HE CRUSTA OF THE CEREBRAL PEDUNCLE AND ITS GANGLIA. 413 



of the nerve-cell layer. This layer coalesces posteriorly with 

 the hook convolution. Its presence exhibits the uniform 

 applicability of a law of formation by virtue of which the 

 whole surface of the vesicles of the hemispheres is covered with 

 cortical substance, and by which, consequently, also the septum 

 pellucidum comes to be classified among the cortical substances. 

 The coalescence of the temporal extremity of the cauda with 

 the temporal process descending from the third segment of 

 the lenticular nucleus (pedunculus nuclei lenticularis) occurs 

 close behind the amygdaloid nucleus. The substance of the 

 caput of the corpus striatum, folded around it like a gutter, 

 invests the external (ventricular) surface of the septum pellu- 

 cidum at the height of about eight millimeters, forming the 

 nucleus septi pellucidi (fig. 241, J). 



The tissue of the substance of the corpus striatum is com- 

 posed of a delicately punctated connective tissue, like that of 

 the cortex of the cerebrum, with similar apparently free nuclei 

 sparingly distributed through it. The nerve corpuscles of the 

 corpus striatum are of two sizes. Some are large, with many 

 processes, and attain a diameter of 30 p, whilst others, and 

 these are by far the most numerous, are small, being only 15 JJL 

 in length, but are also multipolar. It is probable that part of 

 these cells form cells of origin for the spinal cord, whilst others 

 are cells of origin for the fibres of the cerebellum ; and for the 

 following reason. The mass of the crusta of the cerebral 

 peduncle, which is continued into the pyramids of the medulla 

 oblongata, is at least three times the size of the latter ; and 

 this diminution is due to the turning aside, within the pons, 

 of fibres of the crus cerebri into the fasciculi of the crura 

 cerebelli of the pons through the agency of grey substance. 



There cannot, consequently, be any doubt that the ganglia 

 of origin of the crusta of the cerebral peduncle are also centres 

 of origin for the fibres of the cerebellum. A motor function 

 must therefore be attributed to the cerebellum even from this 

 morphological point of view alone. For no other view can be 

 taken, than that the impulses conveyed from the cortex to 

 the corpus striatum and the lenticular nucleus, besides their 

 conduction into the spinal cord, at the same give rise to definite 

 modes of activity of the cerebellum. 



