1878. ] Microscopy. 259 
and attached by any strong varnish, and the joint finished off 
with white zinc cement. The objects appear with great distinct- 
ness, lying with their upper surfaces on a level and close to the 
cover glass, but looking as if they were at the bottom of a dark, 
deep cell. This method is also applicable to many of those 
objects which show well as opaque objects when immersed in 
balsam. ; 
IMAGES IN THE EYES AFTER SUDDEN DEATH.—Mr. Henry C. 
Hyde, the newly elected president of the San Francisco Micro- 
scopical Society, in his opening address, gave a very interesting 
summary of the recent remarkable. discoveries of Profs. Boll, of 
Rome, and Kiihne, of Heidelberg, in the anatomy and physiology 
of the eye. He said that the popular notion that the murderer's 
image is found photographed as it were on the retina of his vic- 
tim’s eye may have some foundation in fact, viewed in the light 
of these recent discoveries, especially those of Dr. Kühne. His- 
tologists have always considered the rods and cones of the retina, 
which are taken to be the terminal organs of the optic nerve, to 
be in a natural condition when under examination. Prof. Boll 
found, however, that when the animal, say a frog, is killed rapidly 
and the retina viewed as quickly as possible, it has peculiarities 
never before observed, and throwing new light on the physiology 
of vision. 
ce the experiments of Dr. Kühne are more elaborate and 
extensive than those of Prof. Böll, a sketch of them will be most 
instructive. Prof. Boll found that the newly removed retina had 
a rosy purple tint, which was difficult to examine, because expo- 
sure to light changed it in ten seconds toa satiny lustre, and then 
after fifteen minutes of transparency to a turbid opacity. Dr. 
uhne discovered that if kept in the dark, or in sodium (yellow 
light, the delicate “vision purple” of the removed retina could 
be retained as long as wished, thus making a series of very 
original and incisive experiments possible. It is proved that the 
retina contains a substance which, under the influence of light, 
darkness, then the retina can be kept in its natural condition, 
purple colored, the batteries ready charged to signal to the brain 
