146 
PROSPECTIVE CONTRIVANCES. 
jaws, the palate, the pharynx, the larynx, are all perfect* 
the teeth alone are not so. This is the fact with respect 
to the human mouth: the fact also is, that the parts above 
enumerated are called into use from the beginning; whereas 
the teeth would be only so many obstacles and annoyances, 
if they were there. When a contrary order is necessary, 
a contrary order prevails. In the worm of the beetle, as 
hatched from the egg, the teeth are the first things which 
arrive at perfection. The insect begins to gnaw as soon 
as it escapes from the shell, though its other parts be only 
gradually advancing to their maturity. 
What has been observed of the teeth, is true of the horns 
of animals, and for the same reason. The horn of a calf 
or a lamb does not bud, or at least does not sprout to any 
considerable length, until the animal be capable of brows¬ 
ing upon its pasture; because such a substance upon the 
forehead of the young animal, would very much incommode 
the teat of the dam in the office of giving suck. 
But in the case of the teeth , of the human teeth at least, 
the prospective contrivance looks still farther. A succession 
of crops is provided, and provided from the beginning; a 
second tier being originally formed beneath the first, which 
do not come into use till several years afterwards. And 
this double or suppletory provision meets a difficulty in 
the mechanism of the mouth, which would have appeared 
almost insurmountable. The expansion of the jaw (the 
consequence of the proportionable growth of the animal, 
and of its skull,) necessarily separates the teeth of the first 
set, however compactly disposed, to a distance from one 
another, which would be very inconvenient. In due time, 
therefore, i. e. when the jaw has attained a great part of 
its dimensions, a new set of teeth springs up (loosening 
and pushing out the old ones before them,) more exactly 
fitted to the space which they are to occupy, and rising also 
in such close ranks, as to allow for any extension of 
line which the subsequent enlargement of the head may 
occasion. 
II. It is not very easy to conceive a more evidently 
prospective contrivance than that which, in all viviparous 
animals, is found in the milk *of the female parent. At the 
moment the young animal enters the world, there is its 
maintenance ready for it. The particulars to be remarked 
in this economy are neither few nor slight. We have, first, 
the nutritious quality of the fluid, unlike, in this respect, 
every other excretion of the body; and in which nature 
hitherto remains unimitated, neither cookery nor chemistry 
