90 THE STORY OF LIFE'S MECHANISM. 



PROTOPLASM. 



(a) Discovery, As it became evident that the 

 cell wall is a somewhat inactive part of the cell, 

 more attention was put on the cell contents. For 

 twenty years after the formulation of the cell 

 doctrine both the cell substance and the nucleus 

 had been looked upon as essential to its activities. 

 This was more especially true of the nucleus, 

 which had been thought of as an organ of repro- 

 duction. These suggestions appeared indefinitely 

 in the writings of one scientist and another, and 

 were finally formulated in 1860 into a general 

 theory which formed what has sometimes been 

 called the starting-point of modern biology. 

 From that time the material known as protoplasm 

 was elevated into a prominent position in the 

 discussion of all subjects connected with living 

 phenomena. The idea of protoplasm was first 

 clearly defined by Schultze, who claimed that 

 the real active part of the cell was the cell sub- 

 stance within the cell wall. This substance he 

 proved to be endowed with powers of motion 

 and powers of inducing chemical changes asso- 

 ciated with vital phenomena. He showed it to 

 be the most abundant in the most active cells, 

 becoming less abundant as the cells lose their ac- 

 tivity, and disappearing when the cells lose their 

 vitality. This cell substance was soon raised into 

 a position of such importance that the smaller 

 body within it was obscured, and for some twenty 

 years more the nucleus was silently ignored in 

 biological discussion. According to Schultze, the 

 cell substance itself constituted the cell, the other 



