THE CELL DOCTRINE. 41 



at that time may be easily inferred.* Nor is mention 

 here made by Henle, of the nucleus of the cell, as the 

 primary seat of the segmentation. The surface of the 

 cell is said to be " corded in," or " furrowed," deeper 

 and deeper, until the division takes place. This de- 

 scription is still adhered to by many physiologists 

 of the present day, who consider that there is a sim- 

 ple disappearance of the germinal vesicle or nucleus 

 of the ovum after fecundation, rather than a division 

 of it into two, and substitution of these for the orig- 

 inal one. 



* While endeavoring to trace out the steps by which the present 

 most generally accepted views with regard to the origin of cells, were 

 arrived at, it must not be forgotten that other dissenting views were 

 also advanced, though tending differently from those incorporated 

 in the text, where it is desired more particularly to trace those 

 culminating in existing doctrines. Thus did Reichert 1 early (1840), 

 dissent from Schwann, since he failed to find the nucleus univer- 

 sally present in the yolk. Karsten 2 (1843), published a dissertation 

 upon the cell, in which he stated that cells originate without a pre- 

 existing nucleus, and by the expansion of amorphous granules of 

 organic matter; and more recently (1863), the same author practi- 

 cally reiterates this view, since he says that all " cells of vegetables 

 originate as minute free vesicles in the fluid contents of previously 

 existing cells," and regards the nucleus as a "small tertiary cell, 

 retarded in its development." 3 Again, "when the nucleus is 

 present, the origin of new cells is quite independent of it." 4 In 

 addition to the statement contained in the text, Henle also (1843), 

 alleged that some of the so-called fibrous tissues were "formed by the 

 aggregation of granules in a certain way without the intervention 



1 Reichert, Das Entwickelungelebun im Wirbelthierreich. Berlin: 1840, 

 pp. 6, 93. 



2 Karsten, De Cella vitale Dissertatio. Berlin : 1843. 



3 Karsten, Ann. and Mag. of Nat. History, vol. xiii, p. 268. London : 

 1864. 



* Karsten, Ann. and Mag. Nat. History, vol. xiii, p. 281. 



