OBJECTS FOR THE MICROSCOPE. 33 I 



the instances which occur of such imitations ; and I sluiU only remark- 

 that, generally speaking, these arms and instruments in structure and 

 finishing far exceed those which thev resemhle." 



INIETHOD OF DISSECTING INSECTS. 



Swammerdam excelled in the preparation of insects. Neither difli- 

 culty nor disappointment could make him abandon the pursuit of any 

 object until he had obtained a satisfactory idea of it. But, unhappily, 

 few of the methods he used in preparing his objects for the micro- 

 scope are now known. Boerhaavc examined with the strictest atten- 

 tion all the letters and manuscripts of Swammerdam which he could 

 find; but his researches were far from being successful. The follow- 

 ing are all the particulars which have come to the knowledge of the 

 public. 



For dissecting small insects Swammerdam had a brass table, to 

 which were affixed two brass arms moveable at pleasure to any part of 

 it. The upper part of these vertical arms was constructed in such a 

 manner as to have a slow vertical motion ; by which means the ope- 

 rator could readily alter the height as he saw convenient. One of 

 these arms was to hold the minute objects, and the other to apjily the 

 microscope. 



The lenses of Swammerdam's microfjcopes were of various sizes as 

 well as foci; but all of tliem the best that could be procured both for 

 the transparency of the glass and the fineness of the workmanship. 

 His observations were always begun with the smallest magnifiers, from 

 which he proceeded to the greatest; but in the use of them he was so 

 exceedingly dexterous, that he made every observation subservient to 

 that ^7hich succeeded it, and all of them to the confirmation of each 

 other and to the completing of the description. His chief art seems 

 to have been in constructing scissars of an exquisite fineness, and 

 making them very sharp. Thus he was enabled to cut very minute 

 objects to much more advantage than could be done by knives and 

 lancets; for these, though ever so sharp and fine, are apt to disorder 

 delicate substances by displacing some of the filaments and drawing 

 them after them as they pass through the bodies ; but the scissars cut 

 them all equally. The knives, lancets, and styles he made use of in his 

 dissections, were so fine that he could not see to sharpen them without 

 the assistance of a magnifying glass ; but with these he could dissect 

 the intestines of bees with the same accuracy that the best anatomists 

 can do those of large animals. He made use also of very small glass 

 tubes, no thicker than a bristle, and drawn to a very fine point at one 

 tnd but thicker at the other. These were for the purpose of blowing 



