_Prognosis._--The rate of growth of the subcutaneous and mixed forms of nævi varies greatly. They sometimes increase rapidly, especially during the first few months of life; after this they usually grow at the same rate as the child, or more slowly. There is a decided tendency to disappearance of these varieties, fully 50 per cent. undergoing natural cure by a process of obliteration, similar to the obliteration of vessels in cicatricial tissue. This usually begins about the period of the first dentition, sometimes at the second dentition, and sometimes at puberty. On the other hand, an increased activity of growth may be shown at these periods. The onset of natural cure is recognised by the tumour becoming firmer and less compressible, and, in the mixed variety, by the colour becoming less bright. Injury, infection, or ulceration of the overlying skin may initiate the curative process. Towards adult life the spaces in a subcutaneous nævus may become greatly enlarged, leading to the formation of a cavernous angioma. _Treatment._--In view of the frequency with which subcutaneous and mixed nævi disappear spontaneously, interference is only called for when the growth of the tumour is out of proportion to that of the child, or when, from its situation--for example in the vicinity of the eye--any marked increase in its size would render it less amenable to treatment. The methods of treatment most generally applicable are the use of radium and carbon dioxide snow, igni-puncture, electrolysis, and excision. For nævi situated on exposed parts, where it is desirable to avoid a scar, the use of _radium_ is to be preferred. The tube of radium is applied at intervals to different parts of the nævus, the duration and frequency of the applications varying with the strength of the emanations and the reaction produced. The object aimed at is to induce obliteration of the nævoid tissue by cicatricial contraction without destroying the overlying skin. _Carbon-dioxide snow_ may be employed in the same manner, but the results are inferior to those obtained by radium. _Igni-puncture_ consists in making a number of punctures at different parts of the nævus with a fine-pointed thermo-cautery, with the object of starting at each point a process of cicatrisation which extends throughout the nævoid tissue and so obliterates the vessels.