130 



MAREY'S SPHYGMOGRAPH. 



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 (Fig. 46). Fix the slide holding the smoked 

 paper in position. The best paper to use is that with a very smooth surface 

 (albuminised or enamelled card) smoked over the flame of a turpentine lamp, or 

 over a piece of burning camphor. The writing-style is so arranged as to write 

 upon the smoked paper with the least possible friction. The most important part 



Fig. 46. 



Marey's improved sphygmograph as used when a tracing is taken 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 amount of 

 pressure ; K, K, straps for fixing the instrument to the arm, and the arm to 

 the double-inclined plane or support (Byrom Bramwell). 



of the process is to regulate the pressure exerted upon the artery by means of the 

 milled head, L. This must be determined for each pulse, but the rule is to 

 graduate the pressure until the greatest amplitude of movement of the lever is 

 obtained. Set the clock-work going, and a tracing is obtained, which must be 

 " fixed " by dipping it in a rapidly drying varnish e.g., photographic. In every 

 case scratch on the tracing with a needle the name, date, and amount of pressure 

 employed.] 



g- :: c::==="-="; sr! 



Fig. 47. 



Fig. 48. 



[Fig. 47. Scheme showing the' essential part of the instrument when in working 

 order i.e., the turned up knife-edge, B", of the short lever in contact with 

 the writing lever, C. Every movement of the steel spring at A" i.e., the 

 artery will in this position be communicated to the writing lever. 



[Fig. 48. Scheme showing the essential parts of the instrument after increase of 

 the pressure. The knife-edge, B", is no longer in contact with the writing 

 lever, and the movements of the steel spring, A" i.e., the artery are no 

 longer communicated to it. In order to put the instrument into working 

 order, the knife-edge, B", must be raised to the position indicated by the 

 {lotted lilies. This is effected by means of the screw, D (Byrom Bramwell).] 



