NERVOUS SYSTEM. (Nervous Cenrres. ABNoRMAL ‘ANATOMY.) 
scopical examination, which discloses the cha- 
racteristic pus globules with little or no liquor 
puris, and by mixing some of it with liquor 
potasse, when it becomes converted into a 
viscid material resembling white of egg. 
Pus in the brain is frequently of a green 
colour, and very commonly exhales an ex- 
_ tremely fetid odour. 
The cerebral matter around the purulent col- 
lection is either somewhat indurated or it is in 
an edematous state, or in one of inflammatory 
softening. When in this latter state the ab- 
Scess is not so defined; the softened cerebral 
Matter around it is broken up and mingled 
with pus; this, however, is rare. 
An abscess of the brain may open upon the 
exterior and so evacuate its contents. This 
_ May occur either into the nose through the 
_ cribriform plate, or into the tympanic cavity or 
the external auditory meatus. It is sometimes 
_ difficult to determine whether inflammatory dis- 
_ ease had arisen in the ear, extending to the brain 
_ and exciting the formation of abscess, or whether 
the abscess already formed in the brain had not 
burst into the ear. A cerebral abscess may 
_ empty itself into either of the ventricles. 
} Abscesses are most commonly found in one 
of the cerebral hemispheres, or in the cerebel- 
lum; they are very rarely met with in other 
‘parts of the brain. Sometimes collections of 
_ pus form upon the surface of the brain between 
_ the pia mater and the grey matter of the cere- 
bral convolutions. And pus or puriform mat- 
ter is frequently found between the arachnoid 
and pia mater, where there has been inflamma- 
Li ion of either or of both those membranes. This 
is most common in children. 
 Hyperemia and Anemia.—An organ so 
largely supplied with blood as the brain, is 
liable to variations in the amount of that sup- 
ly under various circumstances. It is unne- 
@essary to recapitulate here the arguments 
‘already adduced to show that the opinions of 
those who maintain that the quantity of blood 
in the brain cannot vary, is erroneous. Indeed 
it is much to be wondered at how persons 
eee to inspect the brain post mortem 
‘ould have adopted such a doctrine. 
ba the greatest degree of hyperemia of the 
in, all the vessels of the organ are full; 
the veins which lie between the convolu- 
tions are full; the vessels of the pia mater are 
fally injected. Often there are diffused extra- 
vasations through the areole of this membrane, 
Causing a red blotch over more or less of the 
surface of the brain. The grey matter of the 
convolutions is extremely dark in colour, and 
if a small portion of it be examined under the 
microscope the minute vessels which abound in 
it are found distended with blood. On the sur- 
}face of a section of the white matter numerous 
jbloody points are found, being the orifices of 
jvessels cut across. These points are sometimes 
jvery large; sometimes they are surrounded by 
jsmall extravasations of blood, proceeding from 
he rupture of some small vessel. In this state 
of the brain the vessels of the choroid plexus 
and of the velum interpositum are very full, 
jand also those of the dura mater. 
720c 
Cerebral hyperemia is generally caused by 
some obstruction to the free return of the blood 
to the right side of the heart. Hence we see it 
always after death by asphyxia, and very com- 
monly in cases of disease of the heart. When 
the breathing has been seriously impeded just 
before death, there will always be considerable 
hyperemia of the brain. Hence in judging of 
the nature of a cerebral hyperemia, the anato- 
mist may be materially assisted in coming to a 
correct conclusion if he can ascertain the cause 
of death and the symptoms immediately pre- 
ceding it; a fact which clearly denotes how 
little is the value of mere dissection of morbid 
parts, unassociated with some knowledge of the 
symptoms manifested during life. 
In the bodies of persons dead of epilepsy, 
during or immediately after the epileptic fit, 
there is always cerebral hyperemia. In these 
cases the hyperemia is due to the retardation 
and obstruction of the venous circulation, occa- 
sioned by the convulsive struggles of the pa- 
tient and the resulting impediment to respira- 
tion. It may be caused, likewise, by an in- 
creased attraction of blood to the organ taking 
place at the moment of the occurrence of the 
fit. For the same reason, whenever death is 
ushered in by convulsions, the brain will be 
found in a state of congestion, the amount of 
which will vary with the quantity of blood in 
the body. Whatever may be the condition of 
the brain prior to the epileptic paroxysm, it is 
always in a more or less congested state during 
and immediately after it. The too prevalent 
notion that cerebral congestion is the cause of 
the epileptic paroxysm has but little foundation, 
while there is abundant evidence to prove that 
the epileptic paroxysm may give rise to cerebral 
congestion. It is well known that animals 
bled to death die in convulsions; and many 
cases of puerperal convulsions are clearly 
caused by excessive loss of blood resulting 
from parturition. 
Hyperemia of the brain is frequently found 
after death from depressing and exhausting 
maladies, typhus fever, &c., all diseases of the 
low typhoid type, and in cases of general 
paralysis. The powers by which the circulation 
is carried on in the vessels are greatly depressed, 
and the blood accumulates in them, especially 
in the veins. ' 
I know of no means of distinguishing active 
from passive hyperemia, excepting probably 
that the capillaries may be more injected in the 
former, and the veins more filled in the latter. 
To enable the anatomist to make a correct dis- 
tinction, the detail of symptoms during life must 
be called to his assistance. , 
Aneémia.—This condition, the opposite to 
that last considered, is very common. It is 
frequently met with in children, and in such 
cases is accompanied with more or less of 
serous fluid, either in the subarachnoid space 
or within the ventricles. The brain of the ill- 
nourished strumous child is generally an anemic 
brain. 
Anemia of the brain occurs when death has 
been caused, whether quickly or gradually, by 
the loss of blood, It is also present when the 
