Anatomiste de talent, Bartolomeo
Eustachi a fait progresser cette science dans la
seconde moitié du XVIe siècle. Outre la
fameuse trompe d'Eustache, il a
révélé l'existence de la valvule qui
porte son nom, des surrénales, du canal
thoracique.
Le grand oeuvre de Bartolomeo Eustachi devait
être un traité d'anatomie « De
dissensionibus ac controvesiis anatomicis ». Il
devait comporter 47 planches anatomiques,
dessinées avec l'aide de Pier Matteo Pini,
richement détaillées et
légendées. Seulement 8 planches furent
publiées de son vivant. Les 39 autres, perdues,
ont été longtemps recherchées. Elles
ont été retrouvées 162 ans plus tard
chez un descendant de Pier Matteo Pini. Publiées
en 1714 sous le titre « Tabulae anatomicae
Bartolomaei Eustachi quas a tenebris tandem vindicatas
» (illustrations anatomiques de Bartolomeo Eustachi
sauvées de l'obscurité), elles font de leur
auteur, avecVésale, l'un des pères de
l'anatomie moderne.
Yawning is a complex somatical reflex
serving the purpose of augmenting the tonus of
the limbs and trunk muscles no less than the
negative pressure in mediastinum, both of which
agents elicit the outflow of venous blood from
the perifery to the heart. From this point of
view we can easily understand the nature and
purpose of the stretching movements of the limbs
and the body accompanied the phenomenon in
question. The forwarding factor in producing
these reflexes is always weariness after hard
work in connection with the decline of the
general tonus and blood pressure so that even at
awakening from a long rest prolonged yawning
reflex dominates the clinical picture. Likewise
the feeling of hunger and thirst, living in
unaired rooms for a long time (oxygen
deficiency) and especially acute anemic status
after hemorrhages as well as resulting from the
disturbances of general metabolism and blood
circulation within the brain, are accompanied by
yawning. In the second place yawning be
considered as an expression of the feeling of
exhaustion and weariness, analogous to the
related automatical phenomenon of laughter
expressing contentand selfreliance.
On the other hand we can sometimes observe
yawning as a consequence of augmented nervous
tonus during prolonged and anxious waiting. This
also explains the fact that the eliciting factor
of yawning could even be the imagination as well
as the sight of a yawner. In the last case the
unconscious process ocurs which is defined
commonly as yawning by imitation and belongs to
the mimical automatisms elicited by suggestion.
The view of a yawner affects onlookers like
infection just as laughing or weeping which
elicit analogous psychic states in observe and
particularly sensible (hysterical) persons as
reflexes with sometimes a spasmatic tint (J.
Schul tz, Jaspar, Hösslin)
The part taken in this reflex by the upper
respiratory organs is very active: tonic
contracture of the mimical muscles, enlarged
nostrils, wide opening of the mouth, tonic
contracture of the soft palate adhering strongly
together with uvula to theposterior pharyngeal
walI, lifting up of larynx opening and tightness
of the glottis, tonic contracture of the
diaphragma. The symptom, concerning the ear are
as follows: Wide Opening of the Eustachius tube
during forced and prolonged yawning causes a
great amount of air to be driven into the middle
ear which press towards the fenestra. This fact
elicits changes in the periendolymph pressure
marked by a considerable hardness of hearing for
low and middle tones and noises. Tympanophony,
in yawning is characteristic for the patulous
Eustachius tube.
In order to prove the influence of yawning
on the variations of air pressure in the
tympanal cavity I have chosen 5 cases of
tympanic membrane scars, being situated mainly
in the posterior part of the tympanic membrane
movable and not adherent to the tympanal cavity.
During deep inspirium these scars are subject to
floating movements. in yawning they yield
inwards. The short expirium is responsible for
pushing out the whole tympanal membrane, which
could be easily observed by using the
anastigmatic otoscope of Brünings. The said
movements I have tried to register with help of
one Ear manmetter resembling the one used by
Politzer for the same purpose. It is a glass
tube of 1 mm inner light diameter, U shaped, 15
cm long and with 5 cm between the branches. The
horizontally inflected branch is connected with
a small rubber tube and protected by one olive
end, which could be easily introduced in the
external auditory canal and tightened with a
piece of wool impregnated with glicerin.
Alcohol-fuchsine solution was placed in the
lumen of this mannometer.
The level of this fluid enabled us to read
the variations of airpressure, in the external
auditory canal as a consequence of movements of
the tympanic. membrane and so with help of the
background milimeter scale the diagram could be
established, which illustrate approximatively
the problem in question. The said variations
depend mainly on the changes of airpressue in
the nasopharynx during deep inspirium and
swallowing (v. Dieshoecker Hammerschlag had
asserted that the state of the vessels of the
tympanal mucoso exercise a certain influence on
the said airpressure. When the yawn as deep
inspirium through the nose and a short expirium
by the mouth the diagram of the airpressure
shows lengthened contours from the upper to the
lower end. The amount of air passing into the
tympanal cavity is nearly the same as during
swallowing. In rest the Eustachius tube is
closed. The tightness of its lumen is not
absolute while a pressure of 30-60 cm of water
is able to penetrate this closure resistance
when performing the tests of Politzer or
Valsalva. The reverse direction in cases of an
overpressure in the tympanum is much easier to
penetrate j. e. with a pressure of + 12 cm only.
This attribute is to be called the "valve
mechanisme" of the Eustachius tube, which
explains many disturbances of the ear during
flying and their prevention by yawning or
swallowing.
Rising to the altitude of 300-400 m as well
as quick descent from it to scalevel produce
protracted and repeated yawning as a defense
reflex from the ear. Catarrhal inflammations of
the throat and the nasopharyngeal cavity
especially: pharyngitis chronica granulosa
diffusa et retroarcualis could be the starting
point of the yawning reflex with strong
contractions of the palatal and throat muscles a
phenomenon which might be appreciated by the Ear
as a prolongated inspirium. Moreover I could
state in these cases the phenomenon of aeophagia
on the end of the inspiratory phase as it was
confirmed by the X ray graphy.
From the intracranial complications often
occurring with yawning reflex should be
mentioned: inflammatory processes and neoplasms
in the posterior cranial fossa, especially
cerebellar abscesses and abscessus of the
internal auditory meatus with circumscribed
inflammatory processes of the meninges in the
immediate vicinity of porus ac. mt.
Description of two cases of cerebellar
abscesses in the course of acute supurative
middle Ear inflammation and one case of abscess
of the internal auditary meatus as a consequence
of the purulent labyrinthitis healed by
labyrinthectomy m. Neumann II with chiseling of
the posterior margin of this auditory meatus, in
which repeated and protracted yawning was one of
the important neurological symptoms during the
period of these abscesses in question.
The inflammatory processes in the region of
mesencephalon are seldom joined with yawning,
contrary to the posterior cranial fossa. Markl
and Jedlieka have described a case of
infiltration of the right thalamus of syphilitic
origin spreading the capsula int. as a great
rarity in literature. Clinical examination has
stated a complete paresis of the left half of
the body with involvement of the III rd, VI th,
VII th and XII th nerves. During protracted and
repeated yawning a synergy could be stated in
the form of contraction in the elbow of the
paretic extremity, attesting the influence of
the motoric centres of the opposite hemisphere
(left) stimulated by failing restraining action
of the pyramidal fibres. A case described by O.
Fischer deserves attention relating to the
changes in the basal ganglia thalamus and corpus
striatum on the underlying encephalithic process
in which the yawning reflex did not appear at
all, and also the related automatical movements
of mastication, laughing and swallowing were
absent. This fact has given a fundamental base
to Bertolotti and Vogt who suppose that yawning
as a mimical automatism has its own centre in
the basal ganglions especially in the region of
corpus striatum i. e. the nucleus caudatus and
putamen. H Levy shares this opinion observing
analogous subsisting of automatical movements in
the course of paralysis agitans and stressing
that the overpart of the brain cortex is not
necessary for the purpose of eliciting these
reflexes.
Joseph Toynbee (1815-1866) of England wanted
to do more work with otology. He dissected
more than 2000 temporal bones and formed the
collection which became known as the Toynbee
Collection in the Museum of the Royal College of
Surgeons. In 1860, his work "Disease of the
Ear" was published. It contained
information on the dissection of diseased
ears. Toynbee showed that stricture of the
Eustachian tube was not a common affliction
since he had only one out of his 1523
dissections. He noted that the Eustachian
tube was not permanently open, but lightly
closed, and that it became opened only during
such movements as swallowing or
yawning. In one of his dissections,
Toynbee recognized a fistula of the external
semicircular canal and he pointed out that
infection could extend to the brain by way of
the labyrinth. Tonybee was one of the first
to describe otosclerosis (a condition
characterized by chronic progressive deafness)
and he recognized it in 160 cases.
