Since the cells in the lower layers of the skin are continuously growing and then dying as they get nearer the surface, it follows as a matter of course that they must be got rid of. Only the other day a patient of mine who had his leg out of a cast for the first time in a number of weeks was surprised to find how much powdery skin he could rub off.
This rubbing off of the scales of skin rarely seems to bother people much except when it occurs on the scalp. Then it is called dandruff and it is evident that many people find it a great nuisance. Modern dermatologists apparently do not consider it dignified enough for their consideration. In general man’s skin has not changed much in modern times, and so the book on diseases of the skin that I got in medical school forty odd years ago still serves me very well. It has several pages on dandruff. I have recently consulted two large up-to-date tomes on dermatology and they pay no attention to it except for those rare occasions when it is associated with severe infections. The original idea was that dandruff is an infection. I cannot find much evidence that infection here is really of much importance. My old book talks about seborrhea oleosa and seborrhea sicca. Apparently, all this means is that in some cases a greasy skin rubs off and in other cases a dry one. I think the general public should be trusted to treat themselves accordingly.
Without a constant renewal of the dermis and a rubbing off of the epidermis, the skin would become pretty battle-scarred. It can have rough times, as we have seen, attacked from without or within. This often causes most uncomfortable disfigurement to its smooth pristine beauty. Yet the live cells of our dermis are usually able to repair the damage so that our snug-fitting garment can continue its important duties: to protect, to eliminate waste, and to regulate heat.
With all of these many activities of the skin, is it any wonder that Dr. Walter in his book on the vertebrates speaks of the skin as a jack-of-all-trades? It is the biggest organ in the body. I believe that in a good-sized man there is about twenty-five square feet of surface. It has about two and a half million sweat glands. Despite all its varied activities, we keep it reasonably young by continually renewing it. Perhaps many of you who are familiar with the country know that snakes periodically “slough” off their old skin, appearing in a new one. We also get rid of ours, but we do it continuously. The average man of three score years and ten has shed forty-five pounds of skin in his lifetime.