1871.] and Radial Sphygmo graph Trace. 319 



fixed end, to two silk threads, one of which (d) is attached to the pad and 

 spring above mentioned, and the other to a small spring (g) which moves, 

 it when it is less acted on by the stronger spring. The apparatus is so 

 arranged that the lever works perfectly when it is so placed as to be above 

 the registering part of the sphygmograph, when the latter is in position. 

 The tip of the lever carries a steel pen (£). 



Fig. 1. 



To use the instrument, the sphygmograph is first fixed on the left arm 

 as usual, the recording paper being adjusted to its place. The arm is then 

 moved until the attached instrument rests on the board first mentioned ; 

 and it is maintained in position by certain pegs and holes in the board, 

 which respectively come into contact with the main parts, and receive the 

 projections of the instrument. 



The arm and attached apparatus are then moved until the pad of the 

 cardiograph spring is brought into contact with the spot, between the fifth 

 and sixth ribs, at which the heart's pulsation is most marked — the position 

 of the pad in relation to the board having been previously so fixed as to 

 enable this to be done with facility, the whole being maintained in the 

 horizontal position. The contact of the pad with the chest-wall causes the 

 lever to recede ; and it is allowed to do so until its pen arrives above the 

 recording-paper, the whole apparatus being steadied by the right hand. 

 When the levers of the two instruments are both found to be moving 

 freely, the watchwork of the sphygmograph is set in action by means of a 

 string, connected at the other end with the stop-block of the train of 

 wheels ; and when the recording-paper has run its length, a combined 

 trace is found, as in figure 2. 



Fig. 2. 











MM 







— yv-? — j 



If 









The commencement of the two traces is easily defined with precision; 



