1907-8.] Middle Cells of Grey Matter of Spinal Cord. 
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XXXVI.— The Middle Cells of the Grey Matter of the Spinal Cord. 
By J. H. Harvey Pirie, B.Sc., M.D., M.R.C.P. Ed. Abstract of Thesis 
for the Degree of M.D. Edin. Univ., 1907. {From the Pathological 
Department of the Royal Infirmary , Edinburgh.) Communicated 
by Dr Alexander Bruce. (With Two Plates.) 
(MS. received February 6, 1908. Read February 17, 1908.) 
These cells were first described and recognised as a separate and distinct 
group by Waldeyer (1). From his paper the following notes are taken : — 
ic The middle cells are found at the junction of the anterior and posterior 
cornua, but especially in the former. They are small and medium-sized 
polygonal cells, arranged sometimes in a fairly compact group, sometimes 
more loosely scattered over a wider area. They are never so closely 
aggregated as are the cells of Clarke’s column or those of the intermedio- 
lateral tract (Seitenhorn), but they are close enough to be regarded, 
especially in the upper cervical region, as a special nucleus of cells. Their 
situation varies somewhat in the different regions of the cord. As a group, 
they are most distinct in the upper cervical region. They lie here closely 
compacted to the outer side of, or a little in front of, Clarke’s column. In 
the lower cervical region they form a less distinct group near Clarke’s 
column, but quite internal to the postero-lateral motor group. In the 
upper dorsal region they are also abundant. They are situated laterally, 
and even somewhat posteriorly, to Clarke’s column, extending into the 
posterior horn and into the scattered cells (Zerstreutenzellen) of the anterior 
cornu without a distinct limit. They are always quite distinctly internal to 
the margin of the grey matter. With the growth of Clarke’s column in 
the dorsal cord the middle cells become fewer. In the lower dorsal region 
they again become more numerous, no longer form a distinct group, but are 
more in their former position on the outer or antero-external aspect of 
Clarke’s column, in great numbers. Similarly in the lumbar cord, though 
less abundantly developed. In the sacral cord there is a group of cells 
which, from their character and situation, are probably middle cells, but 
at this level no characteristic distribution of the various cell groups is 
recognisable.” 
Other small cells in the grey matter of the cord named by Waldeyer 
must also be referred to. His account of the intermedio-lateral tract is 
sufficiently noticed in Bruce’s paper on that tract (2). The cells which he 
