Annual Address by the President. 
11 
on anthrax soon followed, and then came the growth of pure cult- 
ures of several pathogenic 'bacteria. 
“The work of Pasteur and Koch afforded the first basis on which 
the study of artificial immunity could be again undertaken. The 
possibility of voluntarily producing a number of the most import- 
ant infectious diseases of men and animals, and of modifying at 
will pure cultivations of bacteria, either, according to Jenner’s 
precedent, by passage through the animal body, or otherwise in 
artificial culture media, laid the foundation on which advancement 
could proceed. Pasteur himself was the first, after J enner, to pro - 
duce an artificial immunity by using an attenuated virus; and he 
was also able to introduce the procedure to some extent into practice 
with most beneficial results. Still the theoretical explanation of 
all these facts lagged far behind their practical effect. The very 
able investigations of Metschnikoff and his theory of phagocytosis 
were, to many investigators, inconclusive/’ 4 
Numerous attempts were made to formulate adequate theoretical 
explanations of the accumulated facts concerning the phenomena 
of infectious diseases. The followers of Sydenham looked upon 
the specific disease itself as an entity; while Lotze and Virchow 
viewed it as a process. It was clear that a mechanical or dynamical 
process could not be a living entity. The physiologists Haller, 
Rail and J ohannes Muller had established this principle for normal 
life processes, and its extension to abnormal life processes was 
simple enough. “Whatever be the outside forces that act, the eye 
perceives only light, and the ear only sound; the glands simply 
secrete and the muscles contract. It is, therefore, the internal 
condition of the organism, of its organs, tissues or cells, that alone 
determines the character of the effect. The impulse that must 
come from the outside to produce these effects is called the stimulus. 
Hence, there must exist a fundamental internal organization ; that 
is to say, a predisposition to something external * * *. Dis- 
ease, then may be regarded as the effect produced by quantitative 
changes in normal conditions, either when the physiological organ- 
ization is too feeble or the stimulus too intense.” 5 Disease may be 
viewed as a phenomenon of adaptation. 
Against this conception, the parasitic or germ theory developed 
by Plenciz, Eisenmann, Henle, Davaine, Pasteur, Klebs, F. Cohn, 
J. Schroter, and Koch, appeared to introduce an entirely new 
qualitative element. It asserts: “That many diseases are due to 
the presence and propagation in the system of minute organisms 
having no part or share in its normal economy.” 6 
Another conception is that of Pettenkofer, which holds that the 
