Aveust 27, 1897.] 
ment is made in various places. The extensive 
scope of the book is well shown by an outline 
of the various chapters: (1) The microscope 
and its parts. (2) The manipulation of the 
same. (8) The interpretation of images. (4) 
Magnification and measurement. (5) Drawing. 
(6) Micro-spectrosecope and polariscope. (7) 
Technique of the object. (8) Photo-micrography. 
To these are added a copious appendix on 
methods of testing and on preparing figures for 
publication, while the whole is terminated by 
an extensive bibliographical list and by a good 
index. The bibliography is to be especially 
commended for its accuracy and complete- 
ness. A careful review of its five pages of 
closely printed type discloses only one omission, 
though that is rather a striking one, the Zeit- 
schrift fir angewandte Mikroskopie. 
The book is full of valuable information, not 
only for the student, but for those of consider- 
able experience in microscopic technique, and 
the number of good hints which,are given is 
very large. Of course, every man has his own 
ideas with reference to details of technique, and 
undoubtedly no one would agree with the exact 
plan outlined by the author. For instance, 
some would undoubtedly criticise the state- 
ments that balsam mounts should be sealed, as 
also that collodion is the most generally ayail- 
able imbedding material. Many will find fault 
with the detail of instruction given for the use 
of the mathematical tables. These are, however, 
particulars in which the manual is suited to the 
course given by Professor Gage, and easily 
capable of omission by those who use the book 
with other ideas in mind. 
It may be fairly questioned whether the 
amount of space given to the microscope and 
its accessories from an optical standpoint is not 
excessive ; aS compared with Behrens, Kossel 
& Schiefferdecker, for instance, the extent of 
space devoted to this branch of the topic is 
rather striking. In the latter work about 30 
per cent. of the space is devoted to the instru- 
ment, while 50 per cent. is spent in the consid- 
eration of the preparation of the object. 
In Professor Gage’s book the microscope and 
its accessories occupy about 80 per cent. of the 
entire work ; and even when one considers that 
some parts are discussed here more fully in the 
SCLENCE. 327 
light of recent development in certain branches 
of the subject, it is still questionable whether 
the technique of the object has not been slighted 
in favor of the technique of the instrument. 
As the reviewer has pointed out elsewhere, itis 
undoubtedly by the development in the manipu- 
lation of the object that recent years have ad- 
vanced so far, and it is to this advance that we 
are indebted for our rapidly growing knowl- 
edge with reference to more fundamental phe- 
nomena of biological science. Some years ago 
in his address, ‘A Plea for Physiological His- 
tology,’ Professor Gage himself emphasized this 
side of the question. The various methods of 
reconstruction are, in the opinion of the re- 
viewer, of much greater general importance to 
the student in every branch of biological science 
than some of the difficult mathematical discus- 
sions of optics which are treated at length in 
the book, and yet the topic of reconstruction 
has not even been mentioned. This is all the 
more striking when one recalls that we are in- 
debted to Mrs. Gage for a most admirable and 
inexpensive method of reconstruction, and when 
the various methods have been so largely ap- 
plied both by her and by the author in their vari- 
ous researches. 
The treatment of the microscope as an op- 
tical instrument, with its various accessories, is 
exceedingly complete ; so much so that Profes- 
sor Gage gives us fourteen full pages of cuts of 
microscopes, in which good, bad and indifferent 
stands are mixed with rare impartiality. There 
is no discussion of the principles on which the 
construction of the various types is based, and 
no choice expressed with reference to which are 
the most reliable or would best perform certain 
sorts of work. The beginner, or even a stu- 
dent of some experience, would sit dazed be-~ 
fore this collection of figures in his efforts to 
decide which he needed. The inclusion of so 
many cuts was, perhaps, a necessity of the case, 
seeing that the electrotypes were donated by 
the manufacturers and it would have been un- 
wise to have slighted any particular firm ; and 
yet it might have helped a little to have dis- 
cussed briefly the general principles of con- 
struction involved. 
Among minor defects one might mention a 
lack of care in type-reading, which shows itself 
