20 CELL THEORY BEFORE 1860 VIRCHOW. 



components of another cell." The cell wall being given up, the 

 threefold nature of the cell as the elementary vital unit disap- 

 pears, and physiologists go back to Schleiden's idea of its dual 

 nature ; but the two elements are now nucleus and cell con- 

 tents, and as long as the cell theory is maintained, the import- 

 ance of the nucleus becomes essential. "A plasma-lump 

 without a nucleus is no longer a cell," says Hackel (" Gen. 

 Morph.," i. 273). Upon the consistence, and structure, and 

 physiological nature of the nucleus, the most conflicting and 

 manifold statements and opinions are given by botanists and 

 zoologists. It would be tedious and superfluous to go into 

 these in detail, so I will merely note here the position it occu- 

 pied in the cell theory up to 1860. It is said to be always 

 round, or a more or less prolonged oval, whatever be the shape 

 of the cell, and to be of the same chemical composition as the 

 protoplasm in which it lies embedded, or hardly distinguish- 

 able from it. It frequently contains within it a smaller similar 

 body, the nucleolus, and sometimes within that may be detected 

 a still smaller one, the nucleolinus. The essentiality of this 

 body, and its supposed functions in the cell theory, were thus 

 summed up by Virchow, in 1858 : 



" The nucleus plays an extremely important part within the 

 cell .... less connected^ with the function and specific office 

 of the cell, than with its maintenance and multiplication as a 

 living part. The specific (in a narrower sense, animal) function 

 is most distinctly manifested in muscles, nerves, and gland cells ; 

 the peculiar actions_of which contraction, sensation, and secre- 

 tion appear to be connected in no direct manner with the 

 nuclei. But that whilst fulfilling all its functions the element 

 remains an element, that it is not annihilated nor destroyed by 

 its continual activity this seems essentially to depend upon 

 the action of the nucleus " (" CeUular Path.," p. 10). Doubts, 

 however, were thrown before this on the universality of the 

 nucleus, and in 1854, Max Schultze had described a non-nucle- 

 ated Amoeba found in the Adriatic the Amoeba porrecta. The 

 phenomena spoken of by Virchow will afterwards be seen to 

 be capable of quite different explanation, nevertheless, the cell 

 theory in the altered form (contents and nucleus) above noted 



