DECEMBER 13, 1918] 
he probably means merely that in no such 
series have all of the changes in material con- 
figuration been ascertained. If this is true 
then both views are doubtless corect; for it 
can not be disputed that some of the changes 
in material configuration in series ending in 
reactions have been discovered in numerous 
instances, and it can not be demonstrated 
that all such changes have been discovered in 
any instance. 
Take for example, one of the very simplest, 
if not the simplest of all responses, changes in 
ameboid movement. It has been maintained 
that this reaction is due to changes in surface 
tension. Similar movements can be induced 
in inanimate systems. If a bit of potassium 
bichromate is brought near a drop of mercury 
in ten per cent. nitric acid the mereury will 
flow toward the bichromate. This is due to 
a local reduction in surface tension. This and 
numerous similar experiments, it is main- 
tained, show that movements in Ameba are 
due to changes in surface tension. It has, how- 
ever, recently been demonstrated that changes 
in surface tension can not produce the force 
required in certain ameboid reactions. Other 
factors have consequently been postulated to 
supply this deficiency. Now this is a per- 
fectly legitimate procedure in scientific in- 
vestigation. All that I wish to emphasize here 
is the fact that ameboid movement has not yet 
been completely reduced to mechanics. Even 
if it were conclusively demonstrated that every 
movement and every change in movement in 
Ameba is directly the result of changes in 
surface tension, it could still be maintained 
that the series of changes in material con- 
figurations associated with these phenomena is 
not completely known for such a demonstra- 
tion would have no bearing upon the problem 
of the regulation of the movements. 
Ameba can move in a homogeneous en- 
vironment. Consequently, if its movements 
in such an environment are due to changes in 
surface tension, such changes are the result 
of internal factors concerning which practic- 
ally nothing is as yet known. These factors 
may be purely physical and chemical, but it 
o certainly can not be maintained that it has 
SCIENCE 
585 
been demonstrated that they are. For all that 
is known to the contrary there may be non- 
material factors, entelechies and psychoids, in- 
volved in this regulation. Do not misunder- 
stand me, I do not maintain that there are 
such factors involved, I merely hold that it has 
not been demonstrated that such factors are 
not involved. 
In reference to regulation which constitutes 
the very essence of vital phenomena, we have 
indeed as yet traveled but a short way on the 
road toward reduction to mechanical prin- 
ciples, and it is mainly in this region that the 
anti-mechanist operates. 
If we are correct in our analysis thus far, 
the essential difference between the mechanist 
and the antimechanist or yitalist is found in 
the fact that the former maintains that all re- 
actions are completely determined by material 
configurations, and that all of the changes in 
such configurations can be ascertained, while 
the latter maintains that the reactions are not 
thus completely determined and that the 
changes in material configurations ending in 
reactions can be ascertained only in part, 
Which of these views is correct will be known, 
if it is ever known, only after every possible 
sequence associated with reactions has been 
ascertained. Thus it is evident that the me- 
chanistie and vitalistic programs are, in so 
far as they pertain to experiment and obser- 
vation, precisely the same. The mechanist 
holds that all reactions can be reduced to me- 
chanical principles. Consequently he proceeds 
to ascertain by experimental methods every 
possible sequence of phenomena ending in re- 
actions. The vitalists hold that some reac- 
tions or certain phases in some reactions can 
not be reduced to mechanical principles. He 
also must proceed to ascertain by experimental 
method every possible sequence of phenomena 
ending in reactions. For this is the only way 
he can be certain as to where mechanism 
breaks down and non-material factors begin to 
act. 
But mechanists frequently maintain that 
faith in vitalism tends to inhibit experimenta- 
tion, and that it inculeates superficiality. 
They maintain that when the vitalist gets into 
