HISTORY OF "CELL" AND "PROTOPLASM." 21 



by the misleading character of the term "cell." The word itself 

 shows that cells were at first regarded as cavities (like the cells 

 of a honeycomb or of a prison) surrounded by solid walls ; and 

 even Schleiden and Schwann had no accurate conception of their 

 true nature. Soon after the promulgation of the cell-theory, 

 however, it was shown that both the walls and the cavity might 

 be wanting, and that therefore the remaining portion, namely, 

 the protoplasm with its nucleus, must be the active and essential 

 part. The cell was accordingly defined by Virchow and Max 

 Schultze as " a mass of protoplasm surrounding a nucleus, ' ' and 

 in this sense the word is used to-day.* The word cell became 

 thereafter as inappropriate as it would be if applied to the honey 

 within the honeycomb or to the living prisoner in a prison-cell. 

 Nevertheless, by a curious conservatism, the term was and is re- 

 tained to designate these structures whether occurring in masses, 

 as segments of the plant or animal body, or leading independent 

 lives as unicellular organisms. 



Protoplasm was observed long before its significance was 

 understood. The discovery of its essential identity in plants and 

 animals and, ultimately, the general recognition of the extreme 

 importance of the role which it everywhere plays, must be reck- 

 oned as one of the greatest scientific achievements of this cen- 

 tury. It was Dujardin who in 1635 first distinctly called atten- 

 tion to the importance of the "primary animal substance" or 

 "sarcode" which forms the bodies of the simplest animals. 

 Without clearly recognizing this substance as the seat of life, or 

 using the word protoplasm, he nevertheless described it as en- 

 dowed with the powers of spontaneous movement and con- 

 tractility. The word protoplasm (^pc5ros, first; n\acr)ji<x, 

 form) was apparently first used for animal substance by Purkinje 

 in 1839-40, and next by II. von Mohl, in 1840, to designate 

 the granular viscid substance occurring in plant-cells, although 

 both workers were ignorant of its full significance. In 1850 

 Colin definitely maintained not only that animal sarcode and 

 vegetal protoplasm were essentially of the same nature, but 

 also that this substance is the real seat of vitality and hence to 

 be regarded as the physical basis of life. To Max Schultze 



* It is possible that in some of the lowest and simplest organisms even the 

 nucleus may be wanting as a distinctly differentiated body. See p. 193. 



