604 
Proceedings of the Koyal Society of Edinburgh. [Sess. 
where, but are frequently elongated in one direction. Both central and 
post-central cells are sometimes with difficulty separated from the reticular 
group of the intermedio-lateral tract, especially when there are isolated 
cells of the latter group left stranded in the central area, a feature which is 
not uncommon in this segment. 
D 4. — See fig. 13, Plate II. — Appearances very much as in D 3. Central 
grouplets are the commonest, but para-central and post-central are not 
uncommon. In other regions they are chiefly just loosely scattered cells. 
Fig. 5. 
D 2 — 173 L ( x 32 ). 
a. Two small groups of anterior middle cells. 
b. Apical group of intermedio-lateral tract. 
c. Scattered middle cells in central area. 
d. Posterior basal cells, indistinguishable from middle cells. 
e. Para-central group of middle cells. 
/. Three cells of Clarke’s column. 
g. Post-central group of middle cells. 
D 5. — Anterior scattered cells, not abundant ; they vary considerably in 
size, and at times it is difficult to distinguish some of them from motor cells, 
on the one hand, and from reticular group (intermedio-lateral tract) cells, on 
the other. In other regions, also, not abundant ; may be disposed any- 
where around the whorl of fibres surrounding Clarke’s column, in front as 
a para-central group, to the outer side or even behind as a central or post- 
central group. The occurrence of any group is, as usual, short-lived. Most 
cells are distinctly polygonal ; the anterior often have one long axis, while 
some of the central and post-central are almost rounded. 
D 6. — Cells nowhere numerous. Usual erratic distribution, scattered or 
grouped ; small groups in base of anterior horn or centrally are probably 
the most frequent. With the still further relative increase in size of 
