CIRCULATION. 481 



According to Ringer, 1 the substances thus far mentioned are effective in the 

 following order : normal saline is the least effective ; next is saline containing 

 sodium bicarbonate; then saline containing tricalcium phosphate; and best of 

 all, saline containing tricalcium phosphate together with potassium chloride. 

 He recommends the following mixture : Sodium chloride solution 0.6 per 

 cent., saturated with tribasic calcium phosphate, 100 cubic centimeters; solu- 

 tion potassium chloride 1 per cent., or acid potassium phosphate (HK 2 PO 4 ) 

 1 per cent., 2 cubic centimeters. 2 



There has been considerable dispute over the part played by oxygen in 

 the beat of the frog's heart. McGuire 3 and Klug* were of opinion that 

 the beat is largely independent of the amount of oxygen in the circulating 

 fluid. Yeo 5 concluded that the contracting heart uses more oxygen than 

 the resting heart, and that the consumption of oxygen increases with the work 

 done. Kronecker and Handler, 6 on the contrary, believe that the oxygen con- 

 sumption is increased by an increase in the rate of beat, but is independent of 

 the work done. 7 More recent observers are united on the necessity of oxygen 

 to the working heart. Oehrwall's studies in this field are especially interesting. 

 He finds that a volume of blood sufficient to fill the frog's ventricle will main- 

 tain contractions for hours provided the heart is surrounded by an atmosphere of 

 oxygen. The heart is brought to a stand by lack of oxygen and may be made 

 to beat again, even after an arrest of twenty minutes, by giving it a fresh sup- 

 ply. The heart fails in oxygen-hunger probably because the chemical process 

 by which the stimulus to contraction is called forth no longer takes place, and 

 not because of a failure in contractility, for even after long inaction a gentle 

 touch on the pericardium will cause a vigorous contraction. 



Carbon dioxide* is injurious to the heart when present in the circulating 

 fluid in considerable quantities. The force of the contraction is reduced before 

 the rate of beat. The heart poisoned with carbon dioxide often falls into 

 irregular contractions, exhibiting at times "grouping" and the "staircase" 

 phenomenon, a series of beats regularly increasing in strength. 



Organic Substances. An unsuccessful effort has been made to prove that 

 only solutions containing proteids, for example blood-serum, chyle, and milk, 

 can keep the heart active. 9 Recent observers have shown the incorrectness of 

 this claim. The inorganic salts of serum alone suffice. 10 Locke 11 found that the 

 addition of 0.1 per cent, of dextrose to a suitable inorganic solution kept a frog's 



1 Ringer, 1886, p. 294. 



2 Ringer, 1893, p. 128 ; for the action of rubidium, strontium, and caesium on the heart see 

 Ringer, 1884, p. 370. 



3 McGuire, 1878, p. 321. 4 Klug, 1879, p. 478. 



5 Yeo, 1886, p. 119. Handler, 1890, p. 253. 



7 Hetfler, 1892, p. 52; Albanese, 1893, p. 311 ; Oehrwall, 1893, pp. 42, 44. 



8 See Kronecker and Stirling, 1874, p. 200; McGuire, 1878, p. 322; Klug, 1879, p. 478; 

 Saltet, 1882, p. 567; Kronecker and Mays, 1883, p. 263; Langendorff, 1893, p. 417; Ide, 1893, 

 p. 492 ; Ringer, 1893, p. 129. 



9 Martius and Kronecker, 1882, p. 562; v. Ott, 1883, p. 26; Popoff, 1889, p. 438; Brinck, 

 1889, p. 472; White, 1896, p. 344; compare Stienon, 1878, p. 277, and Ringer, 1886, p. 363. 



10 Merunowicz, 1876, p. 166; Howell and Cooke, 1893, p. 204. " Locke, 1895, p. 333. 

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