470 
Sir Everard Home’s Ohseivatioju' 
SECTION I. 
The effects produced by an undue pressure of zvater upon the Brain. 
Before I enter into the particular effects that take place 
when pressure is made upon the brain by means of water, it 
is necessary to mention that sudden pressure of any kind upon 
the cerebrum, takes away all sensibility, whether made upon 
the external surface through the medium of the dura mater,^ 
or upon the internal parts through the medium of the ven- 
tricles, 'f and sensibility returns as soon as the unusual pres- 
sure is removed. 
Faintness is the consequence of the pressure, to which the 
cerebrum has been accustomed, being suddenly taken off. J 
I am induced to believe that pressure to a certain degree uni- 
formly kept up, is necessary for the performance of the healthy 
functions of the cerebrum ; and any increase or diminution 
of this pressure puts a stop to them. It is asserted, that in 
addition to this pressure, the pulsatory motion of the blood in 
the arteries of the cerebrum is also necessary ; but the late 
John Hunter, whose accuracy in a point of this kind is not to 
be doubted, retained his senses although the heart had appa- 
rently ceased to act.§ 
* After the operation for the trepan, before the skull at that part is ossified, pres- 
sure upon the brain with the finger produces insensibility. 
t This I have seen in cases of spina bifida, by pressing upon the tumour in the 
back, and forcing the water up into the ventricles. 
X The removal of a coagulum of blood, half an inch thick, between the skull and 
dura mater, made the pulse nearly stop, but as soon as he recovered from this faint 
state, the person was perfectly well, 
§ Vide Life of John Hunter prefixed to his work on the Blood, Inflammation, and 
Gun-shot Wounds. The account is transcribed from his own notes. 
