THE FILARIA SANGUINIS HOMINIS 33 



a very widespread condition, and is of very special 

 interest because niosquitos Avhicli had previously 

 sucked the blood of persons harbouring the larval 

 forms were found later to contain them in a furtlier 

 state of development, man thus acting as the definitive 

 host and the mosquito as the intermediary host. The 

 discovery of this inter-relationship paved the way, as 

 we shall see, to the discovery of the mode of the 

 transference of the virus of malaria and yellow fever. 

 Therefore, as very great interest attaches to this 

 discovery, I reproduce here the account which its 

 discoverer. Sir Patrick INIanson, gave early this year 

 (1909) at a meeting of the Authors' Club. He said : 



" Let me go back to my early years of tropical 

 experience. I was then in the island of Formosa. I 

 took a great interest in the diseases of the people. One 

 disease had a special fascination for me — ElepJiantlusis. 

 1 puzzled over what might be the cause of this disease, 

 but without finding a satisfactory solution. Later I 

 went to Amoy, a large town on the coast of China, 

 where I saw many more cases and many more forms 

 of the same disease. Still I failed to find an ex- 

 planation. 



" In 187-4 I came to London, and there for the first 

 time I heard that Timothy Lewis, who had done so 

 much in the study of tropical diseases, had discovered 

 that in the blood of a proportion of the inhabitants in 

 certain districts of India there was to be found an 

 organism which he called the Filaria sanguinis hominis. 

 This is a microscopic animalcule, eel-shaped, and 

 enclosed in a loose sac, or sheath, within which it 

 wriggles about in the blood very actively. It is some- 



3 



