STRUCTURE OF THE LOBES OF THE CEREBELLUM. 381 



the interruption of the middle arch by the two transverse central 

 convolutions, and (2) by the coalescence of the inferior and middle 

 arches near the vertex (Bischoff). The development of the con- 

 volutions of the convexity alone stands in relation to the size of the' 

 hemispheres and the higher indications of cerebral development. 

 The development of the entire series of convolutions of the middle 

 ring keeps pace with that of the olfactory lobes. Whilst in Man and 

 Monkeys the gyrus fornicatus, compressed to the inner surface, is still 

 completely invested by the external arch of the convex surface of the 

 hemisphere, in brains of lower type it reaches the outer surface both 

 at the temporal and the frontal extremity. It even may, in such 

 cases form the whole frontal extremity of the cerebral lobe, pressing 

 forward in front of a transverse groove (absent in Man) (fig. 238, S), 

 which forms with the falciform fissure a sulcus cruciatus (Leuret) and 

 covering the olfactory lobules ; so that in Man and Monkeys different 

 parts of the brain are situated behind the frontal bone than those 

 which are there situated in other Mammals. 



Within this external conformation of the cerebral cortex there 

 appears to be 



1. A common type of textural lamination, characterizing the 

 cortex of the vault of the hemispheres and that portion of the 

 gyrus fornicatus which encircles the section of the corpus 

 callosum. As special types may be enumerated in addition 



2. The type of the occipital apex. 



3. The type of the Sylvian fissure. 



4. The type of the cornu Ammonis. 



5. The type of the bulbus olfactorius. 



1. The general or five-laminated type of the cortex of the 

 cerebrum. The first layer is principally composed of that 

 equally punctated matrix which characterises all the grey sub- 

 stances of the cerebrum, and through which ganglionic cells are 

 irregularly distributed. This matrix has been termed the epen- 

 dyma formation by Rokitansky, neuroglia by Yirchow, con- 

 nective tissue by Kolliker, spongy substance by Deiters, and 

 coalesced ganglion-cell substance by Henle and E. Wagner ; 

 as it occurs in the olfactory lobes and the cornu Ammonis, it 

 has been termed gelatinous by Clarke, and molecular substance 

 by Kupfer. Like Henle and Wagner, who have also called this 

 layer the centric investing lamina, Stilling regards it, together 



