THE TEGMENTUM OF THE CRUS CEREBRI AND ITS GANGLIA. 451 



Whilst the compact transverse section (fig. 249) of the crusta 

 is broken up (fig. 250) into secondary fasciculi by the pene- 

 trating transverse fasciculi of the brachia of the pons, the 

 most posterior transverse fasciculi of the brachia of the pons 

 cut off* the hindermost part of the crusta, which in its 

 further course belongs to the tegmentum, forming the inner- 

 most portion of the fillet (lemniscus). Notwithstanding that 

 this fasciculus belongs alternately to the crusta and the teg- 

 mentum of the cms cerebri, its morphological characters are 

 those of the latter, and it therefore unquestionably belongs 

 to the posterior tract of the cerebral peduncle, since it takes 

 no part in the decussation of the pyramids, which is the 

 essential characteristic common to the spinal fasciculi of the 

 crusta. 



It thus appears that a still unknown region of ganglia of 

 origin of the crusta must be enumerated with the centres of 

 origin of the tegmentum. These latter ganglia are charac- 

 terized by the concurrence of both sensory and motor tracts in 

 their interior, a point differentiating them from the ganglia of 

 the crusta, which is of the highest importance to enable us to 

 understand the duplicity of origin of the spinal cord. Within 

 the ganglion of origin of the crusta, however, there is, in point 

 of fact, a region which is connected with a sensorial surface 

 just as, for example, the optic thalamus is connected with the 

 retina by converging radii of the olfactory lobe ; namely, the 

 base of the caput of the corpus striatum above the lamina 

 perforata anterior. This region is at the same time charac- 

 terized by textural peculiarities resulting from the form and 

 arrangement of the nerve corpuscles, showing it to be a mass 

 which, though fused with the corpus striatum, is by no means 

 homogeneous with it. 



The hypothetical reference to this territory of origin of 

 fasciculi of the crusta is perhaps appropriate for the purpose 

 of indicating the direction that should be pursued in a decisive 

 and accurate investigation of the origin of the fasciculi not 

 proceeding from the corpora quadrigemina, that is, of what are 

 called by Reichert the layers of the fillet. 



The organization of the tegmentum is thus completed at the 

 level at which its inferior ganglia of origin, the corpora quadri- 



G G 2 



