Dr. Alison on a new Sphygmoscope, S91 



extreme slowness, the sensations obtained from the two hands im- 

 pressed at nearly the same time, do not admit of a distinct difference 

 in respect to time being made out. It has been to this very defect 

 that the erroneous idea, that the beat of the heart and the beat' 

 of the pulse are synchronous, or nearly so, has owed its origin and 

 continuance. 



The hand-sphygmoscope, placed upon the radial artery, shows a 

 rise of the liquid while there is a fall in the sphygmoscope placed 

 over the heart. As the liquid in the one instrument starts from 

 below, the liquid in the other starts from above, and as the liquid \ 

 in the one reaches the top of its ascent, the liquid in the otheri 

 reaches the bottom of its descent, to renew their opposing course. 

 The movements in the two instruments at the same instant are always ; 

 opposed, and the whole time occupied in the movement of one in- 

 strument in one direction appears to be occupied by the movement 

 of the other in the opposite direction. The movements alternate 

 with as much apparent exactitude as the arms of a well-adjusted 

 balance. When the lapse of time between the beat of the heart and 

 the pulse at the wrist was first observ^ed, suspicion of disease of the 

 aorta was entertained, but the subsequent examination of many 

 persons proved that this alternation was natural. In some twenty 

 persons subjected to examination, the complete alternation has been 

 made out without the shadow of a doubt. These persons were of all 

 ages above childhood, and had the pulse of different degrees of rapidity ^ 

 from 60 to 100. 



Hand-sphygmoscopes placed upon the carotid, the brachial, the 

 radial, the femoral, and the dorsal artery of the foot, rise at the 

 same instant, and fall at the same point of time. 



These facts prove the existence of two great laws not previously ■ 

 enunciated, — 1st, that the heart's beat alternates with the pulse at i 

 the wrist ; 2ndly, that the pulse of arteries beyond the chest takes 

 place in all parts at the same instant, and without any appreciable 

 interval. 



The pulse, it appears, occurs during the retirement of the hearfe^ 

 from the thoracic walls, and the collapse or fall of the arteries takes ? 

 place during the impulse of the heart. During the rise in the hand- 

 sphygmoscope placed over the arteries, the second sound of the 

 heart has been distinctly heard, and during the fall, the first, softer < 

 and more prolonged sound has been easily distinguished. '■ 



The horse has been subjected to examination, to learn the relative' * 

 time of the beat of the heart and arteries, but the respiratory move-' • 

 ments and the motions of the animal have hitherto restricted the^ 

 application of the instruments. However, it has been most distinctly 

 ascertained, by the hand placed upon the heart and upon the plantar 

 artery, that between the beat of these parts there is a decided inter- 

 val. The slowness of the action of the heart in the horse renders 

 this experiment less open to error than in man. In these experi- 

 ments upon the horse, Mr. Ajfayor;, the eminent veterinarian, gave his ' 

 valuable aid. iVii^i;t^i^.L;vsj- • -^Vj^j^dvj, _ ] 



The sphygmoscope forms a good pneumoscope. It delicatelyn. 



