28 MEMOIR OF SWAMMERDAM. 



spective dates 1667, 1679, 1738, the two former in 

 8vo, the latter in 4to. 



All his scientific pursuits, however, were suddenly 

 interrupted in the course of this year by a severe 

 attack of quartan ague, by which he was so much 

 reduced, that he was obliged to refrain, for a time, 

 from all mental and bodily exertion. When able 

 to resume his labours, they were directed to a sub- 

 ject which had temporarily been superseded by other 

 interests, but to which he always reverted with the 

 ardour of a first affection, viz. the Anatomy of In- 

 sects. An impulse was given to his zeal by the in- 

 terest which men of rank and science now began to 

 manifest in his investigations; and many of them visit- 

 ed him to witness some of the arcana of nature re- 

 vealed by his singular dexterity and penetration. 

 Among the most eminent of his visitors, in regard to 

 rank, was the Grand Duke of Tuscany, who had 

 come to Holland, accompanied by Mr. Thevenot, partly 

 with the design of examining whatever was most 

 interesting in nature or art in that country. As this 

 prince was a lover of natural history, Swammerdam 

 was eager to gratify his curiosity, and made several 

 dissections of insects in his presence ; demonstrating, 

 among other things, that the forms of the perfect 

 Butterfly can be detected in the Caterpillar, and 

 actually extricating all its parts, and rendering them 

 distinctly recognisable, an operation of sufficient 

 delicacy to evince his consummate address, and the 

 perfection of his instruments. So much struck was 

 the Duke by his ingenuity, that he tried to prevail 



