352 



SCIENCE 



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



111 order to ascertain whether this change in 

 permeability is reversible the tissue was re- 

 placed in sea water. In the course of an hour 

 its resistance returned again to the original 

 condition.' The experiment was then re- 

 peated three times on the same lot of material 

 with the same result; it was then allowed to 

 stand over night in sea water. On the follow- 

 ing day there was no appearance of injury and 

 its resistance was the same as that of the con- 

 trol which had remained in sea water through- 

 out the experiment. The tissue was then 

 placed in the sea water plus lanthanum and 

 left until its resistance had increased about 

 150 ohms; it was then put back into sea water 

 and left until the resistance fell to normal. 

 This was repeated three times and the tissue 

 was then allowed to stand over night in sea 

 water. On the third, fourth and fifth days 

 the same experiment was repeated four times. 

 On the fifth day the tissue appeared to be in as 

 good condition as the control and had a re- 

 sistance which was slightly higher. There was 

 therefore no reason to suspect that the changes 

 in permeability had been attended by any in- 

 jurious effect. 



Similar experiments were performed in 

 which calcium chloride was used in place of 

 lanthanum nitrate. In this case 3.3 gm. an- 

 hydrous CaCl^ were added to each 1,000 c.c. 

 of sea water. Owing to the fact that the rise 

 in resistance took place more slowly than when 

 lanthanum was iised, the experiment was per- 

 formed twice on each of the five successive 

 days. On the sixth day the material was in 

 as good condition as the control and had the 

 same resistance. 



It is therefore evident that the permeability 

 may be greatly decreased and then restored to 

 the normal several times on five successive 

 days without any trace of injury. Further 

 experiments showed that the permeability may 

 be alternately increased and decreased twice 

 daily for five days without injury. The 

 amount of increase and decrease was about the 

 same as in the experiments just described. 



' If the material is left in sea water plus lan- 

 thanum nitrate the increased resistance is main- 

 tained for a long time unaltered. 



Experiments on dead tissue (killed by heat 

 or by formalin or allowed to die a natural 

 death) showed that the results described above 

 are due entirely to the living cells. 



A very marked decrease of permeability may 

 be produced by a considerable variety of other 

 salts. 



The addition of these salts in solid form 

 simultaneously increases the conductivity of 

 the solution and decreases the conductivity of 

 the tissue. This affords the most convincing 

 proof that the change in the conductivity of 

 the tissue in these experiments can not be due 

 to any cause other than a change in per- 

 meability ; for the concentration of the ions of 

 the sea water remains unchanged, and if they 

 were able to penetrate as freely as they did 

 before the addition of the salt the resistance 

 would not increase. It would, in fact, dimin- 

 ish on account of the increased conductivity 

 of the solution held in the cell walls, as is 

 clearly shown by experiments on dead tissue. 



It may be remarked incidentally that these 

 experiments effectually dispose of the possible 

 objection that the current passes between the 

 cells but not throug'h them. "Were this objec- 

 tion well founded the decrease in conductivity 

 could be explained only as the result of a 

 decrease in the size of the spaces between the 

 cells. This decrease could not be brought 

 about except by greatly reducing the thickness 

 of the cell walls. Both macroscopic and 

 microscopic measurements show most conclu- 

 sively that this does not occur. The contrary 

 effect would be produced by the addition of 

 salts in solid form, for they would tend to 

 produce plasmolysis and thereby to increase 

 the space between the cells. 



Results. — 1. It is possible to cause rapid 

 and very large changes in permeability by 

 means of electrolytes. 



2. These changes may consist in either an 

 increase or a decrease in permeability. 



3. Within wide limits these changes may be 

 completely reversible and entirely devoid of 

 injurious effects. 



w. j. v. osterhout 

 Labokatory of Plant Physiology, 

 Harvard University 



