ii2 The Science of Life. 



not only in different organisms, but even in one and the 

 same cell. 



The term protoplasm was first used by Purkinje 



(1840) in reference to the formative material of animal 



embryos; it was taken over by Von Mohl 



' (1846) to designate the substance within the 



cells of plants; and was extended by Max Schultze 



(1861) to the animal cell, superseding the equivalent 



term sarcode. 



It may be briefly defined in Huxley's famous phrase 

 as "the physical basis of life", but it is used by different 

 authors in slightly different ways. It is often used as 

 a morphological or topographical term for the physically 

 complex cell-substance ; it is often used as a physiologi- 

 cal term for the whole cell-substance in so far as that 

 is actively concerned in metabolism, that is for the cell- 

 substance minus obviously lifeless inclusions, precipi- 

 tates, &c. ; it is often used to designate an unknown 

 quantity the genuinely living stuff. A fourth usage, 

 which contrasts protoplasm and nucleus, should be 

 abandoned in favour of the terms cytoplasm and nucleo- 

 plasm. 



It is at present profitless to attempt to gain a forced 

 clearness in regard to protoplasm. The lack of lucidity 

 is not due to lack of logic, but to a scarcity of facts. 



In regard to a few facts there is no doubt. Thus it 

 is certain that the material of a cell has a complex 

 structure, but the fact does not help us much. As Prof. 

 Burden Sanderson says, we must "hold to the funda- 

 mental principle that living matter acts by virtue of its 

 structure, provided the term structure be used in a sense 

 which carries it beyond the limits of anatomical investi- 

 gation, i.e. beyond the knowledge which can be attained 

 either by the scalpel or the microscope". It is hardly 

 too much to say that a single experiment in ' ' micro- 

 scopic vivisection", as Prof. Gruber calls it, showing, 

 for instance, that a unit bereft of its nucleus may move 

 and be irritable for a time, but can neither grow nor 

 persist, has been of more physiological moment as yet 

 than all the descriptions of cytoplasmic architecture. 



One general idea, however, the study of cytoplasmic 



