CIRCULATION. 191 



heart needs is supplied by increasing the tension of the gas in the plasma. 

 Haldane kept his animals alive in oxygen at a pressure of two atmospheres 

 after the oxygen-carrying function of the red corpuscles had been destroyed 

 with carbon monoxide. The experiment has been repeated with the extir- 

 pated mammalian heart by Porter, 1 Locke, 2 and Rusch. 3 Serum and even 

 saline solutions will serve, if the oxygen tension is high or if the volume of 

 oxygen reaching the tissues is increased simply by causing the nutrient liquid 

 to circulate more rapidly. 



Carbon dioxide 4 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. Recent observers have shown the incorrectness of 

 this claim. A mixture of the inorganic salts, sodium chloride, potassium 

 chloride, and calcium chloride, alone suffices. Locke 5 found that tin- addi- 

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

 heart working under a load of 3.5 centigrams, and under an " after-load " of 3 

 centigrams in spontaneous activity for more than twenty-four hours. The 

 sustaining action which dextrose appears to exercise is shared, according to him, 

 by various other organic substances. 



Physical Characteristics. — Heffter and Albanese, 6 having observed that 

 the addition of gum-arabic to the circulating fluid was of advantage, declared 

 that the nutrient solutions should possess the viscosity of the blood. The 

 favorable action of gum-arabic may, however, more probably be ascribed to the 

 compounds which it contains rather than to its physical properties. 7 



Mammalian Heart. — The success attained within the past two years in the 

 isolation of the mammalian heart opens up an hitherto unexplored region in 

 which systematic investigation will surely bring to light facts of wide interest 

 anil value. At present, however, little is known as to the constituents of the 

 blood which are essential to the life of the mammalian heart. An abundant 

 supply of oxygen is certainly highly important. 8 



1 Porter: American Journal of Physiology, 1K9S, i. p. 511. 



2 Locke: Centralblatt fur Physiologic 1808, xii. p. 5(58. 



5 Rusch : Archil' filr di<> gesammte Physiologie, 189S, lxxiii. p. 535. 



*Langendorff: Archivfur Physiologie, 1893, p. 417 j [de: Ibid., p. 492; Oehrwall: Skcmdin- 

 avisches Archivfur Physiologie, 1897, vii. p. 222. 



5 Locke: Journal of Physiology, 1895, xviii. p. 332. 



6 Albanese: Archivfur experimenteUe Pathologie unci Pharmakologie, 1893, \\\ii. p. 311; 

 Archives ilaliennes de Biologic, 1896, xxv. p. 308. 



7 Howell and Cooke: Journal of Physiology, 1893, xiv. p. 216. 



8 Literature is given by Magrath and Kennedy : Journal of Experimental Medicine, 1897, ii. 

 p. 13; and I led bom : Skandinavisches Archivfur Physiologie, 1898, viii. p. H7. See also tiering: 

 Archivfur die gesammte Physiologie, 1 s '. ,s , lxxii. p. 163 ; Bock: Archiv fur experimenteUe Path- 

 ologie und Pharmakologie, 1898, xli. p. 158 ; and Cleghorn : American Journal of Physiology, 1899, 

 ii. p. 273. 



