376 Journal of Comparative Neurology. 



cells at the sides of this commissure, lying apparently in the 

 course of the spinal V tract in the medulla. Caudally the cells 

 continue nearly to the end of the cord. 



I have twenty-one series of Golgi sections in the three 

 planes which show these cells, and in eleven series of longitudi- 

 nal sections many cells are impregnated in all segments of the 

 cord and also in the medulla in the position indicated above. 



The cell bodies are rounded, pear-shaped, or cuboidal and 

 are about equal in size to the spinal ganglion cells in the same 

 sections. There is always a single dendrite arising from the 

 caudal or lateral end of the cell. In some cases the dendrite is 

 slender near the cell (Figs. 4 and 7), while in the majority of 

 cases it is thick throughout its whole extent. The dendrite 

 runs caudally from the cell for a variable distance (compare cells 

 shown in Fig. 2), near the dorsal surface of the cord and be- 

 tween the median line and the dorsal tracts (Figs. 5 and 6). It 

 then bends dorsally or dorso-laterally and emerges from the 

 cord. At this point the dendrite thickens greatly, if it is slen- 

 der in its earlier course. As it rises toward the dorsal surface 

 of the body the dendrite is often sinuous and very commonly 

 makes loops in its course (Fig. 2, A, C, and Fig. 7). Fre- 

 quently it retains its thickness until it reaches the surface, where 

 it ends with a small knob apparently just beneath the epidermis. 

 There may be branches in these cases which have not been im- 

 gregnated. In many cases, at least, one or two branches are 

 found and in a few cases the terminal branching appears to be 

 well developed (Figs. 2, 4, 5). All the cells which have been 

 impregnated have dendrites of the above description, and in 

 many cases the dendrites have been impregnated without the 

 cell body taking the stain. 



Each cell has two neurites, although occasionally only one 

 neurite appears in the section, possibly owing to incomplete 

 impregnation. In rare cases a single neurite divides in 

 T-form. Of the two neurites, one is directed rostrally, 

 the other caudally. The rostral neurite arises from the cell 

 body, soon turns laterally and joins the dorsal tract of its 

 side. Some fibers of the dorsal tracts are always impreg- 



