. The American journal of roentgenology, radium therapy and nuclear medicine . FlG. I. Motor and shutter mounted on handle andconnected by very short flexible shaft. Yet another American stereofluoroscopeis described bv Dr. Heck, in the issue ofthe American Journal of Roentgen-ology for September, 1920. Dr. Heck usestwo rotating shutters. He also uses twoCoolidge tubes, each with its own trans-former and control. The shutters are con-nected through suitable gearing to a solidshaft on the other end of which is a twelve-inch arm whose extremities travel close totwo semicircular rods, each of whi
. The American journal of roentgenology, radium therapy and nuclear medicine . FlG. I. Motor and shutter mounted on handle andconnected by very short flexible shaft. Yet another American stereofluoroscopeis described bv Dr. Heck, in the issue ofthe American Journal of Roentgen-ology for September, 1920. Dr. Heck usestwo rotating shutters. He also uses twoCoolidge tubes, each with its own trans-former and control. The shutters are con-nected through suitable gearing to a solidshaft on the other end of which is a twelve-inch arm whose extremities travel close totwo semicircular rods, each of which isconnected to one of the Coolidge electric motor drives this system at aspeed of 900 revolutions a minute. Bythis means the eve gets fifteen light impres-sions per second. The objections to thisapparatus would seem to be its size andlack of flexibility. In the July, 1921, num-ber of the Journal of the Roentgen Society,London, is a description of an apparatusdesigned bv Prof. Tyndall and Mr. objects have been simplicity and. Fig. 2. Views from the side, and from above, I tintube in carrier. tance equal to the diameter of the circledescribed by (p). This can be varied byplacing the pin in any one of a series ofholes at different distances from thecenter of the disc (c). An excursion ofabout one inch was found to be the mostefficient, and a speed of about ten revolu-tions a second to give satisfactory persis-tent pictures. Under these conditions noundue strain is placed on the tube. Arotating shutter is used (Fig. 3). My cnti-
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