﻿Bones of the Skeleton as an Index of Nutrition. 203 



least a part of the truth, and that the muscles do, through 

 the strains and stresses which they throw on the bones, 

 profoundly modify their general contour, and in many 

 cases act as determinants of the sites of cresting and 

 tuberculisation. And so it becomes necessary for us to 

 seek a fuller explanation and interpretation of the meaning 

 of these appearances — an explanation which will, on exam- 

 ination, prove less unsatisfactory than that of Topinard's. 



In the course of this paper evidence will be produced 

 which, I think, fairly conclusively demonstrates that the 

 roughness of the bones of the appendicular skeleton is 

 directly associated with, and is the permanent monument of, 

 a relatively vigorous and even unfavourable type of meta- 

 bolism, and that its apparent association with sex and age 

 and muscular activity is in one sense accidental, and of 

 value only so far as age and sex and muscular activity are 

 themselves determinants of the prevailing type of meta- 

 bolism. 



It is not possible to proceed to the demonstration of this 

 point without reviewing briefly the theory of growth. 



2. The Theory of Growth. 



(a) The Grovjth of the Cell. — Expenditure of energy is an 

 essential characteristic of the living cell. This energy it 

 derives from the food which it intussuscepts and uses to 

 replace the de-energised matter within itself. But if there 

 be food absorbed surplus to the actual needs of the moment, 

 and if the surplus be retained, the cell, of necessity, is larger 

 than before. 



Now, Spencer has pointed out that as a sphere becomes 

 larger its mass increases as the cube, its surface as the 

 square of its diameter. The importance of this is obvious, 

 for it means that the area of cell surface must become 

 diminished relatively to the amount of cell mass, which, 

 in turn, means that the difficulties in obtaining the non- 

 storable parts of the food, as, for example, oxygen, and the 

 difficulties of excretion must increase with the diminution 



