THE PERMEABILITY OF MEMBRANES 125 



to 24 volumes of the 0*5 molar sodium chloride prevents the contraction, and also 

 the loss of pigment. 



Fluri (1909), again, found that three days' immersion in O01 per cent, solution 

 of aluminium sulphate makes Spirogyra permeable for most salts as well as glucose, 

 and that the effect can be removed, so that the cells become normal again, by 

 return to pure water. 



Newton Harvey (1911, p. 546) states that sodium salts makes the membrane of 

 Spirogyra and of Elodea permeable to sodium hydroxide, to which, as we have 

 seen in Warburg's experiments, it is normally impermeable. 



Another fact which may be mentioned is that M'Clendon (1912, i. p. 296) 

 found that the eggs of Fundulus lose magnesium in pure sodium chloride solutions. 



Siebeck (1913) showed that frog's muscle, if immersed in isotonic potassium 

 chloride, swells, showing that the action of the potassium salt is to diminish or 

 abolish the impermeability to potassium, which the muscle normally possesses in 

 the presence of sodium and calcium. 



Wachter (1905) showed that the passage of sugars from the cells of the onion 

 was inhibited by the presence of potassium nitrate. 



Osterhout (1910) shows that the root hairs of Dianthus barbatus, grown in 

 distilled water, contain no crystals of calcium oxalate. If the water be changed 

 for a solution containing calcium salts, the crystals soon make their appearance. 

 They may easily be detected by observation between crossed Nicols in the 

 polarising microscope. 



Gerard (1912) found that, on feeding animals with excess of potassium salts, 

 the blood maintains its constant composition, while the cells of the tissues lose sodium. 



-These various facts are given in order that the reader may grasp the fact that 

 the cell membrane is capable of changes in its permeability. 



Instructive experiments may easily be made with slices of the root of the red beet. It will 

 be found that the pigment does not leave the cells when immersed in tap water. (It is well 

 to rinse the slices previously for a minute or two in tap water in order to remove the contents 

 of the cells which have been injured in the process of cutting the slices.) If, on the contrary, 

 they be placed in pure sodium chloride of O31 molar ( = 1 '82 per cent. ) strength, which is about 

 isotonic with the cell contents, the pigment will gradually come out. Addition of 0'17 per 

 cent, of calcium chloride to the pure sodium salt prevents this effect. It is convenient to take 

 3 '64 per cent, solution of sodium chloride and to dilute it with an equal volume of water or of 

 0'34 per cent, calcium chloride as the case may be. Many other experiments on permeability 

 may be made with the red beet ; chloroform, bile salts, soap, warming to 50, all cause loss of 

 pigment, but in most cases the cells are killed. If it be desired to make quantitative experi- 

 ments, the cane-sugar, which escapes along with the pigment, may be estimated by an appro- 

 priate method. In this case, the slices to be compared must, of course, be of equal dimensions. 



It seems evident from the various instances quoted that calcium must produce 

 some change in the properties of the cell membrane and of such a kind as to 

 make it less permeable, and that sodium has the opposite effect. Osterhout 

 (1912, ii. p. 114), in fact, states that visible effects are to be detected under 

 the action of calcium. This antagonistic nature of calcium and other ions is 

 of much importance and will require treatment in Chapter VII. 



A matter of some practical importance is the action of cane-sugar on the cell membrane. 

 For the investigation of the effect of various salts, it is necessary to have cells suspended in 

 an isotonic solution of a non-electrolyte. Now, while cane-sugar appears to be the least 

 injurious, and at the same time convenient, especially if not in contact with the cells for too 

 long a time, there are several facts which show that it increases the permeability of the 

 membrane if the contact is prolonged. Bethe (1908, p. 560) found that the contractions of 

 meduste were slowed if one part of isotonic cane-sugar was added to nineteen of sea water. 

 Magnus (1904, p. 131) found that the movements of the excised intestine in Ringer's solution 

 were weakened by the addition of cane-sugar above 0'02 per cent. Kiister (1909) noticed that, 

 on plasmolysis of the cells of the onion in hypertonic cane-sugar, the protoplasm broke up 

 into separate clumps and that, on placing in water, these clumps did not fuse together again, 

 while the surface membrane seemed to be fixed or coagulated. According to Bang (1909, p. 263) 

 blood corpuscles give up salts to isotonic cane-sugar, after prolonged contact with it. Muscle, 

 on the contrary, is relatively resistant to the action of cane-sugar, giving up in twenty-two 

 hours to repeated changes scarcely more salts than those contained in the spaces between the 

 cells (Fahr, 1909). Overton (1902, ii. p. 349) showed that a muscle, which had lost its 

 excitability by lying in cane-sugar solution, owing to removal of sodium salts from between 

 the cells, quickly regains its excitability when placed in sodium chloride, so that no permanent 

 injury is inflicted. 



