584 
ing the mechanics of the reactions involved, 
and owing to their extreme complexity little 
is likely to be known for years to come. I 
should like to emphasize this point, for there 
are those who appear to hold that a study in 
behavior which does not deal with the re- 
duction of reactions to physico-chemical prin- 
ciples has no practical value. 
The study of modifiability im behavior 
should be much extended, especially in the in- 
vestigation of the lower forms where it has as 
yet received but little attention, and closely 
associated with this is the problem of regula- 
tion, so clearly set forth by Jennings in the 
closing chapters of his book on the behavior of 
lower organisms. 
Comparative behavior then, in spite of its 
anthropomorphic tendencies is valuable in cer- 
tain lines of investigation, and I hope that 
what I have said may counteract the strong 
opposition that has developed against it. 
However, no matter what may be the imme- 
* diate object of behaviorists, practically all of 
them desire to see reactions reduced, as far as 
possible, to mechanical principles. What has 
been accomplished in regard to this, and what 
are the prospects in reference to it? 
THE MECHANICS OF REACTIONS 
One of the foremost physiologists says in 
substance: Many reactions have already been 
reduced to physical and chemical or mechan- 
ical principles and all reactions together with 
all life-phenomena can be thus reduced. An- 
other equally prominent physiologist says: 
“The attempt to analyze living organisms 
into physical and chemical mechanisms is 
probably the most colossal failure in the whole 
history of science.” 
How is it that the results obtained by two 
eminent and practical investigators in the 
same general field have led them to conclusions 
so diametrically opposed, the one maintaining 
that many vital phenomena have been and that 
all vital phenomena can be reduced to mechan- 
ics, the other apparently maintaining that no 
vital phenomena have been and that no vital 
phenomena can be thus reduced? The differ- 
ence in these conclusions is in part, if not en- 
SCIENCE 
[N. 8. Vou. XLVIIT. No. 1250 
tirely, due to different conceptions as to what 
a reduction to mechanics involves. 
Fundamentally all scientific knowledge is 
the same. It concerns the order of phe- 
nomena not the cause of the order. It is 
rooted in experience and founded upon the 
conviction that Nature is orderly, that a phe- 
nomenon that occurs under a given set of con- 
ditions will occur again whenever this set of 
conditions obtains. All of the scientific laws 
that have been formulated are merely ex- 
pressions summarizing the results of experi- 
ence, and their validity depends upon the ex- 
tent of the experience. They are in no sense 
absolute; any and all of them may have to be 
modified as more experience is gained. To 
ascertain and to regulate the order of phe- 
nomena in nature is the purpose of science. 
Mechanics deals with the relation between 
events or phenomena and changes in the con- 
figuration of material systems associated with 
such events. ‘The reduction of behavior to 
mechanical principles consists in ascertaining 
the relation between reactions in animated 
systems and changes in material configura- 
tions within and outside of such systems. In 
other words, it consists in ascertaining the 
sequence in series of changes in material con- 
figurations ending in reactions. For example, 
suppose we have an alkaline medium contain- 
ing paramecia and add a bit of acid, thus in- 
ducing avoiding reactions. The substance or 
material in the alkaline medium has a certain 
arrangement or configuration. When the acid 
is added this configuration is changed and this 
sets up changes in the material configuration 
within the paramecia which result in a re- 
sponse. That is, we have a series of changes 
in material configuration ending in a reaction, 
and similar series of changes precede all re- 
actions. 
Now, when the mechanist says that re- 
actions have been reduced to mechanical prin- 
ciples, he probably means merely that some of 
the changes in material configuration in the 
series ending in reactions have been ascer- 
tained. And when the anti-mechanist says 
that the attempt to reduce reactions to me- 
chanical principles has been a colossal failure, 
