THE CEREBRAL HEMISPHERES 



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depths of the fimbriodentate fissure, along the dentate gyre, the dentatofasciolar 

 groove intervening, to be continued as the fasciola cinerea (gyms fasciolaris of 

 Iletzius) over the splenium of the corpus callosum. 



If the hippocampal gyre be depressed'for the purpose of examining the depths 

 of the hippocampal fissure, there is revealed a narrow, gray band whose surface 

 is scored by numerous incisures and whose edge is notched at frequent intervals. 

 This corrugated band is the dentate gyre or fascia dentata. Partly overlapping it, 

 but farther laterad, lies a white band the fimbria extending caudad from the 

 uncus to become continued as the fornix. 



FIG. 682. Trans-section of the hippocampal gyrus. (Edinger.) 



The dentate gyre is demarcated from the hippocampal gyre by the hippocampal 

 fissure, from the fimbria by the fimbriodentate fissure, in whose depths lies the 

 narrow continuation of the uncus or gyrus intralimbicus the fasciola cinerea. 

 Extending caudad, and for the most part parallel with the fimbria, it loses its 

 corrugated appearance on approaching the splenium, then fuses with the fasciola 

 cinerea, parting company with the fimbria (which now becomes fornix), to be 

 continued upon the corpus callosum as a thin, broad plate of gray substance 

 the indusium or gyrus epicallosus. At the uncus the dentate gyre makes an abrupt 

 turn to appear upon the mesal surface, out of the depths of the hippocampal fissure, 

 and encircles the neck of the uncus, forming the frenulum Giacomini. Beyond 

 this point it can be traced, in rare instances, to the gyrus semilunaris. 



The gyri Andreae Retzii are rudimentary gyral formations consisting of small, 

 rounded, oval or spirally corrugated eminences situated ventrad of the splenium 

 in the angular interval between the dentate and the hippocampal gyres. Struc- 

 turally they have been shown to belong to the hippocampal formation. 



