132 PHYSIOLOGY. 



Neither can they be compared to a flute pipe, in which the sound 

 is produced by the vibration of the column of air contained in the 

 tube, and the pitch of the note determined by the length of the 

 column, slightly modified by its diameter. There is nothing in the 

 form or dimensions of the column of air between the larynx and 

 mouth which can be conceived to render it capable of such vibra- 

 tions as are required to produce the tones of the human voice. 



The third class of instruments are the reeds, and to these the 

 vocal organ bears more analogy than to any of the others. In the 

 reed instrument, a thin plate or lamina vibrates freely m a frame 

 that allows the air to pass readily round it. In the accordion the 

 variations in the tone are produced by different lengths in the reeds. 

 In the vocal apparatus there are laminoe formed by stretchmg the 

 mucous membrane over the vocal ligaments, and by increasmg or 

 diminishing the tension of these, various notes can be produced. In 

 this respect it resembles a reed instrument. In regard to the pro- 

 duction of falsetto notes nothing certain is known. MuUer supposes 

 that in them merely the border of the glottis vibrates. 



The intensity of the voice, or, as it is commonly called, the 

 volume of the voice, results in part from the force with which the 

 air is driven from the lungs, and from the size of the thoracic cavity ; 

 and in part from the facility with which the vocal cords of other 

 parts of the larynx are able to vibrate. These modifications explain 

 the difference which exists between the male and female voices. 

 The vocal cords in the male are longer than in the female in the 

 proportion of 3 : 2, and their voices are commonly an octave lower. 



The power of the will in determining the exact degree of tension 

 necessary to produce a given note, is extremely remarkable. The 

 natural compass of the voice in most persons is two octaves or 24 

 semitones. Now a singer can produce ten distinct intervals between 

 each semitone, or 240 intervals. There must, therefore, be 240 

 difl^erent states of tension of the vocal cords all produceable at 

 pleasure when a distinct conception exists as to the tone required. 

 And all these different notes can be produced without a greater varia- 

 tion in the length of the vocal cords than one-fifth of an inch. 



The peculiar timbre, or quality of the voice which each person 

 possesses, and its imperfections, depend on the smoothness or rough- 

 ness of the cartilages of the larynx, or on the different aptitudes for 

 vibration which the parts of the organ possess. 



In the production of voice the inferior ligaments are the impor- 

 tant agents. If we remove the superior ligaments, voice continues, 

 though more feeble; but if we divide the inferior ligaments, voice 

 is destroyed. Even the ventricles of the larynx may be cut into 

 and yet voice continue. The use of the ventricles is to allow free 

 vibration of the vocal laminse. , , • r u 



All the articulated tones or sounds which form the basis ot speech 



