44 BORDER LINES OF KNOWLEDGE 



dentally settled in the course of these new investiga- 

 tions. Thus, Mr. Clarke's dissections, confirmed by 

 preparations of Mr. Dean's which I have myself ex- 

 amined, place the fact of the decussation of the pyra- 

 mids — denied by Haller, by Morgagni, and. even by 

 Stilling — beyond doubt. So the spinal canal, the ex- 

 istence of which, at least in the adult, has been so often 

 disputed, appears as a coarse and unequivocal anatomi- 

 cal fact in many of the preparations referred to. 



While these studies of the structure of the cord 

 have been going on, the ingenious and indefatigable 

 Brown-Sdquard has been investigating the functions 

 of its different parts with equal diligence. The mi- 

 croscopic anatomists had shown that the ganglionic 

 corpuscles of the gray matter of the cord are con- 

 nected with each other by their processes, as well as 

 with the nerve-roots. M. Brown-S^quard has proved 

 by numerous experiments that the gray substance 

 transmits sensitive impressions and muscular stimula- 

 tion. The oblique ascending and descending fibres 

 from the posterior nerve-roots, joining the " longitudi- 

 nal columns of the cornua," * account for the results 

 of Brown-S^quard's sections of the posterior columns.f 

 The physiological experimenter has also made it evi- 

 dent that the decussation of the conductors of sensi- 

 tive impressions has its seat in the spinal cord, and 

 not in the encephalon, as had been supposed. Not 



* Dean's Memoir, Fig. 8. 



t Lectures, (Philadelphia, I860,) Lect. 11. p. 26, and Plate L fig. 7. 



