IN THE HUMAN FRAME. 
53 
cial, or more evidently artificial, than that which is seen 
in the vertebrae of the human neck. [PI. VII. fig. 1.] Two 
things were to be done. The head was to have the power 
of bending forward and backward, as in the act of nodding, 
stooping, looking upward or downward; and, at the same 
time, of turning itself round upon the body to a certain 
extent, the quadrant we will say, or rather, perhaps, a hun¬ 
dred and twenty degrees of a circle. For these two pur¬ 
poses, two distinct contrivances are employed: [PI. VII. 
fig. 2, 3, 4.] First, the head rests immediately upon the 
uppermost of the vertebrae, and is united to it by a hinge- 
pint; upon which joint the head plays freely forward and 
backward, as far either way as is necessary, or as the liga¬ 
ments allow; which was the first thing required.—But 
then the rotatory motion is unprovided for. Therefore, 
secondly, to make the head capable of this, a farther me¬ 
chanism is introduced; not between the head and the up¬ 
permost bone of the neck, where the hinge is, but between 
that bone, and the bone next underneath it. It is a me¬ 
chanism resembling a tenon and mortice. This second, 
or uppermost bone but one, has what anatomists call a pro¬ 
cess, viz. a projection, somewhat similar, in size and shape, 
to a tooth; which tooth, entering a corresponding hole or 
socket in the bone above it, forms a pivot or axle, upon 
which that upper bone, together with the head which it 
supports, turns freely in a circle; and as far in the circle 
as the attached muscles permit the head to turn. Thus 
are both motions perfect, without interfering with each 
other. When we nod the head, we use the hinge-joint, 
which lies between the head and the first bone of the neck. 
When we turn the head round, we use the tenon and mor¬ 
tice, which runs between the first bone of the neck and the 
second. We see the same contrivance, and the same prin¬ 
ciple, employed in the frame or mounting of a telescope. 
It is occasionally requisite, that the object-end of the in¬ 
strument be moved up and down, as well as horizontally, 
or equatorially. For the vertical motion, there is a hinge, 
upon which the telescope plays; for the horizontal or 
equatorial motion, an axis upon which the telescope and 
the hinge turn round together. And this is exactly the 
mechanism which is applied to the motion of the head: 
nor will any one here doubt of the existence of counsel and 
design, except it be by that debility of mind, which can 
trust to its own reasonings in nothing. 
We may add, that it was, on another account also, ex¬ 
pedient, that the motion of the head backward and for- 
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