CELL. 



[ 117 ] 



CELL. 



appear to become divided into two; the cells 

 are then constricted in the middle and finally 

 resolved into two, each with a nucleus (PI. 

 40. fig. 43-6). 



A peculiar kind of cell-growth, most nearly 

 allied to division, occurs in the cells of the 

 ivory of the teeth ; in which, while continu- 

 ally elongating, the nuclei enlarge from time 

 to time and become constricted, so that 

 whilst that portion next the ivory ossifies, 

 the remainder serves to a certain extent as a 

 reserve for the subsequent formation of 

 newly ossifying portions (fig. 114). 



BIBL. The various treatises on Physiology, 

 Schwann, Ueber die Einstimmung, fyc. (Sy- 

 denham Society') ; ibid, Wagner's Physiology, 

 by Willis; Valentin, 1. c. ; Kolliker, Ge- 

 'webelehre d. Menschen (and the literature 

 therein) ; Siebold, Ueb. einzelllge Pflanzen, 

 und Thiere, Zeitschr.f. Wissench. Zoolog. i. 

 p. 2/0. 



CELL, ANIMAL, artificial formation of. 

 When oil is immersed in a liquid containing 

 albumen, it becomes surrounded by a layer 

 of coagulated albumen, forming a cell ; and 

 this cell will exhibit the phenomena of 

 endosmose and exosmose in the same manner 

 as any natural cell. The same phenomenon 

 has been observed with metallic mercury and 

 albumen, chloroform and albumen, chloro- 

 form and chondrine, &c. It has not yet 

 been satisfactorily explained. The natural 

 formation of cells has been supposed to be 

 produced by this method; but it appears 

 inapplicable to the purpose, as the nuclei or 

 masses of blastema, around which cells are 

 formed, do not consist of fat. 



BIBL. (of the above). Ascherson, Mullens 

 Archiv, 1840, p. 44, &c.; Wittich,De hymeno- 

 gonia albuminis, Regimont, 1850 ; Halting, 

 Neder. Lane. Sept. 1851 ; Melsens, Bull, de 

 1'Acad. de Belg. 1850 ; Panum, Archiv f. 

 Path. Anat. iv. 2; Bennett, Ed. Month. 

 Journ. viii. p. 166 ; Kolliker, Gewebelehre 

 d. Mensch. p. 10; Schmidt, transl. in Taylor's 

 Scientific Memoirs, v. p. 10. 



CELL, VEGETABLE. The term cell has 

 long had a very definite and natural signifi- 

 cation in Vegetable Physiology, although the 

 same word has come to be used in a very 

 different sense among animal anatomists; 

 but recent investigations, together with the 

 conclusions which are properly derivable 

 from them, threaten to create some confusion 

 on this otherwise simple point. The fore- 

 going requires a little explanation which will 

 not be misplaced here. The definition of 

 the term cell in vegetable anatomy, ordina- 



rily adopted, is, a closed sac composed of an 

 (originally] imperforate membrane formed of 

 the chemical substance called cellulose j this 

 membrane enclosing fluid contents so long as 

 the cell retains its vitality. All the solid 

 permanent structures of plants are formed of 

 cells answering to this character, the differ- 

 ences of the full-grown tissues depending 

 upon peculiar modifications and alterations 

 of the original cells. In regard to animal 

 structures, on the contrary, the term cell is 

 commonly used as indicating structures of a 

 totally different nature and origin, and indeed 

 in a manner which exhibits great want of 

 scientific precision; not only is it applied 

 to structures really analogous to the cells of 

 plants, but also to structures analogous to 

 the contents of the true cellulose cells, which, 

 however, are indeed in all cases the important 

 living parts of the structure. All young 

 vegetable cells contain a quantity of semi- 

 fluid nitrogenous formative substance called 

 protoplasm, which protoplasm may be chiefly 

 adherent as a thickish and more or less con- 

 tinuous layer to the inside of the cellulose 

 wall, forming a kind of lining to it, and 

 therefore enclosing all the rest of the con- 

 tents, in which case it is called the primordial 

 utricle (primordial-schlauch of Mohl), or this 

 dense protoplasm may fill up the whole 

 cavity of the cell as a gelatinous mass, or, 

 finally, the gelatinous mass of protoplasm 

 may emerge from the cellulose sac, with a 

 definite form and organization, furnished 

 with cilia enabling it to move freely in water, 

 and here the primordial utricle presents 

 itself as independent, and indeed as the 

 primary element of all cellular tissue ; it is 

 found in this condition in the Confervoid 

 Alga3, in the zoospores. These free bodies, 

 devoid at first of a cellulose wall, are 

 evidently analogous to the cell constituting 

 certain animals, such as Amo2ba, while the 

 epithelium cells, &c. of animals are analo- 

 gous to the cellulose sacs of plants ; so that 

 the confusion which exists in the animal 

 tissues is likely to extend to vegetable 

 tissues if we adopt the name which has been 

 proposed by the Germans for these free 

 protoplasmic organisms, namely, that of pri- 

 mordial cells. Since the structure to which 

 the name cell is at present applied in vege- 

 table anatomy, is in pretty close accordance 

 with the common acceptation of that word 

 in ordinary language, indicating a hollow 

 case, it seems unadvisable to change the 

 received nomenclature, while it is evident 

 that the use of the prefix primordial to the 



