534 PROFESSOR MARSHALL ON THE BRAIN OF A BTT SHW OMAN ; AND 
more vertical than in the healthy cerebrum. The angle formed by the two fissures of 
Rolando posteriorly is a little more acute than in the perfect brain, owing to the 
narrownes of the brain in front of them. These fissures are far more simple in the 
idiots than in the highest Apes. 
The external perpendicular fissure is traceable further on the upper surface of the 
cerebrum than in the perfect state, but cannot be followed at. all on the lateral aspects 
of the hemispheres as in the quadrumanous brain. 
Assuming the total length of each cerebrum to be 100, the relative lengths of the 
three regions, in front of the fissure of Rolando, between it and the external perpen- 
dicular fissure, and behind that fissure, when seen from above are in the preserved 
brain of the idiot woman about 46, 30, and 24 ; in the idiot boy 38, 34, and 28. In 
the healthy brain, the proportionate dimensions of these regions are 54, 23, 23. Mea- 
sured longitudinally over the vertex in the cranial casts, the same regions occupy the 
following relative spaces: in the idiot woman, 46, 29, 24; in the idiot boy, 42, 32, 26 ; 
in the healthy brain, 54, 23, 23. In both idiots the frontal region is therefore strikingly 
defective, the parietal region is proportionally increased, whilst the occipital region 
exceeds somewhat the healthy ratio. The frontal region is larger in the idiot woman, 
the parietal and occipital regions are larger in the boy. The preponderance of the 
parietal region in the boy is very remarkable. In the Chimpanzee, the corresponding 
spaces are 46, 28, and 26 ; so that the idiot woman presents nearly similar proportions ; 
whilst in the idiot boy the frontal region still exhibits a marked deficiency ; whilst the 
parietal region is in exactly corresponding excess, and the occipital region equal. 
The parallel fissure is at first more vertical, and extends further back than in the per- 
fect brain. The internal perpendicular fissure, short and simple in its course, still 
approaches the human type in its inclination backwards, contrasting very remarkably 
with its vertical direction in the Ape. The fissure of the hippocampi is less horizontal 
than in the perfect brain, slanting upwards behind, in accordance with the want of 
depth in the occipital lobe — in this respect approaching the quadrumanous character. 
In the idiot woman, on the left side, this fissure is anomalous in its junction with the 
collateral fissure, which is elsewhere regular. 
The Lobes . — Considered as defined by the several fissures, and compared with the per- 
fect brain, the frontal lobes (Plates XXI. & XXII. F), in both idiots, are remarkably 
contracted both in length, in width, and in vertical height, being very short, pointed, 
and shallow, especially in the idiot hoy. The parietal lobe (P) is defective in the 
antero-posterior direction in the idiot woman, and in the transverse direction in the idiot 
boy ; whilst it is comparatively long in the boy, and wide in the woman. The occipital 
lobe (O) is much and equally contracted in the two, especially in its vertical measure- 
ment. The temporal lobes (T) are larger proportionally than any other part of the 
cerebrum, and are fuller and rounder in the idiot woman than in the idiot boy. The 
central lobe, or island of Reil (C), lies on the surface, but is slightly developed in the 
idiot woman, and scarcely recognizable as an eminence in the idiot boy. As regards 
