NAIL FORMATION AND SOME NAIL DISORDERS 411 REFERENCES (1) Lewis, B. L. Microscopic Studies of foetal and mature nail and surrounding soft tissue. Arch. Derrnatol. 70 592 (1955). (2) Boas, I.E. V. Zur Morphol. Wirbeltierkralle. Morphologic Jahrbuch Bd. 111 281 (1894) Quoted by Pinkus, F. in Jadassohn, J. Handbuch der Haut und Geschlechtskrankeiten 1/1, 289. (1927) (Julius Springer, Berlin). (3) Zaias, N. The regeneration of the primate nail. Studies of the squirrel monkey Saimiri. J. Invest. Derrnatol. 44 107 (1965). (4) Zaias, N. and Alvarez, J. The formation of the primate nail plate, an autoradiographic study in the squirrel monkey. J. Invest. Dermatol. 51 120 (1968). (5) Achthen, G. L'ongle normal et pathologique. Dermatol. 1116 229 (1963). (6) Hashimoto, K., Gross, B. G., Nelson, R. and Lever, W. F. The ultrastructure of the skin of human embryos. III. The formation of the nail in 16-18 weeks old embryos. J. Invest. Derrnatol. 47 205 (1968). (7) Rein, C. R. and Rogin, J. R. Allergic eczematous reactions of the nail bed due to "Undercoats". Arch. Derrnatol. $1 971 (1950). (8) Lazar, P. Reactions to Nail Hardeners. Arch. Derrnatol. 04 446 (1966). (9) Samman, P. D. Onychia due to synthetic nail coverings. Experimental studies. Trans. St. John's Hosp. Derrnatol. Soc. 40 68 (1961). (10) Samman, P. D. and Johnston, E. N.M. Nail damage associated with the handling of paraquat and diquat. Brit. Med. J. 1 818 (1969). DISCUSSION MR. M. G. DENAVARRE: Did I understand that when you see extensive whitening in the nail this indicates that the nail is splitting? Do you mean between the lamellae? THE LECTURER: Actual splitting of the layers. MR. K. V. CURRY: You showed us the effect of nail preparation on finger nails, and on a particular slide there were three fingers which presumably came from the same person. On two of them one could see the staining of the nail. On the third one it was much worse. Do you come across this effect often in that one or more finger nails respond completely differently to the rest, and is this due to some other factor that perhaps has not been discovered yet? THE LECTURER: This was done deliberately. The patient was removing all her varnish and was asked to leave some so that we could see the original colour. There- fore the finger that showed a lot of colour was showing the varnish and not the 'leak' from the varnish, which was the paler colour seen on the other nails. MR. J. M. BLAKEWAY: Did you go back to the manufacturer to find out which particular dye or colour was causing the trouble? TI•E LECTURER: Yes, it has been published by Cainan (11). MR. R. CI•uDzi•owsKx: American regulations allow 4% formaldehyde in nail hardening preparations. Do you consider this level safe? TI•E LECTURER: I find it rather difficult to answer that question. MR. J. S. CA•ELL: You mentioned the injurious effects that can arise from the use of concentrated solutions of paraquat. Those are concentrated solutions but I (11) Cainan, C. D. Reactions to artificial colouring materials. J. Soc. Cosmet. Chern. 18 215 (1967).

412 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS wonder whether there is any danger at all in the normal, garden use, of paraquat solutions? THE LECTURER: Absolutely no danger from the ordinary use once it is diluted to the concentration advised. For the ordinary gardener it is put up in granular form which is even safer and can be handled with impunity, but even the diluted liquid is claimed to be safe. DR. C. PROTTEY: Would you comment further on your statement that enzyme- detergents have caused nail loss? Is this due to a synergistic effect of either the detergent upon enzyme action or vice versa? Does either the enzyme or the detergent penetrate to the matrix? Is the complaint due to excess concentrations of enzyme- detergent, as in paraquat-induced nail loss? Is this complalnt a common one? TI/E LECTURER: It seems probable that there is a dual effect here. The solution gets underneath the nail and causes separation, and secondly, it may destroy the cuticle and get right through to the matrix in that way. It might be due to either of these two mechanisms. DR. C. PROTTEY: Were the concentrations used high compared with, say, the paraquat effect where you state that the effect is due to very high concentration? Are you saying that this is relatively uncommon because the concentrations in this par- ticular case were high? Or is it more common than we would believe? Ti•E LECTURER: In ordinary handlers of the detergent {housewives or equivalent) it was the same as recorded in the Nottingham group with dermatitis due to it. The solutions would therefore not have been concentrated. PROF. F. J. EB•.•NG: Women are the sex who are mostly putting their hands in detergents, and who are constantly grooming their nails. In view of the emphasis you put on the value of the cuticle in preventing damage to the base of the nail, would you recommend that women do not groom their nails? THE LECTURER: I always recommend that the patients must not push back the cuticle. I think if done carefully by a cosmetologist it is safe, but if done by the patients themselves, it can be dangerous. Leuchonychia striata is shown in Fig. 6 and is entirely due to pushing back the cuticle. It must have been done quite viciously. As soon as we stopped the nurse doing it the nail grew out normally, there was no question as to the cause. MR. J. M. BLaKEWaY: I was struck by the slide of the thumb that had been treated with cortisone under occlusion. The state of the skin on the occluded side was very much smoother and demonstrated very well the effect of cortisone on the skin. In the early part of your paper you reviewed at least three series of nail formation. You referred to the Barton-Lewis theory, the last as I recall, of these three. Which do you think is the more valid? TaE LECTURER: I do not think there is any doubt that the traditional view of nail formation, viz. that it all arises from the matrix is the commonest form. Especially under pathological conditions. Lewis's theory is correct, but there may be some argument here as to whether one is using the definition of a nail correctly. Is the material that is being added from the nail bed true nail or is it something else, an