56 MEMOIR OF SWAMMERDAM. 



separate a membrane equably, without the laceration 

 or disorder which a single edge, however sharp, is 

 apt to produce in delicate substances. These, as 

 well as his variously formed knives, lancets, styles, 

 c., were so small and fine, that he could not sharpen 

 them without the aid of a microscope. He employed 

 to very great advantage, and with a dexterity entirely 

 his own, slender glass tubes, sometimes no thicker 

 than a bristle, and of a similar shape, being wide at 

 the one end and tapering to a point at the other, to 

 blow up the smallest vessels discovered by the micro- 

 scope, or to inject them with some coloured fluid, by 

 which their course, convolutions, and implications 

 could be traced. 



The insects designed for dissection were killed by 

 immersion in water, spirits of wine, or of turpentine, 

 and allowed to remain in some one or other of these 

 substances for some time, which prevented putridity, 

 rendered the parts firmer and stronger, and the dis- 

 sections consequently easier. When he had laid 

 open with fine scissors the body of the insect, he 

 carefully noted the relative situation of the parts be- 

 fore proceeding farther ; he then extracted the viscera 

 in a very leisurely and cautious manner, separating 

 and washing away with very fine carnel's-hair pencils 

 the fat which surrounds them. After extraction he 

 frequently floated the delicate viscera in water, and, 

 by shaking them gently, separated the different parts 

 from each other, and thus obtained a better oppor- 

 tunity of examining them. In this way he was very 

 successful in getting a distinct view of the air-vessek 



