532 PEOFESSOE MARSHALL ON THE BEAIN OF A BTJSHWOMAN ; AND 
d. The Fissures , Lobes, and Convolutions of the Idiots’ Cerebra. 
The Fissures. — The fissure of Sylvius (Plates XXI. & XXII. figs. 12 & 16, e-e) is not 
only absolutely, but relatively short, measuring l - 3 of an inch in the idiot woman, and 
l’l in the idiot boy. In both brains it is comparatively shallow. In the idiot woman 
its direction is nearly vertical ; in the idiot boy it is more oblique, being pressed back 
by the large parietal lobe. Its posterior margin is well defined ; but the anterior mar- 
gin in the idiot boy, on the left side, is interrupted, and gives otf a long branch towards 
the vertex. At the entrance of the fissure in the idiot woman is seen a slight elongated 
ridge, which runs transversely inwards and joins the feebly developed eminence (C) 
which represents the island of Reil ; in the idiot boy this ridge is very narrow, and there 
is scarcely any insular eminence. In the idiot woman its upper end is simple on the 
left side, slightly bifurcated on the right ; in the idiot boy it is more deeply bifurcated 
on the two sides. 
The fissure of Rolando (Plates XXI. & XXII. figs. 10, 12, 14, & 16, d-d), in both 
these brains, is better marked on the right hemisphere. In the female idiot, on that 
side, it forms a simple sulcus, commencing, by a slight curve, in front of the Sylvian 
fissure, and then running, less obliquely than usual, backwards towards the longitudinal 
fissure. On the left side, the symmetry of this fissure is interfered with, in a remark- 
able manner, in both brains, by the upward intrusion of a triangular convolution, which 
appears to be the rudiment of the intended perfect anterior border of the fissure. In 
the idiot boy, on the right side, the anterior margin of this fissure is also irregular. 
It may be noticed, then, thus early, in our examination of the cerebral surface of the 
idiots’ brains, that they are at once distinguishable from the quadrumanous brains, and 
assert, even in their imperfect condition, their human character by an absence of sym- 
metry in primary fissures and convolutions, so nearly symmetrical in the highest Apes. 
The external perpendicular fissure (Plates XXI. & XXII. figs. 10 & 14, h) can be 
traced, in the case of the idiot woman, on each side for - 75 of an inch on to the surface 
of the hemisphere, defining accurately the parietal from the occipital lobe. It then 
divides into two deep sulci, the hinder one being the continuation of the fissure, which 
is not prolonged over the side of the hemisphere. In the idiot boy the external per- 
pendicular fissure cannot be traced so far outwards from the longitudinal fissure, being 
sooner interrupted by the connecting convolutions. 
The great parallel fissure (Plates XXI. & XXII. figs. 12 & 16,/-/) of the tem- 
poral lobe is well marked in the idiot woman’s brain, running at first nearly vertically, 
and then backwards on the occipital lobe. It is of unequal extent on the two sides of 
the brain, reaching, on the right side, completely to the posterior border of the occi- 
pital lobe. It presents a curious wavy course. In the idiot boy this fissure is not 
quite so extensive, and ends, on both sides, further forward on the occipital lobe; on 
the left side it presents a simpler outline than on the right. 
On the internal surface of the hemispheres, the calloso-marginal or fronto-parietal 
