T-HE SPINAL CORD 



27 



While the cells of the anterior horns are collected into distinct groups, those of the 

 posterior horn are usually scattered irregularly through the gray matter. There is, however, 

 one distinct group of cells found at the base of the posterior horn on its median side at 

 certain levels of the cord, viz. the Clarke column of cells. This extends from the mid-lumbar 

 region upward to the lower cervical region. It has also been called the dorsal group of 

 Stilling. A few cells are grouped in the same location in the lower sacral region (Stilling's 

 sacral nucleus), and in the upper cervical region (Stilling's cervical nucleus). The cells of 

 this group are from 45 /i to 90 p in size. Under some stains they appear to be pear- 

 shaped, with but one projecting process. But the Golgi stain shows them to have both 

 dendrites and a neuraxon. 



Plate IX. shows this group of cells, one of which is successfully stained. It is seen to 

 the left of the centre of the plate. It has four dendrites, and a long fine neuraxon which 

 passes forward, and then turns outward through the gray matter. The neuraxons of these 

 cells pass through the median gray matter and through the lateral column to its surface, 

 where they turn upward, and traversing the entire length of the cord, forming the direct 

 cerebellar column, turn outward in the inferior peduncle of the cerebellum, and finally reach 

 that organ (cell d and column V. in Fig. i, on page 16; also i in Fig. 7, page 42). The 

 probable function of these cells is to receive from the posterior root fibres those sensory im- 

 puls'es which are necessary to our appreciation of equilibrium, and without which the nice 

 adjustment of balance is impossible. These impulses are transmitted from these cells to the 

 cerebellum by the direct cerebellar column. 



