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which run in the usual course, transversely outwards, the most anterior taking a direction forwards and downwards into the substance of the anterior lobes, affording, as in the case published by Mr. Paget, in Vol. xxix. of the Transactions of this Society, an additional confirmation of the correctness of Burdach's remark, that "many fibres from an anterior part of one hemisphere go to a somewhat more posteriorly situated part of the other."

It is interesting to trace, in a vertical section of the brain along the mesial line, the posterior and perfect border of the corpus callosum reflected downwards and forwards to be connected with the fornix, which, however, is very imperfect in condition, insomuch that it is not more than half an inch in length, and extends no further forward than the transverse lines marking the junction of the anterior and posterior horns of the corpora quadrigemina. The sides of the fornix are continued on each side into a tenia hippocampi, but its soft condition rendered it impossible to trace its continuity with the convolutions of the hippocampus. The imperfect portion of the corpus callosum also consists of transverse fibres, from the under portion of which their laminæ can be separated, and which are traceable downwards to the lamina cinerea, and appear to consist of longitudinal fibres.

From the description which has been given, it will easily be understood that there is no sign of a septum lucidum or fifth ventricle, and that it is principally the middle and anterior portion of the fornix which is wanting.

The patient whose brain exhibited this peculiarity of structure was named Thomas Platt, and at the time he died was fifteen years old. He was brought up and educated at the Foundling Hospital, a circumstance which, while it afforded an opportunity of ascertaining the condition of the boy's own mind, necessarily precluded the possibility of obtaining any evidence as to that of his parents.

He is described, at the hospital, to have been civil and well-conducted, but exceedingly slow in acquiring knowledge in the school. About three years before his death, he

received a serious injury to the head from the blow of a cricket ball, which confined him to the hospital for twelve months, at the expiration of which time he had completely recovered his usual health, and was apprenticed to a cabinetmaker. I could not learn that either his character or his intellect was at all affected by this accident.

The person to whom he was apprenticed informed me that the boy could read and write well when required, though prone to fall asleep when thus occupied, a propensity which was a constant subject of ridicule with the other boys in the shop. It was found extremely difficult to teach him his trade, or to engage him in any mental exercise; though in making bargains and in obtaining full value for his money he showed a remarkable degree of acuteness. When suddenly questioned upon any subject he would appear bewildered, and require some moments consideration before being able to give a distinct reply, exhibiting in this, as in other respects, rather a sluggishness than an actual deficiency of mind.

Mr. Paget's paper on "Imperfect Corpus Callosum" entered so fully into the literature of the subject, as to leave no field for further research, there not having been, as far as I am aware, any cases recorded to which he has not alluded; and with regard to the physiological and metaphysical inquiries arising out of their consideration, I have purposely refrained from referring to them.

It is a point worthy of observation, however, that the mental condition of the patient whose case forms the substance of this paper presents, in several particulars, a complete antithesis to that of the girl who fell under Mr. Paget's notice. Neither of them can be said to have been of healthy mind, and yet the mental deficiency was of an opposite character in each.

In the girl, the peculiarity was "vivacity, and a want of caution, showing themselves in a habitual rapidity of action, and want of forethought, deliberation and attention;"

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MR. HENRY ON MALFORMATION OF THE BRAIN.

whilst in the boy it was a disproportionate degree of caution and want of vivacity, showing themselves in an extreme slowness, amounting almost to stupidity.

EXPLANATION OF PLATE III.

This plate exhibits the relation of the various parts, as described in the preceding paper on "Malformation of

the Brain."

WA. Delamotte, del

B Gearge. hth. 54. Hatton Gardas

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