THE PHYSICAL BASIS OF LIFE 



269 



the botanist Nagcli had studied this living substance, and 

 perceived that it was nitrogenous matter. This was a dis- 

 tinct step in advance of the vague and indefinite idea of 

 Schleiden, who had in reality noticed protoplasm in 1838, 

 but thought of it merely as gum. The highly accom])lished 

 investigator Nageli (Fig. 84) made a great place for himself 



Fig. 85. — Hugo von Mohl, 1805-1872. 



in botanical investigation, and his name is connected with 

 several fundamental ideas of biology. To \^on Mohl, how- 

 ever, belongs the credit of having brought the word proto- 

 plasm into general use. He stands in the direct line of 

 development, while Purkinje, who lirst employed the word 



