The subject we have chosen is certainly too vast to be covered even in a full semester of lectures, and our title is surely much too ambitious. Yet, as you will see, the topic which we plan to discuss deals with only the few very topmost layers of that magical thin envelope called the skin and concerns itself almost exclusively with findings and theories and hypotheses, many of which have been advanced within the last six to seven years.
The human skin surface of which we shall speak is, by convention, the region which extends from the topmost or outermost limit of the skin down to and including the lowermost horny layer. This lowermost horny layer or stratum lucidum is also called the stratum conjunctum or compactum, or "barrier zone" (Szakall1-3). The zone designated as "the skin surface" is about 0.02 mm. to 0.04 mm. in thickness on the
SULZBERGER MB, HERRMANN F. Some New Observations on the Biology of the Skin Surface. AMA Arch Derm. 1960;81(2):235–244. doi:10.1001/archderm.1960.03730020071011