Whilst most of the senses (hearing, sight, smell and taste) have their own organs, the tactile sense is dependent on the sensory nerve endings of the periph- eral processes of the nerve cells in the spinal ganglia. These nerve endings are distributed over the entire body. They vary in number and structure according to the nature of the tissue. For instance, the quantitative innervation of the mucosa differs from the innervation of the periosteum or the articular capsules. The skin and its related tissues are relatively richly innervated, but here too there are regional differences. Some...