THE TIME TAKEN UP BY CEREBRAL OPERATIONS. 227

the chronoscope and its battery, so that the current flows through the contact at C. This contact is closed as long as the armature is held by the magnet, but is broken the instant the magnetism in the soft iron disappears or is weakened so that the spring can draw away the armature. The armature is not held against the magnet, the contact being at the point G. FIG. 8.