DURING POST-NATAL DEVELOPMENT. 



499 



The relative surface-area and relative volumes of the chief regions of the body 

 in the cases cited may be expressed in percentage of total area and total volume as 

 follows : 



TABLE 7. 



A study of this table will show that the chief differences in relative surface- 

 area as estimated by the Du Bois method and by Meeh are a slightly greater head- 

 surface area and a slightly smaller upper extremity surface-area by the former. 

 Making allowance for this and remembering that a low index of build means relative 

 thinness, a high index means large bulk, the following points seem clear: 



The volume of the trunk including the neck is approximately 50 per cent of the 

 total volume of the body throughout life; the surface-area is approximately 37 

 per cent of the total surface-area; the ratio of area to volume is approximately 3: 4. 

 Both volume and surface-area of the trunk are relatively greater in fat than in thin 

 individuals and in men than in women. They are also probably greater in short 

 than in tall adults, although this point as regards volume is not well brought out 

 in this table. 



The relative volume of the head decreases from about 27 per cent in the infant 

 to 7 per cent in the adult. The relative surface-area decreases from about 18 per 

 cent in the infant to 6.5 per cent in the adult. The ratio of relative surface-area to 

 relative volume therefore changes from about 2 : 3 in the infant to nearly 1 : 1 in the 

 adult. The relative surface-area and volume of the head are probably usually 

 greater in short than in tall individuals, in men than in women, and in the thin than 

 in the fat. 



The relative volume of the lower extremities increases from about 15 per cent 

 in the infant to about 30 per cent in the adult. The relative surface-area increases 

 from about 25 per cent to about 40 per cent. The ratio of relative surface-area to 

 relative volume is about 5: 3 in the infant, 4: 3 in the adult. Both relative volume 

 and relative surface-area are greater in women than in men, in tall than in short 

 individuals, and in the thin than in the fat. 



