Note P — Chapter IV · LABORATORY TESTS

For registering the curves a Hering kymograph was used, with a loop 2½ metres long. The kymograph rested on felt. With the aid of the Marey model a pneumographic record was taken now of the thoracic, now of the abdominal, breathing, never both simultaneously, since this was extrinsic to my purpose, and it would have made the whole experiment too complex. The time was recorded by means of the Jacquet chronograph. For purposes of making more exact measurements the acoustic current interrupter of Bernstein was used, attuned to 100 vibrations per second. But this necessitated such rapid revolution of the drum of the kymograph that the curves were not compact enough for purposes of demonstration. The levers were all fitted with micrometer adjustments. They wrote tangentially and, except the one registering the breathing curve, all points lay in one vertical line. The error of deflection and that due to the rondure of the writing-surface were both very slight on account of the comparative length of the levers and the small extent of the excursions, and for that reason synchronous points lie practically in one perpendicular. Only the breathing curve has been moved somewhat to the left, 7.5 millimeters in figures 6 and 7, 2 millimeters in figure 8, 4.5 millimeters in figure 9. (When the breathing was very profound, as occasionally happened, the error of deflection would, of course, have to be taken into account.) The curves here used as illustrations have been reproduced in the exact size of the originals by the zinco-graphic method, though somewhat compressed vertically in order to economize space.