OF THE HUMAN VOICE. 
557 
table by ciphers, the C 1 answering to 256 vibrations ; the notes below C have no 
cipher. Muller states that the numbers of vibrations in these experiments are not 
exactly in direct ratio of the square roots of the stretching forces, and that the weights 
4, 16, 64 did not produce the octaves, but generally from a semitone to two or 
three tones lower. Now this result should have been anticipated ; but it does not 
seem to have occurred to him that whilst he increased the tension he at the same 
time increased the length, and we know (eq. 3.) that the number of vibrations in this 
case varies as ^/te n sion ^ an q consequently the numbers actually produced by 
-v/length of cord 
the weights above-mentioned, ought (agreeably to Muller’s experiments) to be less 
than those which correspond with octaves. We see by the first experiment in the 
above table that the tension sufficient to produce 818 musical vibrations is 64 loths, 
or very nearly 33 ozs. If, therefore, we take the mean length of the vocal ligaments 
under the greatest tension at '91 of an inch, and substitute in equation (3.) their 
values for all known quantities, remembering that P represents the tension of one 
vocal cord, we shall find the weight of each ligament, viz. 
a6A=-^^2-=M44 grs (4.) 
In an adult male I found that the two vocal ligaments, when divested of mucous 
membrane, weigh one grain, Avhich is scarcely one-half their weight by theory ; hence 
it appears that a considerable portion of mucous membrane is connected with the 
vocal cord in the production of sound, which agrees with the anatomy of these parts. 
It is now necessary to offer some explanation respecting the vital state of the vocal 
ligaments. The state of repose is the ordinary condition of the vocal ligament in the 
living subject, when the voice is not exercised ; but we must not therefore conclude 
it to be incapable of further contraction. In fact, the state of repose during life is a 
state of tension, for the ligaments being connected with the thyro-arytenoid muscles, 
not in a few points, but continuously throughout their whole length, must obey the 
motions of these muscles, which, like all muscles, are in a state of tension during re- 
pose. We also know by experience that when we produce a sound lower than the 
usual pitch of our voice, the crico-thyroid chink is opened principally by the con- 
traction of the same muscles, and the ligaments must therefore at the same time be 
relaxed. It appears, then, both from the anatomy and physiology of the human 
larynx, that the ordinary state of the vocal cords is one of considerable tension, 
which admits of being lessened, and thereby produces the range of lower notes. If 
we suppose the glottis to be partially closed when we are talking, that is at the ordi- 
nary pitch of our voice, and to be more opened as the tones become graver, this of 
course will cooperate with the relaxation of the vocal cords. In the production of 
the higher notes the crico-thyroid chink closes, and the thyro-arytenoid muscles, 
and consequently the ligaments are elongated. Since, therefore, the vocal ligaments 
have been proved to extend and contract for acute and grave tones respectively, and 
