xvi The LIFE of JOHN SWAMMERDAM. 
in oil of turpentine, and that they could not be preferved. in balfam: 
and this difcovery he always made the greateft fecret of, becaufe the fat 
of infeé&s when melted, and then dried, looks like lime f{cattered over: the 
parts, fo as to obfcure the vifcera, and make it utterly impoffible to examine 
them; but then, however confufed and immerfed they might have been 
before, they fhew themfelves after this procefs very plainly and diftinaly, 
on- being long and thoroughly wafhed with fair water. Very often he fpent 
whole days in cleanfing of its fat in this manner, the body of a fingle 
Caterpillar, in order to difcover the true conftruction of that infect’s heart. 
His fingular fagacity in {tripping off the fkin of Caterpillars that were upon 
the point of {pinning their nefts, deferves particular notice. This he effected 
by letting them drop by their threads into fealding water, and fuddenly with- 
drawing them, for by this means the epidermis peeled off very eafily; and 
when this was done, he put them into diftilled vinegar and fpirit of wine 
mixed together in equal portions, which, by giving firmnedfs to the parts, 
gave an opportunity of feparating them with very little trouble from the 
exuvie or fkins, without any damage to the vifcera, fo that by this con- 
trivance the Nymph could be {hewn wrapped up in the Caterpillar, and 
the Butterfly in the Nymph. All thefe wonders he performed by the 
light of the brighteft mid-day fun, and had brought his arts to fuch per- 
fection, that he could exhibit whenever he thought proper, the manner in 
which infeéts were enclofed in infeéts, and were to be extricated from their 
enclofures. He could at laft change the Caterpillar to a Chryfalis at his 
pleafure, and alfo could as he pleafed forward, ftop, and regulate its motions. 
He affirmed nothing but what he faw, and was able to demonftrate every 
thing he affirmed. He in good earneft followed Lord Bacon’s advice; for 
' his opinions were the fruit of his experience, and he could effet the very 
things, whofe exiftence he maintained. Obfervations alone, made with the 
moft wonderful patience by experienced fenfes, affifted with the fitteft 
inftruments, led him into the method followed by nature in all her opera- 
tions; and he fo {crupuloufly adhered to that great guide, that whenever 
he formed a rule from particular obfervations, he did. it with fo much 
caution, as to let it include thofe particulars only, from which he had 
deduced it, and extracted his canon. In explaining the works of nature, he 
ufed to reafon by comparing his obfervations with one another, and never 
admitted the ufe of a general application of them upon any other cccafion. 
Thus he began, carried forward, and perfected without any afliftance, in a 
private and middling ftation of life, more difcoveries than all the writers of 
all the preceding ages. By thefe means he found there were little creatures 
that breathe at the tail, and others that govern themfelves in the water by 
the help of a little bubble of air, which they expand at pleafure to afcend 
‘ to the 'furface, and comprefs in like manner, when defirous to fink to the 
bottom; and can regulate it in fuch a certain manner, that they can fufpend 
themfelves in any part of the water they choofe. Some again he difcovered, 
who have their legs fixed to their jaws ; and others in which the penis of the 
male receives in copulation the vulva of the female, and a few which are 
of both fexes at once, and aé reciprocally upon each other as fuch at one 
and the fame time. In fine, from fuch an infinite number of new and un- 
common obfervations, he formed a fyftem fuperior by many degrees to any 
thing of the kind that had as yet appeared. He even colleted the materials 
upon which this fyftem was founded, rendered them durable, and digefted 
them, in order to have always at hand undeniable vouchers for the truth of 
every 
