THE ORIGIN OF THE HEART BEAT 337 



NaCl 0.65 percent. 



KCl 0.03 per cent. 



CaCl2 . 25 per cent. 



Even the mammalian heart may be kept beating for many hours by perfusing it 

 with this solution. The best results, however, are obtained if the solution is first 

 charged with oxygen before it is allowed to enter the coronary vessels. Locke'- 

 recommends a perfusion fluid containing 0.9 per cent, of NaCl, 0.024 per cent, of 

 CaCla, 0.042 per cent: of KCl, 0.01-0.03 per cent, of NaHCOs, and 0.1 per cent, 

 of dextrose. This fluid should be warmed to 35° C. and charged with oxygen. 

 The dextrose is said to prolong the -period of contraction and to renew the vigor 

 of those hearts which have ceased to beat while still being perfused with the pure 

 solutions of the aforesaid salts. With the aid of this solution, Locke and Rosen- 

 heim^ have succeeded in reviving the isolated heart of a rabbit on four consecutive 

 days, keeping it in activity each* time for several hours. In a similar way, Kuli- 

 abko^ has been able to incite contractions in a rabbit's heart three and four days 

 after its removal from the body. Hering^ revived the heart of a monkey 28 and 54 

 hours after the death of the animal. Very similar results have been obtained with 

 human hearts. 



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Fig. 175. — Tracing op Contracti6ns of a Frog's Heart, Showing Effect of 

 Adding a Trace of CaCl2 to the NaCl Solution Used Previously for Perfusion. 

 (Ringer.) 



It is evident, therefore, that these salts give rise to an osmotic environment 

 which is well adapted for cardiac muscle. The action possessed by each salt 

 individually, has been brought out by the work of Kronecker,^ Howell,^ Loeb^ 

 and others. By making use of strips of the ventricle of the frog or turtle, it has 

 been shown that the preceding solution is capable of inciting a rhythmic activity 

 which may last for niany hours. The same end may be attained by immersing 

 these preparations in a 0.7 per cent, solution of sodium chlorid. The contractions 

 appear as a rule after a latent period lasting from 5-20 minutes, and attain a 

 maximal height and length in the course of a few minutes. It is to be noted, 

 however, that while this salt excites the contractions, it does not maintain the 

 beats for any considerable length of time. The muscle presently ceases its activity 

 in the state of relaxation. " The sodium salt, therefore, favors contractility and 

 irritability. If a small quantity of a solution of calcium chlorid is now added 

 to the former in slight excess of the sodium, the strip of muscle again begins to 

 contract. Later on, however, its contractions become more and more forced until 

 it remains in a condition of tonic shortening, known as calcium rigor. By the 

 addition of a small amount of potassium chlorid, this strip may then be activated 

 again. An excess of potassium, however, leads to a slowing and a possible cessa- 

 tion of the contractions. The muscle is then retained in a state of extreme 

 relaxation. 



1 Jour, of Physiol., xviii, 1895, 332; also see: Mines, Ibid., xxxvii, 1908, 408, 

 and xlii, 1911, 251. 



2 Ibid., xxxvi, 1907, 205. 



3 Pfluger's Archiv, xcvii, 1903, 539. 



4 ibid.^ cxvi, 1907, 143. 



^ Festschr. fur C. Ludwig, 1874. 

 6 Am. Jour, of Physiol., ii, 1898, 47. 

 "^ Festschr. fiir Fick, 1899. 



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