

THE PRESENT EPIDEMIC OF MALARIA. 873 



which are responsible for the communication of the disease from man 

 to man. You will thus understand that it is a subject well worthy of 

 consideration hy this Society. 



Malaria is a very ancient disease. It was well-known even at the 

 time of the Roman Empire, but it was not carefully differentiated 

 from other fevers till the discovery of Cinchona bark in the begin- 

 ning of the 17th century. The fevers which were found to yield to 

 treatment with this drug were thus more definitely distinguished from 

 other fevers and were found to possess peculiar features of their own. 

 The fact that quinine destroyed the poison of this malady led to 

 the assumption that the poison, which produced the disease, must 

 be of a specific kind. Many wild guesses were made as to its 

 nature. On the one hand, it was thought to be a gas, evolved, 

 it might be, from decomposing vegetable matter ; on the other 

 hand, it was held to be a parasite. Various fungi and bacteria 

 were from time to time believed to be the cause of the disease, 

 among the most famous of these was the bacillus malarias of the 

 Italian School. Meanwhile, however, a more minute scientific 

 study of the disease showed that it was associated with the 

 appearance of a black or brown pigment in the blood and 

 organs of the sick. How came this pigment to be produced was 

 the question next to be solved. It remained for Laveran to show 

 that the pigment was formed in the bodies of minute animal para- 

 sites (quite distinct from bacteria) which infested the red blood cells 

 of persons afflicted with the disease. 



The life history of this parasite in man was soon worked out and 

 at least three varieties of the parasite were recognised. Then arose 

 the question: How could the parasite gain an entrance into the 

 blood of the sick, and how could it escape from the sick to infect 

 other persons ? A minute study of the various forms of the parasite 

 as it appeared in the blood of man showed that in each particular 

 variety of parasite two series of forms could be differentiated. One 

 series of forms appeared to be associated with an asexual process of 

 multiplication within the body of man, while another series of forms 

 appeared to be differentiated into males and females. Further, it 

 was observed, that after the parasites had been removed from the 

 body of man together with the blood, the male and female forms 

 conjugated. Here evidently was a clue to the continuance of the 



