ON DISTRIBUTION OF THE CELLS IN THE INTERMEDIO-LATEKAL TRACT. 119 



and are more separated by bundles of white fibres than in D. 5 (fig. 10, D. 6, 253 R.). 

 The cells in the apical group are frequently of a large size, measuring 40-50 m. The 

 vascularity of the group is very remarkable, and it is noticed that the main supply 

 comes from the vessels of the periphery of the cord. 



Seventh Dorsal Segment. — This segment was divided into 518 sections. The 

 intermedio-lateral tract on the right side contains 8282 and on the left 8739 cells. 

 Sixteen groups can be counted on each side, and they present a very uniform character 

 throughout the segment. They are rather more distinctly demarcated on the right 

 than on the left side. They present the mound-like appearance found in the lower half 

 of D. 6, with rounded tops, but with less tendency on the whole to the formation of 

 small superposed spires. The maximum number of cells is generally between 30 and 



urn 



Fig. 10 (D. 6, 253, R.). — The reticular cells are widely scattered, are fewer in number, and have 

 no triangular outline. The apical group contains cells of large size. 



40, and the minimum usually under 10. The largest number of cells in this segment 

 is 43 (in section 368 on the right side). There are no complete intervals between the 

 groups. Although the graphs are fairly similar on the two sides, there is a marked 

 difference in the form of their lateral horns. On the right side, in the lower part of the 

 segment, the lateral horn remains as a distinct spike, whereas on the left side it is 

 almost entirely absent, being limited to a slight rounded prominence (fig. 11, D. 7, 

 151). The reticular group forms a less distinct feature than the apical one. It 

 is difficult to delimit, especially on the inner side. It is either continuous with or 

 separated from the apical group. The apical group is either fairly compact or its cells 

 are more widely scattered. In both groups the cells are relatively large, presenting 

 frequently a close resemblance in size to the motor cells of the anterior cornua (fig. 12, 

 D. 7, 316). Their exact measurements are 40 m to 60 m. 



Eighth Dorsal Segment. — This segment was divided into 430 sections. The inter- 

 medio-lateral tract contains on the right 5943 cells and on the left side 6223. The 

 graph is, on the whole, similar to that of D. 7. The groups are somewhat more definitely 



