Play is primarily the instinctive work of the brain, but it is brain activity united in the subtlest way to bodily activity.

In the play-function of sex two forms of activity, physical and psychic, are most exquisitely and variously and harmoniously blended.

We here understand best how it is that the brain organs and the sexual organs are, from the physiological standpoint, of equal importance and equal dignity.

Thus the adrenal glands, among the most influential of all the ductless glands, are specially and intimately associated alike with the brain and the sex organs.

As we rise in the animal series, brain and adrenal glands march side by side in developmental increase of size, and at the same time, sexual activity and adrenal activity equally correspond.
Lovers in their play--when they have been liberated from the traditions which bound them to the trivial or the gross conception of play in love--are thus moving amongst the highest human activities, alike of the body and of the soul.