28 
MEMOIR OF SWAMMERDAM. 
spective dates 1667, 1679, 1738, the two former in 
8 vo, 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ject which had temporarily been superseded by other 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 w r hieh he always reverted with the 
ardour of a first affection, viz. the Anatomy of In- 
sects. An impulse w f as 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, w r ho 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 tbc 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 
