42 
MR. C. S. SHERRINGTON ON OUT-LYING 
related to them, might also be so arranged and a little difficult of discovery. A cross 
section of a bipolar cell, imbedded in the fibres of the white column, even when the 
plane of the section passed through it allowing recognition of the nucleus, might be 
somewhat hard to detect. In longitudinal sections they should be clearly discover¬ 
able. I have not, however, obtained specimens which prove that the cells exist 
beyond the limits mentioned above. I have not found ilrem in the region of the 
sacral nucleus of Clarke''" and Stilling, nor in the upper cervical cord where a cell- 
group, in some respects resembling the posterior vesicular column, is obvious. 
As to the particular position in the radicular zone occupied by the out-lying cells, 
they may be far removed from the limits of the grey matter [cf. figs. 9, lOt), in the 
middle of the extero-posterior column, indeed, near the edge of that column where it 
abuts upon the, in this region of the cord, ill-defined confines of the column of Goll. 
The cells far distant from the gre}^ matter appear in my .specimens more numerously 
in the lumbar than in the thoracic cord, although there are many in the latter. The 
distant ceils are not so numerous as others, quite resembling them, which lie in the 
portion of the root-zone that is nearer to (fig. 11, Plate 3), and close outside (figs. 12, 
13, Plate 3), the grey matter of Clarke’s column. Occasionally the cells are situated 
far ventrally, near the dorsal commissure. Even from that district of the extero- 
posterior column, not a few bundles of fibres proceed towards Clarke’s group ; it is 
presumable that these are root bundles, if so, the radicular zone extends ventrally 
sufficiently far to include them and the out-lying cells in question. The position of 
the isolated ganglion-cells upon these bundles favours the supposition. 
A point to be mentioned is that just as Clarke’s group at its lower end is placed 
well backward in the base of the dorsal horn, considerably behind the niveau of the 
dorsal commissure, and when traced up\vards is found to rapidly exchange this 
position for a more ventral one, so do the out-lying cells in the posterior columns 
experience a shift of their general position in the same sense. In the lower levels of 
their distribution they lie nearer the dorsal part of the periphery of the cord than in 
levels situated higher. A comparison of fig. 9, from near the exit of the 2nd lumbar 
nerve-root with fig. 10, from the level of the 8th thoracic, shows this difference in 
general position of the cells within the posterior column. 
The proportion of the number of out-lying cells to the number of the cells of 
Clarke’s column, varies in different secfions from the same level, and at different 
levels. Two out-lying cells to eight of Clarke’s cells is a high ratio. In the middle 
of the thoracic region, several successive sections may not reveal a single out-lying 
cell, even if the sections be made as thick as is compatible Muth a satisfactory 
examination of them, and as many as eight or nine of Clarke’s ceils are to be found 
in the section of the vesicular column. 
* Clarke latterly did not consider that this nucleus corresponded to his posterior vesicular column of 
the lumbo-thoracic region. 
t The positions of the cells ani marked by crosses. 
