STRUCTURAL CHANGES DUE TO DAMAGE. 



335 



of new formation springing from the living portion. If this 

 takes place, the cells of the latter portion multiply and reassume 

 those formative activities that they possessed during the develop- 

 ment of the tissues in earlier life. The division of the cells al- 

 ways takes place by the indirect method, that of karyokinesis. We 

 must not, however, assume that because the cells of a tissue may, 

 under the influence of damaging agents, contain karyokinetic figures, 

 they must necessarily possess the power of regenerating lost por- 

 tions of tissue. More than mere observation of those figures is re- 

 quired to establish that fact. Such figures are occasionally met with 

 in the ganglion-cells of the central nervous system, and they show 

 that the nuclei of those cells retain, at least to a certain extent, the 

 power of division. But this by no means implies that new ganglion- 

 cells, capable of full functional activity, can be produced by the 

 division of an adult nerve-cell, and, as a fact, such an occurrence 



FIG. 297. 



a 



FIG. 299. 



Phases in the regeneration of the gastric mucous membrane; dog. (Griffini and Vassale.) 

 a, regenerated columnar epithelial cells covering the base of the wound ; b, c, karyokinetic 

 figures indicative of proliferation. 



does not appear to take place. In Fig. 293, zone 6, karyokinetic 

 figures are seen in the renal epithelium ; but it is doubtful whether 

 they signify the beginning formation of new renal tissue to replace 



