- To most minds yawning is an infectious habit
of the bored ; but it may also arise from
hunger, overeating, drowsiness, or bad
ventilation; and it may come on with
gastro-intestinal disturbances, after severe
haemorrhage, in association with hysteria, as an
aura of epilepsy, and in encephalitis,
Huntington's chorea, and cerebellar abscess or
tumour.
-
- The yawn may not be restricted to man.
Crämer suggested
that the gaping of fishes, amphibians, and
reptiles was closely analagous; and the gaping
hen beating its wings on tiptoe is an everyday
sight to the poultry-keeper.
-
- Mayer found that
during the first part of the inspiratory phase
there is expansion of the chest with descent of
the diaphragm and larynx, elevation of the alae
nasi and soft palate, downward and backward
displacement of the tongue, abduction of the
vocal cords, and opening of the mouth. This is
immediately followed by closing of the eyes and
stretching, notably of the muscles of the neck
and upper limbs.
-
- Mayer described yawning as an automatic
expression of cerebral fatigue, in the sense
that crying and laughing are expressions of
sorrow and joy; while Hauptmann
suggested that it combated the loss of
muscle-tone which results from enforced
inactivity of the higher cerebral centres.
-
- Dumpert suggested
that it occurred when the cerebral circulation
was unfavourably adjusted to maintain an alert
state; he also held that it augmented the venous
return to the heart, which in turn improved the
arterial blood-supply to the tissues.
-
- Heusner
reviewed the evidence and showed that in the
fingers and toes of normal adults yawning was
followed by vasoconstriction, which was roughly
proportional to the depth and duration of the
inspiratory movement, and that it was attended
by transient acceleration of the heart.
-
- These changes are similar to those recorded
after deep inspiration. There is thus some
reason for regarding the yawn as a mechanism for
countering physiological aberration.
-
- Yawning the
Lancet 1905
- Yawning Lancet
1952
- Yawning: its
physiology and psychology Lancet
1921
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