PHOTOGRAPHING FROM THE RETINA. ONE of the first fruits of the daguerreotypic art was the suggestion that unknown murderers could be detected by photographing the last image left on the retina of the murdered person's eye. The idea that this could be done seems to have taken strong hold of many imaginations, and we believe this suggestion is repeated to the police authorities of New York on the occurrence of every noticeable and mysterious murder. That such a detective task will ever be accomplished by photography is extremely doubtful, on account of the length of time that usually passes before the discovery of a murder. But science has now advanced so far that the image on the retina _has been fixed and photographed_. This has been done by Prof. Kühne of Heidelberg, but not with human subjects, as decapitation is one necessary part of the process. Prof. Kühne placed a rabbit four and a half feet from a closed window, in the shutter of which was an opening twelve inches square. The animal's head was first covered by a black cloth for five minutes and then exposed for three minutes. The head was then instantly cut off, and one eye taken out in a room illuminated by yellow light. The eyeball was opened and instantly plunged into a five per cent. solution of alum. This occupied two minutes, and the other eye, still remaining in the head, was then exposed at the window just as the first had been. It was then taken out and placed in the alum solution like its fellow. The next morning the two retinæ were carefully isolated, separated from the optic nerve, and turned. On a beautiful rose red ground a sharp image, somewhat more than one millimetre (one-twenty-fifth inch) square was found. The image on the first retina--that which was exposed during life--was somewhat reddish and not so sharply defined as that on the other.