334 Dr. Foville's Researches on the Anaiomy of the Brain. 



examined, and from the same line, is separated a second plane, 

 which from its destination we shall be warranted in calling the 

 plane of the hemisphere. This plane at first ascending parallel 

 to that of the corpus callosum, to which it is applied in the first 

 part of its course, afterwards quits that plane where it is re- 

 flected inwards, and continuing in a nearly vertical direction, 

 reaches the cineritious matter of the convolutions along the 

 curved line, at which the convex external and the flat internal 

 surface of the hemisphere meet each other; that is to say, it 

 reaches the most elevated part of the hemisphere along its 

 whole length. 



Both to the inner and the outer side of its insertion this 

 plane is expanded beneath the grey matter which it lines in 

 the form of a white layer, of which the fibrous structure is not 

 nearly so evident as is that of the plane itself. This expan- 

 sion follows all the folds of the gray substance, and con- 

 jointly with it, constitutes the convolutions which are applied 

 to the two surfaces of the plane of the hemisphere. 



When this plane is examined on its upper surface, we see 

 fibres, of which all the bundles radiate towards the circum- 

 ference, where they are inserted, and converge towards the 

 expansion of the crura, of which its fibres are evidently the 

 continuation. 



^rd Plane. — Beneath this plane of the hemisphere, but still 

 arising from the same line, there proceeds a third plane, of less 

 extent than the two preceding, and taking quite a different 

 direction. 



This plane, immediately after its emersion from the origin 

 common to it and to the two first-mentioned planes, descends 

 to the outer side of the inferior half of the gray substance of 

 the corpus striatum, invests it below, and advancing inwards 

 meets the corresponding plane from the opposite side, and 

 ascending in juxta-position with it on the median line forms 

 the septum luciduin of the ventricles. 



It is not all the fibres of this plane which go directly to the 

 septum lucidum. A considerable portion pass backwards, of 

 which some form an expansion belonging specially to the tem- 

 poral lobe ; whilst others reach the large extremity of the cornu 

 Ammonis, and becoming continuous with the corpus fimbria- 

 tum, pass into the fornix, and thus form another communica- 

 tion with the septum lucidum. 



I have too much consideration for the time of the Academy 

 of Sciences to allow myself to enter more minutely into ana- 

 tomical details, and now proceed to the examination of the com- 

 bination and mutual relation of the parts, to the consideration 

 of which the preceding facts naturallv lead. 



If 



