94 Journal of Comparative Neurology and Psychology. 



, ^ f near nerve 



1 7th segment < . , , ^ 



' *' (^ midway between nerves 



,, , f near nerve 



iQth segment < •, , . 



[. midway between nerves 



J ^ f near nerve 



22nd segment < • , , ^ 



° ( midway between nerves 



17 cells 

 15 cells 

 21 cells 



18 cells 

 29 cells 

 21 cells 



In other words, the numbers of the larger cells found'in 

 the twenty sections (an extent of 0.6 mm.) from each locality of 

 the segments were : 



f/ear nerve viidtvay between nerves 

 17th segment 341 cells 303 tells 



19th segment 420 cells 365 cells 



2:;nd segment 576 cells 432 cells 



There were many cells smaller than \o tx. It is very prob- 

 able that many of the cells having a mean diameter of 10 /i 

 and above belong to association neurones and therefore do not 

 give origin to ventral root fibers at all. The largest cells and 

 those considered as undoubtedly giving origin to efferent fibers 

 gave mean diameters ranging from 25 to 45 //. These, howev- 

 er, while much inore abundant near the nerve, were scattered 

 throughout the segment indicating perhaps that many of the 

 efferent fibers, being drawn toward the level at which the root 

 is assembled, course some distance through the substance of the 

 cord before emerging from it. In longitudinal section most of 

 the largest cells appear fusiform in shape with their long diame- 

 ter drawn more or less parallel with the long axis of the cord. 



The grouping of the cell-bodies in the gray substance is 

 very indefinite. The largest cells appear more abundant in the 

 regions of the ventrolateral and lateral groups. Occasionally a 

 large cell can be found lying in the beginning white substance 

 about the lateral periphery of the gray figure. Frequently one 

 or two cells of the largest type occur in the base of the dorsal 

 horns (Streeter's dorsal group) and perhaps correspond to the 

 nucleus dorsalis or Clarke's columns in other animals. 



Throughout the entire thoracic cord and extending into the 

 cervical region, there is found in the lateral periphery of the spinal 

 cord of the emu a line of scattered cells representing the 7121- 

 cletis marginalis vmwr described for the birds and reptiles. In 

 the emu it is situated within and against the ventral border 



