OUTSTANDING BIOLOGICAL ADVANCES 17 



no matter how complex, begin their existence in the 

 condition of a single cell. 



This " master-stroke of generalization r had a 

 wonderful unifying effect in bringing all animals and 

 plants under one view as to origin and structure. 



The names of two men, Schleiden and Schwann, 

 are associated with the launching of this theory. 

 Schleiden was a botanist, and Schwann, an anat- 

 omist a happy combination in biological investi- 

 gation. They are commonly spoken of as the 

 co-founders of the cell-theory. This statement, how- 

 ever, requires qualification, for the part played by 

 the two men was very unequal. Schwann, so to 

 speak, was the star and Schleiden played a subordi- 

 nate part. 



Schleiden's work was auxiliary. He had observed 

 cell formation and cell structure of plants and pub- 

 lished a small paper on this subject in 1838. In a 

 friendly conference, he assisted Schwann, whose 

 researches were already the more extensive, by sug- 

 gesting that the nucleus (cytoblast) of the animal 

 tissues, examined by Schwann, was the same as the 

 nucleus of plants and this, apparently, flashed into 

 the mind of Schwann, the identity of organization of 

 animals and plants. 



