DETERMINATION OF SIZE OF HEART BY X-RAYS 451 



deducted from the weight of the body and kidneys by means of a 

 Hnear equation with an average error of about 8 per cent. If the 

 mean heart weight of the cases studied by these authors be di- 

 vided by the mean body weight, the heart weight is found to be 

 approximately 0.575 per cent of the body weight. Individuals 

 show a variation from this mean per cent of body weight of about 

 25 per cent in either direction that is, from about 0.45 per cent 

 of body weight to 0.70 per cent of body weight. 



These figures probably very nearly express the average relative 

 weight of the heart. Other investigators who have studied a 

 greater number of individuals have furnished data which differ 

 more or less widely according to the material studied and meth- 

 ods used. As a rule the data have been presented from the stand- 

 point of average body weight and average heart weight for a 

 given age. By dividing the one by the other one obtains a 

 rough estimate of the proportion between heart weight and body 

 weight for a given age. Data obtained in this way have led to 

 somewhat divergent results as may be seen in table 7. 



Boyd studied a large number of individuals at the Marylebone 

 Infirmary and a smaller number at the Insane Asylum at Som- 

 merset. The figures for the latter are placed immediately below 

 those for the former for age groups above 30. It will be noted 

 that in general the hearts studied by Boyd are heavy in relation 

 to body weight, running from 60 to 80 per cent of the body weight 

 instead of less than 60. There is no great difference between the 

 relative size of male and female hearts but the hearts studied at 

 Sommerset are notable relatively smaller in size than those 

 studied at Marylebone. The figures from Thoma are based on 

 a mathematical study of the average heart weight found by 

 Caspar-Liman, Blosfeld, Reid, Peacock and Boyd for a given 

 age combined with Thoma's. study of the average body weight 

 for corresponding ages. They show a low relative weight of the 

 heart and indicate that the high relative weight shown in Boyd's 

 figures is due largely to body emaciation. The hearts studied by 

 W. Mtillerare from a more carefully selected material and average 

 relatively smaller in size than those of Boyd, 0.604 per cent of 

 the body weight in males; .594 per cent in females. The very 



