International Review of Educational Cinematography (Jan-Dec 1934)

86 THE CINEMA IN TEACHING 3) Slow seriography, which also deserves at least brief mention. X-Ray Cinematogra The chief difficulty enphy with Direct Ra countered was always diography. due tQ ^ abso,ute necessity of taking at least sixteen pictures per second of the organ in movement, so that when they were projected in the same order and in rapid series on the screen, they would give the retina the sensation of a single image in the course of its natural movement. Very short poses had to be adopted, therefore, so short that they were almost instantaneous, that is to say, they must be from a 32nd to a 100th part of a second. This necessitated an excessively rapid change of the radiographic plates and the diminishing in size of the radiograms thus obtained, in order that they might be projected. Lastly, the number of images obtained in this way had to be sufficient to reproduce every phase of the movement under examination. Photography by means of X-rays began with the direct utilization of ordinary plates, that is to say, glass prepared with a layer of gelatine. But, unfortunately, these plates had to be very large, at least 18 by 24 cm., especially for the heart and gastro-duodenal region, which are the viscera most studied. It must be obvious to anyone that the necessity of changing glass plates of this size at the rate of 16 per second makes the task of taking good cinematographic pictures of this kind excessively difficult. It was quite impossible, in the early days of radiology, to take really correct pictures of this kind. I will limit my review to the most important stages. The first attempts go back to 1897-98, when Roux and Bathazard studied the stomach movements of small animals by means of the radiography of a moving film, which they repeated twelve times, with poses of one second at regular intervals. Thus began the first steps in Rontgencinematography. The experiments were resumed in 1905 by LevyDorn and in 1907 by A. Kohler, with results which, when presented to the various Congresses, aroused the admiration and hopes of all. But these authors and their followers had necessarily had recourse to a trick, which, for that matter, they frankly confessed : they had taken a large number of radiograms, with a maximum pose of one per second, and thus fixed, of course by chance, the most varied phases of the movement, and had then combined the images one after another in a series that gave the impression of the real movement, when the reduced radiograms were projected on the screen. LevyDorn, for instance, radiographed 20-22 phases of movement in 20 seconds, and each phase was repeated twice, one after another. In 1908, Eijkmann succeeded in obtaining X-ray cinematographs of the act of deglutition. The slight thickness of the organs of the throat had enabled him to take instantaneous radiographic poses, that is, poses corresponding to an opening of the primary current of Ruhmkorff's coil. Unfortunately, his process, which was easy to carry out with suitable electric controls and very small plates, laid the operator open to all the dangers connected with the excessive use of X-rays, causing the hair to fall and provoking erythema, and in addition it could not be used for large organs like the s,tomach and heart, which would have necessitated enormous intensities of X-rays for the taking of radiograms of such short duration, and we had not these intensities in these days. But great improvements soon began to be made in radiological apparata, which, with the elimination of the closing currents, gave us a very high intensity of X-rays, namely, 100 and more mA, while our technique, which was continually making progress, was enriched by the so-called reinforcement screen, the first really excellent examples of which were constructed by Gehler of Leipzig. The reinforcement screen is formed of a plate which is very easily penetrated by the X-rays ; it is covered on one side by a salt that transforms the rays into ordinary light. If this covered side is closely attached to the sensitive surface of the photographic plate, we can make use of this system to take much