Writers on forensic medicine have enumerated the various circumstances, by which the countenance of an individual may be so changed, as to defeat every attempt to identify him. Foderé mentions the following, age; loss, or acquisition of fat; change in the colour of the eyes or hair; the effects of climate, diet, diseases, and passions of the mind. These may also be metamorphosed by art. The influence of mental anxiety in changing the countenance is universally acknowledged—
Danger, long travel, want, or woe,
Soon change the form that best we know;
For deadly fear can time outgo,
And blaunch at once the hair;
Hard toil can roughen form and face,
And want can quench the eye’s bright grace,
Nor does old age a wrinkle trace
More deeply than despair.
Marmion, Canto I.