22 



normally sized heart affects more exclusively when it is placed upon 

 the fifth intercostal space. 



The sphygmoscope 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. If a very long 

 and forcible inspiration be made and the breath then suspended, 

 the movement is somewhat reduced; but when the respiration is again 

 allowed to take its normal course, the movement is seen to be in- 

 creased for a short time. 



The sphygmoscope rises during the first sound of the heart 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 delicate in its impressions that it 



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

 meter of much the same construction was invented some twenty years ago by 

 Mons. le Docteur Herrison, and that a memoir upon 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. 



