The gulf that divides medicine, in practice, from biology has often been deplored. Modern biologic research compels the physician to free himself occasionally from the traditional medical viewpoint of disease and consider his problems afresh from the biologic approach.
The dermatologist, especially, can gain new light by a study of the manner in which the human skin and its appendages have developed (both ontogenetically and phylogenetically), the factors which promote or inhibit their growth and the development of disease-producing agents, such as bacteria—in other words, the evolutionary process in its relation to the etiology of diseases of the skin. This paper will, therefore, be limited to an attempted clarification of the role of evolution in dermatology.
It is known that the human embryo begins its development after fertilization by the division of a single cell, outwardly similar to the process of fission by protozoa. This single cell eventually gives rise