486 HEIGHT AND WEIGHT IN RELATION TO BUILD 



those of the wealthier classes up to adolescence, but that during adolescence the 

 former continue to grow for a longer period; so that, although the difference is not 

 completely made up, there is at a given age less relative difference in size between 

 adults of the two classes than between children of the two classes. The school 

 children studied by Baldwin (1914) grew on an average much faster than those 

 studied by other American observers up to adolescence, but the adolescents were of 

 normal size. In table G, p. 596, data are given on rate of growth in American children. 



Variation in rapidity of growth in stature and weight is, to an extent as yet 

 incompletely determined, correlated with chronological variation in such processes 

 as dentition (Boas and Wissler, 1904; Bean, 1914; ossification (Rotch, 1910), pubes- 

 cence (Crampton, 1908), and the beginning of menstruation. 1 Cramp ton's observa- 

 tions support the view that there is a closer correlation between these processes and 

 growth in height and in weight than there is between them and chronological age. 

 In contradistinction to chronological age he uses the term physiological age to 

 characterize a stage in which events connected with these processes occur. Weis- 

 senberg (1911) states that menstruating girls 13 years of age usually have the 

 stature normal for 15-year old girls, while 15-year old girls who have not menstruated 

 are usually of subnormal stature. It would doubtless be of great value to the 

 study of human anatomy if anatomists would make a habit of recording, so far as 

 practicable, the characteristics of the physiological age as well as the chronological 

 age of the individual. Stratz (1915) has published a chart to illustrate ossification 

 and dentition in relation to growth. 



While study of the correlation of the development and structure of one part of 

 the body with that of another part is of great value, the study of each part should 

 be correlated with that of the size and general proportions of the body as a whole. 

 Measurements of stature and of weight are the most common and the most impor- 

 tant measurements of size. Linear measurements, other than those of stature, 

 such as those of sitting-height or chest-girth, are of value in the study of bodily 

 proportions but prove of greatest interest when viewed in relation to stature. Where 

 practicable, it would be helpful to record the volume of the body as a whole, but the 

 difficulties of technique exclude this as a routine procedure. Instead, we may 

 estimate volume from weight. While such an estimate must necessarily be imper- 

 fect, since the specific gravity of the body as a whole varies, it adds considerable 

 interest to the study of the size of the body to think of weight in terms of volume. 



VOLUMETRIC PROPORTIONS. 



The specific gravity of the different tissues of the body varies greatly. The 

 data tabulated by Vierordt (1906) show that the densest tissue is the enamel of the 

 teeth 2.380 (Davy), and next to this, bone 1.717 to 1.9304 (W. Krause and G. 

 Fischer) . On the other hand the air cavities in the head, including the nose, mouth, 

 pharynx, and air sinuses, the air in the lungs and the gas in the stomach and intes- 

 tines, all add to the volume of the body without increasing its weight. Most of the 



1 For the correlation existing between retardation and acceleration in growth and school grade the reader is referred to 

 Poiter (1893), MacDonald (1897-8), Boas and Wissler (1904), Smedley (1900), Crampton (1908), and Courtis (1917). 



