hes
its maximum in the condition of hyperthyreoidism characteristic of
exophthalmic goitre or Graves' disease (p. 614).

The skin over the goitre is freely movable, and the tumour itself can
be moved transversely, carrying the larynx and trachea with it, but it
cannot be moved vertically. It moves up and down with the larynx on
swallowing--a point of great diagnostic value. Of the mechanical
symptoms dyspnoea is the most constant. It may only amount to
shortness of breath on exertion, or the patient may suffer from sudden
and severe dyspnoeic attacks, especially when lying on the back during
sleep, and such an attack may prove fatal. This may be due to the
weight of the tumour pressing on the trachea, which has been softened
and distorted by the goitre, or to temporary congestion and
engorgement of the mucous membrane of the air-passages. In these cases
there is marked stridor both on inspiration and expiration, but no
aphonia. In rare cases the goitre presses upon the recurrent nerve,
causing spasmodic dyspnoea, hoarseness, and aphonia from impaired
movement of the vocal cords, and these symptoms, especially if
accompanied by pain, raise the suspicion of malignancy. Disturbance of
the heart's action may cause palpitation and sudden attacks of
syncope; and pressure on the blood vessels may give rise to a feeling
of fullness in the head, and giddiness.

The occurrence of haemorrhage into the substance of the goitre or into
a cyst, produces a sudden aggravation of the symptoms.

In _intra-thoracic_ or _retro-sternal goitre_ the tumour displaces and
compresses the trachea and causes dyspnoea, and there are occasional
paroxysmal attacks of breathlessness, which may be mistaken for
asthma, particularly as the patient is usually the subject also of
bronchitis and emphysema. In some cases the patient can, by a violent
expiratory effort, such as coughing, project the goitre upwards into
the neck. When the goitre is fixed in the thorax, the clinical
features are those of a mediastinal tumour with lateral displacement
of the trachea, and engorgement of the veins of the neck.

_Treatment._--The patient should change his residence to a
non-goitrous district. The evidence regarding the benefit derived from
the internal administration of thyreoid extract, or of preparations of
phosphorus or of iodine, is conflicting.

Operative treatment is indicated when there are symptoms referable to
pressure on the air-passage, and in goitr