688 
chapter, he adopts the automatic theory for 
the explanation of animal intelligence, and 
carries it farther into the range of human 
action than any psychologist has hitherto ven- 
tured to do. 
His theory of the dependence of mental ac- 
tivity upon the degree of perfection of sensory 
organs in animals is ingenious, but- his own 
statement of the typical form and function of 
the sensori-motor system is opposed to it. 
That system is a double one, and no amount 
of development in one half can compensate 
for a lack of development in the other half. 
However fine the structure of a sensory organ, 
it is useless, unless a corresponding develop- 
ment has occurred in its governing centre and 
executive motor apparatus. An example in 
point is the olfactory apparatus in man, which 
is a beautiful piece of mechanism, without 
a correspondingly complex central organ, — a 
survival of a formerly valuable sense, at present 
almost useless. Nor can Dr. Calderwood’s 
conclusion that the complexity of brain struc- 
ture is proportionate to muscular development 
be admitted in a causal connection. There is, 
doubtless, a parallelism. But the one settled 
fact of brain physiology is, that, through the 
entire range of vertebrate animals, but two 
convolutions of the brain are the seat of motor 
functions. The other convolutions have noth- 
ing to do with governing muscular action; 
and it is inconceivable that they have devel- 
oped simply to keep pace with the two motor 
convolutions which form but a small fraction 
of the entire brain. From a comparison of 
the habits of the dog and the horse, and of the 
dog and the ape, Dr. Calderwood concludes 
that the dog is a more intelligent animal than 
the others. He finds the dog’s brain a com- 
paratively simple structure, and then states 
his wide generalization that complexity of 
structure has no relation to intelligence. But 
a few pages farther on he takes care to show 
that the dog’s intelligence is due to a thousand 
years of man’s training. Is it not possible 
that the horse and ape, under the same con- 
ditions, might have made even a greater prog- 
ress than the dog has made? And as long 
as this possibility remains, does it not invali- 
date the generalization ? 
It is impossible, in a limited space, to follow 
the author in all his arguments. It is only 
necessary to call the attention of readers to 
the fact that Dr. Calderwood’s explanations of 
the facts he so clearly states, are not the only 
ones to be considered. The chief defect in the 
entire discussion of animal intelligence is the 
lack of discrimination between various grades 
SCIENCE. 
[Vou. III., No. 70. 
of reflex action. There are lower and higher 
reflexes, simple and complex reflexes, accord- 
ing as the reflex centre excited lies farther from 
or nearer to the cortex of the brain. Each 
higher reflex centre not only possesses a power 
of its own, but also exerts an inhibitory action 
upon those below it. It is this inhibitory action 
which makes reflex action purposive. A com- 
plex reflex centre receives numerous sensory 
impulses, compares them, and selects the proper 
response. If we admit that the cortex can 
act automatically, we must admit, that, in such 
automatic action there, the centres receive, 
oroup, distinguish, and co-ordinate many vari- 
ous impulses arriving in them from different 
organs at once, and respond by sending out 
a complex and co-ordinated impulse to the 
muscies. An example is the balancing of the 
somnambulist as he walks a narrow bridge. 
This is very different from the simpler reflex 
which draws back a finger from the flame. 
But when this complex reflex is analyzed, it is 
found to contain many of the elements which 
Dr. Calderwood would limit to conscious intel- 
ligence of man. Im the anecdotes given on 
pp. 2386 and 248 we have examples of a 
‘sensori-motor activity,’ which was certainly 
the result of the animal’s interpreting its own 
former sensory experience, and comparing 
past with present acts with a view to the reg- 
ulation of conduct. In a word, we have in 
these animals’ actions a proof of conscious- 
ness and intelligence in the strict sense in 
which the author applies these terms. ‘ Mind’ 
must be given a place within the area of nerve 
apparatus. It may be admitted that we have 
no proof of the existence of consciousness in 
others; but, if we argue consciousness from 
action, we must include the actions of animals 
as well as of our friends. We are reduced to 
one of two alternatives: either much that Dr. 
Calderwood advances as evidence of mind in 
man is really evidence of a more complex 
sensori-motor activity, or much that he ex- 
plains away in animals is true intelligence. 
There is such a continuity of development, 
both in organism and in intelligence, that any 
attempt to draw a boundary-line between sen- 
sori-motor activity and intelligence at once 
raises objections on both sides, — a conclusive 
proof that we are not yet able to draw the 
boundary. | 
We do not care to follow the author through 
the more psychological part of his work, as 
his explanations lose much of their force in — 
view of these objections. It is gradually 
becoming evident that a rich field for cultiva- 
tion in psychology lies,within the domain of 
