472 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



columns. Deiters was therefore justified in stating that, be- 

 sides the compact nuclei, the scattered clusters of nerve cor- 

 puscles stand in a certain relation to the roots of origin of the 

 nerves. I shall hereafter have occasion to recur to this 

 point. 



The system of the fibres arcuatae (indicated in figs. 252 

 258 by the letters MFE, MFI, MF, in FM, V8, and by ar, a, 

 AS, Am) presents itself at first sight as the characteristic con- 

 stituent of the tissue of that portion of the posterior tract of 

 the peduncle of the cerebrum which extends from the ter- 

 mination of the decussation of the superior peduncle of the 

 cerebellum to the extremity of the inferior olivary body. The 

 largest number of these transverse fasciculi are given off from 

 the peduncle of the cerebellum, and participate in the inter- 

 lacement of the projection system. The remainder proceed 

 from the nuclei of origin (to be described hereafter) of the roots 

 of the cerebral nerves. The course pursued by the interlaced 

 fasciculi cannot be laid down for all regions, and it is obvious 

 is least evident for planes of section passing through the greatest 

 convexity of the pons, and through the origin of the fifth nerve 

 (figs. 252 and 253) in which the transverse section of the pe- 

 duncle of the cerebellum is not yet visible, through which it 

 is possible lower down to identify the termini of the fibrse 

 arcuatse. Let us call this obscure region the 



1. First or superior interlacement. It is certain that the fibrse 

 arcuatse are here connected with clusters of the small-sized 

 nerve corpuscles, and through these with the projection fasciculi 

 (antero-lateral column of the spinal cord). Probably, how- 

 ever, the posterior divisions of these fibrse arcuatse pass back- 

 wards into the cerebellum, internally to the superior peduncle 

 (fig. 252, left side) ; and on the other hand we may suppose 

 that their extremities are inclined forwards, in order, on the 

 other side of the raphe', to become continuous with the anterior 

 fibrse arcuatse, which, as will afterwards appear, are always 

 associated with the transverse section of the corpus restiforme. 



2. The second or middle interlacement includes the dentated 

 nucleus of the superior olivary body, which, in consequence of 

 the transverse striation produced by medullary substance, 

 acquires a vermiform appearance (figs. 256, 253, 254, 255, o). 



