w growth, and give rise to inconvenience chiefly by their bulk, and
should be removed.

[Illustration: FIG. 258.--Papillomatous Angioma of left side of tongue
in a woman aged 26.]

_Papilloma_ may occur on any part of the tongue, and at any age. It
may be single or multiple, pedunculated or sessile, and is liable to
become malignant, especially when associated with leucoplakia. It
should be freely removed by excising a wedge-shaped portion of the
tongue.

_Dermoid_ cyst is met with beneath the tongue, lying in the middle
line, between the genio-glossi (genio-hyoglossi), and on the upper
surface of the mylo-hyoid muscles. It may be noticed soon after
birth, or may only attract attention during adult life. The cyst
usually projects under the chin, forming a soft swelling of putty-like
consistence, which varies in size from a pigeon's to a turkey's egg
(Fig. 259). When it bulges towards the mouth it is liable to be
mistaken for a retention cyst of one of the salivary glands. It is
distinguished by its medial position, its yellow colour, and its
opacity, the retention cyst being to one side of the middle line,
purplish in colour, translucent and fluctuating. The cyst should be
dissected out, either from the mouth or from under the chin, according
to circumstances.

[Illustration: FIG. 259.--Dermoid Cyst in middle line of neck.

(Mr. J. W. Struthers' case.)]

A _sebaceous cyst_ may reach such dimensions as to simulate a dermoid
or thyreo-glossal cyst.

_Hydatid and cysticercus cysts_ have also been met with in the tongue.

#Thyreo-glossal Tumours and Cysts.#--Tumours may develop in the
embryonic tract which passes from the isthmus of the thyreoid gland
to the foramen caecum at the base of the tongue--the thyreo-glossal
tract of His. They have the same structure as the thyreoid gland, and
occupy the dorsum of the tongue, extending from the foramen caecum
backwards towards the epiglottis, in some cases attaining considerable
size. They are of a bluish-brown or dark red colour, and are liable to
repeated attacks of haemorrhage. These tumours sometimes become cystic,
the cysts being lined with ciliated epithelium and containing colloid
material. Bleeding may take place into a cyst, causing it to become
suddenly enlarged, or the cyst may burst and the blood escape into the
mouth. These variations in size and repeated attacks of bleeding help
to distinguish thyreo-glossal cysts from other swellings of the
tongue. Treatm