THE SPINAL CORD 



THE SPINAL CORD 



THE general appearance of a transverse section through the human adult spinal cord is 

 shown in Plate I. The level is at the upper part of the lumbar enlargement. This section 

 was stained by the Weigert haematoxylin method. The diagram (Fig. i) will assist in the 

 explanation of its chief features, and the details of structure are shown in Plates II. to XI. 



The H-shaped arrangement of the gray matter of the cord, and the fact that the gray 

 matter is everywhere surrounded by white columns, which are darkly stained, is clearly marked. 

 It is evident that the anterior horns form the larger part of the gray matter ; that their 

 contour is irregular, owing to the massing of cells into groups, which cause a projection of 

 the gray into the white matter; and that they do not reach the surface of the cord. In the 

 diagram three cells (a) are shown representing three groups of anterior horn cells. These 

 cells are motor in function, presiding over the reflex movement and nutrition of the muscles, 

 each group representing a single muscle, or a group of muscles whose action is conjoined. 

 Many fibres are seen in the plate to issue from the anterior horns of the cord and to pass 

 through the anterior column to the surface. These are the anterior nerve roots. Their course 

 is shown in the diagram. In their course while in the gray matter they give off fine branches 

 which end about other cells in the vicinity. 



The posterior horns of the cord are smaller than the anterior horns ; they nearly reach 

 the surface of the cord and present a club-shaped appearance at their extremities where the 

 substance of Rolando is situated. The cells of these horns are too small to appear in the 

 plate, but are shown in the diagram. It will be noticed that two of these cells (V) send their 

 neuraxons into adjacent columns of white matter, while a third (c) is confined to the posterior 

 horn itself. At the base of each posterior horn, on its median side, a group of cells is to be 

 seen in the plate ; this is the Clarke column of cells. It is indicated in the diagram by a 

 single cell (d) whose neuraxon is seen to pass outward to the periphery of the cord where 

 it turns upward in the direct cerebellar column. 



In the gray matter of the cord, scattered irregularly through it, between and within the 

 anterior and posterior horns, there lie many cells whose existence is better shown in Plate II. 



