REVIEWS. 227 
and a high success can rarely be attained except by those whose 
dexterity and skill in effecting mechanical and optical results have 
been matured by long use before the exigencies of a full medical 
‘practice rendered abundant drilling in the work impossible. For 
these reasons, Medical Microscopy will always remain to some ex- 
tent a specialty, most conveniently referred to the few physicians 
more particularly devoted to it. But for the microscopical work 
which physicians, as such, can do to advantage, for the using of 
the microscope, like the stethoscope and the test-tube, as an ey- 
ery-day aid to diagnosis,.a really available guide book is now 
for the first time published. For the general reader it is too 
technical and uninteresting to be compared with other works that 
are available; to the scientific physician it is a valuable aid. 
Students of this book should begin in the middle of it; reading 
the first part last, if at all. Nothing less than the author’s excel- 
lent success as a microscopist could save a beginner who had waded 
through the opening chapters from abandoning the work in con- 
fusion and disappointment. The first two chapters are devoted to 
a description of instruments, apparatus, etc., and it is astonishing 
that so good a microscopist could be so bad a critic in regard to 
his own tools. Aside from the tediousness and general confusion 
prevailing’ in this part of the work there is much that is liable, 
unless corrected, to seriously mislead the beginner. 
The simple microscope is described as one of a single lens; 
and the compound microscope, by way of contrast, as one in which 
. lenses are so arranged that each adds to the power of the other. 
This is precisely what occurs when a doublet or a triple combi- 
nation is used as a simple microscope, and is radically different 
from the action of the compound microscope where one lens, or 
set of lenses, by magnifying the image formed by the other, mul- 
tiplies its power instead of adding to it. 
Three or four of the microscopes first mentioned are described 
as furnished with sets of separating objectives like those on cheap 
European instruments, and these lenses are spoken of with some 
approval, although it would be more safe to state hat to render 
such instruments really available it is necessary to discard such ob- 
jectives and furnish at least second-class lenses by some respect- 
able maker. The objectives of Tolles’ students’ microscopes are 
very properly called by their honest name, for they are soona- 
quality lenses and nothing else, but it should have been intimated 
AMER. NATURALIST, VOL. V. 15 
