THti CIRCULATION. 



275 



Then Ringer, in 1883, discovered that his solution, known by his 

 name, was capable of keeping the heart beating for hours. It consists 

 of sodium chloride solution, 0.7 per cent.; calcium chloride, 0.00026 

 per cent. ; solution of potassium chloride, 0.035 per cent. Oxygen is 

 very beneficial when added to the Ringer solution. 



Blood-corpuscles are not necessary for the contraction of the 

 mammalian heart. Carbonic acid reduces the contractile force and 

 rate of the heart-beat. 



Locke found that, by add fag a 1-per-cent. solution of dextrose 

 to Ringer's fluid provided with oxygen, it kept the mammalian heart 



Fig. 88. To Illustrate the Varying Excitability of the Frog's Heart 

 at Different Periods of Systole and Diastole. (WALLER.) 



The excitability is lowest during the first half of systole, greatest during 

 the second half of diastole. 



beating for hours. Hering, by an artificial circulation, restored the 

 heart-beat for several hours in a man who had been dead eleven hours. 

 Kuliabko, by Ringer's solution, restored the heart in animals who had 

 been dead four days. 



D'Halluin obtained in the heart of infants, by means of Locke's 

 solution, feeble rhythmic contractions of the ventricles 24 hours after 

 death. He also observed energetic contractions of the. auricles 42 

 hours after the infant's death. In a dead monkey, Hering, with 

 artificial circulation, found the vagus retained its inhibitory power 

 for six hours after death, whilst the accelerator was active over fifty- 

 three hours after death. 



Porter has found that the mammalian heart beats best when sup- 



