58 
MEMOIR OF SWAMMERDAM 
humours and greater part of the viscera, and then 
filling the empty shin with wax or some other sub- 
stance, 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 mat- 
ter 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 un- 
dergo their metamorphosis was ingenious. He allow- 
ed 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 Boer- 
haave, he could change the caterpillar to a chry- 
salis at his pleasure, and could as he pleased for- 
ward, stop, and regulate its motions. 
