74 ON SPHYGMOGRAPHY. 
radial rise (the second cardio-arterial interval) varies but little with 
different pulse-rates, while that between the primary radial rise and 
the closure of the aortic valve (the conjugate cardio-arterial interval) 
does so much more rapidly, both being longer in slow pulses. This 
also greatly influences the appearance of the pulse-trace, for, as pre- 
viously shown, the small rise and fall at the end of the sphygmo- 
systole results from the shock of closure of the aortic valve, and as 
this occurs in slow pulses an appreciable time after the primary rise 
has reached its maximum, it is clearly seen as a separate element of 
the curve. But in quick pulses the second cardio-arterial interval is 
nearly as long as in the slow ones, while the conjugate cardio-arterial 
interval is much shorter, consequently the shock-rise and fall follow- 
ing the aortic valve closure is thrown back, as it may be termed, on 
the primary rise, and, being blended with it, is not separately distin- 
guishable. This is the cause of the simplicity in the sphygmosystole 
of quick pulses. 
