390 *, Roi^al Society .^-^ no?f(A M 



normally sized heart affects more exclusively when it is placed upon 

 the fifth intercostal space. 



The sphyguioscope indicates with exactitude both the absolute and* 

 the comparative influence upon the heart, of food, cordials, stimu- 

 lants, and tonic medicines. It does the same in respect to depress- 

 ing causes, such as hunger, cold, and sedatives. 



With the aid of this instrument the fact is demonstrated, that 

 the action of the heart may be great when the pulse is small, — 

 that the heart may strike the instrument with force when the 

 pulse scarcely affects the liquid of the hand-sphygmoscope. It 

 affords a remarkable 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 accompanying increased force of the heart. 



The influence of respiration upon the action of the heart is mani- 

 fested, in some degree, by the instrument placed over the region of 

 the heart. If the breath be stopped after an ordinary expiration, 

 the movement of the liquid is seen to be increased. It a very long 

 and forcible inspiration be made and the breath then suspended, 

 the movement is somewhat reduced ; but when the respiration pig. 2. 

 is again allowed to take its normal course, the movement is ^ 

 seen to be increased for a short time. 



The sphygmoscope rises during the first sound of the heart 1; 

 and falls at the second. 



The sphygmoscope reduced (fig. 2), deprived of its stand, 

 having a level elastic wall instead of protruding one, and 

 having a glass tube with an almost capillary bore, forms a 

 remarkably delicate indicator of the pulse*. It is so deli- 

 cate in its impressions that it is appreciably affected by the 

 regurgitant wave in the jugular veins, and by the wave in 

 arteries greatly smaller than the radial. From its nicety in 

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

 and is called the hand-sphygmoscope. 



By means of this hand instrument applied to the arteries, 

 a comparison is readily ma le between the tim^ 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 suf- „ , 

 ficient nicety to the mind to tell with certainty the relative sphvgrao. 

 time of the beat of the heart and arteries. Excei)t in cases of scope. 



* Since this instrument was contrived, the author lias learned that a sphygmo- 

 meter of much the same construction was invented some tw«ity years ago by 

 Mons. le Docteor Ilerrison, and that a memoir ui>on it was presented to the In- 

 stitute of France. The liquid employed was mercury — too heavy to indicate feeble 

 impulses, and the moveable wall was of gold-beater's skin, which is inelastic. It 

 may be added, that M. Magendie reported against the practical application of the 

 invention. 





t.tn.r 

 lOlft 



