IN THE HUMAN FRAME. 
55 
ing likewise, if he pleases, his arm at the elbow at the 
same time,) in competition with the comparatively slow and 
laborious motion with which his arm can be made to turn 
round at the shoulder, by the aid of a ball and socket joint. 
III. The spine, or back bone, is a chain of joints of very 
wonderful construction. [PI. IX. fig. 1, 2.] Various, dif¬ 
ficult, and almost inconsistent offices were to be executed 
by the same instrument. It was to be firm, yet flexible, 
(now I know no chain made by art, which is both these; 
for by firmness I mean, not only strength, but stability:) 
firm, to support the erect position of the body; flexible, to 
allow of the bending of the trunk in all degrees of curva¬ 
ture. It was farther also (which is another, and quite a 
distinct purpose from the rest) to become a pipe or conduit 
for the safe conveyance from the brain, of the most important 
fluid* of the animal frame, that, namely, upon which all 
voluntary motion depends, the spinal marrow; a substance 
not only of the first necessity to action, if not to life, but 
of a nature so delicate and tender, so susceptible, and so 
impatient of injury, as that any unusual pressure upon it, 
or any considerable obstruction of its course, is followed 
by paralysis or death. Now the spine was not only to 
furnish the main trunk for the passage of the medullary 
substance from the brain, but to give out, in the course of 
its progress, small pipes therefrom, which, being afterwards 
indefinitely subdivided, might, under the name of nerves, 
distribute this exquisite supply to every part of the body. 
The same spine was also to serve another use not less want¬ 
ed than the preceding, viz. to afford a fulcrum, stay, or 
basis, (or, more properly speaking, a series of these) for 
the insertion of the muscles which are spread over the 
trunk of the body; in which trunk there are not, as in the 
limbs, cylindrical bones, to which they can be fastened: 
and, likewise, which is a similar use, to furnish a support 
for the ends of the ribs to rest upon. 
Bespeak of a workman a piece of mechanism which 
shall comprise all these purposes, and let him set about to 
contrive it; let him try his skill upon it; let him feel the 
* It seems proper to remark here, that the form of expression made 
use of in this case implies what is not strictly true. The spinal marrow, or 
more properly the spinal nerve, is not a fluid but a solid cord extending 
from the brain down through the canal of the spine, from which branches 
are distributed to all parts of the body. Dr. Paley in this instance prob¬ 
ably had in view the animal spirits, a subtile fluid, which was formerly 
believed to be seated in the brain, and carried through the nerves to the 
different parts.— Ed. 
