LOBES AND GYRI OF MEDIAL AND TENTORLA.L SURFACE. Q7 



subcallosus, and he thinks they form the most important part 

 of the receptive olfactory center. This region represents the 

 lobus pyraformis of osmatic animals and, according to Elliot 

 Smith (as quoted by Cunningham) it is the only part of the gyrus 

 hippocampi which properly belongs to the rhinencephalon. 



Limbic Lobe. The parts of the limbic lobe may now be 

 enumerated as follows: (i) The gyrus fornicatus (g. cinguli 

 and g. hippocampi*); (2) the fascia dentata, fasciola cinerea, 

 supracallosal gyrus (longitudinal striae), and subcallosal gyrus 

 (peduncle of the corpus callosum); (3) one- half of the septum 

 pellucidum; and (4) a lateral half of the fomix. The limbic 

 lobe is rudimentary in the human brain. The structures enumer- 

 ated above under No. 2 and No. 3 are but faint representatives 

 of the strong dentate gyrus seen in animals having no corpus 

 callosum. The development of the corpus callosum encroaches 

 upon and partially destroys the dentate gyrus. The limbic lobe 

 in part belongs to the rhinencephalon. According to the re- 

 searches of Elliot Smith the posterior inferior part of the gyrus 

 hippocampi, that part behind the uncus and below the subiculum, 

 and the whole gyrus cinguli belong to the neopallium and not to 

 the rhinencephalon. 



The peripheral ring on the medial and tentorial surface of 

 the cerebral hemisphere is composed of five gyri (Figs. 28 and 26). 

 Beginning under the corpus callosum anterior to the area parol- 

 factoria and going forward to the frontal pole, then along the 

 supero-medial border to the occipital pole and, finally, along the 

 infero-lateral border to the temporal pole, these gyri are as follows : 

 The gyrus rectus and gyrus frontalis superior (g. marginalis) 

 ending behind as lobulus paracentralis which closes the superior 

 end of the central sulcus; the praecuneus inclosed between the 

 marginal end of the sulcus cinguli and the sulcus occipito-pariet- 

 alis; the cuneus, located between the occipito-parietal sulcus 

 and the posterior calcarine fissure ; the gyrus lingualis, which 

 forms much of the medial occipital border and lies between the 

 calcarine and collateral fissures; and lastly, the gyrus fusiformis 

 (temporo-occipital gyrus}, which lies below the collateral fissure 

 and extends from the temporal pole almost to the occipital pole, 

 7 



