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For ordinary patients, Drs. Stewart, Hoffman & Ghiselin operate the moving picture camera at a standard speed of 16 frames a second, or 32 frames for the cycle. For unusually thick patients, through whom x-rays do not penetrate easily, the operators slow the camera twelve or eight frames a second. Thin people can stand 24 frames a second. The four chambers of their hearts then can be seen contracting on the projection screen.
The positive print of such an x-ray film may be cemented into a loop in a projector and run over and over to show a roomful of observers precisely how the patient breathes, throbs, swallows, belches.