Unconsciousness │ From— │ Recovery of consciousness after— │ │ after— │ │ 23 sec. = 17 km. │18 km. │156 sec. = 4.6 km. [55,800 ft.] │ [59,100 ft.] │ [15,090 ft.] 20 sec. = 18.5 km. │19 km. │173 sec. = 3.7 km. [60,700 ft.] │ [62,300 ft.] │ [12,140 ft.] 17 sec. = 19.75 km. │20 km. │178 sec. = 3.2 km. [61,520 ft.] │ [65,600 ft.] │ [10,500 ft.] 15 sec. = 20.875 km. │21 km. │1 min., 10 sec. after [68,490 ft.] │ [68,900 ft.] │ reaching 0 m. From 21 km. [68,900 ft.] altitude only one experiment was made in this series, just as in the falling experiments, with oxygen breathing since the pumps achieved the evacuation of the main chamber necessary for a pressure drop to 21 km. altitude only after hours of overloading and the fact that the mercury barometer used in these experiments had its limit of measurement at this altitude. The two experiments were considered only as an orientation on the behavior of the human organism at this altitude at which the ebullition point of the blood had already been far surpassed. A systematic working over of these altitudes must be carried on with perfected measuring instruments and a two-stage pump aggregate in a new experimental series. The result of this falling experiment from 21 km. altitude was made unreliable through the fact that the subject experienced a paralysis of breathing from 11 to 7 km., through which his recovery was doubtless greatly delayed. However, no permanent damage occurred. _4. Falling experiments with oxygen breathing_ Falling experiments with oxygen breathing were undertaken only in small numbers for crude orientation for the following reasons: The altitude [page 22 of original] was limited by the available equipment to a maximum of 21 km. [68,900 ft.], but indeed from this altitude falling experiments without oxygen breathing had already been profitably carried out. It is self-evident that oxygen breathing during parachute jumps from such extreme altitudes greatly increases in any case the chances of success of the jump and, therefore, is to be unconditionally demanded. For that reason it devolved upon the experimenters only to determine to what degree the results of the experiments are influenced by oxygen breathing, especially in regard to the recovery of consciousness, which, of course, followed without oxygen only at relatively low altitudes. As was to be expected, these experiments showed clearly the favorable effect of oxygen breathing. (Table 6): Table 6.—Falling experiments with oxygen breathing