In their book:

http://www.amazon.com/Tying-Emergers.../dp/1571883061

Schollmeyer and Leeson break down the foot into three regions (ppgs. 28 -29). Region 3 - "...from the middle of the foot to the heel is the prime stuff. It is fine, soft crinkly, densely packed on the skin and nicely translucent. Ordinarily, contains few, if any,'underfur' type hairs and most of the fur here grows to quite nearly a uniform length..."

Split the foot for better access.

PT/TB