THE CELL THEORY 243 



Schleiden was educated as a lawyer, and began the prac- 

 tice of that profession, but his taste for natural science was 

 so pronounced that when he was twenty-seven years old 

 he deserted law, and went back to the university to study 

 medicine. After graduating in medicine, he devoted himself 

 mainly to botany. He saw clearly that the greatest thing 

 needed for the advancement of scientific botany was a study 

 of plant organization from the standpoint of development. 

 Accordingly he entered upon this work, and, in 1837, arrived 

 at a new view regarding the origin of plant cells. It must 

 be confessed that this new view was founded on erroneous 

 observations and conclusions, but it was revolutionary, and 

 served to provoke discussion and to awaken observation. 

 This was a characteristic feature of Schleiden's influence upon 

 botany. His work acted as a ferment in bringing about new 

 activity. 



The discovery of the nucleus in plant cells by Robert 

 Brown in 1831 was an important preliminary step to the work 

 of Schleiden, since the latter seized upon the nucleus as the 

 starting-point of new cells. He changed the name of the 

 nucleus to cytoblast, and supposed that the new cell started 

 as a small clear bubble on one side of the nucleus, and by 

 continued expansion grew into the cell, the nucleus, or 

 cytoblast, becoming encased in the cell-wall. All this was 

 shown by Nageli and other botanists to be wrong ; yet, curi- 

 ously enough, it was through the help of these false observa- 

 tions that Schwann arrived at his general conclusions. 



Schleiden was acquainted with Schwann, and in October, 

 1838, while the two were dining together, he told Schwann 

 about his observations and theories. He mentioned in par- 

 ticular the nucleus and its relationship to the other parts of 

 the cell. Schwann was immediately struck v.iih the simi- 

 larity between the obser\ationsof Schleiden and certain of liis 

 own upon animal tissues. Together they went to his labo- 



