88 BastiaN; on the so-called Pacchionian Bodies. 
scope, altered portions of the plexus only, rendered more 
opaque by the deposition in their interior of calcareous matter, 
in the form of brain sand.^ Cruvelhier, moreover, altogether 
denies the similarity of the opaque granulations occasionally 
found on the choroid plexuses to Pacchionian bodies. 
Agreeing with Rokitansky"^ and Luschka as to the fact of 
these bodies being invariably growths from the arachnoid, 
though diflPering from the latter observer as to the fact of 
their ever springing from its parietal layer, I will first speak 
of them as they may be observed on the visceral portion of 
this membrane. 
When the dura mater is reflected we frequently see in more 
or less abundance a number of small, opaque, almost milk- 
white looking granulations, varying much in size, but seldom 
exceeding that of a rice-grain, situated on each side on the 
arachnoid along the median contiguous edges of the cerebral 
hemispheres. They exist most abundantly over the middle 
and commencement of the posterior third of the hemispheres, 
where the largest veins enter the longitudinal sinus, and are 
found principally at the angle and over the upper surface of 
the brain immediately contiguous to it, but are not met with 
on the vertical surface entering into the great median fissure. 
Occasionally, however, alittlepatch of these bodies may be seen 
over the upper surface of the hemisphere at a distance of an 
inch or more from the median line, and distinctly separated 
from those in this situation. The portion of arachnoid from 
which the Pacchionian bodies arise is invariably opalescent or 
opaque, and more or less thickened, and they are generally 
most numerous on the membrane over and covering the large 
veins as they leave the pia mater to enter the longitudinal 
sinus. They vary extremely in form, as may be seen by 
reference to PI. X, fig. 1, which represents some of the shapes 
most frequently met with. Some are simple, others compound 
in various degrees, with ternary or even quaternary buds from 
the primary growth. Some are sessile and attached by a 
broad base to the arachnoid, whilst others are fixed only by 
comparatively long and attenuated pedicles, or may present 
all intermediate conditions between these two extremes. 
Luschka figures a compound growth resembling a small 
bunch of grapes, and so far as I have seen, this distinct 
pediculation, whether simple or compound, is most frequent 
in the early stages of these growths before they become very 
apparent to the naked eye. 
Pacchionius also described bodies of a similar kind existing 
in large numbers in the longitudinal sinus, now well known 
* 'Patholog. Anat.' (Syd. Soc), vol. iii, p, 329. 
