The Voice and its Modifications. 79 
Yawning is caused by debility or the sluggish action of the mus- 
cles of respiration, and consequently a diminished force in the circu- 
lation; anda smaller quantity of air is admitted to the lungs and carbon- 
ic acid gas being accumulated in the bronchiz, nature makes this ef- 
fort to dispel the torpor and relieve the air cells. 
Snoring is effected by the inactivity of the muscles of the extrem- 
ities, in consequence of which the blood returns more sluggishly to 
the heart; some of the muscles of respiration are thus impeded, and 
the remainder have to labor more violently to overcome the deficien- 
cy, for the lungs require a certain quantity of air to preserve their 
function ; what they fail in receiving in the regular inspirations they 
make up by more frequent inhalations, and what they want in the 
frequency of inspirations, they endeavor to compensate by the quan- 
tity admitted. In snoring, the mouth is besides but slightly extended, 
the palate is depressed, a larger volume of air is admitted into the nose, 
and hence the peculiar nasal resonance. 
Sneezing results from the irritation of the membrane lining the na- 
sal cavity and the sudden action of the muscles of respiration. Na- 
ture here strikingly shows the precautions she has taken to expel ir- 
ritating bodies from the nose. ‘The entrance from the mouth to the 
nares is guarded by the velum palati, and in sneezing, this part of the 
roof of the mouth is greatly depressed, the passage of course is more 
open and the exit by the mouth more hindered, and hence the pecu- 
har nasal sound. 
Hiccup arises from the spasmodic action of the diaphragm com- 
pressing the lungs with more or less violence. ‘The length of time 
between two successive inspirations cannot be always fixed, for hab- 
it, circumstances, and the will, cause such alterations in this interval 
as to strike with surprise many unacquainted with the fact.* 
When these inspirations are partial, short and quick and are modi- 
fied by the position of the mouth, we have sobbing or sighing. 
Groans are labored, deep and lengthened expirations. 
Laughing is a continued expiration, with catches, or more properly 
there is, at intervals, from the action of the d‘aphragm and muscles of 
the chest, an increased velocity in the exit of the air. ‘These inar- 
ticulate sounds are little affected by the larynx, whilst other modifica- 
tions of the human voice which are used to convey ideas, are so de- 
* The pearl divers of India have accustomed themselves to exert the muscles of 
respiration so as to admit a larger quantity of air than usual and thus endure an ab- 
sence from the open air, which is truly wonderful. 
