720F 
uantity from half an ounce to several ounces. 
metimes it is milky, and has shreds of lymph 
floating in it; at other times it may be sero- 
purulent, but this is extremely rare, and only 
occurs when the lining membrane has been the 
seat of acute inflammation and of inflammatory 
i 
e lining membrane of the ventricles, which 
in health is of extreme tenuity, becomes fre- 
quently thickened and partially opaque in chro- 
nic disease of the brain, where the ventricles 
are more or less dilated. In acute disease 
lymph is sometimes deposited upon it in large 
and loose flakes, easily removeable from it. 
And sometimes there is a deposit all over its 
surface of a fine granular semitransparent 
lymph, which gives to the internal surface of 
the membrane the appearance of an extremely 
fine and delicate reticulation. 
As the choroid plexus are covered by a pro- 
longation of the membrane of the ventricles, 
their investment is apt to participate in any 
morbid process which may take place in the 
former. In acute affections it will be covered 
with lymph, as the membrane lining the ven- 
tricles is elsewhere. When much water has 
been accumulated in the ventricles, the choroid 
plexus are pushed against their floor, flattened, 
and rendered pale by maceration. On the other 
hand, whatever causes much vascular congestion 
in the vessels of the brain will produce the same 
effect in a marked manner upon those of the 
choroid plexus. 
Earthy concretions are sometimes found in 
the choroid plexus, which may probably be an 
augmentation of the crystalline matter found in 
them in their healthy state. These appear to 
agg chiefly of phosphate and carbonate of 
ime. 
A very common appearance found in the 
choroid plexus consists in certain vesicles, very 
variable both in size and number. These are 
simple cysts, containing a straw-coloured fluid. 
Formerly they used to be regarded as hydatids, 
but they are now known to be essentially dis- 
tinct from them. They occur frequently in 
brains which exhibit no other departure from 
the normal condition. Of their precise nature, 
and of their cause and mode of formation, 
nothing is known; and as they are seldom of 
a large size they are not likely so to disturb 
the functions of the brain as to give rise to 
symptoms by which their presence could be 
detected. 
On the pseudo-morbid appearances of the 
nervous centres and their coverings——The ac- 
tual indications afforded by any departure from 
- the normal physical condition of the nervous 
centres after death are so important to the attain- 
ment of right conclusions respecting the patho- 
logy of the nervous system, that it behoves the 
anatomist to take fully into account all those 
circumstances which may give rise to appear- 
ances in the cerebro-spinal centres or their 
membranes simulating disease. Such appear- 
ances, not inappropriately termed pseudo-mor- 
bid, occur in the greater or less vascular fulness 
of the membranes and of the centres themselves, 
in the variations in the quantity of fluid around 
NERVOUS SYSTEM. (Nervous Cenrres. Asnormat Anatomy.) 
or within the brain, or around the spinal cord, — 
and in the consistence of the nervous matter, 
The circumstances which affect the amount 
of blood in the vessels are the mode of death 
and the position in which the head has beer 
laid after death. Death by asphyxia, wheth 
rapid or gradual, favours the accumulation ¢ 
blood in the vessels of the brain. Convulsion 
preceding death likewise cause turgescence o 
these vessels. Any impediment to the cireu 
tion through the heart has the same effect, bi 
to the greatest degree when the impediment 
much felt on the right side of the heart. 
The position of the head after death affe 
the vascular fulness by favouring the accumu 
tion of blood in the most dependent pa 
From this circumstance and from the custo 
of placing bodies on the back, we always fi 
the posterior lobes of the cerebral hemisphere 
and the cerebellum most filled with blood, at 
it is on this account that the straight and oth 
posterior sinuses of the dura mater are 
filled with blood. a 
The quantity of fluid around the brain at 
spinal cord is least in the young and greatest 
the old: it is influenced by the bulk of 
brain or spinal cord, sometimes disappearin 
entirely when the brain is so large as to fill @ 
cranial cavity ; it is inversely as the quantity 
blood, and therefore is considerable in ¢ 
of anemic brain, unless the bulk of the org 
have increased from some other cause. Sk 
deaths from chronic disease favour the act 
mulation of this fluid by diminishing the sup 
of blood to the brain. In phthisis and c 
lingering maladies there is almost always a 
siderable amount of subarachnoid fluid. 7 
practitioner should bear in mind that the 
sence of subarachnoid fluid is always abnorr 
and is in general due to an enlargement of 
brain from hyperemia or from some other eat 
Softening of the nervous matter n 
pseudo-morbid. The spinal cord soften 
soon after death; but if examined 
twenty-four hours it exhibits more densi 
the brain. With the advance of decompos 
the cord becomes extremely soft and alt 
diffuent. In the brain the pseudo-m 
softening is colourless, and may be re 
mistaken for disease. That the brain is 
prone to imbibe fluids is shown by Dr. Pi 
son’s experiments. The brains of sheep 
allowed to remain for a certain nun 
hours in a given quantity of water, which 
rapidly absorbed. The weight of the b 
was increased proportionally to the quan 
water which had been imbibed, and the 
most exposed to the fluid were found in i 
ened state. In one instance the brain w 
rived of its membranes on one side, an 
ours after death it was immersed in a mi 
composed of equal parts of ox-bile and ¥ 
It weighed three ounces, seven drams, and 
grains when prepared for experiment. A 
remaining in the mixture thirty-six hour 
weighed eight ounces and one dram.* Th 
* On the pseudo-morbid appearances of 
meee Ed. Med. and Surg. Journ. for 
vol, . ad 
