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TEXT-BOOK OF PHYSIOLOGY 



delicate lever the free extremity of which is provided with a writing 

 point. 



By transmitting the movement through a column of air enclosed in a 

 rubber tube the two ends of which are attached to a metallic capsule, 

 covered by a rubber membrane, termed a drum or tambour. When 



the membrane of the 

 first tambour is pressed 

 or driven inward, the 

 air is forced through 

 the rubber tube into 

 the second tambour 

 and its membrane is 

 pushed outward. As 

 soon as the primary 

 pressure is removed, 

 the membranes return 

 to their former con- 

 dition. If the mem- 

 FIG. 342. A RECEIVING TAMBOUR. , , 



brane of the first tam- 

 bour is drawn outward, the air in the system is rarefied and the mem- 

 brane of the second tambour is pressed inward. For the purpose of 

 registering the movement transmitted by the column of air, the second 

 tambour is provided with a light lever supported by a vertical 

 bearing resting on a small metallic disc. The membrane of the first 

 tambour is frequently provided with a button, which is placed over the 

 moving structure. The inward movement of the membrane of the 

 first tambour produces an outward movement of the membrane of the 

 second tambour, indicated, though magnified, by the rise of the free 

 end of the lever. The 

 reverse movement of 

 the membrane is at- 

 tended by a fall of the 

 lever. The first tam- 

 bour is termed the re- 

 ceiving, the second the 

 recording tambour 

 (Figs. 342, 343). 



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 467); 

 or (2) a tambour and lever (page 357); or (3) a mercurial manometer 

 carrying a float and pen (page 343). The space between the part 

 investigated and the vessel is filled with fluid. The variations 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 carrying 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. 



FIG. 343. A RECORDING TAMBOUR. (Marey.} 



