138 THE CELL DOCTKINB. 



spot remains as a nucleus of the ovum when the ger- 

 minal vesicle is no longer seen. 



Similar statements were made by Leydig,* and 

 Bischoff'jt the former with regard to Piscicola, and 

 the latter in the case of mammals. 



The Cell-contents and Cell-wall. — As cells grow older 

 and are farther removed from the bloodvessels which 

 nourish them, there is found to be, exterior to the 

 nucleus, a portion which no longer admits of staining 

 by carmine solutions of the strength which will tinge 

 the nucleus. Further, the extreme periphery of this 

 is often found condensed so as to present under the 

 microscope a double contour, and to form an actual 

 limitary membrane to the cell. To the former the 

 name " cell-contents " has come to be applied, and to 

 the latter, " cell-wall." 



With regard to the " cell-contents," it is plain that 

 a strict adherence to the term would require to be 

 included the nucleus and nucleolus when present, 

 and such was the original scope of the term when a 

 cell was defined as a " closed vesicle or bag with cer- 

 tain ' contents/ among which is essentially a nu- 

 cleus,"' a definition now very properly rejected. It 

 is to this portion of the cell also, that the German 

 histologists of the present day apply the term "proto- 

 plasm," instead of to the nucleus and nucleolus, which 

 in many cells, at least, alone possess the endowments 

 suggested by the word protoplasm (^/owtot, first, T^kaaixa, 



* Leydig, Zur Anatomie von Piscicola Geometrica, Zeitsch. f. 

 Wiss. Zoologie, vol. i, 1849. 

 f Bischoff, Entwickelungsgeschichte des Kaninchen eies, 1842. 



