298 Examination of the Matured Framework [BOOK n. 



from the new direction, but completed a series of excellent 

 investigations connected with the new questions in the theory 

 of cell-formation. The most important of these was his enquiry 

 into the nature of protoplasm, to which he gave the name still 

 in use. In his treatise, ' Die Vegetabilische Zelle,' which came 

 out in 1851 in Wagner's Dictionary of Physiology, he even 

 gave an excellent account of the modern theory of cell-forma- 

 tion ; but notwithstanding all this, and the great authority 

 which he rightly continued to enjoy, he was no longer the 

 guide who led the way in the domain of phytotomy, as he had 

 been before 1845. 



His zeal as an observer had at all times been chiefly attracted 

 to the solid framework of vegetable structure in its matured 

 condition, though a number of his most important works were 

 devoted to the study of cell-contents. 



Except in his 'Anatomic der Palmen' (1831), where he ex- 

 pended much and to some extent even unnecessary labour on 

 figures representing the general appearance of the tissue (histo- 

 logic habit), von Mohl's microscopic drawings do not aim at 

 giving the collective impression, but at facilitating the under- 

 standing of the delicate structure of single cells and their combi- 

 nations by aid of the simplest possible lines. He always despised 

 pictures from the microscope, such as were introduced at a later 

 time by Schacht, a kind of artistic restoration of the originals 

 and to some extent a playing with science ; and in his later 

 publications he was more sparing of illustrations or omitted them 

 altogether, in proportion as he acquired the power of giving 

 clear verbal explanations of even difficult structural conditions. 



Von Mohl's scientific activity was so wonderfully productive 

 thatjt is not easy to present the reader with a clear account of it ; 

 but we must endeavour at least to furnish such a summary of 

 its chief results as may serve to give a general idea of his 

 importance in the history of our science. We may here pass 

 over such of his treatises as do not bear on the main questions 

 of phytotomy, and notice only those that relate to the structure 



