Biographies de neurologues
Nouvelle Iconographie de La Salpêtrière
 L'histoire des neurosciences à La Pitié et à La Salpêtrière J Poirier
The history of neurosciences at La Pitié and La Salpêtrière J Poirier 

mise à jour du
22 février 2010
Lancet 22 oct 1921
p 866
Yawning: its physiology and psychology


YAWNING is one of those curiously modified respiratory acts which has important physiological and psychological relations, not the least remarkable of the latter being what might almost be called its "infectious " nature, associated with imitation on the part of the beholder, and which in some people may be excited by thinking intensely of the act itself.
C. Mayer in Zeitschrifl f. Biologie (vol. Iv., 1921) gives the results of his investigations in man by inspection, laryngoscopy, and X rays.
The act itself he divides into three phases:
The initial phase, beginning with inspiration, widening of the chest, descent of the diaphragm and larynx until a certain depth of descent of both is reached, elevation of the wings of the nostrils, of the soft palate, drawing of the tongue upwards and backwards, dilatation of the rima glottidis.
The acme stage, full dilatation of the thorax to its greatest extent by means of the intercostal and accessory muscles, and descent of the diaphragm and larynx to their lowest position, accompanied by maximum depression of the lower jaw, further retraction of the tongue, and elevation of the soft palate. Tonic contraction of a varying number of individual muscles of the neck, shoulder, and region of the trunk. Wide lateral expansion of the mouth, closing of the eyelids, noise in the ears due to contraction of the tensor tympani, and a subjective feeling of pleasure and satisfaction.
Final ihase, a short expiration, relaxation of the contracted muscles, ascent of the diaphragm and larynx, and elevation of the lower jaw, secretion of tears, and deglutition.
The duration of the tonic contraction of the individual muscles is about 246 seconds, that of the whole inspiratory phase (phases 1 and 2) about 55 seconds.
The biological significance of the acts seems to lie in the energetic ventilation of the lungs. The tonic phenomena accompanying the act can only in part be explained by the irradiation of the inspiratory impulses. This circumstance, along with the accompanying stretching of the arms and extension of the trunk, seem to indicate that the act of yawning and the participation therein of the pronounced contraction of certain muscles is of importance for aiding both the circulation and metabolism.
The act itself would seem to be sub-cortical in origin, though it may be excited or discharged by psychical impulses. Spontaneous yawning is an expression of cerebral fatigue and the processes leading up to it stands in intimate relation to the function of sleep. If the optic thalamus is the part of the brain intimately concerned with sleep, then at a certain stage of fatigue the motor impulses for the act of yawning may proceed from it.
In certain cases of encephalitis lethargica the execution of the act of yawning may be disturbed and modified.
Yawning the Lancet 1905
Yawning Lancet 1952
Yawning: its physiology and psychology Lancet 1921