luhnojqm^ ^p^ciedmgs ol Learned Societies. 



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ifnh a/fi :^aififBlnoo royal society. 

 ^/.^'■\Air>n^ii\ .-^'1 . ,f}f ti [Continued from p. 316.] 

 Jan. 31, 1856. — The Lord Wrottesley, President, in the Chair. 



THE following communication was read : — 

 *' A Description of a new Sphygmoscope, an Instrument for 

 indicating the Movements of the Heart and Blood-vessels ; with an 

 Account of Observations obtained by the aid of that Instrument." By 

 S. Scott Alison, M.D. 



The sphygmoscope (fig. 1) consists of a small chamber containing 

 spirits of wine or other liquid, provided with a thin india-rubber 

 wall, where it is to be applied to the chest. At the opposite extre- 

 mity the chamber communicates with a glass tube, which rises to some 

 height above the level of the chamber. Liquid is supplied to the 

 instrument until it stands in the tube a little above the level of the 

 chamber. The pressure of the column of liquid in the tube acts 

 upon the elastic or yielding wall of india-rubber and causes it to pro- 

 trude. This protruding part or chest-piece is very readily affected 

 by external impulse ; it yields to the slightest touclv and being 

 pushed inwards, causes a displacement of the liquid in the non-elastic 

 chamber, and forces a portion of liquid up the tube. The protruding 

 wall of india-rubber is driven inwards when it is brought in contact 

 with that portion of the chest which is struck by the apex of the 

 heart, and a rise in the tube takes place. When the heart retires, 

 the india-rubber wall, affected by the pressure of the column of 



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liquid in the tube, is pressed back, follows the chest, and permits 

 the liquid to descend. The degree to which the india-rubber wall is 



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