540 
PROFESSOR MARSHALL ON THE BRAIN OE A BUSHWOMAN ; AND 
& 17, is/ — is?), the prolongation "upwards and backwards of the callosal convolution, . is, 
owing to the deficient development of itself and of the portions of the cerebrum in front 
and behind it, less compressed than in the perfect state, so that it has a roundish and not 
angular outline, and forms a perfectly smooth, bent or knee-like, and not quadrate lobule, 
ascending in front of the internal perpendicular fissure (k). Though thus rudimentary 
and smooth, it has the oblique direction backwards characteristic of this part in the 
human brain, and not the nearly vertical position which it exhibits in the Apes. Indeed 
the angle which its posterior border, bounding the internal perpendicular fissure, forms 
in both idiots with a base line passing through the corpus callosum is nearly 145°, i. e . 
greater than in the perfect brain, owing probably to the very scanty development of the 
occipital lobule behind it. 
The triangular occipital lobule (Plates XXI. & XXII. figs. 13 & 17, 25 ), like the qua- 
drilateral lobule, is so feebly developed in both the idiots’ brains, that it does not appear 
to fit closely in between the parts in front and behind it, but forms a mere ridge of 
cerebral substance, widening as it passes from below upwards and backwards to the tip 
of the occipital lobe, interposed between the internal perpendicular fissure ( Jc ) and the 
posterior part ( l ) of the fissure of the hippocampi. This simple, smooth, but slightly 
flexuous ridge takes the place then of the triangular and complexly convoluted lobule 
seen in the perfect brain. This condition coincides with the simplicity of the upper 
external connecting convolution, with the region of which this occipital lobule corre- 
sponds. It is far less developed than in the Apes. 
On the under surface of the idiots’ brains, the convolution of the corpus callosum 
(Plate XXII. fig. 17, is) is, as usual, continued beneath the cerebral peduncle by a ridge 
of cerebral matter (#) into the middle internal temporal convolution, or uncinate convolu- 
tion (19). This connecting ridge is proportionally wider than in the perfect cerebrum ; 
it is said by Gratiolet to be peculiar to the human brain ; it certainly does not exist in 
every Chimpanzee’s brain, though it is met with again in lower Quadrumana. 
Of the internal temporal convolutions , the upper , or dentate convolution , is very narrow, 
and on neither idiot’s brain can the fascia dentata be traced. In the idiot woman, how- 
ever, the parts are much damaged here, and in the idiot boy somewhat injured also. 
The middle internal temporal convolution (Plate XXII. fig. 17, 19), ending anteriorly in 
the unciform lobule (19/), is proportionally well developed. On the right hemisphere of 
the idiot woman’s brain, the unciform termination, or crochet, is well marked ; on the 
left hemisphere this convolution is much narrower, and the crochet scarcely recognizable. 
In the boy this convolution is very broad on both sides, and the crochet neatly defined, 
though small. The lower internal temporal convolution (9 — 9), which is the same as the 
lower external one, is also well marked. On both sides these two last-named convolu- 
tions are proportionally more simple than in the perfect human brain, or even than in 
the higher Apes. They are continued, as usual, backwards into the occipital lobe, and, 
owing to the imperfect development of that lobe, seem to extend almost to its tip. 
They are broader in the idiot boy. 
