FORMATION OF CELLS. 349 



of the centres, inasmuch as the nuclei must, as was long 

 since shown by John Groodsir, be regarded as the central 

 organs of the cells. 



If now, gentlemen, we advance a step further in these 

 processes, we come to the new formation of the cells them- 

 selves. After the multiplication of the nuclei has taken 

 place, the cell may certainly, as we have seen, continue to 

 subsist as a coherent structure ; still the rule is, that even 

 after the first division of the nuclei, the cells themselves 

 undergo division, and that after some time two cells are 

 found lying closely side by side, separated by a more or 

 less straight partition, and each provided with a nucleus 

 of its own (Fig. 6, b, b). This is the natural, regular 

 manner in which the real multiplication of cellular ele- 

 ments takes place. Then, the two cells may separate, if 

 the tissue is one which possesses intercellular substance 

 (Fig. 6, c, d) ; or may remain lying close to one another, 

 in the case of a tissue simply composed of cells (Fig. 27, 

 C). This series of processes, which in their subsequent 

 course lead to a continually proceeding division of the 



FIG. 106. 



cells, and to the production of large groups of cells from 

 single ones (Figs. 9, 22), occurs in the adult body just as 

 unquestionably as the result of a direct irritation of the 

 tissues, as the class we spoke of before. If, for example, 

 we follow up a little farther the case which we before 

 considered, of the production of a simple mechanical 

 irritation by drawing a thread through the parts, we usu- 



Fig. 106. Cells from the central substance of an intervertebral cartilage of an 

 adult. Intra-capsular multiplication of cells. 300 diameters. 



