THE SPINAL CHORD. 
381 
forget that the subject was proposed at the moment, access to 
all books and notes was impossible, and the pupil could draw 
only from his own resources. 
THE SPINAL CHORD, BY MR. SIMPSON. 
s * 
The spinal chord is considered as a continuation of the medul¬ 
lary substance of the brain, lodged within the vertebral canal, 
and enveloped by three membranes continuous with the mem¬ 
branes of the brain. It is divided into six portions or columns, 
having',a small aperture in the centre, first noticed, 1 believe, 
by Mr. Sewell. These six columns give origin to nerves of 
different functions; the two lateral columns to the nerves of or¬ 
ganic life, the central superior to the nerves of sensation, and the 
central inferior columns to the nerves of motion. The sensitive and 
motor nerves arise from their respective columns by numerous 
filaments; and as they emerge from the sheath of the spinal chord 
they unite together, and are distributed over the body in insepara¬ 
ble and indistinguishable union with each other. But there are parts 
of the body where one or other of these systems of nerves predo¬ 
minates ; thus, the sensitive filaments are much more numerous, 
or, in fact, exist alone in the skin, which we know’ by the pain 
manifested on cutting through that portion of the animal frame : 
the motor filaments evidently abound in greater quantities in 
muscles, which evince not so much pain when wounded, although 
they possess the power of motion in an eminent degree ; and we 
infer that the motor fibres are diminished in numbers below' the 
knee and hock, because there cannot be any use for them there, 
as the power of motion resides in the muscles above those parts ; 
and we know r from many circumstances that Nature never gives 
any thing in vain. The spinal chord is continued to the sacrum, 
where it divides into many slender portions, called the cauda 
equina. Between the chord and its sheath there exists a small 
quantity of fluid, which, most probably, has some influence in 
shielding this important part from the effects of injury, more 
especially from concussion. 
% 
THE HORNS OF CATTLE, BY MR. HAMMOND. 
The horns of cattle consist of two distinct parts; an internal 
or osseous part having the cancellated structure of bones, and 
obeying the same laws in its production and growth. Its che¬ 
mical constitution is also similar. The external part may be 
considered as an appendage or continuation of the cuticle : it 
possesses the same properties, and has not any analogy to the os¬ 
seous part to which it serves as an envelope; it separates from it 
by maceration, as the cuticle from the cutis, and is only different 
in its state of condensation and thickness. The osseous part of 
