OF MOVEMENTS OF CHEST-WALL IN RESPIRATION. 253 



no other direction, and which firmly fixes the lever to a 

 sliding-plate working backwards and forwards in a slot in 

 the frame (f) . 



W 



R 



A writing-frame (w) is attached to the instrument by a 

 hinge (h); and a spring (r) keeps it continually pressed 

 against the pencil at c. The whole mechanism is then 

 allowed to rotate upon the pivot (n) in the stand (t). 



It will be readily seen that these arrangements permit 

 the motion of the pencil (c) backwards and forwards, and 

 upwards and downwards, and that these movements will 

 closely correspond to those of the pad (b), with the differ- 

 ence that the upward movement of the pad will produce a 

 downward thrust of the pencil, and vice versa ; and thus, 

 when the pad is placed upon the end of a rib, all its move- 

 ments, with the exception of that directly outward, will be 

 transferred in reverse to the paper or smoked glass con- 

 tained in the writing -frame ; and by having the paper 

 ruled in squares, each one tenth of an inch, the extent of 

 movement in the forward or upward direction can be read 

 off at once. 



In using the instrument it is fixed to a table by a clamp, 

 or by a sufficiently heavy weight attached to its foot, and 

 the back of the subject to be examined is firmly supported 

 by a pad placed opposite the costo-vertebral articulation 

 of the ribs whose movements are to be traced. In this 



