244 Charles G. Rogers. 



contractions become more regular in time and amplitude and 

 last for a longer tune than when the heart is immersed in pure 

 NaCl alone. This may be due to one of two causes: either the 

 calcium is necessary in itself for the long continuance of the con- 

 tractions or it may be necessary to counteract the poisonous effects 

 of the NaCl. A record of a single experiment will indicate the 

 trend of results. The heart was immersed in a solution contain- 

 ing 100 cc. yV m. NaCl plus 3 cc. Vi- m. CaCL. These propor- 

 tions are the same as regards these two salts as were used later 

 in the optimum solution. In this solution the beats continued 

 for a period of more than two hours, probably for more than three 

 but owing to a mechanical defect the heart tracing is imperfect. 

 The record indicates however the main fact which is to be demon- 

 strated — that the addition of calcium chloride to a solution con- 

 taining sodium chloride renders that solution less harmful. In 

 no case did a heart continue to beat for so long a time in a pure 

 sodium chloride solution as in the experiment just mentioned. 



Whether any other salt may be found to fully take the place 

 of the calcium chloride in the solutions I am at present unable 

 •to say. Up to this time none has been found. 



H. Will NaCl Restore to Activity Hearts Which Have Ceased 

 Beatincr in Other Solutions? 



A heart immersed in a solution containing 100 cc. | m. cane 

 sugar and .5 cc. fV m. CaClj beat regularly for a period of fifteen 

 minutes, the beats becoming gradually retarded during that time. 

 During the next fifteen minutes only one contraction was recorded. 

 At the end of half an hour the heart was immersed in a y% m. 

 NaCl solution and rhythmic contractions began at once and con- 

 tinued for about an hour and a half, becoming more rapid and of 

 less amplitude toward the end of the series. It ought to be stated 

 that in this case the response was unusually prompt and long 

 continued. 



In another case an immersion for 50 minutes in a solution con- 

 taining 100 cc. I m. cane sugar, .5 , cc. fV m. CaClj -75 cc. 

 f m. MgSO^, and a slight amount of hydrogen peroxide sufficed 

 to bring the heart to a standstill. The heart was then immersed 

 in a solution of yV m. NaCl and after a latent period of twelve 



