The foot of a Fly (delineated in the first _Figure_ of the 23. _Scheme_,
which represents three joints, the two Tallons, and the two Pattens in a
flat posture; and in the second _Figure_ of the same _Scheme_, which
represents onely one joint, the Tallons and Pattens in another posture) is
of a most admirable and curious contrivance, for by this the Flies are
inabled to walk against the sides of Glass, perpendicularly upwards, and to
contain themselves in that posture as long as they please; nay, to walk and
suspend themselves against the under surface of many bodies, as the ceiling
of a room, or the like, and this with as great a seeming facility and
firmness, as if they were a kind of _Antipodes_, and had a _tendency_
upwards, as we are sure they have the contrary, which they also evidently
discover, in that they cannot make themselves so light, as to stick or
suspend themselves on the under surface of a Glass well polish’d and
cleans’d; their suspension therefore is wholly to be ascrib’d to some
Mechanical contrivance in their feet; which, what it is, we shall in brief
explain, by shewing, that its Mechanism consists principally in two parts,
that is, first its two Claws, or Tallons, and secondly, two Palms, Pattens,
or Soles.
The two Tallons are very large, in proportion to the foot, and handsomely
shap’d in the manner describ’d in the _Figures_, by AB, and AC, the bigger
part of them from A to _dd_, is all hairy, or brisled, but toward the top,
at C and B smooth, the tops or points, which seem very sharp turning
downwards and inwards, are each of them mov’d on a joint at A, by which the
Fly is able to open or shut them at pleasure, so that the points B and C
being entered in any pores, and the Fly endeavouring to shut them, the
Claws not onely draw one against another, and so fasten each other, but
they draw the whole foot, GGADD forward, so that on a soft footing, the
tenters or points GGGG, (whereof a Fly has about ten in each foot, to wit,
two in every joint) run into the pores, if they find any, or at least make
their way; and this is sensible to the naked eye, in the feet of a
_Chafer_, which, if he be suffer’d to creep over the hand, or any other
part of the skin of ones body, does make his steps as sensible to the touch
as the sight.
But this contrivance, as it often fails the _Chafer_, when he walks on hard
and close bodies, so would it also our Fly, though he be a much lesser, and
nimbler creature, and therefore Nature has furnish’d his foot with another
_additament_ much more curious and admirable, and that is, with a couple of
Palms, Pattens or Soles DD, the structure of which is this:
From the bottom or under part of the last joint of his foot, K, arise two
small thin plated horny substances, each consisting of two flat pieces, DD,
which seem to be flexible, like the covers of a Book, about FF, by which
means, the plains of the two sides EE, do not always lie in the same plain,
but may be sometimes shut closer, and so each of them may take a little
hold themselves on a body; but that is not all, for the under sides of
these Soles are all beset with small brisles, or tenters, like the Wire
teeth of a Card used for working Wool, the points of all which tend
forwards, hence the two Tallons drawing the feet forwards, as I before
hinted, and these being applied to the surface of the body with all the
points looking the contrary way, that is, forwards and outwards, if there
be any irregularity or yielding in the surface of the body, the Fly
suspends it self very firmly and easily, without the access or need of any
such Sponges fill’d with an imaginary _gluten_, as many have, for want of
good Glasses, perhaps, or a troublesome and diligent examination, suppos’d.
Now, that the Fly is able to walk on Glass, proceeds partly from some
ruggedness of the surface: and chiefly from a kind of tarnish, or dirty
smoaky substance, which adheres to the surface of that very hard body; and
though the pointed parts cannot penetrate the substance of Glass, yet may
they find pores enough in the tarnish, or at least make them.
This Structure I somewhat the more diligently survey’d, because I could not
well comprehend, how, if there were such a glutinous matter in those
supposed Sponges, as most (that have observ’d that Object in a
_Microscope_) have hitherto believ’d, how, I say, the Fly could so readily
unglew and loosen its feet: and, because I have not found any other
creature to have a contrivance any ways like it, and chiefly, that we might
not be cast upon unintelligible explications of the _Phænomena_ of Nature,
at least others then the true ones, where our senses were able to furnish
us with an intelligible, rationall and true one.
Somewhat a like contrivance to this of Flies shall we find in most other
Animals, such as all kinds of Flies and case-wing’d creatures; nay, in a
Flea, an Animal abundantly smaller then this Fly. Other creatures, as
Mites, the Land-Crab, &c. have onely one small very sharp Tallon at the end
of each of their legs, which all drawing towards the center or middle of
their body, inable these exceeding light bodies to suspend and fasten
themselves to almost any surface.
Which how they are able to do, will not seem strange, if we consider,
first, how little body there is in one of these creatures compar’d to their
superficies, or outside, their thickness, perhaps, oftentimes, not
amounting to the hundredth part of an Inch: Next, the strength and agility
of these creatures compar’d to their bulk, being, proportionable to their
bulk, perhaps, an hundred times stronger then an Horse or Man. And thirdly,
if we consider that Nature does always appropriate the instruments, so as
they are the most fit and convenient to perform their offices, and the most
simple and plain that possibly can be; this we may see further verify’d
also in the foot of a Louse which is very much differing from those I have
been describing, but more convenient and necessary for the place of its
habitation, each of his leggs being footed with a couple of small claws
which he can open or shut at pleasure, shap’d almost like the claws of a
Lobster or Crab, but with appropriated contrivances for his peculiar use,
which being to move its body to and fro upon the hairs of the creature it
inhabits, Nature has furnish’d one of its claws with joints, almost like
the joints of a man’s fingers, so as thereby it is able to encompass or
grasp a hair as firmly as a man can a stick or rope.
Nor, is there a less admirable and wonderfull _Mechanism_ in the foot of a
Spider, whereby he is able to spin, weave, and climb, or run on his curious
transparent clew, of which I shall say more in the description of that
Animal.
And to conclude, we shall in all things find, that Nature does not onely
work Mechanically, but by such excellent and most compendious, as well as
stupendious contrivances, that it were impossible for all the reason in the
world to find out any contrivance to do the same thing that should have
more convenient properties. And can any be so sottish, as to think all
those things the productions of chance? Certainly, either their
Ratiocination must be extremely depraved, or they did never attentively
consider and contemplate the Works of the Al-mighty.
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