PROTOPLASM 49 



the "gemmules" of Darwin, the "biophores" of Weismann, the "pan- 

 gens" of de Vries, and the "ergatules" and " generatules " of Hatschek. 



In a somewhat similar manner a number of the later investigators 

 occupied with the study of the ultimate structure of protoplasm have 

 often been led to inquire which of the constituents of protoplasm are the 

 actually living elements. Among those who viewed protoplasm as a 

 reticular structure some held the material of the reticulum to be the true 

 living substance, the liquid ground substance being lifeless, whereas 

 others held the reverse to be true. Many of those who saw in protoplasm 

 a granular structure regarded the granules as the ultimate living units, 

 and more recently there has even been a tendency on the part of some 

 investigators (Beijerinck, Lepeschkin), who have emphasized the emul- 

 sion nature of protoplasm, to view the droplets of the suspended phase in 

 a similar light. To Biitschli the continuous phase was the essential 

 substance. 



By most modern biologists such attempts to assign the principle of 

 life to any particular constituent unit of protoplasm or of the cell, whether 

 this unit be an observed structural component or a purely imaginary one, 

 are regarded as not in harmony with an adequate modern conception 

 of the term "living." It has been repeatedly emphasized that life should 

 be thought of not as a property of any particular cell constituent, but 

 as an attribute of the cell system as a whole (Wilson 1899) ; or, as Brooks 

 (1899) put it, not merely as a property but as a relation or adjustment 

 between the properties of the organism and those of its environment. 

 This recalls Herbert Spencer's characterization of life as a "continu- 

 ous adjustment of internal relations to external relations." As Sachs 

 (1892, 1895) and others urged, the various elements in the cell should be 

 referred to as active and passive rather than living and lifeless. These 

 elements play various roles in the cell's activity: each contributes to the 

 orderly operation of the whole. When any part fails to function properly, 

 or when the proper adjustment is not maintained, the whole system of 

 correlated reactions, the resultant of which we call life, must become 

 disorganized. As Child (1915) remarks, the theories postulating vital 

 units only transfer the problems of life from the organism to something 

 smaller; the fundamental problem of coordination is no nearer solution 

 than before, and the whole question is placed outside the field of experi- 

 mentation. Harper (1919) also points out that modern cytology no 

 longer looks upon protoplasm as a substance with a single specific struc- 

 ture, or as one made up of ultimate fundamental units of some kind, 

 but rather as a colloidal system or group of systems of varying structure 

 and composition. "The fundamental organization of living material is 

 expressed in the structure of the cell." The cell itself, and not some 

 hypothetical corpuscle, is the unit of organic structure. Protoplasm is 

 accordingly not made up of structural units arranged in various ways to 



