The following is from The Anatomy and Mechanics of the Human Hand CRAIG L TAYLOR, Ph.D. & ROBERT J. SCHWARZ, M.D.and is available as part of the .pdf file Artificial Limbs, May 1955..

It is obvious to all that the human hand represents a mechanism of the most intricate fashioning and one of great complexity and utility. But beyond this it is intimately correlated with the brain, both in the evolution of the species and in the development of the individual. Hence, to a degree we "think" and "feel" with our hands, and, in turn, our hands contribute to the mental processes of thought and feeling.

But obviously, what Taylor and Schartz observe, must not be obvious to all. Or someone beyond the few of us would be doing something about it, restoring the traditional role of the hands in learning and helping all our children to understand that their own learning must take place outside the limitations of available texts.