DETERMINATION OF SIZE OF HEART BY X-RAYS 427 



is comfortable and throws the heart forward toward the plate. 

 The tube is raised high enough to direct the central rays per- 

 pendicular to the center of the plate. These central rays pass 

 approximately through the tenth thoracie vertebra. As a routine 

 the pictures are taken during deep but not forced inspiration and 

 with two half second exposures with an intervening half second 

 so as to insure a. diastolic outline. For special studies we have 

 taken pictures in the prone and standing positions as well as in 

 the sitting position, during inspiration as well as during expira- 

 tion. We have also taken instantaneous pictures timed by special 

 electrical devices at any desired period of the cardiac and re- 

 spiratory cycles. 



The studies of Moritz, Dietlen ('09), and others have shown 

 that as a rule the heart is larger in the supine than in the sitting 

 position and in the sitting than in the standing position. Ac- 

 cording to Dietlen the difference as a rule is more marked in 

 young healthy individuals than in those with less healthy hearts. 

 For normal individuals he gives the average percentage difference 

 in area of heart silhouette between the supine and standing 

 positions as 20 per cent of the supine area with the extremes at 

 30.4 per cent and 10.6 per cent. For those with slight lesions 

 he found an average difference of 12.8 per cent, those with 

 marked lesions a difference of 9.5 per cent and in cases of recent 

 decompensated hearts a difference of only 5.6 per cent. On the 

 other hand in some cases of acute dilatation he found variations 

 of from 23.3 per cent to 34.6 per cent. 



Dietlen's figures for normal individuals seem somewhat high. 

 (Cf. Otten, '11-' 12.) In eight normal individuals, taking the 

 pictures during deep inspiration, I found an average difference 

 in area between the prone position and the sitting position of 

 6.7 per cent of the prone area (extremes 2.8 per cent and 12.1 

 per cent) and between the prone and standing positions of 13.3 

 per cent (extremes 2.4 per cent and 17.4 per cent}. In nine other 

 individuals of whom instantaneous' pictures were taken in the 

 prone and sitting positions during quiet respiration at the height 

 of diastole I found an average difference of 4.7 per cent of the 

 prone area (extremes per cent to 10.9 per cent). Veith's 



