416 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



their way superficially over the intermediate fasciculi. They 

 are clearly to be distinguished from the subsequently de- 

 scribed loops of the cms cerebri, which only partially inter- 

 weave with the cms cerebri of their own side, and never 

 bilaterally. 



The lenticular nucleus, or corpus striatum externum (figs. 

 233, 242, 243, 244, 245), which is the second ganglion of origin of 

 the crusta of the cerebral peduncle, is perfectly identical in its 

 textural structure with the intra-ventricular portion of the cor- 

 pus striatum. The two different-sized forms of nerve corpuscles 

 occur in it, but still no region of aberrant structure is found in 

 it resembling that of the basal portion of the caudate nucleus, 

 which is traversed by the fasciculi of the olfactory lobes. The 

 ganglion is wedge-shaped. The base of the wedge is directed 

 towards the frontal portion of the brain, and towards the in- 

 sula, whilst the apex is prolonged into and continues with the 

 crusta of the cerebral peduncle ; it presents a slender, dentated, 

 sigmoid, curved border. In sections made transversely through 

 its substance (figs. 242, 243, 245), the first glance shows the 

 presence of two systems of fasciculi running in different 

 directions, one arranged radially upon the base of the wedge, 

 the other concentricaDy with the surface of the wedge, and 

 descending from the internal capsule to the base of the 

 brain. The last-mentioned fasciculi form concentric dissepi- 

 ments of the lamince medullares, which break up the len- 

 ticular nucleus, as a rule, into three segments, of which the 

 internal is applied to the origin of the crus cerebri, whilst 

 the external is separated from the claustrum belonging to the 

 cortex of the insula by the thin medullary lamina of the 

 external capsule (figs. 244, 245, Ce, and also in figs. 242, 243). 

 The latter, connected by means of loose cellular tissue, simply 

 lies on the lenticular nucleus, without having any medullary 

 connection with it. A few thin and inconstant medullary 

 fibres of the external capsule, which cut through the super- 

 ficial portions of the third segment of the lenticular nucleus, 

 form an exception to this statement. 



The two internal segments of the lenticular nucleus are 

 distinguished from the third segment, which is the largest 

 of the three, as the globus pallidus, on account of the 



