. The heart and the aorta; studies in clinical radiology . the depth of foreign bodies. It is based for the mostpart on the relation of like triangles. The principal out-lines are these: In Fig. 29, let 0 be the projectile to locate; E, the radio-scopic screen; A, the tube, which is 60 centimeters fromthe screen. In position A, the tube gives a normal raywhich passes through the foreign body 0, the image ofwhich falls at C. This first projection is marked with acrayon on the glass of the screen. The tube is movedfrom A to A, a known distance, 10 centimeters. Thebeam of rays reaching 0 projects
. The heart and the aorta; studies in clinical radiology . the depth of foreign bodies. It is based for the mostpart on the relation of like triangles. The principal out-lines are these: In Fig. 29, let 0 be the projectile to locate; E, the radio-scopic screen; A, the tube, which is 60 centimeters fromthe screen. In position A, the tube gives a normal raywhich passes through the foreign body 0, the image ofwhich falls at C. This first projection is marked with acrayon on the glass of the screen. The tube is movedfrom A to A, a known distance, 10 centimeters. Thebeam of rays reaching 0 projects the image at C. Thisis marked on the glass, C. It is easy to calculate bymeans of a millimetric rule the distance CC which sepa-rates the two crayon marks. On the other hand, AC andAA are known. These three elements allow the graphicconstruction or the mathematical calculation to be made,which, given the two like triangles AOA, COC, gives thevalue OC, that is to say, the distance of the foreign bodyfrom the screen. SHADOW OF HEART IN NORMAL STATE 55 A A. Fig. 29. FIGUBE EEPEESENTING THE METHOD OF DEVIATINGTHE TUBE IN OEDEE TO LOCALIZE FOEEIGN BODIES E, screen; AA, two positions of the tube; O, projectile; CC, projectionsof the foreign body. By repeating the same method, having for the objectthe apex of the heart of a normal subject, and not aforeign body, and by bringing the ray AN tangent to it(Fig. 30, black lines), a projection is obtained of the apexthat is not deformed. Mark with a crayon on the screenpoint N, which coincides with the outer edge of theshadow; then move the tube 10 centimeters toward theleft of the operator. The image of the apex is seen tohave become deformed and displaced toward the a second point (N) to fix the amplitude of the dis-placement. A millimetric rule allows of its calculation. A case of hypertrophy of the left ventricle is presentedhere as an example (Fig. 30, contours and lines dotted).The enlargement in volume has only a bearing
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