248 Charles G. Rogers. 



chloride needed to make a well balanced solution was less than 

 when the full amount (2.2 cc.) was used. 



When we employ a solution containing sodium, potassium and 

 magnesium in the proportions in which they exist in the sea water 

 and add a sufficient amount of calcium to neutralize the poisonous 

 effects of these salts we find that the beats exhibit a remarkable 

 uniformity of contraction which is long continued. When more 

 than 3.0 cc. of calcium chloride is added to 100 of sodium chloride 

 we find that the amplitude of the contractions is lessened, but the 

 beats are slower, more nearly the normal rate, and continue 

 through a longer period than in any of the solutions containing 

 less of the calcium. 



L. The Effect of Sea ffater as a Nutrient Solution. 



In Van't Hoff's solution of y^ m. concentration we have been 

 using the various salts in the proportions in which they exist in 

 the sea water, as it is found in the bay. If the concentration of 

 the various salts in the blood of the animal is the same as in the 

 sea water by which they are normally surrounded we should find 

 that when a heart is mimersed in sea water it would beat as well 

 as in our artificial solution. The water used in this series of 

 experiments was taken from the open ocean and hence of higher 

 concentration than the water of the bay. In order to reduce the 

 osmotic pressure of this water to about that of the water of the 

 bay it was diluted with distilled w^ater. It was found that the 

 most satisfactory results were obtained when 85 cc. of sea water 

 and 15 cc. of distilled water were used. But even this dilution 

 did not give a solution which was so favorable for the action of the 

 hearts as was the artificial solution. In the diluted sea water all 

 the hearts behaved like hearts immersed in solutions containing 

 too much NaCl or too little CaCU. As we have already shown 

 the sea water contains about one part of calcium chloride for 

 every one hundred of sodium chloride. But the artificial solution 

 which had been found most favorable for the long continued 

 heart action contained at least three parts of calcium chloride to 

 every one hundred of sodium chloride. If now we add to the 

 diluted sea water small amounts of calcium chloride so as to raise 

 the proportion of this salt to about that which we have in our 



