MALPIGHI, SWAMMERDAM, LEEUWENHOEK. 579 



"That he was in comfortable if not affluent circumstances is clear 

 from the character of his writings; that he was not troubled by any 

 very anxious and responsible duties is certain from the continuity of 

 his scientific work; that he could secure the services of persons of 

 influence is discernible from the circumstances that, in 1673, De Graaf 

 sent his first paper to the Royal Society of London; that in 1680 the 

 same society admitted him as fellow; that the directors of the East 

 India Company sent him specimens of natural history, and that, in 

 1698, Peter the Great paid him a call to inspect his microscopes and 

 their revelations." 



Leeuwenhoek seems to -have been fascinated bv the marvels of the 

 microscopic world, but the extent and quality of his work lifted him 

 above the level of the dilettante. He was not, like Malpighi and 

 Swammerdam, a skilled dissector, but turned his microscope in all 

 directions; in the mineral, as well as the vegetable and animal king- 

 doms. Just when he began to use the microscope is not known; his 

 first publication in reference to microscopic objects did not appear 

 till 1673, when he was forty-one years old. He gave good descriptions 

 and drawings of his instruments, and those still in existence have been 

 described by Carpenter and others, and, therefore, we have a very 

 good idea of his working equipment. During his lifetime he sent as 

 a present to the Eoyal Society of London twenty-six microscopes, each 

 provided with an object to examine. Unfortunately, these were re- 

 moved from the rooms of the society and lost during the eighteenth 

 century. His lenses were of fine quality and were ground by him- 

 self. ' They were nearly all simple lenses of small size, but considerable 

 curvature, and needed to be brought close to the object examined. 

 He had different microscopes for different purposes, giving a range 

 of magnifying powers from 40 to 270 diameters and possibly higher. 

 The number of his lenses is surprising; he possessed not less than 2-47 

 complete microscopes, two of which were provided with double lenses 

 and one with a triplet. In addition to the above he had 172 lenses 

 set between plates of metal, which gives a total of 419 lenses used by 

 him in his observations. Three were of quartz, or rock crystal, the 

 rest were of glass. More than one-half the lenses were mounted in 

 silver, three were in gold. 



It is to be understood that all his microscopes were of simple con- 

 struction; no tubes, no mirror; simply pieces of metal to hold the 

 magnifying-glass and the objects to be examined, with screws to adjust 

 the position and the focus. We shall perhaps get the best idea of how 

 they Avere used and brought*into focus by reference to Fig. 7, which 

 is copied from Richardson's article in 'The Asclepiad." This shows the 

 way the instrument was arranged to examine the circulation of blood 

 in the transparent tail of a small fish. The fish was placed in water 

 in a slender glass tube, and tlie latter was held in a metallic frame, to 



