Another distinctive feature of both the Porajmos and the Holocaust was the extensive use of human subjects in medical experiments. The most notorious of these physicians was Josef Mengele, who worked in the Auschwitz concentration camp. His experiments included placing subjects in pressure chambers, testing drugs on them, freezing them, attempting to change their eye color by injecting chemicals into children's eyes and various amputations and other brutal surgeries. The full extent of his work will never be known because the truckload of records he sent to Otmar von Verschuer at the Kaiser Wilhelm Institute was destroyed by von Verschuer. Mengele's own journals, consisting of some 3,300 pages, are likely never to be published, and they are suspected to contain denials of the Holocaust. Subjects who survived Mengele's experiments were almost always killed and dissected shortly afterwards.