Members of the Royal Society discussed Leeuwenhoek's observations of hair
Birch, History, vol. IV, p. 103, 16 November 1681 (O.S.) in London:
There being some present, who had not heard Mr. LEEWENHOECK's letter read at the last meeting, it was desired, that the abstract of it might be again read; which was done, and thereupon some conjectures were made about the porosity and pith of several sorts of hair. The prefident remarked, that there was a sort of rabbits, who had a kind of long hair, which was branched towards the top. He mentioned also the cleaving of several sorts of hair, as that of men's heads, and of pigs bristles. He conceived likewise, that the horn of a rhinoceros was a kind of hair; as were also the fins of whales; both which were observed to be very apt to cleave.
Mr. HOOKE shewed the beard of a morse, which was very remarkable, having strong and crooked bristles much like horn, but harder and bigger than the teeth, of a large horn comb, or of a wheat-straw, and hollow at the roots in the flesh.