240 Charles G. Rogers. 



ventricle of the heart of the turtle also does not exhibit rhythmic 

 contractions when it is removed from the body of the animal and 

 in this case also Lingle^ was able to show that the development of 

 rhythmic contractions depended upon the presence of NaCl. 

 Lingle also emphasized the necessity of a large supply of oxygen. 

 Overton^ working independently, and apparently not having seen 

 the reports of the work already mentioned found that in the 

 absence of NaCl, e. g., in a pure sugar solution muscle does not 

 respond to electrical stimuli. 



In the present work we are dealing with a heart of a single 

 chamber and one that continues to beat when it is removed from 

 the body of the animal. We can, hence, only raise the question 

 whether the heart of the crab will continue to beat for a long time 

 in the absence of NaCl while with this salt present it will continue 

 to beat for a much longer period. We may also raise the question 

 w^hether when the contractions of the heart have ceased in some 

 solution lacking in NaCl the addition of NaCl will cause rhythmic 

 contractions again to take place. 



In order to show whether the hearts of the crabs depend upon 

 the presence of NaCl to maintain rhythmic contractions they were 

 immersed in solutions lacking in this salt, but in which the osmotic 

 pressure was kept approximately at the normal height by means 

 of cane sugar. In some experiments no oiiygen was added to the 

 solution in others hydrogen-peroxide was added, following the 

 experiments of Lingle, and in others a current of gaseous oxygen 

 was allowed to bubble through the solution. As the result of 

 these experiments it was found that the fresh hearts of the crab 

 do not cease beating at once when placed in a pure sugar solution 

 and that the length of time during which such contractions may 

 continue is somewhat extended by the presence of oxygen. In 

 no case, however, did the heart in such a solution continue to 

 beat for more than one hour and in the very great majority of 

 cases not more than twenty minutes. There seemed to be no 

 great difference in the action of the hearts when the concentration 

 of the solutions varied between | m. and f m. In a sugar 

 solution the beats are at first not weakened but very soon they 

 lose in strength and soon cease altogether. When no oxygen is 



Lingle, D. American Journal of Physiology, vol. viii, p. 75 ff. 

 ^Overton. Pfluger^s Archiv., Bd. 92. 



