Scratching movements are infinite in their variety, and since the co-operating muscles vary in each case, the question of muscular localisation is of secondary interest. The object in view in the act of scratching is relief from some such source of cutaneous irritation as a pimple, an abrasion, a burn, the bite of an insect, etc., and so long as the cause persists, the function is being rationally exercised; but to persevere mechanically, involuntarily, immoderately, in the absence of pruritus or of other paræsthesiæ, is a sign that the functional act is growing into a tic. Innumerable tics are thus developed, and they are intimately associated with biting tics. S. passes his hand every instant over his forehead, O. over his eyes, T. over her lips, P. over his moustache, young J. over his budding whiskers, etc., etc. These elementary tics are scarcely more than stereotyped acts, and may maintain the semblance indefinitely, though there is also the likelihood of their becoming immeasurably more pronounced. M. scratches his lips with his nails till they are bleeding; E. suffers from a facial tic, and scrapes at his forehead and temples to such an extent that his complexion is perpetually blooming with a crop of little bleeding excoriations; in some places, as a result of ceaseless rubbing and tapping, the skin is thickened and discoloured--a condition that might be known as "scratchers' corns." Madame W. used to tear at her toe nails with her fingers whenever she had retired for the night; and at the present time, as a result of incessantly passing a fine gold chain between the pulp of her fingers and the nails, she has succeeded in half detaching the latter from their bed. A case reported by Raymond and Janet[100] is one of unusual severity. A little girl ten years old was covered from head to foot with scabs and sores, some of which on the body were several centimetres in diameter and looked very ugly. These she had contrived to inflict on herself, in spite of every precaution and admonition. It appeared that successive attacks of measles and of whooping-cough at the age of five had entailed long rest in bed, and had been followed by a tardy convalescence, in the course of which the development of a few pimples on the forehead was the signal for her to commence scratching them and any other part of her body where there was the least discomfort, or where the skin was at all roughened. This merciless self-mutilation ended in the production of large and painful excoriated areas; nevertheless a tic had sprung from the habit, and it remained inveterate. Another analogous case is quoted by the same observers[101]: