There is thus in the female a more complete separation of the urinary and the genital surfaces than in the male.

Practically all of the waste material of the body which results from cell activity and is passed from the cells into the fluid about them is brought by the blood to the kidneys, and removed by these from the blood, leaving the body as urine.
[Illustration: FIG.

8 .-- A LONGITUDINAL SECTION THROUGH THE MIDDLE OF THE BODY SHOWING THE EXTERNAL AND INTERNAL SURFACES AND THE ORGANS.
1.

The skull.
2.

The brain, showing the convolutions of the gray exterior in which the nerve cells are most numerous.
3.