From head to hand to head
Gradually you learn “the election of simples,” the identification of plants, seeds, berries, and leaves, how milkwort differs from soapwort and all the varieties of English plants from adder’s tongue to yarrow. How it looks, how it smells, the ghost of its aroma as it crumbles to dust where you prepare plants for decoctions. You learn preparations.
You learn how to think.
Thinking is through the hands as well as the head. After a couple of years you can tip a phial of X or Y and tell by the speed it moves whether it has the correct viscosity. When you levigate, “make into a smooth, fine powder or paste, as by grinding when moist: a method of separating fine from coarse particles,” you change the direction of the pestle in the heavy mortar. This is apprenticeship: the moving of learning from head to hand to head.