humours and greater part of the viscera, and then filling the empty skin with wax or some other substance, so as to preserve its primitive form. The fat of insects he found to be perfectly soluble in spirits of turpentine—a discovery of the greatest importance to his enquiries, because when melted, and afterwards dried, this substance forms a coating over the viscera, completely obstructing the view of them; but the application of the spirit effectually removes it. He often spent whole days in cleansing the fatty matter from a single caterpillar, that he might obtain a clear view of its internal organization. His plan for stripping off the skin of caterpillars about to undergo their metamorphosis was ingenious. He allowed them to drop by their threads into scalding water, and suddenly withdrew them, in consequence of which the skin came off with great ease: he then immersed them in distilled vinegar and spirits of wine, mixed in equal proportions, which consolidated all the parts. He could thus remove the integuments without injury to the contents, and could shew the chrysalis enclosed within the caterpillar, and the butterfly within the chrysalis. He at last carried his skill to such perfection, that, according to Boerhaave, he could change the caterpillar to a chrysalis at his pleasure, and could as he pleased forward, stop, and regulate its motions.
