3 and 4) will show the principle centres which have been determined; and it is not necessary to dwell upon additional details which are still under discussion.

The areas marked out are in general the same on both hemispheres, and that is to say that most of the centres are duplicated.

The speech centres, however, are on one side only.

And in certain cases the nervous fibres which connect the cortex with the body-organs cross below the brain to the opposite side of the body.

This is always true in cases of muscular movement; the movements of the right side of the body are controlled by the left hemisphere, and _vice versa_.