74 THE STORY OF THE LIVING MACHINE. 



made. This was the formulation of the doctrine 

 of the nature si protoplasm. 



Protoplasm. (a) Discovery. As it became evi- 

 dent 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 formu- 

 lation of the cell doctrine both the cell substance 

 and the nucleus had been looked upon as essen- 

 tial to its activities. This was more especially 

 true of the nucleus, which had been thought of as 

 an organ of reproduction. These suggestions ap- 

 peared indefinitely in the writings of one scien- 

 tist and another, and were finally formulated in 

 1860 into a general theory which formed what has 

 sometimes been called the starting point of mod- 

 ern biology. From that time the material known 

 as protoplasm was elevated into a prominent po- 

 sition 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 

 substance 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 

 parts being entirely subordinate, and indeed fre- 

 quently absent. A cell was thus a bit of proto- 



