80 



GENERAL PHYSIOLOGY 



2. Protoplasm 



The mistake has frequently been made of considering protoplasm 

 a chemically unitary substance. This idea involves a double error, 

 for, first, the conception of protoplasm, as created by the earlier cell- 

 investigators, was not a chemical but a morphological conception, 

 and, secondly, it applied to the whole contents of the cell, with the 

 exception of the nucleus. The cell-contents is, however, in neither 

 the chemical nor the morphological sense a unitary substance, but 

 is a mixture of many morphological constituents ; and it must 

 constantly be borne in mind that, since it is impossible to separate 

 one or another constituent as accessory, the limitation of the term 



Pig. 22.— a, Epidermis-oells from the frog ; the living substance appears completely hvaline b 

 aepgidnna Uattarmn.a unicellular gregarine from the intestine of a cockroach -the nrotnnla sn> 

 is entirely filled with granules. ' ^ •^'.-Fiti. ur 



protoplasm to certain constituents of the cell is wholly inadmissible 

 and leads to evil consequences. The conception of protoplasm, 

 therefore, should be maintained under all circumstances strictly in its 

 original sense as a comprehensive morphological conception; proto- 

 plasm is a sum, a mixture, of very different morphological elements. 

 Even if by degrees its individual constituents become known mor- 

 phologically and chemically, the comprehensiveness of the term 

 will not thereby be set aside. Whatever significations the various 

 substances may have in the vital process of the cell is a wholly dif- 

 ferent questi(3n, and does not affect the conception of protoplasm. 



