CH. XXI.] 



SPHYGMOGRAPHS. 



269 



In disease there are certain variations in the pulse, of which we 

 shall mention only two; namely, the intermittent pulse, due to the 

 heart missing a beat every now and then ; and the water hammer 



Fig. 262. The Sphygmograph applied to the arm. 



pulse, due either to aortic regurgitation or to a loss of elasticity 

 of the arterial walls ; either of these circumstances diminishes 

 the onward flow of blood during the heart's diastole, and thus 

 the suddenness of the impact of the blood on the arterial wall 



Fig. 263. Dudgeon's Sphygmograph. The dotted outline represents the piece of blackened 

 paper on which the sphygmogram is written. 



during systole is increased. When this condition is due to 

 arterial disease, such as athcroma or calcification, this sudden 

 pulse combined with the increased brittleness of the arteries 

 may lead to rupture of the walls, and this is especially 

 serious if it occurs in the arteries of the brain (one cause 

 of apoplexy). 





