September 1955 ]
E.
S.
E.
HAFEZ
243
The chief interest in the ovary lies in the corpus luteum. Its constant big
size during pregnancy suggests that its life is prolonged by maintenance of favourable
conditions of life rather than direct stimulus to growth during pregnancy. Although
the actual size of the corpus luteum does not change during pregnancy, its form
and position in relation to the ovarian stroma alters. The changes in colour asso-
ciated with the age of the corpus luteum of pregnancy are due to its blood content
and to the concentration of luteal pigment. The latter is associated with lipoid drop-
lets deposited in the luteal cells. There is an occasional occurrence of a hollow
centre, not filled with fluid. In cattle it is filled with a pool of fluids [Asdell et al.,
1949]. It seems that all corpora lutea go through a cavity stage after the initial
organization of this body [Hammond, 1928].
During pregnancy there are series of graafian follicles of different sizes which
develop in relays. Large graafian follicles from these do not give rise to ovulations
as it was observed that there were no newly formed corpora lutea. They undergo
an incomplete cycle without the process of ripening. The undischarged follicles
atrophy with the subsequent formation of coloured luteal scars; this also occurs
in the pregnant cow. It should be mentioned here that the external manifestation
of oestrus has never been reported in the pregnant buffalo [Hafez, 1955]. Mean-
while oestrus has been reported in the cow during pregnancy [Hammond et al.,
1928]. It is suggested that the progesterone level is low in the pregnant buffalo,
this inhibits the maturation of the developing graafian follicle. In the cow, however,
it may also be possible that the circulating oestrogens during pregnancy are high
enough to inhibit the effectiveness of the progesterone. The normal endocrine
balance during pregnancy and non-pregnancy must be worked out before one can
draw any conclusive evidence.
In the N. C. L. ovary, the diameter of the largest follicles is bigger during non-
pregnancy than during pregnancy whilst the diameter of the next largest is bigger
during pregnancy than during non-pregnancy. The pre-ovulatory development of
the graafian follicle during non-pregnancy inhibits any further development of the
next follicle in relay. Since the follicles during pregnancy do not reach the pre-
ovulatory stage of development, this allows the next largest follicle to have more
chances of development.
The occurrence of the luteal scars is very frequent during pregnancy in the
buffalo, mainly in the N. C. L. ovary. This is associated with the more frequent
follicular development in this ovary than in the C. L. ovary. The presence and
pressure of an active corpus luteum in the C. L. ovary would tend to lower the
chance of nutrition being favourable for follicular development in that ovary
since the cells of each (of corpus luteum and of graafian follicles) are of the same
origin and probably draw on the same source of nourishment. Luteal scars due to
undischarged follicles are also observed during non-pregnancy in species with non-
spontaneous ovulation (rabbits and ferrets) as reported by Marshall [1943]. The
luteal scar is always coloured and is easily differentiated from the old corpus luteum
periodicum (after actual ovulation). During the process of absorption of luteal
cells on involution of the corpus luteum they become concentrated and give rise to a
deep colour.
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