PHONATION; ARTICULATE SPEECH. 583 



For phonatory purposes it is essential that the respiratory function 

 be temporarily suspended and the vocal bands closely approx- 

 imated. This is accomplished by the contraction of the remaining 

 muscles of the larynx, with the exception of the crico-thyroid, 

 which are collectively known as the adductors oj the vocal bands. 

 During phonation the adductor muscles overcome the activity of the 

 abductors. With the cessation of phonation the abductors immedi- 

 ately restore the vocal bands to their former respiratory position. 



The activities of these two antagonistic groups of muscles are under 

 the control of the central nerve system. The only pathway for 

 the excitatory nerve impulses is through the fibers of the inferior or 

 recurrent laryngeal nerve. The relation of these nerve-fibers both 

 centrally and peripherally, as well as their physiologic action, has been 

 the subject of much experimentation. The results have not always 

 been in accord, owing to the choice of animal, the use of anes- 

 thetics, strength of stimulus, etc. 



As the outcome of many investigations it is believed that each 

 muscle group is innervated by its own bundle of nerve-fibers, both 

 of which are contained in the inferior laryngeal, though coming 

 from two separate centers in the medulla oblongata. Russell suc- 

 ceeded in separating the fibers for the abductors from the fibers 

 for the adductors in the inferior laryngeal, and in tracing them 

 to their terminations. So completely was this done that it became 

 possible to produce at will, through stimulation, either abduction or 

 adduction, without contraction of the muscle of opposite function. 



The laryngeal respiratory center was located by Semon and 

 Horsley, in the cat, in the upper part of the floor of the fourth ven- 

 tricle: Stimulation of this area during etherization was followed by 

 abduction of the vocal bands. The efferent fibers of this center are 

 believed by some investigators to leave the central nerve system in 

 the spinal accessory nerve, by others in the lower roots of the vagus. 



From the continuous activity of the abductor muscle, and the 

 stationary position of the vocal bands, it is probable that the medul- 

 lary center is in a state of continuous activity or tonus, the result 

 probably of reflex influences. 



A cortical representation for laryngeal respiratory movements 

 has been determined by Semon and Horsley in different classes of 

 animals. In the cat especially, stimulation of the border of the 

 olfactory sulcus gives rise to complete abduction of the vocal bands 

 on both sides. The representation is therefore bilateral. 



The phonatory center was located by the same investigators in 

 the medulla near the ala cinerea and the upper border of the calamus 

 scriptorius. Stimulation of this area was invariably followed by 

 bilateral adduction of the vocal bands and closure of the glottis. 



A cortical representation for phonatory movements also was 



