SUPERIOR PEDUNCLES OF THE CEREBELLUM AND VALVE. 457 



THE CONNECTING ARMS (SUPERIOR PEDUNCLES OF THE CERE- 

 BELLUM, OR PROCESSUS E CEREBELLO AD CEREBRUM,) AND 

 THE SUPERIOR MEDULLARY VELUM (VALVE OF VIEUSSENS). 



The expression, " interlacement of the projection system 

 through the cerebellum," does not properly exhaust the mor- 

 phology characteristic of this segment, since in truth a large 

 portion of the fasciculi that pass from the projection system 

 into the brachia of the cerebellum are mingled with it, not only 

 in the pons and superior half of the medulla oblongata, but are 

 already included in the transverse section of the crus cerebri. 

 This primarily refers to the superior peduncle, which was 

 already associated with still higher sections of the projec- 

 tion system, and, as a fasciculus of the corona radiata, even 

 with the medulla of the cerebral lobes, before its fasciculi 

 had become collected together in transverse sections of the red 

 nucleus of the tegmentum. 



We are thus here dealing essentially with a separation of 

 the fibres of the superior peduncle from the projection system, 

 and their liberation as an independent mass of fibres extending 

 into the cerebellum, and in consequence of this the fasciculi of 

 this medullary body exhibit the following phases of arrange- 

 ment : 



Whilst the fasciculi of the superior peduncle are separated 

 in the region of the crus, anterior to the nates, by finely granu- 

 lar grey connective material, containing nerve cells of two 

 different sizes (one having a long diameter of 45 p, and a short 

 of 15 ju, and the other having a length of 15 p, and a breadth 

 of 3 /LI), so as to form the red nucleus; this peduncle becomes 

 reduced in the lower half of the nates, through the disap- 

 pearance of the finely granular grey matter, to a pure tract 

 of white fibres that is obviously of smaller size than the red 

 nucleus. 



This medullary tract has however only become free from the 

 connective material of the red nucleus ; it still contains a large 

 number of nerve corpuscles, and these are still to be found 

 scattered amongst the fasciculi of the superior peduncle in 

 those portions of their course that lead to and from their decus- 

 sation. But these nerve corpuscles exhibit a remarkable and 



