470 C. E. BARDEEN 



the living than in the dead since the condition of the heart with 

 relation to the distention of its chambers is more uniform in the 

 living. We believe that the formula given above enables one 

 to calculate diastolic volume from silhouette area to within 

 5 per cent of the volume in diastole in the majority of instances 

 in the living. 



In cadavers there is a tendency to underestimate volume 

 from silhouette area when the heart is contracted; to overesti- 

 mate volume when the heart is more distended than is normal 

 in diastole. Whether or not this is true in the living we have no 

 means of ascertaining at present. If we take the heart weight 

 considered standard for a person of a given body weight as de- 

 scribed in Section C, p. 449 — and given in tables A and B, and 

 the silhouette area considered standard for a given body weight 

 as described in Section A, p. 431, and given in tables A and B 

 we see that there is a constant relation between silhouette area 

 and heart weight if each is assumed to bear a constant relation 

 to bod}^ weight. We may express this relation by the formula: 



^V area^'^^ X 0.0055 = heart weight. 



The area is here assumed to be the area in square centimeters 

 of the heart silhouette in diastole while sitting at rest and the 

 heart weight that of the whole heart in grams. If the heart is 

 more contracted than is normal in diastole when the body is 

 sitting at rest the weight of the heart in relation to the silhouette 

 area is increased. If the heart is more dilated than is normal 

 for this position the weight of the heart in relation to the sil- 

 houette area is decreased. We thus have a method of deter- 

 mining in a more or less rough way whether or not a heart in 

 the cadaver is more or is less dilated than is normal in diastole 

 when the body is at rest in the living. In table 17 the percentage 

 of divergence of the observed from the heart weight estimated 

 from silhouette area is given for 53 of the 62 bodies in which the 

 relation of silhouette area to volume was studied. From this 

 table it may be seen that of the 17 hearts whose volume was un- 

 derestimated from the shadow area, ten were underestimated 

 from the standpoint of weight and four overestimated. This 



