39. Gift subject to power of revocation.

Where, under any disposition, a person becomes beneficially entitled in possession to any benefit and, under the terms of the disposition, the disponer has reserved to such disponer the power to revoke the benefit, such person is, for the purposes of this Act, deemed not to be beneficially entitled in possession to the benefit unless and until the power of revocation is released by the disponer, or otherwise ceases to be exercisable.