Of the Feet of Flies , &c. 41 
to creep over the hand, he makes his dep as fenfible 
to the touch alfo. 
But as this contrivance often fails the chaffer, fo would 
it the fly, had not nature furnilhed his feet with ano¬ 
ther curious contrivance, which is the palms or foies 
jD D. They are two fmall, thin, flat, and horny fub-’ 
fiances, that arife from the under part of the lad joint 
of the foot, and are feemingly flexible; fo that their 
two fides do not always lie in the fame plane, but 
may be fhut clofer, and as it were grafp a body of 
themfelves : befides, the under fides of thefe foies are 
all befet with fmall briftles, like the wire teeth of a 
card, whofe points tend forward. Hence the talons 
drawing the feet forward as before, and thefe foies being 
applied to the furface of the body, with all its points look¬ 
ing the contrary way, if there be any irregularity, or yield¬ 
ing therein ; the fly fufpends itfelf very firmly and eafily. 
That the fly is enabled to walk on glafs, proceeds partly 
from a ruggednefs of the furface, or a kind of tarnifh or 
dirty fmoaky fubflance, adhering to the furface of that 
very hard body; and though the pointed parts cannot 
penetrate, yet they may find pores enough in the tarnifh, 
or at lead make them. This drudture Mr. Hook fur- 
veyed with great diligence, becaufe he could not com¬ 
prehend, that if there was any fuch glutinous matter 
in thofe fuppofed fponges (as mod that have obferved 
that object in a microfcope, have believed) how the fly 
could fo readily unglew and loofen its feet; and alfo be¬ 
caufe he had found no other creature any ways like it. 
A contrivance nearly alike to this is to be found in 
all kind of flies, and cafe-winged infedls, and in the 
flea, in mites, &c. fome of which have only one fharp 
talon at the end of each leg, which drawing towards 
the center or middle of their bodies, enable thefe exceed¬ 
ing 
