DETERMINATION OF SIZE OF HEART BY X-RAYS 481 



lying was 56.9 cc. per kilo per minute with a pulse rate of 67 or 

 0.85 cc. per kilo per beat. 



/. Relation of size of heart to lieiqlit, age and sex 



In the preceding sections we have considered heart size chiefly 

 from the standpoint of body weight with which it is most closely 

 correlated. In case of a given individual, however, other fac- 

 tors than merely body weight must be taken into consideration 

 before we can form an accurate judgment as to whether or not 

 the size of the heart is normal for that individual. Of these 

 other factors the chief are height, age and sex. 



The size of the heart for a given body weight is estimated in 

 the tables on the assumption of normal height for that weight 

 for a given sex and age. The chief studies on the relations of 

 weight, height, sex and age in the adult have been made by the 

 insurance actuaries. The most important of these studies is 

 the Medico-Actuarial Mortality Investigation vol. 1 published 

 by the Association of Life Insurance Medical Directors and the 

 Actuarial Society of America. For the period of childhood and 

 youth we have a large number of studies made on school children 

 of which special mention may be made of those of Roberts 

 (78-'83), H. P. Bowditch (75, 79, '91), F. Burk ('98), A. Key 

 ('89), F. Boas C96-'97), Hastings, W. W. ('02), Baldwin ('14), 

 W. T. Porter ('94) and Ethel M. Elderton ('14-'15). The pio- 

 neer work in this general field is that of Quetelet ('32, '48) . 



These studies have shown that a closer correlation between 

 height and weight is found if age and sex be taken into considera- 

 tion than if these are ignored. The figures given in tables A 

 and B are based upon an analysis of the data available in the 

 literature together with studies made in the Clinical Department 

 at the University of Wisconsin. A full account of these studies 

 is reserved for publication in a subsequent paper. The figures 

 for height are those which these studies have led us to believe 

 represent a fair normal average for a given weight, for the age 

 and sex indicated in healthy Americans. Weight means weight 

 without clothes; height, height without shoes; age, age at nearest 

 birthday. 



