322 SCIENTIFIC APPARATUS. 



Vesalius based his great work on investigations conducted with 

 no better appliances ; and it was not until the seventeenth century 

 that the powers of vision on the one hand, and the means of dis- 

 criminating structures on the other, were artificially enlarged by 

 the help of optical and chemical discoveries. 



It is true that the very interesting collection of ancient and 

 modern microscopes in the Collection contains a compound 

 microscope, invented and constructed about the year 1590 

 (No. 3,513), but it is little more than a toy. The seventeenth 

 century hands down to us the microscopes of Leuwenhoek (3,512), 

 venerable relics of the epoch at which the foundations of minute 

 anatomy were laid; while that of Lyonet (3,525) reminds us that 

 the eighteenth century saw the production of one of the most 

 perfect 'pieces of minute dissection yet extant the "Traite 

 anatomique de la Chenille qui ronge le Bois de Saule." 



In the hands of Malpighi, Leuwenhoek, Grew, Swammerdam, 

 Lyonet, Hewson, and others, the simple microscope, either as a 

 single lens, or in the doublet or triplet form, did wonders ; while 

 Ruysch's exquisite methods of injection showed how the difficulty, 

 not to say impossibility, of tracing out the more minute vessels 

 and ducts of organized structures by mere dissection could be 

 overcome. 



Dissection, aided by maceration; microscopic investigation, 

 carried as far as the simple microscope would go, and doubtfully 

 assisted by the imperfect earlier forms of compound micro- 

 scope; and injection, by the syringe or by the mere weight of 

 mercury, remained the sole methods of anatomical research up 

 to within the last fifty years. 



The improvement of the compound microscope in the early 

 part of this century (see No. 3,526), by the invention of adequate 

 methods of correcting spherical and chromatic aberration, and 

 of illuminating objects, has enabled anatomists to extend their 

 investigations into minute structure to an unhoped-for degree, and 

 to use magnifying powers of 2,000 to 3,000 diameters with as 



