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THE BEGINNINGS OF LIFE. 



emphatically declared by Max Schultze ^^ that a distinct 

 investing membrane or cell-wall was not an essential 

 character : afterwards the typical cell was still further 

 shorn of its characteristics when it was shown (if 

 this had not been already done by Naegeli and Braun) 

 by Briicke ^^ Kiihne ^^ and others^ that even the nucleus 

 was a non-essential constituent of that body, which 

 was formerly thought to represent not only the morpho- 

 logical, but also the vital unit. So that, in place of 

 the old ^cell"* with its definite characters, this would 

 reduce us to a mere naked, non-nucleated bit of pro- 

 toplasm as the simplest material substratum adequate 

 to display all those vital manifestations which were 

 previously considered as the essential attributes of cer- 

 tain formed elements known as ^ cells/ The power 

 of displaying vital manifestations was, in fact, trans- 



1 ' Reichert imd Du Bois Raymond's Archiv/ 1861. A mere mass of 

 protoplasm with a nucleus was sufficient to constitute a 'cell;' and at 

 the same time it was maintained that the substance of the cell (or that 

 within the wall, where this existed) was protoplasm^ a contractile sub- 

 stance answering to what Dujardin had named sarcode. These later 

 modifications are, however, by no means antagonistic to the notions of 

 Schwann as may be gathered from the following passages: — 'There is 

 no contradiction involved in the supposition that a nucleus may be 

 contained in a solid globule as well as in a cell. ... A given object may 

 really be a cell when even the common characteristics of that structure, 

 namely the perceptibility of the cell membrane, and the flowing out of 

 the cell contents, cannot be brought under observation. . . . The most 

 important and abundant proof as to the existence of a cell is the pre- 

 sence or absence of the nucleus.'— Loc. cit. p. 37, 



2 'Wiener Sitzungsberichte,' 1861, pp. 18-22. 



2 'Protoplasma und die ContractiUtat.' Leipzig, 1864. 





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