Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/297

Rh V O I V I 273 One of Vogler s latest exploits was a journey to Frankfort in 1810, to witness the production of Weber s Sylvana. He continued hard at work, genial and pleasant to the last, and died suddenly of apoplexy at Darmstadt, May 6, 1814. Opinions are strangely divided as to the reality of Vogler s voca tion. Some have pronounced him a genius, others a charlatan. Mozart was strongly prejudiced against him. That he was a bril liant and accomplished performer no one denies. It is certain that he was an excellent, if an eccentric, teacher. But his theories were visionary, and of his numberless compositions not one has survived to the present day. VOICE is produced by the vibrations of the vocal cords, two ligaments or bands of fibrous elastic tissue situated in the larynx. It is to be distinguished from speech, which is the production of sounds intended to express ideas. Many of the lower animals have voice, but none have the power of speech in the sense in which man possesses that faculty. There may be speech with out voice, as in whispering, whilst in singing a scale of musical tones we have voice without speech. Regarding speech, see PHONETICS and SPEECH -SOUNDS; also the articles on the various letters of the alphabet. 1. Physiological Anatomy. The organ of voice, the larynx, is situated in man in the upper and fore part of the neck, where it forms a well-known prominence in the middle line. It opens below into the trachea or windpipe, and above into the cavity of the pharynx, and it consists of a framework of cartilages, connected by elastic mem branes or ligaments, two of which constitute the true vocal cords. These cartilages are movable on each other by the action of various muscles, which thus regulate the position and the tension of the vocal cords. The trachea conveys the blast of air from the lungs during expiration, and the whole apparatus may be compared to an acoustical con trivance in which the lungs represent the wind chest and the trachea the tube passing from the wind chest to the sounding body contained in the larynx. Suppose two tight bands of any elastic membrane, such as thin sheet india-rubber, stretched over the end of a wide glass tube so as to leave a narrow chink between the free borders of the membrane, and that a powerful blast of air is driven through the tube by a bellows. The pressure would so distend the margins of the membrane as to open the aper ture and allow the air to escape ; this would cause a fall of pressure, and the edges of the membrane would spring back by their elasticity to their former position ; again the pressure would increase, and again the edges of the membrane would be distended ; and those actions would be so quickly repeated as to cause the edges of the mem brane to vibrate with sufficient rapidity to produce a musical tone, the pitch of which would depend on the number of vibrations executed in a second of time. The condensation and rarefaction of the air thus produced are the chief cause of the tone, as Von Helinholtz has pointed out, and in this way the larynx resembles the syren in its mode of producing tone (see ACOUSTICS). It is evident also that the intensity or loudness of the tone would be determined by the amplitude of the vibrations of the margins of the membrane, and that its pitch would be affected by any arrangements effecting an increase or de crease of the tension of the margins of the membrane. The pitch might also be raised by the strength of the current of air, because the great amplitude of the vibra tions would increase the mean tension of the elastic mem brane. With tones of medium pitch, the pressure of the air in -the trachea is equal to that of a column of mercury of 160 mm. ; with high pitch, 920 mm. ; and with notes of very high pitch, 945 mm. ; whilst in whispering it may fall as low as that represented by 30 mm. of water. Such is a general conception of the mechanism of voice. The cartilages form the framework of the larynx. They consist of three single pieces (the thyroid, the cricoid, and the cartilage of the epiglottis) and of three pairs (two arytenoids, two cornieula laryngis or cartilages of Santorini, and two cuneiform cartilages or cartilages of Wrisberg), see figs. 1 and 2. The epiglottis, the FIG. 1. Cartilages and ligaments of the larynx seen from the front ; half natural size. 1, epiglottis ; 2, hyoid bone ; 3, small cornu of hyoid bone ; 4, middle thyro-hyoid ligament ; 5, great cornu of hyoid bone ; 6, small nodules of cartilage (cartilage triticea) ; 7, the lateral thyro-hyoid ligament ; 8, left- lamina or wing of thyroid cartilage ; 9, cricoid cartilage ; 10, lower cornu of thyroid cartilage ; 11, part of cricoid united to the thyroid by the middle crico- thyroid ligament ; 12, second ring of trachea. (From Krause.) FIG. 2. Cartilages and ligament of larynx seen from behind ; half natural size. 1, epiglottis ; 2, lesser cornu of hyoid bone ; 3, greater cornu of hyoid ; 4, lateral thyro-hyoid ligament ; 5, cartilage triticea ; 6, upper cornu of thyroid ; 7, thyro-epiglottic ligament; 8, cartilages of Santorini; 9, arytenoid carti lages ; 10, left lamina of thyroid ; 11, muscular process of arytenoid cartilage ; 12, inferior cornu of thyroid ; i3, first ring of trachea ; 14, posterior mem branous wall of trachea ; 15, lamina of cricoid cartilage. (From Krause.) cornieula laryngis, the cuneiform cartilages, and the apices of the arytenoids are composed of yellow or elastic fibro-cartilage, whilst the cartilage of all the others is of the i hyaline variety, resembling that of the costal or rib cartilages. These carti lages are bound together by ligaments, some of which are seen in figs. 1 arid 2, whilst the remainder are represented in fig. 3. The ligaments specially concerned in the production of voice are the inferior t/tyro-arytenoid liga ments, or true vocal cords. These are - j-. composed of fine elastic fibres attached [0 /) behind to the anterior projection of the base of the arytenoid cartilages, processus vocalis, 3 in fig. 3, and in front to the middle of the angle be- 8 tween the wings or lamiiue of the thyroid cartilage. They are practi cally continuous with the lateral crico- thyroid ligaments, 6 in fig. 3. The cavity of the larynx is divided into an upper and lower portion by c 5 the narrow aperture of the glottis or Fio. 3. Right half of the larynx, chink between the edges of the true - from a TCrtical and . slightly ob- vocal cords, the rima glottidis. Im mediately above the true vocal cords, between these and the false vocal cords, there is on each side a recess or pouch termed the ventricle of Mor- gngni, and opening from each ventricle there is a still smaller recess, the laryngeal pouch, which passes for the space of half an inch between the superior vocal cords inside and the thyroid cartilage outside, reaching as high as the upper border of that car tilage at the side of the epiglottis. The ventricles no doubt permit a free vibration of the true vocal cords (Quain). The upper aperture of the glottis is triangular, wide in fiont and narrow behind ; and, when seen from above by means of the laryngoscope, it presents the view represented in fig. 4. The aperture is bounded in front by the epiglottis, c, behind by the summits of the arytenoid carti lages, ar, and on the sides by two folds of mucous membrane, the aryteno-epiglottic folds, ac. The rounded elevations corresponding to the cornieula laryngis and cuneiform cartilages, c, and also the cushion of the epiglottis, c, are readily seen in the laryngoscopic picture. The glottis, o, is seen in the form of a long narrow fissure, bounded by the true vocal cords, ti, whilst above them we have the false vocal cords, ts, and between the true and false cords the open ing of the ventricle, n The rima glottidis, between the .true vocal cords, in the adult male measures about 23 millimetres, or nearly XXIV. 35 lique section; two-thirds natural size. 1, epiglottis; 2, arytenoid cartilage ; 3, processus vocalis of arytenoid ; 4, cricoid carti lage ; 5, capsular thyro-hyoid ligament ; 6, lateral crico-thy- roid ligament; 7, posterior crico- thyroid ligament ; 8, inferior thyro - arytenoid ligament, or true vocal cord ; 9, thyroid car tilage ; 10, superior thyro-ary- tenojd ligament, or false vocal cord; 11, thyro-ary-epiglottideus muscle ; 12, middle thyro-hyoid ligament; 13, hyo-epi glottic liga ment ; 14, body of hyoid bone ; 15, smaller cornu of hyoid bone. (From Krause.)