During the past few years, laboratory research in the physiology and chemistry of the skin has yielded important results. The close alliance between physiologic chemistry and clinical dermatology has been demonstrated, and it is probable that more knowledge of this alliance will have great influence in bringing about an understanding of various skin conditions that are now, for the most part, incomprehensible.
Investigators have been especially interested in the reaction and secretions of the skin in health and disease. It has been shown that an altered reaction affects the skin as a medium and may favor the growth and multiplication of saprophytic and pathogenic organisms. The result is naturally injurious and may even be accompanied by changes in the morphology of the skin cells. But it is difficult and at times impossible to determine when the changes in the reaction of the skin or skin surface are primary, causing