BastiaNj on the so-called Pacchionian Bodies, 95 
frequently does not show the manifest reticulated arrange- 
ment of the fibrous bundles^ elongating cells or nuclei may 
be seen of the ordinary kind (fig. 8). The elastic tissue in 
the Pacchionian bodies is represented by fine fibres, and is 
not very abundant, though I have not had time further to 
make out its mode of development and arrangement. 
As is the case with the arachnoid membrane itself, these 
Pacchionian outgrowths, especially in old people, very fre- 
quently contain deposits of brain sand. Sometimes it exists 
in the form of the usual bright, highly refractive, and 
irregularly rounded nodules of various sizes, situated in the 
midst of the fibrous tissue, with no special envelope of any 
kind ; whilst in others a deposition of the calcareous matter 
seems to occur in small separate granules, and a concentric 
arrangement of cellular tissue, in the form of lamellae, 
appears to take place around them (fig. 9), which in some 
cases is very distinct. Occasionally a large calcareous nodule 
is seen, apparently simple and of the kind first mentioned, 
but which, on alteration of the focus, seems to be made up 
of concentric lamellae, or at all events it presents a series of 
concentric markings. This appearance may perhaps be due 
to the subsequent calcareous infiltration of a concentrically 
arranged fibrous envelope developed around a primary saline 
deposit. All the forms seem to be intimately connected with 
one another, and according to Kolliker,^ brain sand generally, 
after the extraction of the salts, completely retains the 
form of the concretion, and appears as a concentrically 
stratified pale mass.''^ Kolliker also speaks of corpora amy- 
lacea as sometimes existing in the Pacchionian bodies ; these 
I have never met with, unless some of the earthy nodules 
may be bodies of this kind which have undergone calcifi- 
cation. 
Now we come to the question, are the Pacchionian 
bodies to be considered as normal structures, or as the results 
of pathological change? The investigations of the brothers 
Wenzel,t and even more, the later ones of Luschka, supply 
us with important data for the solution of this question. 
As yet these growths have been found only in the human 
subject, notwithstanding the diligent search made for them 
by the above-named observers in many of the lower animals. 
With regard to the ages at which they are found in man the 
brothers Wenzel came to the following conclusions : — In 
children, from birth to the third year, these bodies, if they 
ever occur, must be very few. From the seventh to the 
♦ Loc. cit., p. 243. 
f De penitori iiom. et brut, cerebri structure Tubingse, 1812. 
