Sometimes he put into water the delicate viscera of the insects he had suffocated; and then shaking them gently he procured himself an opportunity of examining them, especially the air vessels, which by these means he could separate from all the other parts whole and intire, to the great admiration of all those who beheld them; as these vessels are not to be distinctly seen in any other manner, or indeed seen at all without damaging them, he often made use of water, injected by a syringe, to cleanse thoroughly the internal parts, then blew them up with air and dried them, and thus rendered them durable, and fit for examination at a proper opportunity. Sometimes he has examined with the greatest success, and made the most important discoveries in insects that he had preserved in balsam, and kept for years together in that condition. Again, he has frequently made punctures in other insects with a very fine needle, and after squeezing out all their moisture through the holes made in this manner, he filled them with air, by means of very slender glass tubes, then dried them in the shade, and last of all anointed them with oil of spike, in which a little rosin had been dissolved; by which process they retained their proper forms a long time. He had a singular secret, whereby he could so preserve the nerves of insects, that they used to continue as limber and perspicuous as ever they had been.
He used to make a small puncture or incision in the tail of worms, and after having gently and with great patience squeezed out all their humours, and great part of their viscera, he then injected them with wax, so as to give and continue to them all the appearance of healthy vigorous living creatures. He discovered that the fat of all insects was perfectly dissoluble in oil of turpentine; thus he was enabled to shew the viscera plainly; only after this dissolution he used to cleanse and wash them well and often in clean water. He frequently spent whole days in thus cleansing a single caterpillar of its fat, in order to discover the true construction of this insect’s heart. His singular sagacity in stripping off the skin of caterpillars that were upon the point of spinning their cones, deserves particular notice. This he effected by letting them drop by their threads into scalding water, and suddenly withdrawing them; for, by these means the epidermis peeled off very easily; and when this was done, he put them into distilled vinegar and spirit of wine, mixed together in equal portions, which, by giving a proper firmness to the parts, gave him an opportunity of separating them with very little trouble from the exuviæ, or skins, without any danger to the parts; so that by this contrivance, the nymph could be shewn to be wrapped up in the caterpillar and the butterfly in the nymph. Those who look into the works of Swammerdam, will be abundantly gratified, whether they consider his astonishing labour and unremitted ardour in these pursuits, or his wonderful devotion and piety. On one hand, his genius urged him to examine the miracles of the great Creator in his natural, productions; whilst, on the other, the love of that same all-perfect Being rooted in his mind struggled hard to persuade him that God alone, and not the creatures, were worthy of his researches, love, and attention.