May 3, 1901.] 
physiologists Haller, Reil and Johannes 
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 deter- 
mines the character of the effect. The im- 
pulse that must come from the outside to 
produce these effects is called the stimulus. 
Hence there must exist a fundamental in- 
ternal organization, that is to say, a predis- 
position to something external. * * * 
Disease, then, may be regarded as the effect 
produced by quantitative changes in nor- 
mal conditions, either when the physiologi- 
cal organization is too feeble or the stimu- 
lus too intense.” Disease may be viewed 
as a phenomenon of adaptation. 
Against this conception, the parasitic or 
germ theory, developed by Plenciz, Hisen- 
mann, Henle, Davaine, Pasteur, Klebs, F. 
Cohn, J. Schroter and Koch, appeared to 
introduce an entirely new qualitative ele- 
ment. 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.’ 
Another conception is that of Petten- 
kofer, which holds that the determining 
cause is to be found in the external condi- 
tions, which vary according to time and 
place. 
It is not difficult to see that these theories 
are upholding entities as the cause of dis- 
ease. While a kernel of truth is to be 
found in each, they all fail to realize the 
continuity of causes in the sense of modern 
exact science. ‘The true and sufficient 
cause of any effect is always something in- 
ternal, something that follows from the 
kind and amount of initial energy, and 
from that quality and quantity alone and 
SCIENCE. 
687 
entirely. * * * It is the absolute thing 
‘that exists behind all change and remains 
primordially the same,’ as Helmholtz ex- 
pressed it.’”? Or as the modern physicist 
would put it: potential energy = cause, 
kinetic energy = effect; and as a liberating 
impulse will change potential energy into 
kinetic energy, so a liberating impulse will 
change cause into effect. 
The cloudiness that characterizes many of 
the theories that have sought to explain the 
phenomena of infectious diseases is largely 
a legacy of Kantism, and is clearly out of 
place in these days of modern science. It 
is somewhat strange that‘ ontological toys’ 
are still to be found in the workshop of 
some really brilliant investigators of natural 
phenomena. Nevertheless, they are there 
—which explains some explanations that 
do not explain. 
The parallelism which subsists between 
the phenomena of fermentation, infection 
and immunity, suggests the mental route to 
be traveled if an insight into our problem 
is to be gained; and for this reason it is 
necessary to first point out a few facts 
about fermentation. 
FERMENTATION. 
If the phenomena of matter be defined as 
periodic functions of the atomic and molec- 
ular masses which constitute it and the 
rates of motion of these masses, and the 
chemical unit be viewed as a ‘center 
through which energy manifests itself,’ then 
the theories of modern chemistry should 
supply an explanation of the phenomena of 
fermentation. 
The crucial test of every theory which 
seeks to explain fermentation is the satis- 
factory explanation of the following phe- 
nomena : 
Enzymes appear to be capable of disrupt- 
ing complex chemical bodies without un- 
dergoing any apparent chemical change 
themselves—that is, they bring about a 
