Monday, December 24, 2018

The Big Little World of Robert Hooke

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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