hysiological hyperaemia--Acute
thyreoiditis--GOITRE--Varieties: _Parenchymatous_; _Adenomatous_;
_Cystic_; _Malignant_; _Toxic_.

#Surgical Anatomy.#--The _thyreoid gland_ consists of two lateral
lobes connected by an isthmus. The lateral lobes lie in contact with
the side of the larynx up to the middle of the thyreoid cartilage, and
with the sides of the first five or six rings of the trachea. The
isthmus lies in front of the second, third and fourth rings of the
trachea, and from it a process of gland tissue--the _pyramidal
lobe_--passes up in the middle line towards the hyoid bone.

The gland lies under cover of the superficial muscles of the neck, and
is surrounded by a process of the cervical fascia--the external
thyreoid capsule of Kocher--which connects it with the larynx,
trachea, and oesophagus, so that it moves with these structures on
swallowing. In this capsule are numerous veins; and in the groove
between the oesophagus and trachea the recurrent (laryngeal) nerve
runs. Enclosing the gland substance is the capsule proper, which sends
in processes to form its fibrous stroma. The arteries of supply--the
superior and inferior thyreoids--are very large for the size of the
gland, and enter it at its four corners. The thyreoidea ima, when
present, goes to the isthmus. Isolated nodules of thyreoid
tissue--_accessory thyreoids_--are sometimes met with in different
parts of the neck; they are liable to the same diseases as the main
gland.

The secretion of the gland is absorbed into the general circulation
through the veins; it consists of a complex colloid substance which
contains an iodine-albumin--iodothyrin--and plays an important part in
maintaining the normal metabolism of the body, particularly of the
central nervous and cutaneous tissues in adults, and of the bones in
children. Disturbance of the function of the thyreoid gland plays a
part in producing the symptoms characteristic of myxoedema, cretinism,
and goitre.

The _para-thyreoid glands_--usually two on each side--lie in the
external capsule along the posterior edge of the lobes of the
thyreoid. They are flattened, elliptical bodies, averaging a quarter
of an inch in length and an eighth of an inch in width, of a light
brown colour, smooth and glistening on the surface, and of a soft,
flabby consistence (W. G. MacCallum). When tetany follows operations
for goitre it is due to the removal of these glands.

#Physiological Hyperaemia.#--The