A rabbit was tied with its head facing a barred window. From this position, the rabbit could only see the window and the cloudy sky. The animal’s eyes were covered with a cloth for several minutes to acclimate it to the dark, i.e. to allow rhodopsin to accumulate in its rods. The animal was then exposed to light for three minutes. He was then immediately beheaded and his eyes removed. An incision is made in the removed eyes, and the back half of the eyeball containing the retina is removed and immersed in an alum solution for fixation.
The next day, Kuhne saw an image of a window with a clear pattern of bars imprinted on the retina with bleached, unmodified rhodopsin: After these studies, Kuhne wanted to conduct his experiments on a human, so in 1880, Kuhne’s eyes were removed from a death row inmate named Erhard Gustav. Reeve was executed after his execution and was handed over to Kuhne’s laboratory at the University of Heidelberg.
Years later, in 1975, the Heidelberg police wanted to re-examine Kuhne’s experiments and results using modern scientific techniques, updated information and advanced equipment. For this reason, they turned to the expertise of Evangelos Alexandridis from Heidelberg University. In a manner reminiscent of Kuehne, Alexandridis was able to create many different high-contrast images from rabbits’ eyes. But he concluded that optics had no potential as a forensic tool.