As the process is painful, a general anaesthetic is necessary.  The current used should be from 20 to 80 milliamperes, gradually increasing from zero, without shock; three to six large Bunsen cells give a sufficient current, and no galvanometer is required.  Steel needles, insulated with vulcanite to within an eighth of an inch of their points, are the best.  Both poles are introduced into the naevus, the positive being kept fixed at one spot, while the negative is moved about so as to produce a number of different tracks of cauterisation.  On no account must either pole be allowed to come in contact with the skin, lest a slough be formed.  The duration of the sitting is determined by the effect produced, as indicated by the hardening of the tumour, the average duration being from fifteen to twenty minutes.  If pallor of the skin appears, it indicates that the needles are too near the surface, or that the blood supply to the integument is being cut off, and is an indication to stop.  To cauterise the track and so prevent bleeding, the needles should be slowly withdrawn while the current is flowing.  When the skin is reached the current is turned off.  The punctures are covered with collodion.  Six or eight weeks should be allowed to elapse before repeating the procedure.  From two to eight or ten sittings may be necessary, according to the size and character of the naevus.

Excision is to be preferred for naevi of moderate size situated on covered parts of the body, where a scar is of no importance.  Its chief advantages over electrolysis are that a single operation is sufficient, and that the cure is speedy and certain.  The operation is attended with much less haemorrhage than might be expected.

#Cavernous Angioma.#—­This form of angioma consists of a series of large blood spaces which are usually derived from the dilatation of the capillaries of a subcutaneous naevus.  The spaces come to communicate freely with one another by the disappearance of adjacent capillary walls.  While the most common situation is in the subcutaneous tissue, a cavernous angioma is sometimes met with in internal organs.  It may appear at any age from early youth to middle life, and is of slow growth and may become stationary.  The swelling is rounded or oval, there is no pulsation or bruit, and the tumour is but slightly compressible.  The treatment consists in dissecting it out.

#Aneurysm by Anastomosis# is the name applied to a vascular tumour in which the arteries, veins, and capillaries are all involved.  It is met with chiefly on the upper part of the trunk, the neck, and the scalp.  It tends gradually to increase in size, and may, after many years, attain an enormous size.  The tumour is ill-defined, and varies in consistence.  It is pulsatile, and a systolic bruit or a “thrilling” murmur may be heard over it.  The chief risk is haemorrhage from injury or ulceration.

[Illustration:  FIG. 69.—­Cirsoid Aneurysm of Forehead in a boy aet. 10.