OF THE LARYNX, AND ITS ACTIONS. 853 



note; but the pitch then suddenly rises again, as in the case of the tube 

 placed beyond the reed. The researches of Miiller, however, have not suc- 

 ceeded in establishing any very definite relation between the lengths of the 

 two tubes in regard to their influence on the pitch of the reed placed between 

 them. 



699. From the foregoing statements, it appears that the true theory of the 

 Voice may now be considered as well established in regard to this essential 

 particular, that the sound is the result of the vibrations of the true vocal 

 cords, which take place according to the same laws with those of metallic 

 or other elastic tongues ; and that the pitch of the notes is chiefly governed 

 by the tension of these laminae. 1 With respect, however, to the mode and 

 degree in which these tones are modified by the shape of the air-passages 

 both above and below the larynx, by the force of the blast and by other 

 concurrent circumstances, little is certainly known ; but no doubt can be felt 

 that these modifications are of great importance, when we observe the great 

 amount of muscular action which takes place consentaneously with the pro- 

 duction of vocal tones, and which seems designed to alter the length and 

 tension of the various parts of the vocal tube, so that they may vibrate syn- 

 chronously with the vocal cords. Thus, during the ascent of the voice from 

 the deeper to the higher notes of the scale, we find the whole larynx under- 

 going an elevation towards the base of the cranium, the thyroid cartilage 

 being drawn up within the os hyoides, so as even to press on the epiglottis, at 

 the same time the small space between the thyroid and cricoid cartilages, or 

 crico-thyroid chink, is closed by the depression of the front of the former 

 upon the latter ( 691) ; the velum palati is depressed and curved forwards; 

 and the tonsils approach one another. The reverse of all these movements 

 takes place during the descent of the voice. A very important adjunct to 

 the production of the higher notes has been pointed out by Miiller, as being 

 afforded by the modification in the space included between the two sides of 

 the thyroid cartilage, which is effected by the thyro-arytenoidei. He had 

 experimentally ascertained that the introduction of a hollow plug into the 

 upper end of the pipe beneath his artificial larynx (and therefore just below 

 the reed), by diminishing its aperture, produced a considerable elevation of 

 the tone. The action may be imitated in the human larynx, when made the 

 subject of experiment, by compressing the thyroid cartilage laterally ; and 

 in this manner the natural voice can be made to extend through a range 

 that could otherwise be only reached by a falsetto. The influence of the 

 prefixed and superadded tubes, in modifying the tones produced by the 

 Human larynx, has been found by Prof. Miiller not to be at all comparable 

 to that which they exercised over the artificial larynx ; the reason of which 

 difference does not seem very apparent. It appears, however, that there is 

 a certain length of the prefixed tube as there is a certain distance of the 

 vibrating laminse, and a certain length or form of the tube above which is 

 most favorable to the production of each note; and the downward movement 



1 It is considered, however, by Mr. Bishop (Cyclop, of Anat and Physiol., vol. iv, 

 p. 1486), that the vocal apparatus combines the properties of a stretched cord, a 

 membranous pipe with a column of air vibrating in it, and a reed; and is the perfect 

 type, of which these instruments are only imperfect adaptations. The Author is 

 unable, however, to deduce from Mr. Bishop's previous statements the grounds upon 

 which he makes this assertion ; and does not understand how any instrument can 

 combine the actions of strings and of tongues, the laws of whose vibration are so 

 different. That the column of air in the air-passages is thrown into vibration con- 

 sentaneously with the production of sound by the vocal cords, and intensifies that 

 sound by reciprocation, can scarcely be doubted; but the reasons previously given 

 appear to the Author sufficient to disprove the notion that this vibration is at all more 

 essential to the production of the vocal tone, than it is in the reed-pipe of an organ. 



