320 Dr. Felix Semon [March 13, 



of the latter muscles consists in keeping the vocal cords during 

 respiration so far asunder from one another that the narrowing of the 

 tube, which is actually produced by the interpolation of the larynx 

 into the respiratory apparatus, is neutralised to the necessary extent, 

 whilst the adductors and tensors as a rale serve only the voluntary 

 and purposive function of phonation, as in speaking and in singing, 

 and are employed only in a secondary fashion for some of the reflex 

 acts of respiration, such as laughing and coughing. 



All these muscles, i. e. the respiratory as well as the phonatory 

 muscles, receive their nerve supply from two small nerves, the 

 superior laryngeal and the recurrent laryngeal nerves. The superior 

 laryngeal only supplies the tensors of the vocal cords, the cricothyroid 

 muscles, with motor fibres, whilst the recurrent is distributed to the 

 adductor as well as to the abductor muscles. It is still an open 

 question whether the recurrent is ultimately derived from the sjnnal 

 accessory or the vagus nerve, both being cranial nerves, the centres 

 of which are situated in the medulla oblongata. The researches of 

 Terrier, Buret, Munk, Krause, Horsley, and myself have shown that 

 the medulla is not the ultimate seat from which impulses are dis- 

 tributed along the motor paths just sketched to the laryngeal muscles, 

 but that there is for the purposive function which the larynx serves, 

 viz. for phonatiou, a distinct centre in the surface or cortex of the 

 brain, situated in the foot of the ascending frontal gyrus, just behind 

 the lower end of the precentral sulcus. It is a very interesting and 

 noteworthy phenomenon, that Professor Horsley and I have only 

 been able to find (except in the cat) a definite area of representation 

 of the action of the vocal cords in the cortex of the brain for the 

 intentional purposive movements of the vocal cords, such as are used 

 in speaking and singing. On stimulation of this area on one side, 

 both vocal cords directly come together (i. e. are adducted), and 

 remain, so long as the stimulation lasts, in the position which they 

 assume when used for either of the last-named purposes. It is never 

 possible, according to our researches, to produce an action of one cord 

 alone, they always act bi-laterally and symmetrically. Equally 

 impossible is it w^hen one looks at the larynx of a human being, of a 

 monkey, or of a dog during the act of phonation, i. e. when the cords 

 are being brought together and put into the proper degree of tension, 

 to make out any difference in time between these two actions. Tension 

 and adduction apparently occur absolutely simultaneously, or at least 

 our retina is not able to distinguish any point of time between the 

 order of execution of these two movements. Only in the cat can it 

 be seen that the mewing is produced by the vocal cords first being 

 brought together, i.e. by the act of adduction being performed, and 

 then, after a measurable interval tension, i. e. elongation of tlie vocal 

 cords, occurring. 



All this may seem rather much of a scientific reSnement, and only 

 in remote, if any, connection with the subject of to-night's discourse. 

 In reality, however, it is easy to show that this connection is a very 



