ON THE BBAINS OF TWO IDIOTS OF EUROPEAN DESCENT. 
541 
It has already been stated that within the double fissure of the hippocampi, in 
the right hemisphere, in the idiot boy’s brain (Plate XXII. fig. 17, l-l ), there is pre- 
sent a projecting ridge of cerebral substance ( 26 ), which appears to be the analogue of 
the calcarine lobule , described by Mr. Flower in the brains of Cercopithecus, Macacus, 
and Cebus, but which is absent in the highest and lowest Quadrumana. It is not pre- 
sent on the left side of the idiot boy’s brain, nor on either side in the idiot woman’s 
brain. In the perfect human brain, I have sometimes found it as a superficial ridge 
extending along the posterior two-thirds of the fissure, sometimes as a well-marked 
concealed ridge ; sometimes it is altogether absent. It is continuous backwards with 
the lowest occipital convolutions. 
The lower internal connecting convolution (Plate XII. fig. 17, s) is feebly represented 
in both idiots, being, as usual, concealed in the idiot woman, but superficial in the idiot 
boy ; the upper one is absent, as usual, in both idiots. 
In the preceding account of the cerebral convolutions in the idiots’ brains, constant 
comparisons have been made between them and the perfect brain, between the brains 
of the one and the other idiot, and between both and the brains of the higher Apes. 
Notwithstanding, it is necessary to state some further general conclusions from the 
facts above recorded. 
1. In the first place it is obvious that the idiots’ cerebra are not merely diminutive 
brains possessing every convolution, both primary and secondary, proper to the perfect 
human cerebrum, each having its natural shape, proportion and position, though on a 
diminished scale ; but, on the contrary, that they are profoundly modified in their con- 
volutional forms, which are not merely smaller in bulk, but are fewer in number, of 
simpler shape, and different in proportion and position, as compared with those of the 
perfect cerebrum. 
2. Nevertheless all the primary and connecting convolutions belonging to the perfect 
cerebrum are represented by definite corresponding parts in these brains, mostly by 
actual convolutional foldings of the cerebral substance of a comparatively more simple 
kind, but sometimes by scarcely convoluted, or even by entirely smooth though slightly 
elevated portions of the cerebral substance. 
3. The parts which can be easily detected as actual convolutions in the idiots’ brains 
are the three frontal rows, the two ascending parietal convolutions, with the lobule of 
the posterior one, the supramarginal and bent convolutions, the external and internal 
temporal convolutions, the marginal and callosal convolutions on the inner surface, with 
the quadrilateral and occipital lobules, and all the connecting convolutions proper to 
the human cerebrum. The parts which are less easily distinguished are the orbital 
convolutions and, especially, the three rows of occipital convolutions. The central lobe, 
or island of Reil, is distinguishable, as a distinct smooth eminence, in the idiot woman, 
but only as a smooth indistinctly elevated surface in the idiot boy. In neither does 
there exist such an expansion of the supramarginal convolution as would form a pro- 
minent supramarginal lobule, a part so characteristically human. 
mdccclxiv. 4 c 
