550 
Notices of Books. 
[October, 
M. Fontaine’s work will be read with interest by all who are 
concerned in the application of electricity to lighting purposes. 
The book is well illustrated, and the translation has been care- 
fully made. 
The Human Eye ; its Optical Construction Popularly Explained. 
By R. E. Dudgeon, M.D. London : Hardwicke and Bogue. 
1878. 
This work commences with an account of various instruments 
which help to illustrate the mechanism of the eye ; lenses are 
discussed, and the refradtion of light by lenses of different form 
and curvature. The eye is compared to a photographic camera, 
and various sedtional diagrams are given to illustrate the views 
expressed. It is asserted that Kulme has found that the image 
of an objedt thrown upon the retina during life remains visibly 
impressed on that membrane after death. The minute structure 
of the crystalline lens receives illustration ; also the conditions 
of long- and short-sightedness. Clossat long ago pointed out 
the fadt that the curvature of the crystalline lens is not that of a 
sphere, but of an oblate spheroid. Dr. Dudgeon proposes the 
use of air lenses for the use of divers under water. Of course 
an air-lens ceases to be a lens as soon as it is out of water. An 
interesting account is given of subaqueous optics and effedts — ■ 
among them the effedts observed by a diver furnished with air- 
lens spedtacles, who is resting on the bottom of a bath, full of 
clear water, with a perfedtly unruffled surface. The eyes of 
fishes are discussed, and diagrams are given of the lenses of the 
skate and turtle. Dr. Dudgeon believes that the lens possesses 
a “ rotation movement ” in accommodation for near vision. “ If 
the transition from near to distant accommodation takes place in 
the dark, there occurs, as Czernak has remarked, a sudden flash 
of light in the eye, which he calls a phosphine . This phenome- 
non is, I believe, caused by the sudden springing back of the 
lens to its normal unaccommodated position, communicating a 
shock to the retina whereby the sensation of light is evoked, — 
just as a slight blow on the eye will produce the sensation of a 
flash of ordinary light. At the same time the sudden relaxation 
of the ciliary muscle, or tensor chloroidese, permitting the stri- 
ated chloroid membrane to resume its position, will intensify the 
shock that produces the flash.” 
The work is clearly written throughout, and embodies the 
results of the most recent German researches on the subjedt, 
and it will be welcomed alike by the old and the young physi- 
ologist. 
