GROWTH OF THE SKELETON 287 



the mature femur, it is seen that while enlargement by magnifi- 

 cation does not reveal any marked differences in the thickness of 

 the shaft, yet it does give us a bone in which the extremities are 

 relatively very large. The actual process of growth brings 

 about, therefore, the changes in proportion which are indicated 

 by a comparison of E with C. The humerus also has been studied 

 in this way and undergoes a similar change in form. 



It appears, then, that as these bones pass from the immature 

 to the mature condition, they become more nearly rod shaped 

 and less clumsy in form, and we note in passing that this change 

 in shape during growth opens a field for study which thus far 

 has been little cultivated. 



What cannot be determined without elaborate investigation is 

 whether this distribution of the bony substance by weight repre- 

 sents the distribution as it would be brought out by compass 

 measurements, but the impression given by a preliminary study 

 of a series of bones, and by figure 1, is that between puberty and 

 maturity the very slight change in the relative linear dimensions 

 of the bones is such as to make the largest full-grown bones 

 relatively a trifle more slender than those which are half grown 

 and younger. 



This result is, we think, contrary to the current view that 

 during postnatal growth bones become relatively thicker as they 

 become older. We may, however, be wrong in our impression as 

 to the current view concerning this change. 



On the relative lengths of the long bones of the limbs when compared 



among themselves 



To obtain the relative length of the bones in the fore limb on 

 the length of the corresponding bones on the hind limb, we divide 

 the sum of the lengths of the humerus plus the ulna or plus the 

 radius, on the one hand, by the sum of the lengths of the femur 

 plus the tibia. The ratios are given as percentages in table 27 

 and the corresponding smoothed graphs in chart 22. 



To compare the growth of the distal bone in each limb with that 

 of the proximal bone, the length of the ulna or of the radius has 



