The function of the suprarenal glands prevails throughout the fetus, because at that stage they perform the duty of many of the internal organs that meanwhile go without a function. But later, they have the function of attracting the purer blood when it is about to circulate, so that it will not be absorbed by the spermatic vessels, and of urging it, through a short circle, into the vena cava, and so into the heart, thus enlivening the blood from its direction, as the brain does from above. But this occurs only so long as the spermatic vessels, or genital parts, are not strongly active; but when they are strongly active, seizing the better elements of the blood, then the renal capsules are deprived of this vital blood, and so the purer serum is taken away from them.