:mr. j, l. claeke on the oeey substance oe the spinal coed. 461 
which it is as exact a copy as possible. But even the loss of the white substance would 
be of no consequence for tracing the course of the nerve-fibres, the axis-cylinders of 
which in these preparations are rendered unusually strong and distinct. And if I wish 
to investigate the natural structure of the nerve-fibres and cells, I select a perfectly fresh 
and unaltered specimen from an animal just killed (as I stated in my first communica- 
tion to the Eoyal Society, 1851) ; for I never think of trusting to any kind of prepara- 
tion, or even to chromic acid, which Stilling uses, and which coagulates the contents of 
the nerve-fibres and alters their appearance after a short maceration. Not that I reject 
other methods ; for 1 find sections of the medulla, simply hardened in chromic acid, of 
great service, and use them largely, particularly for drawing figures under low powers, 
and sometimes for examination under higher powers, when I have been in some doubt 
as to the natm-e of the tissue. In fact, I employ whatever means appears most suitable 
for the occasion and most likely to lead me to the truth. But I still contend, that 
for clearness, sharpness of outline and fine definition under the higher powers, — for the 
advantage of obtaining thick sections of great transgmrency, and for the durability and 
unchangeableness of the preparations when properly made, I know of no method that 
will bear any comparison with this. To confirm this opinion in one respect, I may 
mention the fact, that although Stilling, in his recent work, has described and repre- 
sented the spiral structiu-e of the fibres of the white columns of the Calf under a power 
of 1100 diameters, he has failed to detect the nucleated cells and nuclei which are so 
beautifully seen by means of my method under a power of 350 diameters. 
Explanation of the Plates. 
Fig. 1, Plate XIX. rejiresents a transverse section of the caput cornu posterioris part 
of the cervix cornu, with a portion of the surrounding posterior and lateral 
white columns : from the middle of the cervical enlargement of the Ox ; 
di'awn from a preparation magnified 50 diameters : — A, A, A, part of the poste- 
rior white column ; B, B, part of the lateral column ; the small circles and 
dark spots represent the cut ends of longitudinal and oblique fibres. These 
columns are traversed by a beautiful network of blood-vessels and nerve-fibres 
radiating from all parts of the grey substance. At h, b (the peak of the 
cornu) may be seen extending outwards the processes of nerve-cells situated 
in the network between bundles of the white column. The darker portion 
of the caput cornu consists principally of numerous longitudinal and oblique 
bundles of fibres, with blood-vessels, and of the posterior roots of the nerves, 
with cells chiefly of the small and intermediate size ; the lighter space behind 
and at the sides is the gelatinous substance^ studded with small cells, and 
having a stratum of large cells and marginal nerve-fibres along its posterior 
border next the posterior column, into which some of the processes of the 
cells may be seen to extend. C, C, part of the cervix cornu, containing some 
MDCCCLIX. q t. 
