DETERMINATION OF SIZE OF HEART BY X-RAYS 431 



thorax according to some such formula as that suggested by 

 Kreuzfuchs('12). 



Some investigators add to the measurement of the transverse 

 diameter of the heart the measurement of the long diameter 

 from the point where the curve of the right border of the heart 

 is broken by the line of the aorta or of the superior vena cava 

 to the apex of the heart silhouette. Since, however, an accurate 

 outline of the apex of the heart is the chief difficulty that con- 

 fronts one when he attempts to complete the line of the lower 

 border of the heart the measurement of the long diameter of the 

 heart is subject to the chief error that may arise from measuring 

 the area of the silhouette and the long diameter gives a far less 

 satisfactory standard on which to base an estimate of volume. 

 This is true of the numerous other diameters that may be measured 

 on the^ heart silhouette. The area, which combines them all, 

 gives the best standard from which to estimate the volume of 

 the heart. For study of variations in the shape of the heart 

 however, some of these various diameters may be of value. 



4. TABLES A AND B 



Chosing then the area of the heart silhouette, reduced in case 

 of radiographs to conform in size to the contour of the heart, 

 (see p. 424) as the standard from which to estimate the size of the 

 heart we have tabulated in tables A and B the normal relations 

 of a silhouette area of a given size to transverse diameter, to body 

 weight, to heart weight, to heart volume and to height in either 

 sex at various ages. The data on which these estimates are 

 based may be summarized as follows: 



a. Heart silhouette area and body weight 



The relations of silhouette area to body weight are based 

 primarily on the study of radiographs of 188 men, 42 women and 

 9 children, all healthy and normal from the clinical standpoint 

 which we have studied at the Wisconsin Clinic according to the 

 teleroentgenographic method outlined above. With the data 

 obtained from these studies have been compared the orthodia- 



