Archives of internal medicine . k in the liver shadow that it is absurd to attempt to supply normal hearts this lower border is a fairly straight line, but pathologic-ally it may become considerably curved. Therefore the completed heartoutline represents only the examiners opinion of its size and shape. /. G. VAN ZWALUWENBERG—L. F. WARREN 139 The estimation of the area so enclosed is best accomplished by the useof the planimeter, an instrument used by engineers for measuring irregu-lar^ areas. Its scientific accuracy is limited only by the exactness withwhich the circumference can be fol
Archives of internal medicine . k in the liver shadow that it is absurd to attempt to supply normal hearts this lower border is a fairly straight line, but pathologic-ally it may become considerably curved. Therefore the completed heartoutline represents only the examiners opinion of its size and shape. /. G. VAN ZWALUWENBERG—L. F. WARREN 139 The estimation of the area so enclosed is best accomplished by the useof the planimeter, an instrument used by engineers for measuring irregu-lar^ areas. Its scientific accuracy is limited only by the exactness withwhich the circumference can be followed by a needle-point. By the kind-ness of Professor J. A. Moyer, of the engineering department, we areable to measure all our diagrams by this means. One may assume that the heart shadow approximates an ellipse andapply the formula for the area of this surface, namely, timesthe product of the long axis and the short axis. By drawing the longestdiameter (p-q) of the completed figure, then constructing a short diam-. Fig. 2.—Splanchnoptosis, Case 126, cm.; cm • longdiameter cm.; area 81 sq. em.; index .830. Right auricular shadow doesnot meet the diaphragm shadow. Vertical position. eter (r-s) normal to and bisecting this line, and using these values in theabove formula, results are obtained which vary but little from the plani-meter values (Fig. 4). This longest diameter (p-q) is not the sameas the long diameter (a-d) above described. The latter is drawn fromthe anriculovenous angle and is frequently considerably shorter than aline drawn from some other point on the right border. To make theapproximation closer, this line should be drawn as near the center ofinertia of the figure as possible, although, actually, it often lies a short 140 THE ARCHIVES OF ^TERNAL MEDICINE distance above it. The average error of the method in our series is inthe neighborhood of 3 or 4 per cent, and the highest was 8 per cent, ina heart of ver} irregular shap
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