258 Examination of the Matured Framework [BOOK n. 



in the instrument and the appearance of the advantages which 

 phytotomy derived from it; thus in 1824, Selligue exhibited 

 to the Academy of Paris an excellent microscope with double 

 lenses, several of which could be screwed on one over the 

 other, and which could be used with ordinary daylight and a 

 magnifying power of five hundred times ; in 1827 Amici made 

 the first achromatic and aplanatic objectives with three double 

 lenses screwed on one over the other, the flat sides being 

 turned to the object. And yet still in 1836 a practised phyto- 

 tomist like Meyen spoke with disapproval of the instruments of 

 his time, and gave the preference to an old English microscope 

 by James Man, though he allowed that the newest instruments 

 by Ploessl were a little better. In his work on phytotomy, 

 which appeared in 1830, all the figures were magnified two 

 hundred and twenty times, as were the very beautiful figures in 

 his prize essay of 1836 ; but in his ' Neues System' (1837), he 

 had already adopted powers that magnified to over five hundred 

 times. How rapid the progress was in the years before and 

 after 1830 is shown by comparing von Mohl's work on climbing 

 plants of 1827 and its antiquated illustrations, with his publi- 

 cations of 1831 and 1833, where the figures have a thoroughly 

 modern appearance. 



The art also of preparing anatomical objects rose by degrees 

 with the improvement of the microscope. It was not in a very 

 advanced state at the beginning of the century, if we judge by 

 the language of writers and by their figures. It was a great step 

 in advance when the younger Moldenhawer in 1812 isolated 

 cells by maceration and decay in water, and was thus enabled to 

 view cells and vessels on every side and in a perfect condition, 

 to see their real shape, and to survey the manner of their com- 

 bination more exactly than had hitherto been done. But even 

 Moldenhawer still made the mistake of submitting delicate 

 microscopic objects to observation in a dry state, though 

 Rudolphi and Link in 1807 had urged the advisability of 

 keeping every part of the preparations moist, especially the 



