170 



THE PULSE. 



[BOOK i. 



wave near the block, but becomes more and more separated 

 from it, the farther back we trace it. Now this is not the case 

 with the dicrotic wave. Careful measurements shew that the 

 distance between the primary and dicrotic crests is either greater 



FlO. 36. NOBMAL PULSE-CURVE FBOM CAEOTID OF BABBIT J 



shewing influence on height and form of curve of changes in the extra vascular 

 pressure which was in a 20 mm., in 6 30 mm., in c 40 mm., and d 50 mm. of mer- 

 cury. 



or certainly not less in the smaller or more distant arteries than in 

 the larger or nearer ones. This feature indeed proves that the 

 dicrotic wave cannot be in any way a retrograde wave. Again, the 

 more rapidly the primary wave is obliterated or at least diminished 

 on its way to the periphery the less conspicuous should be the 

 dicrotic wave. Hence increased extensibility and increased elastic 

 reaction of the arterial walls which tend to use up rapidly the 

 primary wave, should also lessen the dicrotic wave. But as a 

 matter of fact these conditions are favourable to the prominence of 



