Letter from SS-Untersturmführer Rascher to Reichsführer-SS Himmler, April 5, 1942. (Trials of War Criminals Before the Nuremberg Military Tribunals - Washington, U.S Govt. Print. Off., 1949-1953, Vol. I, p. 144-147):
esteemed Reich Leader:
Only continuous experiments at altitudes higher than 10.5 Km resulted in death. These experiments showed that breathing stopped after about 30 minutes, while in two cases the electrocardiographically charted action of the heart continued for another 20 minutes.
The third experiment of this type took such an extraordinary course that I called an SS physician of the camp as a witness, since I had worked on these experiments all by myself. It was a continuous experiment without oxygen at a height of 12 Km. conducted on a 37-year old Jew in good general condition. Breathing continued up to 30 minutes. After 4 minutes the experimental subject began to perspire and to wiggle his head, after 5 minutes cramps occurred, between 6 and 10 minutes breathing increased in speed and the experimental subject became unconscious; from 11 to 30 minutes breathing slowed down to three breaths per minute, finally stopping altogether.
Severest cyanosis developed in between and foam appeared at the mouth ...
One hour later after breathing had stopped, the spinal marrow was completely severed and the brain was removed. Thereupon the action of the auricle stopped for 40 seconds. In then renewed its action, coming to a complete standstill 8 minutes later. A heavy sub archnoid oedema was found in the brain. In the veins and arteries of the brain a considerable quantity of air was discovered."