ON DISTRIBUTION OF THE CELLS IN THE LNTERMEDIO-LATERAL TRACT. 117 



two cell-systems, there being a greater disparity in the size of the cells contained in 

 either group than between those of the two individual groups. This association of 

 the two groups, reticular and apical, as will be seen, could be traced throughout all 

 the lower parts of the region in which the two tracts were found. The reticular group 

 occasionally curves inwards in front of Clarke's column (fig. 8, D. 4, 151). The 

 apical sometimes gives off a small anterior group on the anterior aspect of the lateral 





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Fig. 7 (D. 4, 149, L.). — In this section the apical and 

 reticular cells form one long continuous group, which 

 extends from a point in front of the tip of the lateral 

 horn to a point much behind the level of Clarke's 

 column. Eighty-two cells were counted in this section. 

 A few of them were situated in the white matter. 



Fig. 8 (D. 4, 151, L.). — This figure shows the continuity of 

 the apical and the reticular cells, and also a tendency 

 of the group to extend inwards in front of Clarke's 

 column. 



horn. There are a few outlying cells near the tip of the lateral horn, but a greater 

 number in the formatio reticularis. 



Fifth Dorsal Segment. — This segment was divided into 350 sections, in which the 

 cells of the intermedio-lateral tract on the right side amount to 7407 and on the 

 left to 7958. The segment shows a remarkable difference between its upper third and 

 its lower two-thirds. In the upper third the groups as represented on the graph 

 continue to show a spire-like character, closely resembling that of D. 4, although of a 

 less slender type, and on the whole with less complete intervals. In the lower two- 

 thirds the spire -like character is less marked. There is a remarkable change in the 

 character of the groups, there being a gradual transition towards the types of 

 D. 6 and D. 7, in which the graph suggests mounds with rounded tops on which 

 are superposed short and slender spires. The intervals between the groups in the 

 lower two-thirds are distinctly less than in the upper third. The number of the 



