I 3 4 THE POCKET ANATOMY 



three gyri breves, and a posterior part subdivided into two 

 gyri longi. 



6. The limbic lobe : 



On the inner surface consists of : 



The gyrus fornicatus or callosal convolution lies beneath the 

 marginal convolution, being separated from it by the calloso- 

 marginal sulcus. It commences near the anterior perforated 

 spot, follows the curves of the corpus callosum, near the 

 posterior end of which it becomes continuous with the 

 uncinate gyrus. 



The uncinate convolution (hippocampal) commences below 

 the splenium of the corpus callosum ; here the end of the 

 calcarine fissure cuts into it, leaving a narrow isthmus con- 

 necting it with the callosal convolution. It runs forwards 

 above the collateral fissure into the temporal lobe and ends 

 as the uncus. 



The dentate sulcus (hippocampal) lies along the upper border 

 of the uncinate convolution, and forms the hippocampus 

 major in the descending cornu of the lateral ventricle. 



The dentate convolution (fascia dentata) lies in the dentate 

 fissure, It is formed by the superficial grey matter of the 

 hemisphere, which here ends in a fringed margin. 



7. The olfactory lobe extends from the anterior perforated 

 spot as the olfactory tract, and ends in an enlargement, the 

 olfactory bulb. It lies in the olfactory sulcus on the orbital 

 surface of the frontal lobe. Posteriorly the tract bifurcates, 

 the outer root passing across commencement of Sylvian 

 fissure to the uncinate convolution, and the inner one to the 

 great longitudinal fissure to join the callosal convolution. 



THE INTERIOR OF THE CEREBRUM. 



The centrum ovale minus is the central white mass in each 

 hemisphere seen on horizontal section, the section being made 

 about inch above the corpus callosum. 



The centrum ovale majus, seen on section at the level of 

 the corpus callosum, is the centrum ovale minus of each side, 

 joined by the corpus callosum. 



The corpus callosum lies at the bottom of the great longi- 

 tudinal fissure. It is the great transverse commissure of the 

 hemispheres, and consists principally of transverse fibres. 



Length. About 4 inches, extending to within i inches of 

 the anterior, and 2$ inches of the posterior extremities of the 

 hemispheres. 



Shape. Broader behind than in front, thicker at each end 



