80 INJURY, RECOVERY, AND DEATH 



the tissue was replaced in sea water the resistance soon 

 rose to normal and so continued during the remainder 

 of the day."* 



In this case the conductance of the tissue at the start 

 was l-=-770==0.0013 reciprocal ohms and this changed to 

 1-^580=0.00172 reciprocal ohms, an increase of 32.3%. It 

 would be more convenient to say that the conductance at 

 the start was 1 -~- 100 and that this increased to 1 -r- 75.32. 

 The resistance of the protoplasm at the start* (as distin- 

 guished from that of the tissue as a whole) would 

 then be 140, decreasing to 96.03, a loss of 31.4%. The 

 conductance at the start would be 1 -i- 140 = .007143 

 increasing to 1 -i- 96.03 = .010413 ; or, if we call the proto- 

 plasmic resistance at the start 100, it decreases from 

 100% to 68.60% and the conductance increases from 

 1 _=- 100 = .01 to 1 -f- 68.60 = .014578, a gain of 45.78%.'' 



In order to see whether this increase is accompanied 

 by permanent injury, an experiment was made in which 

 the same piece of tissue was exposed to the action of 

 NaCl several times during the same day, The net resist-, 

 ance of the tissue in sea water was 810 ohms; after 5 

 minutes in NaCl the resistance fell to 84% of the original 

 resistance ; the tissue was then placed in sea water and 

 a reading 10 minutes later showed that the resistance had 

 risen to 100%. In this case the fall of protoplasmic 

 resistance was (100 — 78.94) h- 100 = 21.06% and the 

 increase in permeability (conductance) was [(1-^-78.94) 



"Shearer (1919. A) obtained similar results with bacteria. 



° For the method of calculating this see p. 217. 



' It might be objected that this increase is not necessarily the result of 

 increase in permeability, but may be due to the fact that the protoplasm 

 is more permeable to NaCl than to CaClj and since the number of 

 Na-ions is increased the conductance also increases. But the increase in 

 Na-ions is much too small to account for the effect since it amounts to 

 about 1%. 



