18 THE PRESIDENTIAL ADDRESS. 
the distribution of the common tsetse-fly of the country, Glossina palpalis. 
Where there was no fly there was no sleeping sickness. 
The problem was now solved. The epidemic could be stopped either 
by getting rid of the fly or by removing the natives out of the fly area. 
As the destruction of the fly was impracticable under the circumstances, 
the second method was decided on. The natives were moved from the 
islands and lake shore and placed on healthy inland sites, and the epidemic, 
which had cost the Protectorate some 200,000 lives, speedily came to 
an end. 
This method of preventing disease, by removing man out of the zone 
of danger, is an extravagant one, and can only be done in exceptional 
circumstances. In Uganda the native population could be easily moved, 
but it meant that from about 1910 until the present day some of the most 
fertile land in Uganda has been lying derelict, has returned to the primitive 
jungle. The war delayed things, of course, but it is only now that the 
natives are being returned to their old homes on the islands and lake shore, 
in the hope that the fly by this time has lost its infectivity. 
The other method, by the destruction of the tsetse-fly, has been carried 
out successfully in other places. For example, in the island of Principe, 
off the West Coast of Africa, by destroying the wild animals which supplied 
a large part of the food of the fly and by clearing the jungle the tsetse- 
flies disappeared, and with them the disease. 
This is the method employed in malaria and yellow fever. It was by 
destroying the mosquito carrier that Gorgas drove yellow fever out of 
Havana and, later, both malaria and yellow fever from the Panama Canal 
Zone. 
Thus through the work of Manson, Laveran, Ross, Reed, and others 
has it been made possible to deal with these two scourges of the tropics, 
malaria and yellow fever. 
I include yellow fever among the protozoal diseases, although Noguchi 
in 1919 brought forward strong evidence that it is caused by a spirochaete. 
In regard to yellow fever the victory has been almost won. During 
the last century this disease, known as ‘yellow jack,’ devastated the West 
Indies and Central and South America. 
At the present time, thanks chiefly to the unremitting efforts of the late 
General Gorgas and the International Health Board of the Rockefeller 
Foundation, the disease has been driven out of the West Indies and Central 
America, and only retains a precarious foothold in Colombia and Brazil, 
whence it will doubtless be ejected during the next year or two. 
