The affections of the brain of most anatomical interest are those involving its circulation, the motor areas, and the motor paths. Paralyses may arise from (a) interference with the motor areas in the cortex by hemorrhages, injuries, or tumors; (b) destruction of the motor paths from the cortex to their point of exit from the brain; (c) injury of the nerves at their exit from the brain.

Disturbances of the circulation may be either of the nature of anaemia or ischae-mia, causing softening, or of congestion, causing apoplexy.

Tumors of the brain interfere with the functions of the part in which they are located, as do also wounds. In all of these a knowledge of brain localization is essential.