Nail formation and some

disorders nail P. D. SAMMAN* Presented on loth March lt•71 at the Symposium on 'Appendages of the skin', organized by the Society of Cosmetic Chemists of Great Britain in Eastbourne, Sussex. Synopsis---The flat NAIL of some primates, including man, is unique and is usually formed from one area of the nail fold invagination called the MATRIX. This is deeply placed below two layers of EPIDERMIS and is therefore well protected from injury. Alternative.methods of nail formation more closely resemble the formation of a mammalian claw and may be re-gressions to a more primitive state. Conventional nail cosmetics are well tolerated but modifications to improve their stability or their ease of application have caused DAMAGE to nails on a number of occasions. The use of FORMALDEHYDE as a nail HARDENER has also caused trouble and should be abandoned. Leakage of a few tints from nail varnish, resulting in a yellow pigmentation of the nail, not readily removed, has caused distress in some patients. Damage caused by nail COSMETICS is much less than damage caused by patients themselves either by biting, playing with the nails or over-active MANICURE. The deep position of the matrix has disadvantages when it comes to treatment of naturally occurring DISEASES as it is very difficult to reach with medicaments. The mechanism of nail formation is a subject of debate. The fact that the nail is formed from an invagination of epidermis situated on the dorsum of the distal phalanx is not in dispute. The dispute is concerned with the extent of the invagination which takes part in nail formation. The generally held and traditional view is that the nail is formed only from the proximal part of the floor extending from the junction of floor and roof behind to the anterior margin of the half-moon (lunula) in front. A smal