# The Formation of Lymph in the Ovary

B. Morris, M. B. Sass

## Abstract

The lymphatics of the ovaries of pregnant and non-pregnant ewes were outlined either by direct or retrograde injection of indian ink or Berlin blue and the distribution of these vessels within the ovary was determined. In active ovaries the mature follicles and corpora lutea contained a profuse network of lymphatics. In inactive ovaries the lymphatics were very small and poorly developed. Lymph was collected from the ovaries of conscious ewes for periods of several days. The flow of lymph from ovaries with corpora lutea averaged 4$\cdot$15 ml./h; a maximum rate of flow of 14$\cdot$9 ml./h was recorded in one ewe. The protein concentration of ovarian lymph was 73% of the plasma concentration. When $^{131}$I labelled albumin was injected intravenously into ewes it entered the ovarian lymph very rapidly and the specific activities of albumin in the plasma and lymph equilibrated within 10 to 20 min of injection. The structure of the ovarian blood capillaries provided an explanation for the very high rate of lymph flow and protein leakage in the ovary. The endothelium of the blood capillaries was discontinuous with gaps up to 1 to 2 $\mu$m in diameter through which red cells, indian ink particles and ferritin passed into the interstitial spaces. Where the basement membrane of the capillaries was deficient over gaps the surfaces of the luteal cells came into direct contact with the circulating plasma, and occasionally cytoplasmic extensions from the luteal cells projected into the lumen of the blood capillaries. The lymphatics which were associated with many of the blood capillaries had open intercellular junctions and material could enter these vessels readily from the interstitial spaces. The blood capillaries in the ovarian stroma and those around immature follicles appeared less permeable than the capillaries of the corpus luteum. The association between the development of the corpus and an increase in lymph production in the ovary suggests the possibility that the changes in capillary permeability may be related to the synthesis and secretion of steroid hormones.