418 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



pushes forth its thin extremity to near the apex of the tem- 

 poral lobe, so also does the lenticular nucleus extend a small 

 temporal process (pedunculus nuclei lenticularis) to the tem- 

 poral lobe of the cerebrum in order to receive from it medullary 

 radiations. This process starts from the opposite end of the 

 nucleus to that which is turned towards the frontal lobe. 



The region which in transverse section (fig. 245) appears as 

 the upper border of the lenticular nucleus is its centric pole ; 

 for the fasciculi of the corona radiata here penetrate from the 

 internal capsule into the lenticular nucleus. 



The region appearing in transverse sections as the lower 

 border of the lenticular nucleus and its internal extremity re- 

 presents its peripheric pole, from which a large portion of the 

 crusta of the cerebral peduncle proceeds. The form of the 

 lenticular nucleus necessitates that the radiations directed in- 

 wards from the cortex of the frontal and parietal lobes must 

 be incomparably greater than those from the occipital and 

 temporal lobes. Independently, however, of the quantitative 

 distribution of the fibres, the connection of the lenticular 

 nucleus with the cortex of the cerebrum must be considered 

 to be universal. The walls of the Sylvian fissure (including the 

 insula) also send projection-fasciculi into these ganglia. This, 

 however, is not effected radially by means of the convex 

 portion of the third segment which is in apposition to the 

 island, but by curving fasciculi which wrap round the upper 

 angle of the lenticular nucleus, proceeding from the medulla of 

 the insula into the internal capsule, and enter the lenticular 

 nucleus as its most external fasciculi. If we consider the first 

 and second links of the projection fasciculi connected with this 

 ganglion (independently of the interrupting nodal points 

 of the ganglion cells) as a continuous mass, the projection 

 tracts by no means pursue the shortest course radially through 

 the lenticular nucleus, but they describe complex spirals which 

 are composed of concentric segments with their surface turned 

 downwards, and of radial segments with their surface turned 

 inwards. All radially running middle and inferior fasciculi, 

 as, for example, those in the third segment of the lenticular 

 nucleus, enter this part in sectional planes situated further 

 forwards, beginning with the upper border of its transverse 



