137 



during all the periods of its growth. At birth, it has acquired 

 much more thau one half of its permanent dimensions ; conse- 

 quently it grows, during the nine months of uterogestation, more 

 than from birth to the eighth year, when its development is com- 

 plete. Indeed, it would even appear to increase, during the seven 

 months previous to parturition, more than during as many years 

 after birth. 



The cranium is generally considered as containing a single 

 organ. Now, as it may be supposed, that all parts of the same 

 organ will grow in the same proportion, and, as there is a con- 

 nexion between the development of the cranium and the parts it 

 contains, we should be naturally led to expect, that all parts of this 

 cavity would grow with equal rapidity. Observation, however, 

 proves this supposition to be erroneous ; and demonstrates, that, not 

 only the various parts of the cranium develop themselves in dif- 

 ferent proportions, but also that each portion of the brain has a 

 rapidity of growth peculiar to itself. 



If a line be drawn round the cranium, passing over the nasal 

 and external occipital protuberances, it will be separated into two 

 portions, a superior and inferior. These two portions grow very 

 une jually. The upper part, which is called the vault, is developed 

 much more rapidly than the under, or base. 



Let the vault of the cranium, in its longest diameter, be divided 

 into five equal parts. The two anterior fifths grow less rapidly than 

 the three posterior. Of the three posterior fifths, the two anterior 

 are most rapid in growth. As, therefore, the vault of the cranium 

 grows more rapidly than the base, and as that part of the vault, 

 where the two posterior join the three anterior fifths, is, of all parts 

 of tlie vault, the most rapid in its growth, it follows, that this por- 



VOL. XIII. u 



