242 Charles G. Rogers. 



C. The Effect of the Addition of Calciinu Chloride to a Sugar 



Solution. 



Small amounts (.5 cc. to 3.00 cc.) of a yV m., i| m., or y^ m. 

 calcium chloride solution added to 100 cc. of f m. cane sugar 

 solution in which a heart may be immersed modify very 

 materially the action of the heart. The beats become more uni- 

 form in quality and occur at more regular intervals than when 

 the heart is immersed in a pure sugar solution. At the same time 

 it seems probable that the length of time during which a heart 

 will continue to beat in such a solution is somewhat lengthened. 

 It is difficult to make a definite statement with regard to this last 

 point, however, on account of large individual variations in the 

 actions of different hearts. A very characteristic effect of the 

 addition of calcium is seen in the gradual retardation of the beats, 

 the contractions coming at regularly increasing intervals until 

 they stop altogether. In some cases instead of this retardation 

 we may find a progressive decrease in the amplitude of the beats 

 while the rate remains fairly constant. 



If larger amounts of calcium chloride be added to the solution 

 there is a very evident poisonous effect exerted upon the heart 

 by the salt and in a pure calcium chloride solution the 

 effect becomes very marked, the hearts continuing to beat for 

 only a very few minutes even though a large supply of oxygen be 

 available. 



D. The Effect of the Addition of Potassium Chloride to a Sugar 



Solution. 



The addition of small amounts of a f\ m. solution of potas- 

 sium chloride to a solution of cane sugar in which hearts are 

 immersed brings about a marked increase in the amplitude of 

 the contractions. At first the beats occur much more rapidly 

 than in the pure sugar solution and these contractions are very 

 powerful. After the first series of very strong contractions, which 

 lasts for only a few minutes (eight or nine at the most) comes a 

 series of contractions of nearly normal amplitude but somewhat 

 more rapid than usual. Following these but coming more slowly 

 is another series of exceedingly strong contractions which is 

 finally followed by a rapid decline in the ampJitude of the beats. 



