58 MEMOIR OF SWAMMERDAM 



humours and greater part of the viscera, and then 

 filling the empty skin 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. 



