56 EDWARD C. DAY 



back to the normal 25 of graph 15^ In graph 16^ is also seen 

 the restoration to normal, 21 beats, after the high increase to 

 85 beats exhibited by the preceding graph as a result of 

 removing the ganglion. The dorsad series shows a normal of 

 25 in graph 15^ and a recovery to 24 and 28 beats, respectively, 

 in graphs 15'* and 15^. The dorsad series of 16^ b also shows a 

 normal of 25 beats, but after recovery from the effects of the 

 ganglion the number of beats falls short of the normal 21 and 22 

 beats in 16^ a and 16*^ h, respectively, and 19 beats in 16^ Thus, 

 except for the 28 beats in graph 15"^, the 24, 21, 22, and 19 beats 

 are less than the normal 25 which was selected as the shortest 

 normal dorsad series for comparison. 



These instances substantiate the statement that the number 

 of beats returns to normal or approximately to normal the day 

 following extirpation of the ganglion. The ventrad series approx- 

 imates the normal more closely than the dorsad series does in 

 this respect. 



It must here be remarked that the normal number of beats 

 is itself by no means constant: the number ranges for animal 

 no. 15 from 25 to 30 for the ventrad series and from 21 to 25 for 

 the dorsad: for animal no. 16 it ranges from 21 to 38 for the 

 ventrad and from 25 to 33 for the dorsad. These fluctuations of 

 the normal number of beats may be attributed to minor stimu- 

 lations of some sort or to variations in the general metabolism. 

 It is to be expected, therefore, that similar fluctuations would 

 occur after recovery. 



Now, in the cases above mentioned where the recovered condi- 

 tion was 19, 21, 22, and 24 beats instead of the normal number 25, 

 could this shortage be interpreted as a result of the removal of 

 the ganglion and with it a removal of a tonic influence which, 

 under normal conditions, enables the heart to relax to a state of 

 moderate activity? 



The answer to this question hinges upon whether 25 in the 

 graphs for animal no 16 is the lowest number of beats possible 

 for a normal dorsad series. While it is the lowest on record for 

 this animal, it is not the lowest for animal no. 15, where the 

 normal is as low as 21 beats to a series. This is the case for 



