9 6 



Scientific Proceedings (105). 



following experimental conditions, the general order being varied 

 only to suit particular occasions: 



(1) during normal cardiac action under morphine and chlore- 



tone anesthesia; 



(2) during stimulation of stellate ganglion or accelerator 



nerves ; 



(3) following section of both vagi ; 



(4) during stimulation of stellate ganglion with vagi severed 



and 



(5) during combined stimulation of vagus and accelerator 



mechanisms. 



Using these results, we have found it possible, on the basis of 

 the duration of systole and diastole of a long vagus beat to con- 

 struct for each animal a theoretical volume curve and to calculate 

 from this the theoretical relations of systole and diastole at all 

 heart cycles in that animal provided the "law of uniformity" 

 applies. With these "theoretical systoles" in different cycle 

 lengths we compared (best in the form of a plot) the actual systole 

 lengths of different cycles during the above mentioned experi- 

 mental activities. 



Results. — We find as follows: 



1. The lengths of normal systoles agree very closely with those 

 of theoretical systoles. 



2. Vagus section, causing cardiac acceleration, decreases the 

 length of systole slightly but in accordance with its theoretical 

 duration. 



3. Vagus stimulation, causing only a moderate slowing, in- 

 creases the length of the actual systole, practically in accordance 

 with the theoretical values at different rates. 



4. Accelerator stimulation shortens the length of actual systole 

 far more than that of the corresponding theoretical systole, in- 

 dicating that in some way the accelerator nerves are capable of 

 shortening systole more than can be accounted for by the mechanical 

 operation of the law of " Uniformity of Behavior. 11 



We append a few data of a single experiment typical of many 

 others to support these conclusions. 



