256 SIR CHARLES BELL ON THE RELATIONS BETWEEN 



the anatomist has recognised the parts, and verified the descriptions of the author, 

 he will of course vary his mode of proceeding to satisfy himself. 



Lay a portion of the spinal marrow, of two or three inches, on the dissecting board, 

 and pin it so as to look upon the posterior surface of that cord. Begin by making 

 a clean transverse section of it near one extremity, and inspect the newly-divided sur- 

 face (see Plate III. fig. 1.). The first thing which we distinguish is the cineritious 

 matter in the centre of the medullary. If we introduce the curette into the softer 

 cineritious matter, we can separate the medullary columns (as in figg. 2. & 3.), and 

 we distinguish these parts: the posterior columns, deeply divided by their sulcus; 

 the lateral columns ; and the anterior columns. 



In making these divisions, directed by the natural sulci and by the cineritious 

 matter, we may soon satisfy ourselves that there is but one absolute bond of union 

 by nervous matter. We find the anterior columns tied together by a sort of commis- 

 sure, and to that commissure is attached the anterior portion of the posterior columns 

 at two points (fig. 3. d.). 



Having contemplated the section of the spinal marrow, we proceed to the dissec- 

 tion by splitting up these columns. We raise the posterior columns together, in one 

 piece ; to do which we must divide them at the point of union with the anterior 

 columns (fig. 4. b.). But except at this angle, the whole tract is raised without the 

 slightest breach of its proper surface. When the columns are thus separated, the 

 surfaces are found to be covered with cineritious matter. We have split the cine- 

 ritious substance, and some of it lies on the lower surface of the part raised, and some 

 on the upper surface of that which is below. 



If we now clear away the cineritious substance from the columns below, we shall 

 first discover the two lateral tracts or columns. We see them in their course, regular 

 as nerves. These columns or cords, in this aspect and condition, take a rounded 

 form, although they are of a different shape when packed together in their natural 

 state. 



And now may be observed a structure which is not without interest. If we make 

 a slight breach upon the surface of the columns when divested of their cineritious 

 covering, and insinuate the point of the curette, we raise a thin pellicle, like a distinct 

 coat, and which we may separate all round. Having done this, and the remaining 

 surface being smooth, we may pierce it again, and in a similar manner separate a 

 third and a fourth layer, which, smooth and delicate themselves, leave the part below 

 as regular as the natural or exterior surface. It appears that the superficial layers 

 furnish the roots of the higher nerves, and that the lower layers go off into the roots 

 of the nerves as they successively arise. 



If we now follow the sensitive or posterior roots of the spinal nerves towards their 

 origins, we find them entering and dispersing in the substance of these lateral 

 columns. Some authors describe these roots as derived from the cineritious matter. 

 This is quite at variance with my dissections. The cineritious matter is not of a con- 



