Dr. Foville on the Anatomy of the Brain. 23 



hemisphere and the concave surface of the orbital region of 

 its base. The respective limits of these two classes of convo- 

 lutions are indicated on the one hand by a grand line of con- 

 volutions which courses along in its whole extent the large 

 circumference of the hemisphere, commencing in front at the 

 anterior margin of the perforated quadrangle, and terminating 

 behind at the posterior margin of the same quadrangle ; and 

 on the other hand by another line of convolutions, which forms 

 the inclosure of the fissure of Sylvius, arising before and end- 

 ing behind like the preceding grand line at the opposite mar- 

 gins of the perforated quadrangle. 



Thus contiguous and united at their extremities, these two 

 lines diverge from each other throughout the rest of their 

 extent, the grand line traversing successively the internal 

 border of the orbital region of the base of the brain, the great 

 convex border of the hemisphere, and lastly, the external 

 border of the basilary cerebello-temporal zone; whilst the 

 convolutions of the inclosure of the fissure of Sylvius travels 

 in succession along the anterior border, the superior bor- 

 der, and lastly, the inferior border of the fissure which it 

 bounds. 



All the principal divisions found by each of these two lines 

 of convolutions correspond to those formed by the other. That 

 part of the large circumference which forms the internal 

 border of the orbital region corresponds to the convolution- 

 ary inclosure of the fissure of Sylvius, forming the external 

 limit of the same orbital region. The great convex boundary 

 of the hemisphere corresponds to the superior border of the 

 fissure of Sylvius ; and lastly, the external border of the ce- 

 rebello-temporal zone answers to the inferior border of the 

 fissure of Sylvius. The anterior angle formed by the union 

 of the first and second parts of the inclosure of the fissure of 

 Sylvius, answers to the angle formed at the anterior extremity 

 of the brain by the union of the great convex border of the 

 hemisphere with the external border of the orbital region. 

 The posterior angle of the fissure of Sylvius, subtended by 

 the line which forms its superior border, meeting with that 

 which forms its inferior border, answers to the angle formed 

 by the meeting of the great convex border of the hemisphere 

 with the external border of the cerebello-temporal zone at the 

 posterior extremity of the brain. Lastly, as these two lines 

 meet at their extremities, in contact with the perforated qua- 

 drangle, it is seen that the convolutions included in the in- 

 terval between them occupying all the convex external aspect 

 of the hemisphere and the orbital region of its inferior aspect, 

 are quite distinct from those situated at the internal aspect 



