240 ANNUAL OF SCIENTIFIC DISCOVERY. 



with an orifice may be supplied. When employed, the glass tube is left open 

 to permit of the passage of the air to and fro. 



Figure 1 represents an instrument without a stand; figure 2 is another form 

 of it without a stand ; and figure 3 is the most perfect form, but is not quite 

 so convenient. 



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

 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 (fig. 3.) 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 receive the blow of the apex 

 of the heart. The liquid in the tube is now observed to be in motion. With 

 persons in ordinary health, the liquid 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 advance- 

 ment and retirement of the wall of the chest during the acts of respiration. 

 The shorter rise and fall arc again repeated, and arc 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. Thin 

 persons are very favorable for examination ; on the other hand, the corpu- 

 lent, less readily affect the instrument. Placed upon the heart, it indicates 

 strokes of that organ which are so feeble as to have no corresponding pulse 

 at the wrist. 



No pause whatever in the movement of the liquid has been at any time ob- 

 served when the sphygmoscope has been carefully placed so as to receive the 

 full beat, and fall back with freedom. This would go to show that the heart, 

 however slow, is in constant motion, and, contrary to the belief of many 

 physiologists, enjoys no pause. There is no pause in the descent of the 

 liquid, which takes place when the heart retires from the thoracic walls, in 

 the middle of which movement, it has been said, a very short pause is to be 

 observed in living animals having the heart exposed. 



When the heart is excited, the liquid in the sphygmoscope rises and falls 

 more than usual ; but the rise and fall of the excited enlarged heart is much 

 the same as the rise and fall of the excited normal organ. For the most 

 part, the enlarged heart gives movements to the instrument when placed 

 upon the ribs and sternum, whilst the normally-sized heart affects it more ex- 

 clusively when it is placed upon the fifth intercostal space. 



The sphygmoscope indicates with exactitude both the absolute and the 

 comparative influences upon the heart, of food, cordials, stimulants, and tonic 

 medicines. It does the same in respect to depressing 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 



