772 
For objects to be viewed only from one side 
or where two specimens, one for a dorsal view 
and one for a ventral view, can be used, the 
introduction of a strip of milky or black glass 
as wide as the diameter of the tube or a trifle 
less is an improvement for observation. 
The method is of special value in the labora- 
tory and lecture room. For toto specimens of 
animals (or organs admitting of this treatment) 
to be used by large classes it is excellent. The 
specimens can be examined closely and can be 
handled freely without danger of being ruined. 
In no other way known to me can meduse, 
ctenophora and similar delicate animals be 
handled and studied so freely without injury to 
the specimen. Moreover, magnifying glasses 
can be used very easily and profitably. 
Even many museum specimens can be thus 
preserved permanently and relieve the curator 
of the dread of a possible evaporation. Dr. 
MacDougal has found the method admirably 
adapted to many things in botany. 
In the study of the embryology of many 
animals material thus preserved is of great 
value. The various stages thus preserved are 
marked in agreement with the series of sections 
of corresponding stages. In many cases the 
specimens can be stained and put up in balsam 
or damar or any other mounting medium for 
transparent objects. Such preparations in con- 
nection with serial sections are often invaluable 
and to the student are always a help well worth 
having on hand. 
After I had used round tubing for some 
time it occurred to me oval tubing might be 
better because it would magnify and distort the 
objects less. The experiments made with large 
pig and chick embryos do not, however, favor 
the oval tubing, which, moreover, is more ex- 
pensive than the circular tubing. Professor 
MacDougal, however, prefers it for some of his 
plant preparations. 
Various details, such as mounting and label- 
ling the tubes for the museum, suspending the 
specimen by means of a fine wire, etc., must be 
left to individual genius, likes and dislikes. 
Henry F. NACHTRIEB. 
UNIVERSITY OF MINNESOTA. 
SCIENCE. 
[N. 8. Von. X. No. 256. 
SCIENTIFIC BOOKS. 
Methods of Knowledge ; an Essay in Epistemology. 
By WALTER SmiTH, Ph.D., Professor of 
Philosophy in Lake Forest University. New 
York, The Macmillan Co. 1899. 12mo. 
Pp. xxii + 340. 
Although Locke must be regarded as the 
founder of the philosophical discipline known 
variously as Epistemology, Noétics, Theory of 
Knowledge, it remains true that thinkers who 
use English have lagged behind their German 
brethren in cultivating its special field. Thanks 
to Kant, to the renewed interest in his work 
after 1860, and to the direct influence of the 
particular sciences—which brought German 
thought back to Locke just at the moment 
when Britain and the United States were going 
to school with Hegel—Epistemology achieved 
an importance through writers like Schuppe, 
Cohen, Riehl, Avenarius, Busse, and to some 
extent, Lotze and Wundt, such as it has never 
enjoyed with us, and in all likelihood, will not 
soon gain. Professor Smith’s work has, there- 
fore, a place to fill ; moreover, the author suc- 
ceeds in presenting some fresh, if not striking, 
ideas. 
Yet, no matter how favorably one may be in- 
clined to view it, Epistemology suffers still from 
several capital defects. The delimitation of its 
precise sphere cannot be called complete by 
any means. Its relation to logic remains a 
moot point. Its commerce with psychology, 
and particularly its debt to psychological 
methods are undetermined or, at all events, 
subject to large variation of view. While, once 
more, even British experts, who have not found 
so much reason to trouble about its province as 
their German colleagues, have deemed it neces- 
sary to execute some excellent wrangling over 
its relation to metaphysics. Traces of this dis- 
pute remain in the work before us. The weak- 
nesses of Dr. Smith’s book appear to be direct 
products of the two last points. His epistemol- 
ogy, by accident or design I cannot profess to 
determine, overlaps the psychological sphere 
extensively. Possibly, one ought to forgive 
this tendency, because it imparts concreteness 
to abstract investigations of an exceedingly dif- 
ficult kind. Again, his conception of the rela- 
