical Record, May 27, 1899. p. 737 (English traslation). Paper 

 read before the Academy of Medical, Physical and Natural Sciences of Havana. Nov. 

 1.-.. ls'.is. 



