74 
OF THE MUSCLES. 
Movable joints, I think, compose the curiosity of bones, 
but their union, even where no motion is intended or want¬ 
ed, carries marks of mechanism and of mechanical wis¬ 
dom. The teeth, especially the front teeth, are one 
bone fixed in another, like a peg driven into a board. The 
sutures of the skull are like the edges of two saws clap¬ 
ped together, in such a manner as that the teeth of one 
enter the intervals of the other.* We have sometimes one 
bone lapping over another, and planed down at the edges; 
sometimes also the thin lamella of one bone received into 
a narrow furrow of another. In all which varieties, we 
seem to discover the same design, viz. firmness of juncture, 
without clumsiness in the seam. 
CHAPTER IX. 
OF THE MUSCLES. 
Muscles, with their tendons, are the instruments by 
which animal motion is performed. It will be our business 
rendered useless, had there not been a provision against this mechanical 
effect. This provision is a disposition to grow, or rather to shoot out of 
their sockets; and this disposition to project, balances the pressure which 
they sustain; and when one tooth is lost, its opposite rises, and is in dan¬ 
ger of being lost also, for want of that very opposition.— Hell’s Treatise 
on Animal Mechanics. 
* Most of the bones of the skull are composed of two plates or tablets, 
with an intermediate spongy, vascular substance; the outer tablet is fib¬ 
rous, having the edges curiously indented and united by a dove-tailed 
suture; the inner from its brittleness is called vitreous, and therefore 
merely joined together in a straight line ; this mode of union is not acci¬ 
dental—not the result of chance, but design. The author of the treatise 
on “Animal Mechanics” gives the following admirable illustration of the 
structure:— 
“ Suppose a carpenter employed upon his own material—he would 
join a box with regular indentations by dove-tailing, because he knows 
that the material on which he works, from its softness and toughness, 
admits of such adjustment of its edges. The processes of bone shoot in¬ 
to the opposite cavities with, an exact resemblance to the fox-tail wedge 
of the carpenter. 
“ Bpt if a workman in glass or marble were to join these materials, he 
would smooth the edges and unite them by cement; for if he could suc¬ 
ceed in indenting the line of union, he knows that his material would 
chip off on the slightest vibration. 
“ Now apply this principle to the skull; the outer table, which resem¬ 
bles wood, is indented and dove-tailed; the inner glassy table has it# 
edges simply laid in contact.”— Paxton. 
