L24 



I) It ALEXANDER BRUCE 



graphic representation of the groups shows a return to broad spires somewhat similar to 

 those of D. 3. There are 13 groups on the right and 15 on the left. The greatest 

 number of cells in any one section is 62 (in section 232 on the right side). While the 

 apical group still remains the larger, the reticular has now a maximum number of 35 

 cells. As in D. 11, the reticular cells are arranged in nests with complete intervals in 

 which there are no cells. These intervals are, however, shorter than in D. 11, so that 

 the reticular group has a relatively greater value in this segment. The apical group is 

 situated partly at the spike-like tip of the lateral horn and along the posterior border, 



Fig. 19 (D. 11, 181, L.).— The lateral horn forms merely a 

 slight rounded elevation without any definite pointed 

 tip. The cells of the intermedio-lateral tract are distri- 

 buted along the margin. The most posterior of them 

 pass as far back as the hinder limit of Clarke's column. 

 Internally they have no definite boundary. The apical 

 and reticular groups are here quite inseparable. 



u 



Fig. 20 (D. 11, 312, R.). — The lateral horn has a prominent 

 tip, directed slightly backwards, and lying at a level 

 behind the central canal. Apical and reticular groups 

 are both particularly well-developed. The lateral ex- 

 tends further back than the hinder limit of Clarke's 

 column. 



and occasionally has outlying cells amongst the fibres in the neighbourhood of the tip. 

 The reticular group is found either round the re-entering angle and continuous with the 

 apical group, or (fig. 21) it forms a separate group extending somewhat inwards towards 

 the central canal (fig. 22). The two groups show no characteristic difference in the cells, 

 although many of them appear in both groups to be of comparatively large size. The 

 lateral horn is not pointed in the upper half of the left side (fig. 21). On the right and 

 in the lower half of the left it is pointed, and increases in size towards the lower end 

 (fig- 22). 



First Lumbar Segment. — This was divided into 352 sections. The intermedio-lateral 

 tract contains 7655 cells on the right side and 7053 on the left. The groups in this 

 segment present in the graph an arrangement into lofty and for the most part slender 



