on the Functions of the Brain. 471 
Although insensibility is the common effect of undue pres- 
sure upon the cerebrum, it appears from what will be stated, 
that it is not a necessary consequence of undue pressure upon 
the cerebellum. 
The facts which have been stated appear to point out the 
use of the water in the ventricles of the brain, and they ac- 
count for the great variety which is met with in the form 
and extent of the posterior cornua of the lateral ventricles, 
their size varying according to the quantity of water which 
is necessary to keep up the pressure required. 
The size of the ventricles would appear to be very imma- 
terial, since even when they are increased so as to contain 
above six ale pints, tlie functions of the brain are all carried 
on, and the growth of the body proceeds ; but after the skull 
is completely ossified, an increase of two or three ounces pro- 
duces insensibility. 
That the ventricles should admit of being increased to so 
great an extent, without any of the senses or faculties of the 
brain being destroyed, is in itself a curious fact, and of so 
much importance with respect to the physiology of the brain, 
that I shall detail the two following cases, which illustrate one 
another. 
In the one, the accumulation of water proceeded, as it will 
appear, as far as it could go without materially impairing the 
organ ; it then stopt, and the boy grew up, with all his fa- 
culties : in the other the water continued to increase, the sub- 
stance of the cerebrum was absorbed, and the faculties of the 
brain were destroyed. 
A boy at a month old had so rapid an increase of the size 
of his head, as to evince an accumulation of water in the brain ; 
and when he was five years old, the head was so large that the 
3 P 2 
