Afferent pathways of lymph flow within the popliteal node in sheep.

Lymph enters the popliteal node in sheep either at the subcapsular sinus, or through terminal afferent lymphatics which pass within trabeculae to medullary sinuses. Lymph from the subcapsular sinus traverses trabecular sinuses and/or a network of tubular sinuses in the cortex before entering the medullary sinuses, which are very extensive. Carbon particles, injected either into an afferent lymphatic or subcutaneously into the leg, were initially found mainly in a circumscribed area of the subcapsular sinus. Within a few hours they were present within macrophages in and around medullary sinuses in a band which extended around virtually the whole medulla. It was concluded that the pathways taken by lymph constituents in the sheep node may differ from those described for mice, rats and rabbits.