122 DR ALEXANDER BRUCE 



The lateral horns of the two sides continue to present a marked want of symmetry. In 

 the upper part of the segment on both sides the horn presents a blunted or rounded tip, 

 and the apical group lies either at or behind this. On both sides the apex of the lateral 

 horn lies on a plane which passes through the posterior part of Clarke's column (fig. 15, 

 D. 9, 168). On the right side in the lower part a projecting lateral spike appears, and 

 this contains the apical group (fig. 16, D. 9, 413). On the left side the lateral horn has 

 no sharp point, but simply a slightly bulging outline. The cells of the intermedio- 

 lateral tract lie along the outer side of the grey matter, and they extend as far back as 

 the outer side of Clarke's column. The reticular group lies internal to rather than 

 behind the apical group at the upper part of the segment, and on the left side it is 

 simply a backward continuation of the apical group along the outside of the grey 

 matter without any delimitation from it. The cells are not of uniform size in either 

 group, and very large cells from 40 m to 60 p- are occasionally found scattered through 

 the apical group. The vascularity of the tract, as in D 8, is still very pronounced. 



Tenth Dorsal Segment. — The segment was divided into 511 sections. The 

 intermedio-lateral tract contains on the right 10,203 and on the left 8903 cells. The 

 number of cells on the right side thus exceeds that on the left by 1300. This remark- 

 able difference is greater than that found in any other segment. It is one, moreover, 

 which is not attributable to any accidental cause. The cell groups, as represented on 

 the graph, are rounded on the top, and they tend to increase in size in the lower two- 

 thirds of the segment. They are badly marked off from each other, the minima being 

 rarely under 10. The average maximum on the right is about 40, that on the left 

 about 30, the greatest maxima on the left being 46, and on the right 44. 



As regards the form of the lateral horn there is asymmetry as great as that in D. 9. 

 The left side has practically no lateral spike, but merely a slight rounded bulging of the 

 grey matter. The apical group is placed either at the most prominent part of the 

 swelling, or, more commonly, a little behind it. On the right side in the upper part 

 there is a slight lateral spike in which the apical group is situated, but throughout the 

 greater part of the segment the lateral horn forms a rounded projection similar to that 

 found in the left side (fig. 17, D. 10, 208). On both sides the apical group may be 

 compact or scattered ; most commonly it is spread out along the edge of the grey matter 

 (fig. 18, D. 10, 225). The reticular group lies behind the apical, and is either continuous 

 with it or separate from it. The boundaries of the whole tract, more especially those of 

 the reticular group, are rather indistinct, especially when the cells are few and scattered, 

 many of these cells being small and little different from the middle-cells and the small 

 cells in the neighbourhood of Clarke's column. As showing the indefiniteness of the 

 boundaries, the enumerations of the different observers presented greater variations in 

 this than in any other segment. The cells, especially in the reticular group, are small. 

 Outlying cells are not common. 



Eleventh, Dorsal Segment. — This segment was divided into 413 sections. The 

 intermedio-lateral tract on the right side contains 6498 and on the left 6261 cells. 



