Summary

Bryson begins Chapter 2 with a tour of skin or the body’s cutaneous system. He explains that skin is our largest and most versatile organ. Skin measures about 20 square feet and weighs 10 to 15 pounds. It has an inner layer called the dermis, and an outer layer called the epidermis. The outermost surface of our skin, the one we meet the world with, is made up of dead cells, Bryson notes and is replaced every month as we shed 25,000 flakes of skin a minute. All of the skin’s active systems lie in the dermis, where we have blood, lymph vessels, nerve fibers, roots of hair follicles and reservoirs of sweat and sebum. Skin is perforated, although no one knows for sure how many holes it has.

Next Bryson zeroes in on specific, fascinating parts of the skin. He begins...