20 ATLAS OF NERVE CELLS 



Plate II. shows a transverse section through a human foetal cord at the eighth month 

 stained by the Golgi method. The ratio of the white to the gray matter is very small at 

 this period of development. The cells of the gray matter are, however, already formed, and 

 their processes are well developed, but their separation into groups is not yet very manifest. 

 It will be noticed that the cells are irregularly scattered throughout the anterior horn and 

 the central gray matter, and extend back into the posterior horns to some extent. It will 

 be noticed that the cells are large in comparison with the size of the cord ; that they have 

 very numerous branches which pass in all directions, forming an interlacing mass of fibres 

 which touch but do not unite. In the commissures of the cord it will be noticed that 

 there are many of these fibres crossing from one side to the other. The substance of 

 Rolando is seen to be devoid of cells. The various cells of the cord may be classified as 

 follows : 



I. Root cells, lying in the anterior horn or median portion of the gray matter, whose 

 neuraxons pass out of the cord chiefly through the anterior nerve roots, but also in part 

 through the posterior nerve roots. 



II. Intrinsic or columnar cells, lying in all parts of the gray matter, whose neuraxons 

 do not leave the cord, but pass into the columns, bifurcate, and after traversing some extent 

 of the cord reenter the gray matter and end. Several varieties of these cells are described 

 according to the destination of their neuraxons. (a) Cells of a single column ; the neuraxon 

 passing into one column only. (b) Cells of two columns ; the neuraxon dividing, one branch 

 going to one column, the other to another. (c] Commissural cells ; the neuraxon crosses the 

 middle line and ends in the gray matter, or turns up or down in a column, finally entering 

 the gray matter again. (d) Cells which are both commissural and columnar; the neuraxon 

 divides and one part crosses while the other enters a column on the side of the cell. 



III. Cells of Golgi's second type; 1 the neuraxon divides and subdivides in the gray 

 matter and does not leave it to enter the roots or columns. 



1 C. Golgi, Sulla fina anatomia degli organi central! del sistema nervoso. Milano, 1885. Untersuchungen iiber d. feinere Bau 

 d. Nervensystems. Atlas u. Text. Jena, 1894. 



