THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 347 
cut across in transverse sections, especially well marked near the junction of cervix 
and caput cornu. These longitudinal bundles are often of quite considerable size 
(Fig. 8, h, h). Clarke states that he has “not seen them distinctly below the cervical 
enlargement”; they are certainly more strongly marked, in the cat at least, in the cer- 
vical region, where they may be seen with very great distinctness, but I have had no 
difficulty in making them out very clearly in all my preparations from the lumbar 
enlargement of the calf. Clarke has described these bundles as * running down the 
cord," and this is usually the case, though occasional variations will be met with, 
bundles sometimes running upwards (Fig. 8); the great majority of fibres, however, 
undoubtedly run downwards. 
These bundles of longitudinal fibres, which I propose to call longitudinal columns of 
the cornua, send out fibres anteriorly in all directions, many of them becoming con- 
nected with large cells which are found grouped along the whole length of these 
columns, belonging to Clarke's columne vesiculares posteriores. Fig. 6 represents 
the relation in which the cells stand to the longitudinal columns (a, a, a); they are 
also seen on a smaller scale in Fig. 8. The fibres composing these columns do not 
seem to follow a longitudinal course for any considerable distance, but usually soon 
pass onwards towards the anterior cornu. Many of the fibres pass obliquely to the 
commissures, both anterior and posterior; some pass out into the lateral white columns, 
while others pass forwards, becoming connected with cells, or else directly into the 
anterior roots, with which they are often continuous. Others assume every variety of- 
upward or downward curve before reaching their final destination, a longitudinal sec- 
tion through the anterior cornu often presenting an inextricable web consisting mostly 
of cut-off fibres (Fig. 8). 
A part of the transverse bundles which traverse the substantia gelatinosa do not 
seem to be connected at all with the longitudinal columns of the cornua, their fibres 
being plainly seen to cross these at right angles; they are mostly continued anteriorly 
for a very considerable distance, often becoming lost to view (or cut off), but may 
sometimes be seen to be directly continuous with the anterior roots. 
It will be noticed in my description of the course taken by the fibres derived from 
the posterior roots, that I have given but little attention to that part of their course 
which is mainly traceable in transverse sections; this there was no need of doing, 
since Clarke has described it with so much accuracy in his latest paper (1859). I have 
myself verified most of the results at which he has arrived, and can add nothing. 
Clarke states in his description of the longitudinal columns of the cornua, that a 
part of their fibres “form loops with each other within the gray substance, particu- 
