CONVOLUTIONS AND FISSURES OF SURFACE OF CEREBRUM. 55 



fascia dentata. As you sec, it lies just in front of the involution 

 of the cortex of the gyms hippocampi, by the fissure of the same 

 name, and its cross-section, therefore, is not correctly represented 

 by Fig. 33 B, but rather by Fig. 34. 



The cornu ammonis is, therefore, the bulging in the floor 

 of the ventricle, which is caused by the pushing- in of the gyrus 

 hippocampi by the fissure of the same name. From the cessa- 

 tion of the cortex just at this point, from the fact that the 

 margin of the hemisphere (fimbria and gyrus dentatus) runs 

 along over this involution, arises the coniDlicated cross-section of 

 the cornu ammonis. 



FIG. 33 A. 



FIG. 33 B. 



Unter, Inferior. 



FIG. 34. 



The relation of the gyrus hippocampi to the inferior horn 

 of the lateral ventricle is made clear by Figs. 19. 3 '2, and 38. 



The gyrus fomicatus and its continuation, the gyrus hip- 

 pocampi, are developed early in foetal life. Dorsad of the 

 margin of the hemisphere (arch of the fornix), there is devel- 

 oped in all mammals a furrow which lies parallel with the fornix 

 and accompanies it into the temporal lobe, the_fissura hippo- ~ 

 campi. The convolution between it and the fornix is the errus 



' Ot7 



hippocampi. Anteriorly, the fibres of the corpus callosnm pass 

 transversely through it, and in this region it is called the gyrus 

 fomicatus. Farther back, however, it is called the Lryrns hip- 

 pocampi, and lies next to the fornix. In the lower animals the 



