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Hooke, Robert, 1635-1703 / Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses : with observations and inquiries thereupon
(MDCLXVII [1667])

Observ. XL. Of the teeth of a snail,   pp. 180-181

Page 180

              M    I CROG RA P HI A.
  Diftances of Obje&s alfo, 'tis very likely they diftinguifh, partly
the consonant impreffions made in fome two convenient Pearls, one in
each clufter; for, according as thofe congruous impreffions affed, two
Pearls neerer approach'd to each other, the neerer is the ObjeCt, and
the farther they are diftant, the more diffant is the Obje&t: partly
by the alteration of each Pearl, requifite to make the Senfation or Pi6ture
perfci&; for 'tis impoffible that the Pidures of two Objedts, varioufly
diflant, can be perfealy painted, or made on the fame Ketina or bottom
of the eye not altered, as will be very evident to any one that {hall atten-
tively confider the nature of refraction. Now, whether this alteration
may be in the Figure of the Cornea,in the motion of accefs or recefs ofthe
Retina towards the Cornea, or in the alteration of a crufaline humour, if
fuch there be, I pretend not to determine; though I think we need not
doubt, but that there may be as much curiofity ot contrivance and ftru-
&ure in every one of thefe Pearls, as in the eye of a Whale or Elephant,
and'thelalmighty's Fiat could as eafily caufe the exiftence of the one as
the other; and as one day and a thoufand years are the fame with himnfo
may one eye and ten thoufand.
  This we may be fure of, that the filaments or fenfative parts of the
Retina muft be moft exceedingly curious and minute, fince the whole
Picure it felf is fuch; what muft needs the component parts be of that
Retina which diftinguifhes the part of an objeCt's Pidture that 'muft be
many millions of millions lefs then that in a man's eye? And how exceed-
ing curious and fubtile muft the component parts of the rnediut that
conveys light be, when we find the inftrument made for its reception or
refrafion to be fo exceedingly fmall ? we may,l think, from this fipecula-
tion be fufficiently discouraged from hoping to ditcover by any optick or
other inftrument the determinate bulk of the parts of the medium that
conveys the pulfe of light, fince we find that there is not lefs accurate-
nefs fhewn in the Figure, and polifh of thofe exceedingly minute lenti-
cular furfaces, then in thofe more large and conipicuous furfaces of our
own eyes. And yet can I not doubt, but that there is a determinate bulk
of thofe parts, fince I find them unable to enter between the parts of
Mercury, which being in motion, muft neceftarily have pores, as I fhiall
elsewhere (hew, and here pafs by, as being a digreftion.
  As concerning the horns F F, the feelers or fmellers, GG, the Pro-
I4fcis H H, and 1, the hairs and brifles, K K, I Ihall indeavour to de-
fcribe in the 42. obfervation.
              Obfcrv. X L. Of the 7eeth of a Snail.
T Have little more to add of the Teeth of a Snail, befides the Piture
  of it, which is represented in the firft Fig~ure of the 2 5. scheme, fave
that his bonded body, A B C D E F, which feem'd fafhioned very much
like a row of fmall teeth, orderly plac'd in the Gums, and looks as if it

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