28 MASS STUDIES IN BUILD. 



To derive the desired classes from figure 7, the polygon was some- 

 what arbitrarily divided into five parts, as indicated. Taking 33.5 

 as a starting-point, an equal logarithmic distance was laid off, above 

 and below this point, on the base-line. This was taken as the range 

 of middle class. An equal logarithmic range was accorded the classes 

 next above and below the median respectively. All of the remainders 

 were thrown into the extreme classes to which are given, thus, a 

 somewhat greater range than the interior classes. This seemed desira- 

 ble, since their frequencies were so low. The adjusted classes finally 

 adopted are as shown in table 9. 



SIGNIFICANCE OF VARIATIONS IN BUILD. 



What is the meaning of the great variations of build described in 

 the preceding paragraph? What is known in this matter may here be 

 briefly summarized that it may be held in mind in considering the 

 numerous cases to which we shall have occasion to refer. 



In general, it may be stated that variations in build are due to 

 endogenous causes and exogenous causes. In this book we shall have 

 occasion to examine especially the former — the constitutional or 

 hereditary factors. These include idiosyncrasies of metabolism, in 

 part controlled by peculiarities in the functioning of the endocrine 

 glands; in part, probably, by even finer protoplasmic differences. 

 Thus it is known that the thyroid gland greatly influences metabolism; 

 its activity in growing children tends to produce tall and slender 

 form. On the other hand, deficiency in its activity in childhood leads 

 to the type of obesity known as cretinism, and in middle life to 

 myxedema. The secretions of the pituitary gland cooperate with the 

 thyroid in stimulating growth, especially in the preadolescent stage. 

 When pituitary secretions are deficient there frequently results, it is 

 believed, the adiposogenital syndrome, in which great masses of fat 

 are deposited on breasts, abdomen, hips, and buttocks, and the gonads 

 remain infantile. A case that quite certainly belongs to this cate- 

 gory is shown by Beck (1922, p. 881) and reproduced in plate 8, 

 figures 3, 4, 5 ; 3 of this man's 4 sibs are fleshy and have scant beards. 

 This is quite like our standard very fleshy case (plate 2, fig. 5). See, 

 also, the extreme cases falling under this category described by Lyon, 

 1910. 



Lesions of the pineal gland (Beck, 1922, p. 909) and of the gonads 

 are stated in some cases to induce obesity. Certain it is that, on the 

 other hand, the activity of the gonads tends to slow up growth in 

 stature and to increase the chest circumference (plate 6), and this 

 change is more marked in the male than the female. 



The exogenous causes of build are striking, so much so that many 

 physiologists seem to accept the hypothesis that they are of sole 

 importance, that excess of fat is due merely to excess of calories 

 ingested over those concerned in bodily activity. While no one will 



