INTERLACEMENT OF THE CEREBRAL PEDUNCLES. 471 



includes in its motor area irregularly distributed nerve cor- 

 puscles of various calibre, standing in obvious relation to the 

 interweaving of the peduncle of the cerebellum. 



The cells of smaller calibre, (having a long diameter of 24 

 33 n, and a breadth of 9 12 ju,) of the scattered formations, are 

 chiefly found in the pons below the decussation of the su- 

 perior peduncle of the cerebellum, extending as far as to the 

 planes of origin of the facial nerve (figs. 252, 253, M F, m), 

 where they form very numerous small clusters between the 

 transverse sections of the medulla of the motor area, whilst 

 they are arranged most closely in the layers of the fillet. 



In the lower half of the pons these clusters of cells are con- 

 fined to the transverse section of the fifth nerve, where they 

 are introduced by the transverse fasciculi traversing them, and 

 reappear with these also in the interior of the gelatinous sub- 

 stance as cells of a different size from those that are (there 

 present) characteristic of that part. 



Similar clusters reappear also in the lateral columns in the 

 medulla oblongata, viz., in the region of the vagus nerve, 

 on the one hand as a larger division situated to the inner side 

 of the layers of the fillet, forming the nucleus of the lateral 

 columns of Stilling, Clarke, and Deiters, and on the other 

 in smaller clusters which are shifted further inwards behind 

 the olivary body. 



The cells of larger calibre, having a long diameter of 60 p, 

 and a breadth of 15 p, distributed through the motor area, are 

 very sparingly present at that level of the pons where the 

 cells of small calibre are most abundant, but become more 

 numerous at the level of the origin of the facial nerve, and 

 are abundantly distributed, increasing from above downwards, 

 through all this portion of the medulla oblongata. 



The large nerve cells, however, are not evenly distributed 

 through all the regions of the transverse section of the above- 

 mentioned length of the medulla. Just as the level at which 

 they appear coincides with the level of the closest approxima- 

 tion of the nuclei of the motor nerves (facialis, abducens oculi, 

 hypoglossus, vagus, and accessorius), so do we find they are 

 most abundant around these nuclei in the vicinity of the grey 

 matter of the floor of the fourth ventricle, and in the lateral 



