PRESIDENTIAL ADDRESS 



ON 



THE MODE OF TRANSMISSION OF SOME 

 TROPICAL DISEASES. 



By J. W. W. STEPHENS, M.D., D.P.H., 



Sir Alfred Jones Professor of Tropical Medicine, 

 University of Liverpool. 



[Delivered November 20th, 1914.] 



In a presidential address one may, I think, expect 

 either a consideration of the general principles underlying 

 or on the other hand a summary of what is known about the 

 subject. I do not feel competent to attempt the first nor 

 perhaps is it yet time to attempt it, for the wave of discovery 

 in tropical medicine which began about 1897 has not yet 

 spent itself, and we are still carried along with the current 

 of new facts. I shall endeavour, therefore, to give you simply 

 what I am afraid must be a disconnected account of some 

 of the more recent work on the subject. The great interest 

 of tropical diseases lies, I think, primarily in the fact that 

 in the most important of them one can lay one's finger definitely 

 on the cause. This is often not the case in diseases of temperate 

 climes, e.g., scarlet fever, measles, smallpox, numerous nervous 

 disorders, etc., etc. And secondly, in many tropical diseases 

 the transmission is by some insect. Again many are due 

 to protozoa, an exceptional occurrence in temperate diseases. 

 To this is due the fact that on the whole, perhaps, they are 

 more amenable to attack by drugs, and moreover we have 

 a second great object of attack, viz., the insect transmitter. 

 Knowing thus in many cases the cause and the transmitter, 

 there is the further great interest in studying the life histories 

 of both, and finally the great probability of success in attacking 

 one or other of the possible links in the chains of the life cycles. 



