THE CRUSTA OF THE CEREBRAL PEDUNCLE AND ITS GANGLIA. 419 



section, and descend parallel to its external convex surface 

 before they assume a radial course inwards towards the crusta 

 of the cerebral peduncle. As the sum> of the fasciculi towards 

 the interior increases by aggregation in proportion to the 

 length in transverse section of the line of contact of the re^ 

 ceiving superior border with the medulla of the hemispheres, 

 which sinks to zero at the external extremity of this border, 

 so do these concentric tracts which within the third segment 

 are microscopic, here form coarse, distinctly visible lines, the 

 medullary septa (laminse medullares), between the segments 

 which by the addition of nerve corpuscles, and by decussation 

 with the radial tracts by which they are traversed, form? com- 

 plex ganglionic plexuses. 



The number of large nerve corpuscles is here very remark- 

 able, and the position of their long axes is obviously parallel 

 to the direction of the concentric fasciculi. In the pale 1 clumps 

 (globus pallidus) of the lenticular nucleus, the arrangement of 

 the nervous elements is very close, and the amount of inter- 

 mediate amorphous connective tissue is very small. A portion 

 of the fasciculi taking part in the formation of the laminae 

 medullares does not traverse in its further course one or both 

 of the internal segments of the lenticular nucleus, but runs at 

 the basal surface of this nucleus directly into the peduncular 

 stratum of the internal capsule. These fasciculi form the inner- 

 most area in transverse sections of the crusta, and consequently 

 pass not only over the inferior surface of its ganglion, but 

 also over the external and median fasciculi of the crusta itself, 

 in the form of a transverse sling or loop nearly parallel to 

 the tractus opticus, forming the loop, collar, or fillet of the crus 

 cerebri (figs. 245 and 247, Schl). This constitutes the deepest 

 stratum of the ansa peduncularis of Gratiolet, described at 

 p. 427, or of the substantia innominata of Reil. The haste of 

 these fasciculi to reach over the others from the most external 

 ganglia of origin towards the median line is explained by their 

 being destined to attain elevated points of decussation. 



The innermost fasciculi of the crusta terminate peripheric- 

 ally in the central grey substance of the ventricle within the 

 nates (superior pair of the corpora quadrigemina) as they there 

 penetrate into the nucleus common to the oculo-motor and 



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