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 accomplished 

 investigator N ageli (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 Von 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 first employed the word 



