480 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



Cyon's immediate successors, Bowditch, Luciani, and Rossbach, 1 confirmed 

 his observations. None of these investigators, however, was concerned pri- 

 marily with the nutrition of the heart. The first systematic work on this sub- 

 ject was done, as has been said, by Merunowicz, who attempted to maintain 

 the beat of the heart with normal saline solution containing various quantities 

 of blood, with normal saline alone, with a watery solution of the ash of an 

 alcholic extract of serum, and with a normal saline solution containing a 

 minute amount of sodium carbonate. The direction taken by him has been 

 pursued to the present day, the chief objects of study being the importance to 

 the heart of sodium carbonate or other alkali, sodium and potassium chloride, 

 the salts of calcium, oxygen, proteids and some other organic bodies such as 

 dextrose, and, finally, of fluids possessing the physical characteristics of the 

 blood. The outcome of this work we must now consider. 



The value of an alkaline reaction has been generally recognized. Sodium 

 carbonate is the alkali commonly preferred. The favorable influence of this 

 salt probably does not depend on any specific action, but simply upon its 

 alkalinity. 2 The alkali promotes the beat of the heart by neutralizing the 

 carbon dioxide and other acids formed in the metabolism of the contracting 

 muscle; this, however, may not be its only use. 



Certain of the salts normally present in the blood are necessary to main- 

 tain the beat of the heart. Sodium chloride is one of these. The solution 

 employed should contain a " physiological quantity." Such a solution is said 

 to be " isotonic." The amount required to make a sodium chloride solution 

 "normal" or "isotonic" for the frog is 0.6 per cent., for the mammal nearly 

 1 per cent. Enough of a calcium salt to prevent the washing out of lime 

 from the tissues is also essential for prolonged maintenance of the contractions. 3 

 A heart fed with normal saline solution is before long brought to a stand ; the 

 addition of a calcium salt to the solution postpones the arrest. The character 

 of the contraction, however, is altered by the calcium, the relaxation of the 

 ventricle being sometimes so much delayed that the next contraction takes 

 place before the relaxation from the previous contraction has commenced, the 

 ventricle falling thereby into a state of persistent or " tonic " contraction. The 

 addition of a potassium salt restores the normal character of the contraction, 4 

 calcium and potassium having an antagonistic action on the heart. The 

 importance of calcium to the heart is said to be demonstrated by the disap- 

 pearance of the spontaneous contractions of the heart which follows the pre- 

 cipitation of the calcium in the circulating fluid by the addition to it of an 

 equivalent quantity of a soluble oxalate, and by the return of spontaneous 

 contractions which is seen when the calcium is restored to the solution. 5 



The antagonistic action of calcium and the oxalates was first pointed out 

 by Cyon. 6 



1 Bowditch, 1872, p. 139; Luciani, 1873, p. 113; Rossbach, 1875, p. 90. 



2 Gaule, 1878, p. 294. 3 Ringer, 1885, p. 252. 



* Ringer, 1885, p. 247. 5 Ringer, 1885, p. 85; compare Howell, 1894, p. 478. 



6 Cyon, 1867, p. 203 ; see also Sokoloff, 1881, p. 8 ; Ringer, 1885, p. 86 ; Howell and Cooke, 

 1893, p. 220 ; Howell, 1894, p. 478. 



