22 Dr. Foville on the Anatomy of the Brain. 



one then communicates with the posterior part of the crus 

 cerebri and the nerves of sensation ; the other with the in- 

 ferior part of the crus cerebri and the anterior pyramids, which 

 decussate like the effects of cerebral lesions bearing upon the 

 powers of motion. The first order of fibres are applied to 

 the circumference of the convolutions very near the median 

 line, and the circle which they form is on a vertical plane, di- 

 rected antero-posteriorly ; the second, radiating from within 

 outwards towards the middle of the convex surface of the 

 hemispheres, spread themselves out from thence towards the 

 termination of the convolutions round the corpus callosum, 

 and become connected here with the external margin of the 

 circular band, which extends to the same point of the convo- 

 lutions. 



This remark on the relation of the convolutions to the two 

 orders of fibrous parts, of which the one proceeds from the 

 anterior pyramids and the anterior parts of the spinal mar- 

 row, whilst the other is intimately connected with the sensorial 

 nerve of the brain, and the posterior parts of the spinal mar- 

 row, points out the manner in which the cerebral convolu- 

 tions should be studied. 



If our description is confined to their forms, nothing of im- 

 portance will be revealed. But if on the contrary we endea- 

 vour accurately to determine their relation to the other parts 

 of the system by means of the fibrous parts entering into 

 their composition, the mind will be prepared to apprehend 

 the different offices they are intended to fulfil. This is what 

 I have endeavoured to accomplish in the first place in the 

 human brain, and secondarily in that of a considerable num- 

 ber of mammiferous animals. I shall subjoin here an abs- 

 tract of my researches on this subject. 



Considered in reference to the different connexions of their 

 fibrous parts, the convolutions may be distinguished into two 

 principal classes : first, those clothing the prolongations in 

 the brain of the fibrous bands connected with the olfactory 

 lobes, optic nerves, and posterior parts of the medulla spinalis ; 

 and second, those enveloping the cerebral terminations of the 

 pyramidal fasciculus of the crus. 



The convolutions connected with the prolongations in the 

 brain of the fibrous parts which proceed from the basilary 

 quadrangle, or the common meeting-point of the sensorial 

 nerves and the posterior parts of the medulla, constitute all 

 the plain internal part of the hemisphere, the surface of the 

 basilary cerebello-temporal zone, and the lobule of the insula. 

 Those developed on the terminations of the pyramidal fas- 

 ciculus of the crus, constitute all the external portion of the 



