446 C. E. BARDEEN 



diameter are from five to fifteen times as great. Dietlen's tables 

 show the same thing. 



We have therefore discarded the transverse diameter of the 

 heart silhouette in favor of the area as a means of estimating 

 relative heart size. In order, however, to make possible a com- 

 parison between the results of studies based on measurements of 

 the transverse diameter and the data in our standard tables we 

 have introduced a column showing the approximate transverse 

 diameter corresponding to the silhouette areas given in tables 

 A and B. 



To determine the approximate transverse diameter correspond- 

 ing to a heart silhouette area of a given size we have tabulated 

 the various transverse diameters corresponding to a given area, 

 reported by Dietlen in his study of the hearts of adult men and 

 women, those reported by Veith in his study of the hearts of 

 children, and the data obtained in our own x-ray studies of the 

 heart in the living and those obtained from a study of cadavers. 

 While the variations in the size of the transverse diameter cor- 

 responding to an area of a given size are considerable the formula 

 1.18 \/ area = transverse diameter gives a fair general standard as 

 the following examples may show (table 5). 



In slender, youthful adults, especially during deep inspiration 

 the long axis of the heart tends toward the vertical and hence the 

 transverse diameter of the heart becomes relatively small. The 

 large number of such individuals included in the series studied 

 roentgenographically by me tends to make the transverse diam- 

 eter of hearts with a silhouette area of from 90 to 125 square 

 centimeters average below the figures called for by the formula 

 given above and utilized in tables A and B. The average is also 

 low in several of the older groups of children studied by Veith 

 and in the cadavers of small slender individuals studied by me. 



In order to test out the values of the transverse diameter given 

 in tables A and B from the standpoint of body weight the fol- 

 lowing table has been prepared (table 6) . 



For the lighter weights, the number of observations are re- 

 latively few. Veith's supine individuals number 80. The 

 male individuals sitting are of two groups; (1) is composed of 



