No abstract

Six multiparous ewes, three of which were lactating and the remaining three in an advanced stage of mammary involution, were used to study the distribution of lymphatic vessels in the mammary gland. The lymphatic system was distended by ligation of the regional efferent lymphatic ducts and either reconstituted blood or Latex was used to fill the blood vascular system. After fixation, distribution of lymphatic vessels was studied macroscopically and microscopically.One to three mammary nodes were situated at the postero-dorsal aspect of each gland. Entering and leaving the nodes were 8 to 12 major afferent and 2 to 4 efferent ducts. Four or five of the afferent ducts accompanied the external pudendal artery and vein and their radicles emerged from the deep parenchyma of the gland. The remaining afferent ducts emerged from the parenchyma of the gland independent of blood vessels and their radicles drained both superficial and deep parenchyma.Lymphatic vessels were found in the connective tissue between lobes, within lobes and between lobules. Lymphatic capillaries were observed in the connective tissue within lobules and also in areas adjacent to the alveolar epithelium. Lymphatic vessels in the connective tissue between lobes and the larger vessels were supplied with valves and their walls possessed an endothelial cell lining together with smooth muscle and connective tissue layers. Finer lymphatic vessels appeared to consist of only a simple endothelial cell lining and valves were not found.