350 



SCIENCE 



[N. S. Vol. XXXVI. No. 924 



merely in bringing out the association be- 

 tween a series of obscure and puzzling symp- 

 toms developed in the course of several years, 

 which finally seem to have found explanation 

 in the cancerous growth revealed well toward 

 the end of the series. 



"W J McGee' 



REVERSIBLE CHANGES IN PERMEABILITY PRODUCED 

 BY ELECTROLYTES 



According to one opinion permeability is a 

 relatively fixed property of the cell and is 

 altered only as the result of injury : the altera- 

 tion is then irreversible. 



Another view assumes that there are re- 

 versible changes in permeability which involve 

 no injury and which may form a normal part 

 of the activities of the cell. If such changes 

 occur it is clear that they may control the 

 course of metabolism. That permeability may 

 be altered in this manner is suggested by a 

 number of facts/ but their interpretation is 

 too doubtful to place this view on a firm basis. 

 It is highly important that its truth or falsity 

 be established by rigorous proof. Such proof 

 seems to be afforded by a series of experi- 

 ments, some of which are described below. 



The method pursued in these experiments 

 has been described in a previous paper.^ It 

 consists in cutting disks of living tissue from 

 fronds of the common kelp (Laminaria) and 

 measuring their electrical conductivity in 

 various solutions. Under the conditions of 

 these experiments an increase or decrease of 

 conductivity denotes a corresponding increase 

 or decrease of permeability. 



Upon transferring the living tissue from 

 sea water to pure sodium chloride of the same 

 conductivity (and at the same temperature) 

 an immediate increase of conductivity was 

 observed. The conductivity continued to in- 

 crease at a regular rate for about two hours. 

 At the end of this time the conductivity of 

 the tissue was equal to that of the same 



' Dr. McGee died on September 5, 1912. — Editor. 



' For a recent summary see Hober, ' ' Physikal- 

 ische Chemie der Zelle und Gewebe, " Kap. 7 und 

 10, Dritte Auflage, 1911. 



' Science, N. S., XXXV., p. 112, 1912. 



amount of sea water. At this point it re- 

 mained stationary even when the tissue was 

 replaced in sea water. This signifies that the 

 tissue was dead. 



In this case we are dealing with an irre- 

 versible change in permeability. It is natural 

 to ask whether this change is not, up to a cer- 

 tain point, reversible. In order to test this, 

 fresh living tissue was transferred from sea 

 water to sodium chloride of the same con- 

 ductivity (and at the same temperature) ; 

 readings were then taken at intervals of two 

 minutes. In the course of five minutes the 

 resistance had fallen from 1,000 oluus to 850 

 ohms.^ The tissue was then replaced in sea 

 water and readings were taken at intervals of 

 five minutes. In the course of five minutes 

 the resistance rose to normal and remained 

 unaltered until the following day, when the 

 experiment was discontinued. This experi- 

 ment was repeated many times under different 

 conditions and with a variety of salts. The 

 results were similar throughout. 



In order to make certain that no injury 

 resulted from the treatment with sodium chlo- 

 ride an experiment was performed to ascertain 

 the effect of repeated treatments on the same 

 lot of tissue. In one experiment the tissue 

 was treated with sodium cliloride until the 

 resistance dropped from 1,020 ohms to 890 

 ohms and was then replaced in sea water, 

 after which the resistance rose to 1,020 ohms; 

 this was repeated daily on the same lot of 

 tissue for fifteen days. On the tenth day the 

 tissue began to show a falling off' in resistance, 

 which continued to the fifteenth day, when the 

 experiment was discontinued. As this fall- 

 ing off was also shown by the control, which 

 was kept in sea water throughout the experi- 

 ment, it was not due to the sodium chloride, 

 but to other causes. 



The objection may be made that in this 

 experiment the increase in conductivity was 

 due to an increase in the number of sodium 

 ions and that these may normally penetrate 

 the cell more easily than the other ions of the 

 sea water: it might therefore be unnecessary 



^ All the figures in this paper refer to readings 

 taken at 18° C. 



