1908-9. ] HuMAN EVOLUTION AND HuMAN DISEASE. 
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PRESIDENTIAL ADDRESS. 
HUMAN EVOLUTION AND HUMAN DISEASE. 
By PRoFEsSOR J. J. MACKENZIE. 
(Read rath November, 1908.) 
IN choosing a subject for my address this evening it is natural that 
I should select one from my own particular department of Biological 
Science, viz., the department of Pathology. Perhaps it is not necessary 
to apologize for so doing, but I have a feeling that among scientific men 
generally, and I am afraid also among some Pathologists, there has been 
a tendency to forget that problems of disease, whether in men or in the 
lower animals, are simply problems in Biology. It is certainly true 
that Pathology has gained enormously in the past few years from the 
tendency to view disease phenomena from the broader biological stand- 
point, in contrast to the older methods of viewing them from the narrow 
aspect of human pathological anatomy. 
This received its first impetus from the development of our knowledge 
of bacteria as a result of the researches of Pasteur and Koch, but probably 
the most important step was taken when Metschnikoff in the year, 1884, 
published his paper in Virchow’s Archiv upon the subject of Phagocytosis 
and, in order to explain the method of destruction of disease germs in the 
human body, he studied the activities of the amoeboid cells in lower 
forms of animal life. Our knowledge upon this subject has advanced very 
much since the publication of that paper, but the idea of the activities 
of phagocytic cells has been a fruitful one in the development of all our 
views of disease and to Metschnikoff is due the honour of having first recog- 
nized the importance of the phenomenon. 
But this evening I do not propose to take you into a discussion of 
any of the many problems connected with this question of phagocytosis, 
although they are many and intensely interesting. I wish to speak of 
something about which we have less exact knowledge. To-day, no one 
thinks of studying the phenomena of human disease without regard to 
the disease of the rest of the animal kingdom. Indeed, if the view of the 
older physicians had been held to, that human pathology was something 
which should be studied apart from animal pathology, we could not have 
