96 BastiaNj on the so-called Pacchionian Bodies. 
twentieth year they sometimes are numerous. From the 
latter period to the fortieth year the number is considerable, 
and the nearer we approach the fortieth year the greater does 
it become. Lastly, from the fortieth to the one hundredth 
year these bodies are found in great numbers.'''' Luschka, 
however, says he has never failed to find a certain number 
of these bodies on the arachnoid, at the borders of the great 
longitudinal fissure, at any period of life. Even in the new- 
born infants he has detected very minute outgrowths, which 
he considers as the rudiments of future Pacchionian bodies, 
though in them, as well as in other children dying during 
the first few years of life, their existence is easily overlooked, 
and they can only be detected by the most careful examina- 
tion, since they are then minute pellucid structures of the 
same colour as the unaltered arachnoid. In individuals be- 
tween sixteen and twenty years of age they are easily detected 
on account of their increased size and whiteness ; and though 
at later periods of life they generally become more numerous 
and much larger, still there is a very great difference in this 
respect in different individuals, and in some persons dying 
even at middle age or beyond none of these bodies can be 
detected by the naked eye, though they may be seen by float- 
ing portions of the arachnoid in water, and then examining 
it with a lens. Luschka looks upon these growths as normal 
structures,"^ having a definite aim, which may be considered 
to be in a mature condition in individuals between the ages 
of twelve and twenty years, and to become pathological only 
by reason of their hypertrophy at later periods of life ; and 
he accordingly names them ^ arachnoidal villi.' But the old 
name seems to me a more desirable one, since it involves no 
implication as to their nature; and the possibility of any 
function performed by these bodies seems so doubtful 
that it appears more desirable to look upon them, with 
Rokitansky, merely as hypertrophic vegetations, or polypoid 
excrescences from the arachnoid, notwithstanding the fact 
that the rudiments of them are to be met with even at 
the earliest periods of life. Bearing upon this question, too, 
it is interesting to consider how far a pathological condition 
(assuming it to be such) so constant as the existence of these 
bodies in middle and advanced life, may, in the course of ge- 
nerations, through the influence of hereditary transmission, 
have at last tended to their rudimentary production, inde- 
pendently of the special causes at first potential in giving rise 
* Andral and Dr. Todd regarded them as decided pathological products, 
whilst Cruvelhier, though in doubt as to tlieir nature, was disposed to look 
upon them as of too frequent occurrence to be considered morbid growths. 
