NATURAL PHILOSOPHY. 241 



the liquid of the hand sphygmoscope. It affords proof that the pulse is one 

 thing, and the heart's action another, and teaches that the pulse is only an 

 approximate sign of the state of the heart. It is found also, that while cold 

 at the surface and extremities may depress the pulse, the heart may remain 

 little enfeebled, or even become excited, and that warmth and friction applied 

 to the extremities may cause an excited pulse without there being any ac- 

 companying increased force of the heart. 



The sphygmoscope (fig. 2,) having a level elastic wall instead of a pro- 

 truding one, and having a glass tube with an almost capillary bore, forms a 

 remarkably delicate indicator of the pulse. It is so delicate in its impressions 

 that it is appreciably affected by the regurgutant wave in the jugular veins, 

 and by the wave in arteries much smaller than the radial. From its nicety 

 in manifesting the beat of the blood-wave, it is very valuable. 



By means of this hand instrument applied to the arteries a comparison is 

 readily made between the time of the beat of the heart and the rise of the 

 arteries under the influence of the blood-wave. This instrument is much 

 more delicate than the finger in such an inquiry. The impressions made 

 upon the fingers of two hands fail to be conveyed with sufficient nicety to 

 the mind to tell with certainty the relative time of the beat of the heart and 

 arteries. Except in cases of extreme slowness, the sensations obtained from 

 the two hands impressed 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 

 the erroneous idea, that the beat of the heart and the beat of the pulse are 

 synchronous, or nearly so, owes 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 other reaches the bottom of its descent, to renew their op- 

 posing course. The movements in the two instruments at the same instant 

 are always opposed, and the whole time occupied in the movement of one 

 instrument in one direction appears to be occupied by the movement of the 

 other in the opposite direction. The movements alternate with as much ap- 

 parent 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 

 observed, suspicion of disease of the aorta was entertained, but the subse- 

 quent 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 GO to 100. 



Hand sphygmoscopes placed upon the carotid, the barachial, the radial, 

 the femoral, and the dorsal arteiy 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 enunci- 

 ated first, that the heart's beat alternates with the pulse at the wrist ; 



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