226 THE CONTRACTION OF CARDIAC MUSCLE. 



last for thirty hours. According to Kronecker, this ought to be proof that 

 Ringer's fluid contains serum albumin, especially in view of the statement of 

 Martius, that from one and a half to two hours is sufficient to thoroughly 

 exhaust the heart. 



The great point of Ringer's work was the establishment of the importance 

 of calcium salts for the contraction of the muscular tissue, and the recognition 

 that a definite supply of sodium and potassium must also be contained in the 

 circulating fluid ; in fact, that the ideal circulating fluid must contain a variety 

 of salts in right proportion. It does not at all follow that the fluid recom- 

 mended by Ringer, although unquestionably effective, yet contains the salts 

 in the absolutely best proportion. In fact, Howell and Cooke x removed the 

 proteids from serum, and then found that the remaining solution of the salts in 

 the serum was more efficacious than Ringer's solution. On the other hand, 

 the proteids of the serum, after removal of the salts, were ineffective. 



In view of this, the conclusions of White,' 2 working with Kronecker, 

 Avho, finding that serum would restore a heart after it had ceased contracting 

 with perfusions of Ringer's fluid, supposed this action to be due to the proteid 

 of the serum, are evidently not justified. 



Another series of experiments by Hetfter, 3 Albanese, 4 and Ohm, 5 have led 

 them to the conclusion, that a good circulating fluid must not only contain the 

 right proportion of salts, but also must possess the same physical properties as 

 blood with respect to viscosity, osmotic coefficient, etc. For this purpose 

 they added gum arabic to Martius' solution, and assert that such a solution is 

 as efficacious as serum in keeping up the contractions of the heart. 



Howell and Cooke/ 1 and later, Locke, 7 have pointed out that gum arabic is 

 a combination of arabin with calcium and potassium salts, so that, in this case 

 also, the salts, rather than the physical character of the fluid, are in all 

 probability the important factors. 



To sum up the evidence, the artificial circulating fluid which is most 

 efficient in keeping the heart beating must contain the right proportion of 

 sodium chloride, of a calcium salt, and of a potassium salt. The experiments 

 so far do not prove that any special proteid is necessary in this mixture, and 

 give no definite answer to the question whether the heart contracts at the 

 expense of its own substance, or contracts only as long as a suitable proteid 

 diet (according to Kronecker, serum albumin) is constantly supplied to it. 

 Considering, however, the length of time it can be washed out with a fluid 

 like Ringer's, and yet continue beating, it seems very unlikely that any serum 

 albumin or other proteid can be still left in the capillary spaces, and therefore 

 the probability is that the heart can continue to contract at the expense of its 

 own substance upon an absolutely inorganic supply. 



Luciani's groups. — The second question raised by Luciani's experiments 

 is the question of the meaning of the secondary or periodic rhythm, observed 

 by him when serum was sent through the ventricle. Subsequent experiments, 

 especially by Langendorft'. 8 have endeavoured to determine the conditions 

 necessary for the appearance of such groups as Luciani described ; and the 

 general opinion of physiologists at the present time is that the grouping does 

 not appear unless a condition of asphyxia has been induced in the cardiac 

 tissue. According to Langendortf, it is possible to obtain this periodic 

 rhythmical contraction, not only in the ventricle, but also in the whole heart, 

 by keeping a curarised frog under water for a sufficient length of time, so that, 

 according to his observations, as well as those of Luciani and Rossbach on the 

 isolated ventricle, this method of beating in groups, instead of with a normal 



1 Op. cit. - Jo urn. Physiol., Cambridge and London, 1896, vol. xix. p. 344. 



3 Arch. f. cxpcr. Path. u. Pharmakol., Leipzig, 1891, Bd. xxix. S. 41. 



4 Ibid., 1893, Bd. xxxii. S. 297. B Ibid., 1894, Bd. xxxiv. S. 29. 



6 Op. cit., p. 216. 



7 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 332. 8 Op. cit. 



