Sheet 10. The essential organ is the ovary (ov.), in which the ova
(eggs) are formed. Figure 3 gives an enlarged and still more
diagrammatic rendering of the ovary. There is a supporting ground
mass, or stroma, into which numerous bloodvessels and nerves enter
and break up. The ova appear first as small cells in the external
substance of the ovary (as at 1), and move inward (2 and 3),
surrounded by a number of sister cells, which afford them
nourishment. At (4) an ovum with its surrounding group of cells is
more distinct and near the centre of the ovary; a fluid is appearing
within the ovisac as the development proceeds. (5) is a much more
mature ovisac or Graafian follicle.
Section 138. The ovum (ov.), is now large, and its nucleus and
nucleolus (the germinal vesicle and spot) are very distinct. The wall
of the follicle consists, in the mammal, of several layers of cells, the
membrana granulosa (or "granulosa" simply); the ovum lies on its
outer side embedded in a mass of cells, discus proligerus,
separated from actual contact with the ovum by a zona pellucida.
The ripening follicle moves to the surface of the ovary and bursts, the
ovum falls into the body cavity. In Figure 2, a ripe Graafian follicle
(G.F.), projects upon the ovary.