820 MAN 



the iH'i\L' libcrs proceed toward tlu' l)iill)()|)()ntilf sulcus. The rt-ticular por- 

 tion of the section is the most extensive region in the tegnuntuni. The l)asis 

 contains the elements eharaetenstie ot all pontile IiacIs: the stratum super- 

 ficiale, the stratum eomplexum in w hieh are the extensive pontik' nuelei, the 

 transverse pontile libers and the lilxrs of the |)\ ramidal system, and the 

 stratum profundum. In the dorsal area of this lield are a few scattered 

 I)undles detached trom the main pyramidal mass lorminii; the aberrant p\ ram- 

 idal eontingents ol the pons. The large size ol the pontile nuclei is of 

 particular moment, inasmuch as it indicates the accessions in the reahn oJ 

 the cortical organization lor skilled acts. These nuclei lorm one ot the mam 

 contrasting points between man and apes. The ncrxiis abducens, passing 

 Irom Its nucleus ot origin on the lloor ol tlu' touith \'enti"icle torward to 

 emerge in the bulbopontile sulcus, is seen in this section as it makes its 

 \\a\ through the tegmentum pontis and begins to penetrate the stratum 

 ]:)rolundiim. 



LE\'EL OF THE MIDDLE OF THE PONS VAROLII (fIG. 350) 



At this le\'el a minor alteration has occuirt'd m the contiguration ot the 

 section which belter illustrates the complexity of the pons Varolii and at 

 the same time lurmshes means to estimate the size ot the superior cerebellar 

 peduncle (Sep). The central gia\ matter spreads out as a thin layer 

 undeilymg the lloor ot the \cntiuli' which is approaching the caudal oritice 

 of the Sylvian ac|ueduct. At the iunction of the lloor and the lateral wall is a 

 collection of cells representing tlu' ct'phalic pole ol the nucleus ot Bcchtcrew 

 (NBe), part of the vestibular complex. Closely associated with this is a 

 dense bundle ol libers constituting the ascending mesencephalic root ol 

 the trigeminal nerve (Tmt). The lateral wall of the \enlricular space is 

 tormed by the superior cerebellar |H'duncle (Sep). This pi'duncle is ol 

 interest largely because of its size which, as compared with any of the apes. 



