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TEXT-BOOK OF PHYSIOLOGY. 



3. By enclosing an organ e. g., kidney, spleen, arm, finger, etc. in a 

 rigid glass or metal vessel which at one point is in communication 

 with a recording apparatus e. g., (i) a piston provided with a lever 

 (page 431) ; or (2) a tambour and lever (page 320) ; or (3) a mercurial 

 manometer carrying a float and pen (page 305). The space between 

 the part investigated and the vessel is filled with fluid. The varia- 

 tions in volume of the organ cause a displacement of the fluid and 



give rise to a to-and-fro 

 movement which is taken 

 up and reproduced by the 

 recording apparatus. 

 The writing point may be 

 (i) some form of pen carry- 

 ing ink which records the 

 movement on a white paper 

 surface, or (2) a piece of 

 metal, glass, or paper which 

 records the movement on 

 smoked paper or glass. 



The Recording Sur- 

 face. The surface which 

 receives and records the 

 movements of a pen or lever 

 is usually that of a cylinder 

 which is covered with glazed 

 paper and coated with a thin 

 layer of soot, obtained by 

 passing the cylinder through 

 the flame of a gas burner. 

 The axis of the cylinder is 

 supported by a metal frame- 

 work. If the writing point of 

 the lever be placed against 

 the cylinder and a movement 

 be imparted to it, a portion 

 of the soot is rubbed off, leav- 

 ing a white line behind. If 

 the cylinder be stationary, the 

 rise and fall of the lever are 

 recorded as a vertical line. Such a record shows only the extent of 

 a movement. If the cylinder is traveling, however, at a uniform rate, the 

 rise and fall of the lever are recorded in the form of a curve the width 

 of the two arms of which will depend partly on the rapidity of the move- 

 ment of the lever and partly on the rate of movement of the cylinder. 

 The cylinder movement is initiated and maintained by clock-work or by 

 the transmission of power by belting to a system of pulleys in connection 

 with its axis. As the tracing is wave-like in form, the cylinder is frequently 

 spoken of as a kymograph or wave recorder (Fig. 346). 



From the record thus obtained it is possible to determine not only the 





FIG. 346. KYMOGRAPH. (Boruttau's, Pet- 

 zold, Leipzig.) 



