30 DR DAVID HEPBURN ON 
considerable number of months. Within the last year or 
two (and notably through the able investigations of one 
of my colleagues, viz, Dr Waterston), observations made 
upon the bones and joints of the human foetus at various 
stages of gestation prove that at birth the bones and joints 
of the human infant very closely resemble those of the 
Anthropoid ape, whereas its brain at the same period is 
distinctly a human brain. In other words, at birth the 
human brain is in advance of the human body, and it has 
developed faster than the body. Not only so, but the 
cranium which surrounds the infant brain is not a rigid 
box, since it consists of bones set comparatively widely 
apart, whereby it is possible for the human infant to be 
safely born with a brain in advance of the general bodily 
development, as well as with arrangements which permit 
of continued enlargement of the brain and of the surrounding 
box. 
As the growth of the individual proceeds, brain-growth 
and ossification of the cranial bones continue, until the 
bones are merely separated from each other by those lines 
of union called sutwres to which your attention has already 
been directed, and which tend to disappear by ossification 
as age advances. When a suture disappears, it is no longer 
possible for any increase of the cranial cavity to take place 
in relation to that line of union; but so long as any given 
suture persists, there is the possibility of an increase of the 
cranial cavity either in length, breadth, or height, and I 
take it that in the first instance the determining cause of 
increase in the diameters of the cranium is the growth of 
the brain which it contains. We have here, therefore, 
two conditions of growth, viz., growth of brain and growth 
of cranium ; and so long as these retain their relative rates 
of growth, the proportions of the cranial diameters will 
-correspond with the proportions of the brain diameters. 
If, however, a suture should close sooner than is its rule, 
then the growing brain must adapt itself to the altered 
conditions, not by ceasing to grow, but by accommodating 
itself to the increased space obtained by additional growth 
of the cranium in another direction. We do not know 
what conditions determine the early closure of a suture, 
