462 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



transverse section of the pons, the fasciculi of its brachia be 

 divided into (1) a superficial, (2) an interlaced, and (3) a deep- 

 lying portion (figs. 252 and 254, Trs, P, Trp), one is tempted 

 to think that it is the middle series of the transverse fasciculi of 

 the pons only which conduct the interlaced median portions of 

 the fasciculi of the crus to the cerebellum, and the deep-lying 

 stratum in particular seems like some obscure commissural 

 tract belonging to the cerebellum, having no relation to the 

 projection system. Certain considerations, however, compel us 

 to give up the simple conception of more superficial anterior 

 and deeper posterior crossed transverse bands of the crura 

 cerebelli, and to admit that these pursue a more looped course, 

 within which, moreover, the deep-lying transverse layers only 

 represent portions of tracts that are connected by means of 

 cells with the fasciculi of the projection system. The consider- 

 ations above alluded to are three in number : 1. The deep- 

 lying layer of transverse fibres obviously commences lower 

 down, and ceases higher up, than the superficial strata, on 

 which account hollows (foramina cseca) are formed at the upper 

 and lower edges of the pons over the median fissure of the 

 peduncle. These last without doubt show that the existence of 

 the deep transverse layers depends upon the terminations of 

 the fasciculi of the crus in the cells of the anterior division of 

 the pons, by virtue of which the deep transverse fasciculi 

 are wanting in the uppermost planes, where the transverse 

 sections of the crus have not yet given off any processes 

 (fig. 250), as well as in the lowermost planes, where the trans- 

 verse sections of the pyramids have already become compact, 

 and the giving off of fibres has ceased ; on the other hand, in 

 the centre of the pons, as in the territory of the most extensive 

 termination of the fibres of the crus, they attain their greatest 

 size. 2. We see obviously interlaced fasciculi of one side 

 become fasciculi of the deep layer of transverse fibres of the 

 other side, after curving somewhat posteriorly in the middle 

 line. 3. In all transverse sections fasciculi are found with 

 the deep layer of transverse fibres which wind around the 

 curve of the transverse section of the crus, with their convexity 

 directed outwards (figs. 252, on the right, and 254). After they 

 have penetrated hither from the middle line, and therefore 



