September 13, 1912] 



SCIENCE 



351 



to assume any alteration in the normal per- 

 meability of the protoplasm. This supposi- 

 tion can not be correct, for experiments showed 

 that the other ions of the sea water penetrate 

 with about the same rapidity as those of so- 

 dium chloride, but in order to be absolutely 

 sure of this point it was tested by employing 

 in place of sea water a solution composed of 

 1,000 c.c. NaCl .52M plus 20 c.c. CaCl, .278M. 

 In this solution the proportion of sodium ions 

 to calcium ions is about 100 to 1, as is evident 

 from the fact that both the .52M NaCl solu- 

 tion and the .2T8M CaCh solution have the 

 same conductivity (which is the same as that 

 of the sea water). In this solution the con- 

 ductivity of the tissue is about the same as in 

 sea water. If we now transfer to NaCl .52M 

 there will be an increase of about 2 per cent, 

 in the number of sodium ions. Consequently 

 (on the supposition that sodium ions penetrate 

 more easily than the other ions of sea water) 

 we may not expect an increase of more than 

 2 per cent, in the conductivity as long as the 

 permeability remains unaltered. But if the 

 increase is more than 2 per cent, it signifies a 

 corresponding increase in permeability. 



In the mixture of 1,000 c.c. NaCl .52M plus 

 20 c.c. CaCh .278M the tissue was found to 

 have a resistance of 1,020 ohms: after two 

 hours the resistance was unaltered. The ma- 

 terial was then transferred to N'aCl .52M and 

 left until the resistance fell to 860 ohms. It 

 was then replaced in the mixture of JSTaCl and 

 CaCL : the resistance soon rose to 1,020 ohms 

 and remained unaltered for several hours; it 

 was left in the mixture over night and on the 

 following morning the resistance was still the 

 same. It subsequently remained the same as 

 that of the control which was kept in sea 

 water throughout the experiment. 



In order to find out how much of the resist- 

 ance is due to living protoplasm the tissue 

 was killed by exposing it for ten minutes to 

 2 per cent, formalin in sea water ;"* the resist- 

 ance fell to 320 ohms. On subtracting this 



* Cheek experiments showed that MUing in this 

 way has the same effect on the resistance of the 

 tissue as killing it by means of heat or by iodine 

 vapor or by allowing it to die a natural death. 



from the resistance observed whea the tissue 

 is alive we obtain approximately the resistance 

 due to the living protoplasm; this may be 

 called for convenience the net resistance, while 

 the resistance before the subtraction is made 

 may be called the gross resistance. The net 

 resistance in this experiment was accordingly 

 1,020 — 320 = 700 ohms before treatment with 

 NaCl and 860 — 320 = 540 ohms after treat- 

 ment with NaCl; the net conductance before 

 treatment with NaCl was therefore 1 -^ 700 = 

 .001428 mho. and after treatment with NaCl 1-f- 

 540 = .001852, a gain of 29.7 per cent, (the 

 gain in gross conductance was 18.6 per cent.)." 



It is therefore evident that there has been a 

 very marked increase in permeability which is 

 completely reversible. 



Electrolytes may also cause a reversible de- 

 crease in permeability. The simplest way of 

 demonstrating this is by means of the follow- 

 ing very striking experiment. The resistance 

 of a cylinder of living tissue in sea water was 

 found to be 750 ohms. It was tested an hour 

 later and found to be the same. Sufficient 

 lanthanum nitrate was then added in solid 

 form to make its concentration' in the sea 

 water about .OlM. After five minutes the 

 resistance rose to 900 ohms. As the con- 

 ductance of the dead tissue was found (at the 

 end of the experiment) to be 315 ohms, the 

 net resistance before the addition of lantha- 

 num was 750 — 315=435 ohms and the net 

 conductance 1 -^- 435 = .0023 mho. After treat- 

 ment with lanthanum nitrate the net resist- 

 ance was 900 — 315 = 585 ohms and net con- 

 ductance 1 -^ 585 = .001709, a loss of 25.6 per 

 cent. 



° Owing to the fact that the cylinder of tissue 

 was of the same size in each set of experiments a 

 calculation of the specific resistivity and of the 

 specific conductivity was unnecessary. 



° The concentration was reduced by the precipi- 

 tation of a small amoimt of lanthanum sulphate: 

 this had practically no influence on the subsequent 

 result, since the outcome is the same if we use 

 in place of sea water a mixture of 1,000 c.c. 

 NaCl . 52M + 20 c.c. CaCl^ . 278M, in which case 

 no precipitate is formed. It should be noted that 

 the addition of lanthanum chloride has the same 

 effect as the addition of lanthanum nitrate. 



