9 8 



INSTRUMENTS FOR INVESTIGATING THE PULSE. 



elastic spring (fig. 72, A) is fixed at one end, z, free at the other end, and provided with an 

 ivory pad, y, which is pressed by the spring upon the radial artery. On the upper surface of 

 the pad there is a vertically-placed fine toothed rod, k, which is pressed upon by a weak spring, c, 



Fig. 72. 

 Scheme of Marey's sphygrtiograph. A, spring with ivory pad, ?/, which rests on the artery ; e, 

 weak spring pressing k into t ; r, writing lever ; P, piece of smoked glass or paper moved 

 by clock-work, U ; H, screw to limit excursion of A ; S, arrangement for fixing the instru- 

 ment to the arm of the patient. 



so that its teeth dovetail with similar teeth in the small wheel, t, from whose axis there pro- 

 jects a long, light, wooden lever, v, running nearly parallel with the elastic spring. This lever 

 has a fine style at its free end, s, which writes upon a smoked plate, P, moved by clock-work, 

 U, in front of the style. Marey's instrument, as improved by Mahomed and others, has been 

 very largely used. 



[Its more complete form, as in fig. 73, where it is shown applied to the arm, consists of (1) 

 a steel spring, A, which is provided with a pad resting on the artery, and moves with each 

 movement of the artery ; (2) the lever, C, which records the movement of the artery and spring 

 in a magnified form on the smoked paper, G ; (3) an arrangement, L, whereby the exact pressure 

 exerted upon the artery is indicated on the dial, M ; (4) the clock-work, H, which moves the 

 smoked paper, G, at a uniform rate; (5) a framework to which the various parts of the 

 instrument are attached, and by means of which the instrument is fastened to the arm by straps, 

 K, K (Bt/rom Bmnuccll).] 



[Application. In applying the sphyg mo graph, cause the patient to seat himself beside a low 

 table, and place his arm on the double-inclined plane (fig. 73). In the newer form of instru- 

 ct 



Fig. /, 



Marey's improved sphygmograph. A, steel spring ; B, first lever ; C, writing lever ; C', its free 

 writing end ; D, screw for bringing B in contact with C ; G, slide with smoked paper ; H, 

 clock-work ; L, screw for increasing the pressure ; M, dial indicating the pressure ; K, K, 

 straps for fixing the instrument to the arm, and the arm to the double-inclined plane or 

 support. 



ment, the lid of the box is so arranged as to unfold to make this support. The fingers ought to 

 be semi-flexed. Mark the position of the radial artery with ink. See that the clock-work is 

 wound up, and apply the ivory pad exactly over the radial artery where it lies upon the radius, 

 fixing it to the arm by the non-elastic straps, K, K. Fix the slide holding the smoked paper 

 in position. The best paper to use is that with a very smooth surface, or v an enamelled card 

 smoked over the flame of a turpentine lamp, over a piece of burning camphor, or over a fan- 

 tailed gas-burner. The writing-style is so arranged as to write upon the smoked paper with 

 the least possible friction. It is most important to regulate the pressure exerted upon the 



