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forced in by the apex of the heart ia denoted by a corresponding 

 rise in the tube, and the amount of protrusion of the india-rubber 

 wall which takes ])lace when the heart retires is denoted by a corre- 

 sponding fall in the tube. The tube is supplied with a graduated 

 scale to denote the rise and fall with exactitude. The glass tube is 

 provided at the top with some contrivance, such as a brass screw 

 and collar, to prevent the egress of the liquid when the instrument 

 is not in use, or a bulb with an orifice may be supplied. When 

 employed, the glass tube is left open to permit of the passage, pf the 

 air to and fro. ,, ,,,j,ij 



The sphygmoscope is mounted upon a stand. The chamber and 

 tube are fitted to a horizontal arm, which is made to move up and 

 down so as to carry the instrument to the desired height. The b^ 

 is so made as to secure the requisite immobility. i (iino 



The glass tube is a foot or more long, and the round bore is about 

 the one-eighth part of an inch. If the bore be much larger, the 

 movement will be inconsiderable ; if much less, capillary attraction 

 will interfere and prevent free motion. 



When the instrument is to be employed, mounted upon its stand, 

 it is placed upon a firm table with the chamber projecting beyond it. 

 The person whose heart is to be examined is seated upon a firm 

 chair, with his chest erect and free from motion. The protruding 

 india-rubber wall of the chamber or chest-piece is delicately made to 

 touch the fifth intercostal space so as to receive the blow of the apex 

 of the heart. The liquid in the tube is now observed to be in mo- 

 tion. With persons in ordinary health, the hquid rises and falls 

 about an inch. This rise and fall, after taking place three or four 

 times, is followed by a much longer rise and fall to the extent of 

 three or four inches, due to the advancement and retirement of the 

 wall of the chest during the acts of respiration. The shorter rise 

 and fall are again repeated and are again followed by the longer rise 

 and fall caused by the motions of the chest. During the longer rise 

 and fall due to respiration, the beat and retreat of the heart are still to 

 be recognized by brief interruptions in the rise and fall of the liquid. 

 When difficulty is experienced in obtaining the shock of the heart 

 sufficiently strong to give an appreciable rise and fall, the examinee 

 should make a moderate expiration, and then hold his breath and 

 incline the chest somewhat forward. When the action of the heart is 

 feebly felt at the preecordial region, it may be necessary to apply the 

 instrument to the naked chest; but this is not necessary in the great 

 majority of cases, and it will generally suffice to make the shirt and 

 waistcoat fit tight to the skin. In many trials the sphygmoscope 

 has succeeded in indicating the movements of the heart through the 

 tightly buttoned coat. Thin persons are very favourable for exami- 

 nation ; on the other hand, the corpulent less readily affect the in- 

 strument. 



The movements of the heart, though best indicated at the fifth 

 intercostal space, are to be denoted at other parts of the chest, and 

 in some examples of disease and of large and powerful heart, even in 

 the epigastric region. The moving arm proves convenient in apply- 



