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mere suspension or interruption of it would be attended with 

 total loss of voice, — it would appear, at least, very unlikely 

 that this motion should not have a special mechanical ar- 

 rangement constructed for its performance, but that this im- 

 portant ofBce should be delegated to a muscle having a variety 

 of other functions to fulfil. 



" The vocal cords are attached, as was before stated, to 

 the thyroid cartilage in front, to the anterior spur of the 

 arytenoid behind ; but the arytenoid being smaller and by far 

 more moveable than the thyroid cartilage, a correct knowledge 

 of the motions which can be communicated to the arytenoid 

 cartilages by the laryngeal muscles must be first obtained, 

 before we can estimate the various conditions of the vocal 

 cords. 



*' The principal motions which are enjoyed by the aryte- 

 noid cartilages are the following : — they can be drawn forward, 

 backward, rotated on their vertical axis, or they can revolve 

 on a horizontal axis corresponding to the direction of the an- 

 terior spurs. The effects produced on the vocal cords by these 

 motions will be as follows : — the forward motion will relax, 

 and the backward movement will stretch the vocal cords; 

 the rotation in a direction outwards on the vertical axes will 

 separate, and the rotation inwards will approximate the vocal 

 cords ; the rotation on the horizontal axes inwards and out- 

 wards will cause the anterior spur to revolve, and to carry with 

 it the vocal cord, which will thus alternately incline towards 

 and from the cord of the opposite side. 



" In consequence of the articular surfaces in the cricoid car- 

 tilage, for the accommodation of the arytenoid, being formed 

 more on the external than the internal surface of the cartilage, 

 the arytenoid cartilages are not seated in an erect position ; 

 the axes of the cartilages are consequently divergent, so that 

 the apices are separated from each other above by a conside- 

 rable interval ; and in this state, which is that of repose of the 

 organ, the planes of the vocal cords also diverge from each 



