348 MR. J. LOCKHART CLARKE ON CERTAIN FUNCTIONS OF THE SPINAL 
to sensation and voluntary motion, is the opinion maintained by many eminent 
physiologists and excellent observers. 
In support of this doctrine, Mr. Grainger*, Mr. Solly -I”, and Dr. J. Budge have 
adduced the fact of having traced these fibres in the spinal chord of the vertebrata. 
A similar fact is said to have been established by Mr. Newport^ and Dr. Carpenter 
in the invertebrata. On the other hand, the opinion that all the fibres of the spinal 
nerves enter the grey substance and belong exclusively to the spinal chord, is held 
by Todd and Bowman jj. Stilling^, Volkmann** and others. 
In making the preparations for the investigation of this subject, I employed the 
second method described in my former communication on the Spinal Chord i-f. The 
animals selected for this purpose were the Ox, Calf, Cat, Rat, Mouse, and Frog. 
After many fruitless attempts I succeeded in rendering perfectly transparent the 
entire chords of the Mouse and Frog, but found that their cylindrical form interfered 
considerably with a distinct view of their several parts, and rendered the examination 
unsatisfactory. Having succeeded, however, in a similar way, with longitudinal 
sections of the spinal chord of the Cat, of at least ^i-th of an inch in thickness and 
2 inches in length, with the anterior and posterior roots attached, I was delighted, 
on examining these sections, with a view of its internal structure which far sur- 
passed any I had hitherto been able to obtain. 
On a former occasion, I showed unequivocally, that to the posterior white columns 
the posterior roots, and to the anterior white columns the anterior roots, of the spinal 
nerves are exclusively attached ; while the lateral columns to which both these roots 
were formerly supposed to be connected, are in immediate connection only with 
the spinal-accessory nerve^j. 
Of the Posterior Roots XXIII. exactly represents a longitudinal section 
through the cervical enlargement of the spinal chord of the Cat, from the eighth to the 
twelfth pair of nerves. In this section the bundles which form the posterior roots 
P, P, P, P, are observed to consist of three kinds, which differ from each other partly 
in direction, and partly in the size of their component filaments. 
The first kind, a, a, a, a, enter the chord transversely, and pursue a very remarkable 
course. I have not seen them distinctly below the cervical enlargement. Each 
bundle, after traversing the longitudinal fibres of the posterior columns P, C, in a 
compact form, and at right angles, continues in the same direction to a considerable 
but variable depth within the grey substance G, dilating and again contracting, so 
as to assume a fusiform appearance. It then bends round upon itself, at a right or 
more obtuse angle, and running for a considerable distance in a longitudinal direction 
* Spinal Chord. t Human Brain. I Muller’s Archiv, 1844. § Philosophical Transactions, 1 843 . 
11 Physiological Anatomy, vol. i. 1845. ^ Untersuchungen liber die Textur des Riickenmarks, 1842. 
Nervenphysiologie, in Wagner. ft Philosophical Transactions, 1851, p. 608, Part II. 
II Many of my preparations are in the possession of the Microscopical Society of London, and the Royal 
College of Surgeons. 
