DETERMINATION OF SIZE OF HEART BY X-RAYS 469 



TABLE 17— Continued 



determined for each heart. The hearts were then grouped 

 according to the extent of divergence of observed from calculated 

 volume. Hearts showing a divergence of 2| per cent or less are 

 classed together. The others are classed to the nearest 5, 10, 

 15 or 20 per cent + or — . Markedly distorted hearts have been 

 excluded but no attempt has been made to select hearts that 

 conform to theory. For the sake of comparison the divergence 

 of observed heart weight from the heart weight calculated from 

 silhouette area is likewise given. 



This table shows that of the 62 hearts included in the study 

 the volume was correctly calculated from the area to within 2| 

 per cent in 16 cases, to within the nearest 5 per cent -|- or — 

 in 36 cases and to within 10 per cent (the nearest 10 per cent 

 + or — ) in 45 cases. It is probable that greater accuracy can 

 be obtained in estimating heart volume from silhouette area in 



