Dr. Alison on a new Spkygmoscope, 389 



lug 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. ■■ -'''-.,: - ::;, y\y>,A -mI: .ij;:/' ^ 



By means '6f this instrumeiit^'th6*'bbseri^gf 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 

 intermittent pulse is marked by an imperfect rise, followed by an 

 ordinary fall, and then by a long rise. The rise is sometimes slower 

 than the fall, which is occasionally found to be abrupt. This is 

 observed when the heart, by reason of its great size, and of the some- 

 what bent back posture of the thorax, suddenly falls away from the 

 walls of the chest. 



The movements of the auricles under ordinary circumstances are 

 not indicated by the sphygmoscope, though when it is placed over 

 them, the liquid in the tube is moved upwards and downwards ; 

 but as these movements are synchronous with the movements 

 upwards and downwards of another instrument placed at the apex, 

 it may be inferred that the ventricle is the cause of them all. In 

 some examples of greatly excited heart, as in phthisis, the instrument 

 has revealed movements which seemed to proceed from the auricles ; 

 but further observations are required to settle this point, as well as 

 the question whether the movements of the aorta, in a state of 

 excitement, communicate any influence to the instrument. 



The instrument, placed upon the heart, indicates strokes of that 

 organ which are so feeble as to have no corresponding pulse at the 

 wrist. 



No pause whatever in the movement of the liquid has been at 

 any time observed when the sphygmoscope has been carefully placed 

 so as to receive the full beat, and fall back with freedom. This 

 would go to show that the heart, however slow, is in constant mo- 

 tion, and, contrary to the belief of many physiologists, enjoys no 

 pause. There is certainly no pause in the descent of the liquid, 

 which takes place when the heart retires from the thoracic walls, in 

 the middle of which movement it has been said a very short pause 

 is to be observed in living animals having the heart exposed. 



The force with which the heart beats at the fifth intercostal 

 space may be ascertained by closing the upper extremity of the 

 glass tube, and observing the extent to which the enclosed air is 

 compressed. 



When the heart is excited, the liquid in the sphygmoscope rises and 

 falls more than usual ; but the rise and fall of the excited enlarged 

 heart is much the same as the rise and fall of the excited normal 

 organ. For the most part the enlarged heart gives movements to 

 the instrument when placed upon the ribs and sternum, whilst the 



