112 



BR ALEXANDER BRUCE 



the formatio reticularis are of the small polygonal type characteristic of the " Mittel- 

 zellen " of Waldeyer. 



Note. — It may be stated here that no cells which could be definitely considered to 

 belong either to the apical or to the reticular portions of the intermedio-lateral tract were 

 found in any segment of the cervical enlargement above the limit indicated in C. 8. 

 Any group of cells that was seen in the grey matter between the anterior and 

 posterior cornua and internal to the formatio reticularis belonged evidently to the 

 " Mittelzellen," and not to the intermedio-lateral tract. 



First Dorsal Segment. — This was divided into 202 sections. Its intermedio- 

 lateral tract contains 1720 cells on the right and 1837 on the left side. These are 

 distributed in sharply defined groups, with distinct, and, as a rule, wide intervals between 



Fig. 1 (C. 8, 247, L.). — Two groups of cells belonging to the intermedio-lateral tract are seen. Both 

 are outside the grey matter of the lateral part of the anterior cornu. The larger of the two is a 

 group of closely aggregated cells, close to the margin of the horn, and having their long axes 

 pointing outwards and somewhat forwards. In the smaller group, which is further removed from 

 the horn, the cells are more irregularly placed, but their long axes on the whole point outwards. 



them (see graph, D. l). As in C. 8, the largest cell-groups are situated at the lower 

 extremity of the segment. With one exception (the fourth on the left) the groups 

 resemble each other in that the number of their cells rapidly rises to a maximum and 

 then almost equally rapidly falls away to zero. The graph thus presents the appear- 

 ance of a succession of spires. Of these there are ten (or possibly only nine) on the 

 right and eight on the left side. While there is a close resemblance of form between 



[The figures in the text represent transverse sections of certain of the cells from the various segments examined. 

 The position in the segment is indicated thus : C. 8, 247 means the two hundred and forty-seventh section of the 

 eighth cervical segment. E. and L. indicate right and left sides respectively. 

 a. ra. Anterior median group of motor cells. 

 a. I. Anterolateral „ „ 



p. I. Postero-lateral „ „ 



p. p. I. Post-postero-lateral „ „ 



c. C. Clarke's vesicular column of cells. 

 i. I. t. Intermedio lateral tract. 

 m. c. The middle cells of anterior cornua : the Mittelzellen of Waldeyer.] 



