30 GENERAL ANATOMY OF THE TISSUES. 



cell-development. It is certain that the transverse and longitu- 

 dinal division of the Protozoa is to be placed here, since these 

 animals have the structure of simple cells, and the nucleus-like 

 body they contain takes a share in the process of cell division, 

 like that of the cell nucleus in common cells. In pathological 

 formations cell-division has not yet been observed. In the 

 vegetable kingdom it is rare, and has been seen only in the 

 lower organisms ; unless, indeed, we are to reckon here the 

 constriction of the primordial utricle observed by von Mohl, 

 in the course of endogenous cell-development.] 1 



1 [There can, we think, he little doubt that Von Mohl is quite correct in the view 

 he takes of the multiplication of cells in plants by division, and therefore we are 

 by no means inclined to agree with Professor Kolliker, as to the rarity of this form 

 of cell-multiplication in the vegetable kingdom, nor, consequently, in what he says at 

 the conclusion of the preceding note. All botanists of any note (Niigeli, Von Mohl, 

 Hoffmeister, Alex. Braun, Schacht, Henfrey) maintain at the present time, that the 

 process of cell-division so far from being " rare," is that which occurs in by far the 

 great majority of cases in plants. " That the formation of cells, in all organs of 

 plants (excepting the cells originating in the embryo sac), depends upon the division 

 of older cells, is an opinion which could not for a long time past be opposed by any 

 careful observer, unless he were misled by preconceived notions." (Von Mohl, 

 Anatomy and Physiology of the Vegetable Cell,' 1851, Henfrey's translation). Nor 

 can we agree with Professor KbTliker's estimate of the relative frequency of occur- 

 rence and importance of endogenous cell-development and cell-division in the animal 

 world. In young cartilage, which is cited by our author as a locality in which endo- 

 genous cell-development takes place, we must affirm, on the contrary, that the process 

 is as much one of cell-division as it is in any plant. At this period, the so-called 

 " nuclei" of the cartilage completely fill their cavities (e. g. nasal cartilage of four- 

 months' foetus), and may be seen in all stages of division. The walls of the cavities 

 grow in, pari passu, and eventually form a partition between the two nuclei, or rather 

 primordial utricles, which have been thus developed from one. 



Remak, who, in a very valuable paper (Ueber die Entstehung der Bindegewebes 

 und Knorpels, Mull. Archiv, 1852), has advocated this view so far as cartilage and 

 connective-tissue aie concerned, does not appear to have seen the necessity of 

 extending it to the other tissues. As Reichert, however, long since pointed out (see 

 note, § on Connective Tissue), whatever determines the nature of the cartilage 

 corpuscle and of its matrix, determines that of all the other tissues whose anatomical 

 continuity with cartilage can be traced directly or indirectly. Thus a direct ana- 

 tomical continuity may be shown to exist between the matrix of cartilage, the 

 apparent fibrillae of connective tissue, the fibrillar of muscle, the homogeneous matrix of 

 the cutis and of its papilla;, and the so-called walls of the epithelial cells ; while a per- 

 fect identity in size, structure and relation, may foe traced between the corpuscles of 

 cartilage, the " nuclei" of connective tissue, those of muscle, of the papillae and of 

 the epithelial cells. — Eds.] 



