SPEECH ^17 



of the crico-thyroid muscle and increased tension of the cords. Sec- 

 tion or paralysis of the inferior laryngeal nerves leads to loss of voice 

 or aphonia, and dyspnoea (Fig. 149). Both adductor and abductor 

 muscles are paralyzed ; the vocal cords assume their mean position 

 the position they have in the dead body -and the glottis can neither 

 be narrowed to allow of the production of a note, nor widened during 

 inspiration. It is said, however, that young animals, in which the 

 structures around the glottis are more yielding than in adults, can 

 still utter shrill cries after section of the inferior laryngeals, the 

 contraction of the crico-thyroid muscle alone being able, while in- 

 creasing the tension of the cords, to draw them together. 



Interference with the connections on one side between the higher 

 cerebral centres and the medulla oblongata, as by rupture of an 

 artery and effusion of blood into the posterior portion of the internal 

 capsule (giving rise to hemiplegia, or paralysis of the opposite side 

 of the body), is not followed by loss of voice; the laryngeal muscles 

 on both sides are still able to act. 



