DURING POST-NATAL DEVELOPMENT. 495 



(see table B) show that the volume of the lower extremities is probably relatively 

 greatest in the period preceding puberty, at the time when their length is relatively 

 greatest. The data given above show that tall men have relative volumetric pro- 

 portions of the lower extremities which resemble those of boys in the stage preceding 

 puberty. 



Meeh gives figures for neck-volume which vary considerably for different 

 individuals, probably due mainly to difficulties in the technique used. It seems best 

 to measure the neck above the level of the larynx as a part of the head, below this 

 level as a part of the trunk. In making use of Meeh's data in constructing the line 

 which represents the division between trunk-volume and head-volume in chart K 

 we have transferred about 1 per cent of the total volume from his neck- volume to 

 head-volume and put the rest with the trunk-volume. These data indicate that the 

 relative volume of the head and of the upper extremities is smaller in women than 

 in men. In fat adults the absolute volume of the head measured as above suggested 

 is considerably increased by the "double chin," but the main relative increase 

 usually comes in the trunk (see table B, Meeh's case No. 4, with a height-weight 

 index of 0.610). 



C. D. Spivak (1915) gives some figures on head-volume which show great 

 irregularity in relative head-volume. In general the relative head- volume is low 

 compared with that shown in chart K, even when allowance is made for relative 

 adiposity. Spivak also gives data on volume of the body to the level of the umbili- 

 cus, to the level of the nipple, and to the level of the larynx, and on specific gravity. 

 The work of Mr. Puestow has not yet been completed, but his data correspond 

 closely with those of Meeh described above and have proved of value in the con- 

 struction of the curve for volume of the head. They show furthermore that relative 

 to the volume of the body the volume of the cranial portion of the head is more 

 reduced than the facial portion as the stature increases. 



Further detailed estimates of relative volume are given in tables B, C, and K 

 and in table 7 in the following section. 



SURFACE-AREA. 



The relation of cutaneous surface to volume of the body is one of considerable 

 physiological interest. Surface-area is conditioned by shape and by volume. For 

 a given volume the sphere has the smallest surface-area. Of elongated bodies of 

 constant cross-section the cylinder has the smallest surface-area. In the human 

 body the head is spherical, the neck and limbs are cylindrical, and the trunk may be 

 compared to a flattened cylinder which tends to the spherical in fetal life, in infancy, 

 and in the fat adult. Du Bois and Du Bois (1915) have proposed an ingenious 

 method of estimating surface-area from certain lengths and girths of each of the 

 parts mentioned. The neck is included with the trunk. The constants used in 

 estimating surface-area of each part, corresponding to TT in treating of spheres and 

 cylinders, have been determined empirically by observations on the cutaneous areas 

 of a widely diverse but limited numbers of individuals. Benedict (1916) has pro- 

 posed a method of estimating the surface-area of the body from silhouette photo- 



