In England in 1664, the scientific world was
amazed to see Robert Hooke’s book Micrographia.
Hooke was one of the first people to make expert use of early microscopes. The
intricate drawings in this book remain some of the best art in the world today.
Hooke opened up our vision to a big little world too small for the unaided eye
to see.
Most biology textbooks contain the drawing that
he made of a thin slice of cork. Rather than being a solid material, it
consisted of lots of tiny cubicles, which reminded Hooke of the monastery cells
in which monks lived. This observation began the scientific search that
eventually led to the cell theory: that all organisms consist of cells.
But Hooke did not just look at organisms, nor
did he just look: he also asked questions about what he saw. One of his
drawings was of “gravel in urine,” or kidney stones. When you look at them microscopically,
you can see that the smaller ones are crystalline. This helped to explain where
they came from: from minerals dissolved in the urine which occasionally
crystallize. And because they are crystals formed in the urine, rather than
actual gravel, they can be dissolved back into the liquid and thus, perhaps,
eliminated. “How great an advantage it would be,” he wrote, “to such as are
troubled with the Stone, to find some [liquid] that might dissolve them without
hurting the bladder...” This possible solution to kidney stones would not have
occurred to someone who did not look at them closely, so someone who just
assumed they were gravel.
He also asked questions about the “cells” in
the cork. (He was well aware that no one had ever described them before:
“...indeed the first microscopical pores I ever saw, and that perhaps were ever
seen, for I had not met with any Writer or Person, that had made any mention of
them before this.”) He deduced that these cells, which contained air that could
not escape from them, were the reason that cork could float and why it was
springy. He even deduced that there were also “channels or pipes through which
the...natural juices of Vegetables are convey’d, and seem to correspond to the
veins, arteries and other Vessels of nutrition in sensible creatures...”
Hooke also rhapsodized about the amazing
quantity of tiny objects, such as the cells of cork, of which “a Cubick Inch”
could contain 1259712000, or “twelve hundred millions.” It was “a thing almost
incredible, did not our Microscope assure us of it...”
How could he be sure that his observation of
cork cells was not a mere anomaly of cork? He also looked at (but did not draw)
cells in “the pith of an Elder, or almost any other Tree, the inner pulp or
pith of the Cany hollow stalks of several other Vegetables: as of Fennel,
Carrets, Daucus, Bur-docks, Teasels, Fearn, some kinds of Reeds, &c.”
He also closely observed sensitive plants (a
branch and leaf of which appears right under his drawing of cells) to try to
figure out why and how the leaflets closed when touched.
His drawings of small arthropods revealed a new
world of awe to his readers. Although creatures such as the flea can be
very ugly, one must admire the intricacy of their adaptations, which allow them
to suck blood and to avoid being scratched away or swatted.
Hooke also wrote about the things he saw
through the telescope, and drew craters and mountains of the moon.
The beginning of science is thoughtful
observation. The microscope and telescope extended our observation to the very
small and the very large and allowed us to ask new questions that we could not
have imagined. Thank you, Galileo, and thank you, Robert Hooke.
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