607 
1907-8.] Middle Cells of Grey Matter of Spinal Cord. 
inner portions of the anterior horn, in the area corresponding to the position 
of the now dwindling apical group, or extending right to the margin of the 
grey matter between the apical and reticular groups of the intermedio-lateral 
tract. They are also present in the region sometimes occupied by the tip 
of the triangular-shaped reticular group, and are not always readily 
distinguished from it. The post-central cells are, on the whole, smaller than 
the others, but most are polygonal in outline, although some are rounded ; 
they usually form a band on the outer side of Clarke s column. 
L 1 — 433 L ( x 40 ). 
a. Anterior middle cells. 
b. Apical group, intermedio-lateral tract. 
c. Reticular group, intermedio-lateral tract, of large cells, extending 
well into central area. 
d. Group of fairly large middle cells. 
e. Clarke’s column. 
/. Small, rounded, post-central middle cells. 
L 3. — See fig. 14, Plate II. — The middle cells now form a striking feature 
of the section. They are very numerous, and may be present anywhere in 
the posterior part of the anterior horn, central area, and base of the posterior 
horn. They have also invaded the areas occupied at higher level by the 
reticular group and by Clarke’s column, but in the latter position they are 
never very numerous. They may be scattered or forming loose groups in 
any part of this wide field, but, as at other levels, these groups never persist 
through more than three or four consecutive sections. Groups may be 
present in the reticular formation, but they have none of the characters of 
the reticular group of the intermedio-lateral tract (which dies out in the 
