The maniac lacks control of his attention.
The deluded lacks grasp and flexibility of attention.

The crank can only attend to one thing.

The old man is feeble in the attention, having lost his hold.

So it goes.

The attention is the instrument of the one sort of normal mental activity called Apperception, and so impairment of the attention shows itself at once in some particular form of defect.
Third, it is interesting to know that in progressive mental failure the loss of the powers of the mind takes place in an order which is the reverse of that of their original acquisition.