Chapter XIX 



CYTOPLASMIC ALTERATIONS 



It is impossible to discuss fully the vast and, moreover, incom- 

 pletely known, question of cytoplasmic alterations. We shall con- 

 sider very briefly: (1) the disturbances which accompany the nat- 

 ural death of cells; (2) the morphological alterations which vari- 

 ous physical agents provoke in cells; (3) the reactions shown by 

 the cytoplasm and its morphological constituents under the influ- 

 ence of parasites. 



Alterations produced in dying cells:- When living cells of any 

 tissue are examined, even in Ringer's solution, it is always seen 

 that they more or less quickly manifest those signs of alteration 

 which, sooner or later, end in their death. Such alterations seem 

 inevitable. They are explained by the artificiality of the medium 

 in which the cells are placed, by the pressure of the cover glass, 

 by the lack of air, and by the too intense lighting which is, never- 

 theless, necessary for observation. This is what makes the study 

 of living material so difficult. One manages to retard these altera- 

 tions by examining leaves or bracts which are protected by their 

 cuticle but are so thin as to be transparent. The cells are altered, 

 however, in the region where the organ has been severed from 

 the plant and the alteration is then transmitted, more or less rap- 

 idly, to all the cells. The complicating factor is that one can not 

 know exactly when the alteration of the cell begins. By the move- 

 ments of the cytoplasm, it is possible to determine whether a cell 

 is living. As long as cytoplasmic movements continue, the cell is 

 living and does not present any important alteration. Neverthe- 

 less, cytoplasmic movements do not prove that the cell has not 

 already manifested alterations, for, in general, all wounding causes 

 marked acceleration of the cytoplasmic currents and there are cells 

 in which these movements are to be induced only by lesion. The 

 alteration of the cytoplasm is manifested by a thickening of the 

 chondriosomes and of the plastids, soon afterward accompanied by 

 their transformation into vesicles and later, by interruption of 

 cytoplasmic circulation and its replacement by Brownian move- 

 ment. 



It is difficult to know where the first alterations of the cell 

 begin. We possess relatively accurate data as to the moment at 

 which death of the cell occurs. A first sign of death in a cell is 

 shown when the vacuole, stained with neutral red (the only ele- 

 ment stained in the living cell), abruptly loses its color and the 

 dye is taken up by the nucleus and cytoplasm. This is a universal 

 phenomenon which seems to be brought about by a modification of 

 the perivacuolar membrane, permitting diffusion of the dye accu- 

 mulated in the vacuole. This phenomenon may be compared to 



