Trophic and nervous conditions sometimes cause localized deficiency of pigment which produces white areas in the skin.
That special trophic nerves, however, exist throughout the body, seems to be a myth.
The acute bed-sore is, in some cases, a true trophic lesion occurring, as it may, on parts not subjected to continuous pressure or irritation.
Trophic disturbance in the nutrition of the skin may be so great that a slight degree of external pressure or irritation is sufficient to excite even a gangrenous inflammation.
It forms the trophic centre of Solidarity the cell, just as the nucleus-containing part of every cell is the trophic centre of the whole cell.