558 
MR. BISHOP ON THE PHYSIOLOGY 
after death vibrate in a great measure like musical strings, we think it may be fairly 
inferred that they likewise obey, to a certain extent, during life the laws of the vibra- 
tions of such strings, and that the conclusions which we have derived from the fore- 
going formulas are not far removed from the truth. A further confirmation of these 
views may be derived from the following considerations. The length of a cord of 
invariable weight varies directly as the tension, and inversely as the square of the 
number of vibrations. Now, if we assume the length of the vocal cord, which gave 
G 2 $ under a tension of 32 loths to be '91 inch, which is the mean length of the male 
vocal cord in its greatest tension, according to the first table, and which gave the 
notes A 1 , C l under the tension 8 and 2 loths respectively, the corresponding lengths 
of that cord, according to the formula, will be "83 inch and '58 inch* ; but '58 inch 
is less than the least length in repose in the table. This result is, however, quite 
consistent with the theory here proposed; because after death the thyro-arytenoid 
muscle becomes of itself elongated, and consequently the vocal ligament attached to it, 
and therefore the length of the ligament must be greater in this state than when it is 
in that which we have defined to be the state of repose before it has lost its vitality. 
In experiments made on the larynx by stretching the vocal ligaments with given 
weights, and by forcing a current of air through the glottis, care must be taken to 
keep the organs moist, and of the same temperature which they possess during life. 
The amount of condensation of the air in the vocal tube has been ascertained by 
Cagniard la Tour, and Muller, the former in the living, and the latter in the dead 
subject. In a person who had an opening in the windpipe after the operation of 
bronehotomy, Cagniard la Tour found that the tension of the air in the vocal tube, 
whilst blowing the clarionet, was equal to a column of water of thirty centimetres in 
height, and that to produce a simple vocal sound in the same person, a tension of 
sixteen centimetres was necessary. Muller found that he could produce sound in 
a larynx artificially by a tension of 3'4 centimetres, but for very loud sounds an 
increased tension was requisite. The discrepancy between the experiments of La 
Tour and Muller may be ascribed to the circumstance that the one operated on the 
living vocal organs, but in a state of disease, the other on the organs after death. 
Variations in the hygrometric and thermometric states of the air exert very power- 
ful influence on the pitch of the voice ; during the prevalence of a cold moist state of 
the atmosphere, especially in England, the voices of singers become lower by two or 
three notes, and regain their usual pitch when the air becomes dry-f-. In thus tracing 
V P p 32 
N varies as .\ l varies as then *91 inch : length of cord for A 1 : : 
(427)* 
the length 
of the cord for A‘= - 83 inch ; and the length for C' = '58 inch. 
f When Grassini came to this country, owing to the change from the air of Italy to that of England, her 
voice became one octave lower : after singing for two or three seasons, her natural voice returned, but it had 
lost its attractions with the low tones which had obtained her the greatest applause. — Trans. Lond. Med. So- 
ciety, New Series, vol. i. 1846 ; Art. Aphonia, p. 36. 
