A. I consider him an authoritative physiologist, I am not acquainted with his work in the field of aviation medicine. Q. Mr. President, I previously put in evidence—I want to recall that now—an expert opinion from this Dr. Rein regarding Dr. Ruff. (_Ruff 5, Ruff Ex. 3._) This expert testimony is from Professor Rein. In your own experiments, Witness, you also used conscientious objectors, is that not so? Did I understand you correctly? A. Yes, in some of the experiments. Q. Will you tell us why you used conscientious objectors? Were they particularly adapted for these experiments; or what was the reason for you, as one conducting experiments, to use especially conscientious objectors? A. It was their duty, their volunteer duty to render public service. They had nothing else to do but to render public service. In the experiments in which we used the conscientious objectors, they could devote their full attention to the experiments. Many of the subjects, which I have used, have been medical students or dental students, who besides serving as subjects had to attend their studies in schools. In the experiments we did on the conscientious objectors, they could not attend school at the same time and carry on or perform all the tests they were supposed to perform. For example, we used a group of conscientious objectors for repeated exposure to an altitude of 18,000 feet without the administration of supplemental oxygen. These tests involved the following of a strict diet, they involved the performance of work tests and psycho-motor tests, which required several hours every day to perform. Another group of conscientious objectors that I used were used for vitamin studies in relation to fatigue. These conscientious objectors had to do a great deal of carefully measured work during the day as well as to perform psycho-motor tests so medical students or dental students could not be used. We had to have subjects who could spend their full time on the experiments.[28] * * * * * Q. Witness, from the answers that you have given so far, I am still not clear in my mind precisely why you hit upon conscientious objectors in particular as the experimental subjects. You said there were two groups of them: some were in prison and some had to perform public service. From the latter group you took your experimental subjects, but please give me a clear answer to the question: Why did you specifically use such conscientious objectors for your altitude experiments? A. They could devote full time to the experimental requirements. They did not have to do any other work as was the case of medical students or dental students, the only other type of subjects that I had available to me.