810 
discussions respecting experience and knowl- 
edge. More than often it has been regarded as 
an abstract form of self-evident apprehension, 
whose chief, and perhaps sole, function is to 
mark the limits of reasoning. How it may have 
come into our experience has been humorously 
and seriously debated from Locke downward. It 
may not be an exact source of knowledge, but 
this negation does not exclude the peculiar sig- 
nificance attached to experiencing the relation 
in question. The two cases following indicate 
that there is some meaning to the ‘ principle’ 
when found in conscious processes at an earlier 
time. 
A bright child, Helen B., four years of age, 
whose development has been normal in all par- 
ticulars, perplexed her mother and myself by 
adding to a conversation, in which she was tak- 
ing no part and which had no apparent concern 
for her, these words: ‘‘ Whatever is alike is the 
same. If you are good, you have to be good ; 
if you are bad, you have to be bad. Whatever 
is alike is the same.’’ Tactful questioning 
failed to bring out any evidence that the utter- 
ance was an echo from something the child may 
have heard. The meaning of the statement 
seemed to be clear to the child, though able to 
explain or expand it in no other way. She 
persisted in the assertion with considerable 
show of feeling, amounting almost to triumph. 
Another and more recent instance is that of 
a boy in his sixteenth year. In a certain class 
the teacher was endeavoring to get another 
pupil to complete the sentence, ‘‘ A dog is—,”’ 
for purposes of illustration. After several ex- 
amples and some hesitation on the part of the 
second pupil, the first jestingly ventured to 
supply ‘a dog,’ thesentence then reading: ‘‘ A 
dog isa dog.’’ The teacher accepted the sug- 
gestion as ‘all right,’ and showed how such 
statements could be made. The boy, however, 
was confused with astonishment upon learning 
that his suggestion had passed from jest to 
earnest, and required a rather long period of 
time to recover and adapt himself to this rela- 
tion, which had apparently never occurred to 
him previously. 
These rather opposite cases go to show that 
the ‘principle’ is not utterly void when it first 
arises in the conscious processes, however thor- 
SCIENCE. 
[N.S. Vou. VI. No. 152. 
oughly one may claim it to have been operative 
in primitive mental activities. 
EpwARrpD F. BUCHNER. 
NeEw YORK. 
SCIENTIFIC LITERATURE. 
A Popular Treatise on the Physiology of Plants for 
the Use of Gardeners, or for Students of Horticul- 
ture and Agriculture. By DR. PAUL SORAUER. 
Translated by F. E. Weiss. London and 
New York, Longmans, Green & Co. 1895. 
One of the excellent features of this book is 
that there has been a consistent endeavor on 
the part of author and translator to make ita 
book clearly within the grasp of the persons for 
whom it is intended. 
The author has succeeded in dealing with 
many of the problems‘ of nutrition, diffusion, 
assimilation, ete., in a way that is not only 
attractive, but can be understood by one who 
has had little previous training in the study of 
plants. 
After the introduction the author takes up 
first the structure of the root, and in connection 
with the structure discusses also the function of 
the root in the processes of absorption and con- 
duction of nutrient materials. This is followed 
by a chapter on the nutrition of the root, deal- 
ing with the substances in the soil which act as 
plant food, the effect they have on the plant 
and the form in which they are taken up by the 
plant. Practical suggestions are made concern- 
ing the best treatment of the soil, the nutrition 
of pot plants, etc. The treatment of roots in 
transplanting, in repotting, is also considered. 
The structure of the stem and leaf are treated 
in the same readable way in relation to the 
functions which they play in the general plant 
economy. Theremaining chapters are devoted 
to plain directions for pruning, propagating, 
watering and the general nurture of the plant 
and seed, from the standpoint of the horticul- 
turist and gardener, and this part of the book, 
atleast to one who deals more with the prin- 
ciples of plant development than with horticul- 
tural practice, seems to be admirably done. 
: GEORGE F. ATKINSON. 
Contributions to the Analysis of the Sensations. 
By Ernst MAcu. Translated by C. M. Wit- 
LIAMS. Chicago. 1897. 
