304 
GL ARCHIE STOCKWELL. 
fluid within the cranial cavity, which may present itself in one or 
more of five situations: 1. Between the dura mater and the osse¬ 
ous vault; 2. In the cavity of the arachnoid ; 3. In the pia-mater; 
4. Within the substance of the cerebrum ; 5. Within the ventri¬ 
cles. And the relative frequency thereof is in the following 
order: 
Cavity of arachnoid ; between dura and skull; in the pia- 
mater ; in brain and ventricles. 
Extravasations into the cavity of the arachnoid necessarily 
have their source in the vessels of the pia mater, in the superficial 
veins, or in the great sinuses, and arise with apparent equal facil¬ 
ity from slight or severe wounds. Those between the dura and 
skull originate from small arteries passing from the membrane to 
the osseous vault, from the middle meningeal, or from the venous 
sinuses, and may develop suddenly or slowly, and in greater or 
less amount, according to circumstances. Haemorrhages into the 
pia, and into the ventricles and substance of the brain, are invari¬ 
ably the sequel to laceration of cerebral substance. 
Coagula within the arachnoid and pia are especially prone to 
cover considerable superficial areas, and between the dura and 
vault to speedily take on decomposition whereby are developed 
cerebral and meningeal complications with fatal results. In the 
former, prognosis is always grave ; for even should not death im¬ 
mediately supervene, the attending symptoms of nerve irritability, 
such as migraine, epilepsy, insanity, etc., etc., render the suf¬ 
ferer a burden to himself and to others ; and while it has been 
claimed that absorption may take place within the arachnoid, the 
physiological relations wholly preclude such supposition ! How¬ 
ever, extravasations beneath skull and within the arachnoid have 
been removed by operative procedures, and with little difficulty 
or danger; and for this reason this portion of the subject may 
also be dismissed to discussion on haemorrhage and coagula within 
the brain and ventricles, to meddle with which is almost univer¬ 
sally deemed unjustifiable, even to criminality. 
As a sequel to fracture and extravasation, we may have con¬ 
ditions occurring within cerebral substance as follows: 1. Con¬ 
cussion; 2. Contusion; 3. Compression; 4. Pachy-meningitis ; 
