ON THE BRAINS OF TWO IDIOTS OF EUROPEAN DESCENT. 
551 
next in the two posterior lobes, and the least in the amygdala. A loss in the slender 
lobe is balanced by a gain in the biventral. In the median parts the whole of the 
laminae are counted, and there is a more marked deficiency, as compared with the 
healthy condition, especially in the idiot boy. The floccule, however, presents an excep- 
tion to this, being more complicated in him than in the woman. The laminae of the 
cerebellum in both idiots are not only fewer in number, but are shorter and narrower 
than in the healthy cerebellum. 
The corpus dentatum is represented merely by an elongated streak, differing in colour 
and consistence from the surrounding medullary substance, but presenting no indented 
outline, and no white mass in its interior. 
In a foetal brain the convolutions of whose cerebrum correspond with the idiot con- 
dition, the cerebellum is strikingly small, and would measure transversely not more than 
T5 inch, whereas in the idiot woman its transverse diameter is 3T5 inches, and in the 
idiot boy 3 inches. At the same period of development the laminse visible on its under 
surface are only twenty in number, whilst in the same parts in the idiot woman there 
are thirty, and in the idiot boy twenty-eight. It is obvious, therefore, that in these 
idiots the cerebellum was not arrested in its development cotemporaneously with the 
cerebrum, but continued to increase greatly in size, and to undergo further changes of 
an evolutional character long after the cerebrum had ceased to be affected in the latter 
way. At the same time, from the small relative size of the cerebellum to the body in 
both idiots as compared with the healthy standard at corresponding ages, from the un- 
doubted paucity, shortness, and narrowness of its laminse, from the deficiency in its 
transverse commissural fibres, and from the ill-defined condition of its corpus dentatum, 
it had at length, as well as the cerebrum, succumbed from want of developmental 
energy. In other words, though more evolved than the idiots’ cerebra, the cerebella are 
still imperfectly developed. The date of their final arrest of development is uncertain ; 
it was probably retarded to a period several years after birth ; it may be assumed to 
have corresponded with the condition attained by the healthy cerebellum at about the 
end of the second year of life. 
Postscript. (August 6, 1863.) 
Since the preceding paper was written I have had opportunities of inspecting the 
exterior of two idiots’ brains in the Museum of St. Bartholomew’s Hospital, and of 
examining, besides a wax model and two drawings of an idiot’s brain, a most interesting 
series of models in wax of human foetal brains, from the second month to the full term, 
in the Anatomical Museum at Guy’s Hospital. 
a. Of the two idiots’ brains preserved at St. Bartholomew’s, the smaller one (Catalogue, 
Series A. 123) is that mentioned by Professor Owen as weighing 13 oz. 2 dr. avoirdu- 
pois*. It was the brain of a male idiot, aged 22. The larger brain (Series A. 121) 
was that of a female idiot, also aged 22. 
* See p. 527. 
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