CAUSES OF NECROSIS 317 



ably act by combining with one or more of the constituents of 

 cell protoplasm ; e. g., HgCl 2 probably combines with the pro- 

 teids, chloroform with the cell lipoids (physically?). Kunkel 

 suggests that oxalic acid and fluorides are poisons because they 

 combine the cell calcium, and barium salts may be poisonous 

 because they precipitate the SO 4 ions. We can readily imagine 

 that the combining of even one of the essential constituents of 

 the cell may so upset the normal chemical processes that the 

 cell can no longer take up substances to repair its waste, and 

 hence necrosis ensues. 1 



Physical agents may cause necrosis, usually in ways too 

 obvious to require explanation. With most cells, large portions 

 of the cytoplasm can be destroyed without serious results, for so 

 long as the nucleus is intact the cytoplasm can be reconstructed. 

 The fact that necrosis frequently follows relatively slight inju- 

 ries of the nucleus is perhaps best explained by considering that 

 injury to the nuclear membrane modifies the permeability of the 

 nucleus for substances in solution, which might readily affect 

 its metabolic activities to a serious degree. It is possible, also, 

 that solvents of lipoids, such as chloroform, etc., produce much 

 of their deleterious effects by modifying the permeability of the 

 cell, since the semipermeability of cell membranes depends 

 largely upon the lipoids they contain. 2 



Physical injury of even slight degree may bring on severe 

 alterations in cells, however, and indeed may cause severe 

 chemical alterations. We know that many chemical reactions 

 can be brought about by slight mechanical disturbances, e. g., 

 the explosion of fulminate, nitrogen iodide, etc., and it is quite 

 possible that mechanical disturbances can, likewise, cause chem- 

 ical changes in the protoplasm. Many lower animals devoid 

 of a nervous system respond to mechanical stimuli by chemical 

 activity ; e. g., the production of phosphorescence by marine 

 organisms when agitated by an oar, etc. Possibly, the secretion 

 of thrombokinase by the leucocytes, which occurs whenever they 

 come in contact with a foreign body, is an example of a similar 

 reaction to a mechanical stimulus. We have no good evidence, 

 however, that mere contact with a chemically inert foreign 

 body, unaccompanied by cellular injury, can cause death of 

 tissue-cells. 3 



1 It is hardly profitable here to go further into the theories of the action of 

 poisons, which are generally extensively considered in the treatises on toxicol- 

 ogy and pharmacology (also by Davenport, loc. dt.). 



2 See Pascucci, Hofmeister's Beitrage, 1905 (6), 552. 



3 Meltzer (Zeit. f. Biol., 1894 (30), 464) has shown that bacteria may be 

 killed by violent agitation, which causes disintegration of the cells. 



