The organ-orientated medical specialties arose in the late 1800s. One can reasonably argue that specialties were developed because it became clear that physicians who manifested an interest and developed expertise could more easily diagnose and, in some cases, treat more rationally diseases in their speciality. In one of the earliest organ specialties, ophthalmology, the impetus was helped by Helmholtz' invention of the ophthalmoscope.1 This meant that expertise in the use of a certain instrument gave the physician a diagnostic edge over his or her colleagues.
Dermatology's instrument was the naked eye. But, as everyone has these, why should there be a need for a specialty based on seeing? Could not everyone examine the skin? Could not everyone see the various pathological changes in the skin? The answer in the 1800s was no, and is still no today.
Visual diagnosis is an immensely complex procedure.2 Over the years, a
Jackson R. On a Clear Day You Can See Forever. Arch Dermatol. 1991;127(8):1151-1153. doi:10.1001/archderm.1991.01680070051004