54 EDWARD C. DAY 



tion of the beat which manifests itself near the middle of a series. 

 These changes go hand in hand with one another, and when any 

 one of them is patently present, the others are present too. Ex- 

 ceptions occur in cases where the circulation has been interfered 

 with through operation on the ganglion. 



The effects of stimulation abate and disappear in the course 

 of an hour or a day, depending on the character of the operation, 

 and the beat of the heart again exhibits its original normal 

 characteristics. 



DISCUSSION OF DATA 



It is important to remember before entering upon a discussion 

 of the foregoing results that there was at least one feature of the 

 heart-beat which the method adopted for experimentation did 

 not permit an analysis of, namely, the vigor of the contractions. 



The features which were capable of being analyzed, however, 

 were the number of beats per series, the frequency of beat, and 

 the length of the interval between alternating series. Since the 

 problem was to ascertain what control the ganglion exerted over 

 the heart, each of these features of the beat may now be considered 

 for the . evidence that it contributes toward the solution of that 

 problem. 



One must first determine which of these features is the most 

 delicate indicator of the changes in beat due to stimula- 

 tion. Even though the features mentioned are closely correlated 

 as expressions of changes in heart activity, it may well be inquired 

 whether they are all of equal value or not as indicators of the 

 quantitative aspect of these changes. The feature of the length 

 of the interserial pauses is of minor consequence in comparison 

 with the other two features and will be omitted from the dis- 

 cussion. The question therefore resolves itself into one of 

 whether the alteration of the rate of beat or alteration of the 

 number of beats in a series is the best indicator of the functional 

 state of the heart, for to the most delicate indicator one must turn 

 for the nicest evidence of any ganglionic control that may exist. 



A comparison of graphs 18^ and 18^ furnishes an answer to this 

 question. 



