MALARIA — WATSON 347 



or yellow fever. Success in Panama and Malaya came because Ross 

 did not throw in his hand in the early days and because Sir Patrick 

 Manson, so to speak, sustained Eoss's hand at a critical period. In 

 1915 the Panama Canal represented the greatest engineering and 

 medical triumph the world had seen. Like so many other great things 

 it was so misunderstood and misrepresented, that it almost became a 

 stumbling block, and the honor of starting antimalarial work in the 

 United States fell to two nonmedical men : Professor Herms and H. 

 F. Gray working in California. They began in 1911. In 1916 the 

 Rockefeller Foundation, after sending two distinguished scientists to 

 study Malayan methods, took up the prevention of malaria in the 

 United States and has given a great lead to that country. In passing 

 I would mention that research and practical work carried out on the 

 reservoirs of the Tennessee Valley Authority have developed a new 

 method of controlling mosquitoes. By raising and lowering the level 

 of the reservoirs a potent method of controlling anopheles has been 

 demonstrated. It acts by stunting vegetation on the edges of the 

 reservoirs. A. quadrimaculatus is the main carrier of malaria in the 

 southeastern States of the United States. 



Although A. fnaculipetmis is to be found throughout Europe from 

 the Baltic to Cape Matapan and from Spain to the Caspian Sea, 

 malaria is to be found mainly in the Mediterranean region. For over 

 2,000 years malaria defied all man's efforts to reclaim and cultivate the 

 Pontine Marshes. But within the past decade, Mussolini, by destroy- 

 ing the anojoheles, has colonized this area; perhaps this will be his 

 greatest, or only, abiding claim to fame. I remind you though that 

 25 years earlier we had in Malaya managed to accomplish bigger 

 things in bigger swamps. 



The Dutch quickly grasped the significance of the researches in 

 Malaya on malaria, and when he returned to Holland from the East 

 Indies, Professor Swellengrebel, with the aid of his colleagues, carried 

 out some brilliant researches. Tliey showed that there were two races 

 (or species) of A. macuUpennis, one of which bred in brackish water 

 and carried malaria, the other which bred in fresh water and was 

 harmless. This was the prelude to researches in other parts of 

 Europe, w^hich split A. macidipennis into six races (or species) only 

 some of which carried malaria. This explained many anomalies. 



A couple of hundred years ago malaria was not uncommon in Eng- 

 land, in low-lying areas like the Fens or the Thames Estuary. Indeed, 

 London itself was not free. But drainage and reclamation of land 

 have wrought so many changes that when malaria was implanted in 

 England in 1917-18 by the soldiers returning from foreign lands, it 

 died out within 4 years. 



During a visit to some of Chester Beatty's mines in Serbia, I took 

 an opportunity of visiting Salonika to see an area in wliich according 



