ELECTROLYTES AND THEIR ACTION 



207 



solution, whose composition is known and can be modified at will. The blood 

 plasma of the same species of animal has been supposed indispensable for the growth 

 of excised tissues in the work of Ross Harrison, and others. (But see Thomson, 

 1914.) But if an efficient substitute can be found for other purposes, the advantages 

 are obvious. 



It might be supposed that a solution of any substance, so long as it is not 

 actually toxic, would suffice, provided that the cell membrane is impermeable to 

 the solute and it is present in the correct concentration. Sodium chloride, as one 

 of the salts present in all animal fluids, was selected at an early date and was 

 found to serve well for the histological examination of fresh tissues or for the 

 dilution of blood without causing changes in volume in the corpuscles. But when 

 used by Ringer (1880-82, 1882-83, 1 and 2) for continuous perfusion of the heart 

 of the frog, it was found unable to maintain the normal beat. The work of 

 Ringer on this question is fundamental and enabled a satisfactory perfusion fluid 

 to be made. Although this solution is used everywhere and known as " Ringer's 

 Solution," its origin is apt to be forgotten, so that it is necessary to give a brief 

 account of the re- 



Ftg.l, B. 



A7L/ULA 



FigJ, D. 



FIG. 60. 



THE ACTION ON THE FROG'S HEART OF A SOLUTION 

 CONTAINING SODIUM CHLORIDE ONLY. 



1, B, Tracing obtained eight minutes after replacing blood by pure sodium 



chloride, 075 per cent. 

 1, C, Six minutes later. 

 1, />, After another four minutes' action. 



searches which led 

 to its composition 

 being established. 

 A portrait of Sydney 

 Ringer himself will 

 be found in Fig. 59. 

 When the heart 

 was perfused with a 

 solution of sodium 

 chloride in distilled 

 water, isotonic with 

 the blood, that is, 

 O g 75 per cent., the 

 beats gradually dimi- 

 nished in extent and ultimately ceased (1882-83, 1, p. 31), as shown in Fig. 60. 

 The excitability to electrical stimuli also disappeared. 



We may note here that subsequent work has shown that this action of pure sodium 

 chloride is not only due to the want of some essential salt, but also to a toxic action of 

 the Na - ions, similar to, but less marked than that of potassium ions to be described 

 presently. Clark (1913, 2, p. 77) finds indeed that the ordinary Ringer solution is improved 

 when a part of the sodium chloride is replaced by isotonic cane-sugar, and Abel (1914), 

 to avoid oedema in his " vivi-diffusion" experiments, found it advisable to reduce the 

 sodium chloride to 0'6 per cent. 



I Fcq.l.E 



(Ringer, 1882-83, 1, p. 33.) 



FIG. 61. The effect of adding 5 c.c. of 0"25 per cent, calcium chloride solution to 100 c.c. of 

 the pure sodium chloride solution. The heart-beats, which had ceased under the pure 

 sodium chloride, became spontaneous after one artificial stimulus, but the diastole was 

 prolonged so that the beats fused. (Ringer, 1882-83, 1, p. 33.) 



To proceed with the experiments of Ringer, it was found that, if calcium 

 chloride were added to the pure sodium chloride solution when the heart had 

 ceased to beat, the excitability to stimuli returned and was scon followed by 

 spontaneous beats, but that the relaxation was imperfect and delayed, so that 

 there was a tendency to a tonic, systolic state (Fig. 61). 



This condition is seen, although less markedly, in the figures of Plate 2 of the first paper 

 (1880-82), where saline solutions made with tap water, containing calcium, were used. 



It was next discovered (1882-83, 1, p. 35) that a trace of a potassium salt (1 

 c.c. of 1 per cent. KC1 to 100 c.c. of the solution of sodium chloride in tap water) 

 abolished this tonic action of calcium, without depriving it of the power of neutral- 



