20 



of the heart. The liquid in the tube is now observed to be in mo- 

 tion. With persons in ordinary health, the liquid rises and falls 

 about an inch. This rise and fall, after taking place three or four 

 times, is followed by a much longer rise and fall to the extent of 

 three or four inches, due to the advancement and retirement of the 

 wall of the chest during the acts of respiration. The shorter rise 

 and fall are again repeated and are again followed by the longer rise 

 and fall caused by the motions of the chest. During the longer rise 

 and fall due to respiration, the beat and retreat of the heart are still to 

 be recognized by brief interruptions in the rise and fall of the liquid. 

 When difficulty is experienced in obtaining the shock of the heart 

 sufficiently strong to give an appreciable rise and fall, the examinee 

 should make a moderate expiration, and then hold his breath and 

 incline the chest somewhat forward. When the action of the heart is 

 feebly felt at the praecordial region, it may be necessary to apply the 

 instrument to the naked chest ; but this is not necessary in the great 

 majority of cases, and it will generally suffice to make the shirt and 

 waistcoat fit tight to the skin. In many trials the sphygmoscope 

 has succeeded in indicating the movements of the heart through the 

 tightly buttoned coat. Thin persons are very favourable for exami- 

 nation ; on the other hand, the corpulent less readily affect the in- 

 strument. 



The movements of the heart, though best indicated at the fifth 

 intercostal space, are to be denoted at other parts of the chest, and 

 in some examples of disease and of large and powerful heart, even in 

 the epigastric region. The moving arm proves convenient in apply- 

 ing the instrument to these parts. In many persons with no very 

 excited heart, it is sensibly acted on at the scapular and infra-dorsal 

 regions. 



By means of this instrument the observer can ascertain the fre- 

 quency of the beats of the heart, but as this can be effected in most 

 cases with accuracy at the radial artery, no particular advantage is 

 gained from it in respect to this point. 



The duration of the impulse of the heart upon the chest is well 

 measured by this instrument : the time occupied by the rise, is the 

 time occupied by the impulse. A slow rise after a rapid rise shows 

 a slow beat after a rapid one, and vice versa, a slow fall after an 

 ordinary fall, shows a slow retirement after an ordinary one. An 



