Definition of "spicula"

He concludes this Diſſertation, by endeavouring to explain the Manner of its [olive oil's] operating, which he attributes to its fat inviſcating Nature, whereby it ſheathes the Spicula of the Poiſon.

1738 December, C. Mortimer, “VI. An Abstract by C. Mortimer, M.D. Secr[etary of the] R[oyal] S[ociety] of an Inaugural Dissertation Published at Wittemberg 1736. by Dr. Abraham Vater, F.R.S. Concerning the Cure of the Bite of a Viper, Cured by Sallad-oil.”, in Philosophical Transactions. Giving Some Account of the Present Undertakings, Studies, and Labours, of the Ingenious, in Many Considerable Parts of the World, volume XXXIX, number 451, London: Printed for T. Woodward, […] ; and C. Davis […] ; printers to the Royal Society, page 443

And yet Thoreau camps down by Walden Pond and shows us that absolutely nothing in Nature has ever yet been described,--not a bird nor a berry of the woods, nor a drop of water, nor a spicula of ice, nor summer, nor winter, nor sun, nor star.

1861, Various, Atlantic Monthly, Volume 8, No. 47, September, 1861‎

Introducing the alum-cell, and placing the coating of hoar-frost at the intensely luminous focus of the electric lamp, not a spicula of the dazzling frost is melted.

1906, John Tyndall, Six Lectures on Light‎

Nature 'publishes itself in creatures, reaching from particles and spicula, through transformation on transformation to the highest symmetries.

1904, John Morley, Critical Miscellanies, Vol. 1, Essay 5, Emerson‎