160 Annals Entomological Society of America  [Vol. XIV, 
To trace the development of science, or some particular 
phase of a science is not a mere idle amusement. Regarding 
history Emerson has said it is “‘A looking both before and 
after as, indeed the coming Time already waits unseen, yet 
definitely shaped, pre-determined and inevitable, in the Time 
come; and only by the combination of both is the meaning of 
either completed.’’ So, too, in the field of biology the discovery 
of today is but the fruitage of a tree rooted deep in the past. 
And this fruitage in turn though many of its seeds may fall by 
the wayside will yield the germ from which will come still 
better fruit. 
Many workers have already called attention to early sugges- 
tions or even carefully worked out theories regarding the 
relation of insects to disease. In some cases these suggestions 
have been over-valued, through being interpreted in the light 
of present day knowledge. In some instances it is evident 
that a keen pioneer worker had grasped and all but established 
the truth which was first to be accepted many years later. 
Yet these suggestions were largely lost sight of, and lay 
dormant for decades and even for centuries. Why was not this 
also the fate of the suggestions of twenty-five years ago? The 
answer lies in the history of zoology, and it is this general topic 
in its relation to medical entomology which I wish to touch 
upon tonight. This phase I have already presented in outline 
in an earlier discussion. . 
The subject is a broad one—it might well serve as the 
occasion for pointing out that there are no unrelated truths 
and that all branches of science contribute to genuine advance- 
ment in the field of human knowledge. 
It is obvious that the work of Pasteur and Koch, resulting 
in the development of the science of bacteriology, has had a 
most intimate and profound influence in bringing about an 
understanding of the role which insects and their allies play in 
the transmission of disease. 
However much the influence of modern bacteriology is 
recognized, it is not so generally known that from the time of 
the discovery of bacteria by the Jesuit priest, Athanasius 
Kircher, in 1658, and by Leeuwenhoek, there was a period of 
over a century when the germ theory of disease was the dom- 
inant one in medicine and most profoundly affected workers in 
