98 Bastian^ on the so-called Pacchionian Bodies. 
and at any period of life their number and size seem to be in 
direct proportion to the frequency with which the brain and 
its membranes have been subjected to congestions; thus, even 
in youths or young adults, considerable enlargement of them 
is generally met with in those subject to frequent epileptic 
attacks, and less notably so in habitual drunkards. Startling 
exceptions occasionally exist, however, to this rule; for in- 
stance, I lately examined the brain of a man fifty-six years 
of age, who was known to have led an intemperate life, and 
who had in addition been insane, and perfectly incoherent in 
his conversation, for more than twelve months, and yet there 
was only the faintest opalescence of a small portion of the 
arachnoid, and no Pacchionian bodies to be seen with the 
naked eye. Such cases are, however, very exceptional; so 
that, leaving age out of the question, we may still look 
upon cerebral congestion and excitement as the causes most 
instrumental in bringing about the production or increased 
growth of these structures. This was also the opinion of Dr. 
Todd, who said : " In persons addicted to the excessive use of 
spirituous liquors, in those of irritable temperament, and who 
were frequently a prey to violent and exciting passions, they 
are almost uniformly highly developed.''^ 
Are these enlarged Pacchionian bodies of much pathological 
significance ? It has been thought that they may give rise to 
dangerous symptoms by their pressure upon the brain, and 
by the impediment they may offer to the circulation of the 
blood through the great veins entering the longitudinal sinus 
as well as through the sinus itself. I know of no cases on 
record bearing out this assumption, and am disposed to 
think their effects are not often very serious in the first place, 
because, owing to the slowness of their growth, impediment 
to the flow of blood through any particular vein, if it should 
take place, would, without difficulty, right itself by an in- 
creased flow through the contiguous channels; and in the 
next, from the fact that no growths large enough to produce 
any appreciable pressure upon the brain are ever found be- 
tween the membranes attached to the arachnoid only. Those 
so situated, being non-vascular themselves, receive plasma for 
their further increase only by absorption through the non- 
vascular arachnoid itself, and with which, oftentimes, they 
are only connected by means of a narrow pedicle, so that the 
conditions are by no means favorable to their attaining any 
notable size. Those, on the other hand, which have become 
imbedded between the fibres of the dura mater are enabled 
to absorb more nutritive pabulum directly from this more 
vascular membrane, with which to build up their structure. 
