THE PONS AND THE CEREBELLUM. 143 



where they are lost between the two nuclei globosi. These 



j 



fibres receive their medullary covering as early as the seventh 

 fcctal month. Another band of fibres, which becomes medullary 







at a later period than the last mentioned, but still far in advance. 

 of the bulk of the restiform fibres, arises in the vicinity of the 

 nucleus globosus and passes to the outer wall of the fourth 

 ventricle median to the posterior peduncles. Its most anterior 

 fibres make their exit from the brain along with the trigeminal 

 nerve, others pass off with the acoustic, and still others run 

 caudad. The latter become still fewer in the oblongata, ap- 

 parently because some of them enter the roots of the glosso- 

 pharyngeal and vagus. Still, this fasciculus can be traced in 

 cross-section to the termination of the posterior columns of the 

 cord. The whole tract is called the direct sensory tract of the 

 cerebellum. I shall have occasion later to show it to you in 

 several illustrations. To-day I will call your attention to a sec- 

 tion through the brain of a seven months' foetus, in Avhich you 

 will recognize that portion of the tract which passes into the 

 trigeminus (Fig, 86). 



Lastly, it should be stated that fibres pass directly from the 

 hemispheres to the restiform bodies. 



The arms of the pons can be traced far into the correspond- 

 ing hemispheres (hemisphere fibres). Near the cortex they are 

 lost in the dense tangle of fibres. They receive, however, fibres 

 from the fleece (extra-ciliary fibres). 



In recapitulation we shall find that the anterior peduncles 

 are composed mainly of intra-ciliary fibres, the middle peduncles 

 largely of hemisphere fibres, and the posterior peduncles chiefly 

 of extra-ciliary fibres and fibres from the roof of the vermis. 



/ 



But each peduncle receives auxiliary bands from the point of 

 origin of each of the other peduncles. 



The anterior peduncle and the restiform body also receive 

 an addition from the white substance of the vermis. 



There is a point in the anterior part of the white substance 

 of the vermis where many fibres decussate, the anterior decus- 



