No abstract

A marginal sinus, formed by the anastomosed terminations of white pulp capillaries, bounds the inner edge of the marginal zone. The endothelial lining on the nodular surface is complete. Pores appear along the lateral aspect thus allowing blood to pass freely into the interstices of the marginal zone. A dense aggregation of Marshall's metalophil cells occurs in the region of the marginal sinus. Such cells are lacking in the marginal zone.Intravenous injections of particulate matter were used to determine the course of blood flow and phagocytic potential. Ten minutes after injections, particles were found to be dispersed among the cells of the marginal zone. None were found in the marginal metalophils. In four hours the particles had cleared the marginal zone and were within red pulp macrophages. In a few rats, the marginal metalophils reacted positively to tests for iron. It is concluded that marginal metalophils represent a large reserve of potential phagocytes situated at a point where blood first leaves capillaries to enter tissue interstices.

No abstract

The major arteries which supply the follicular capillaries in the human spleen do not arise as they do in most mammals as lateral or radial branches from the central artery but come from penicillar arteries which penetrate the marginal zone and enter the follicle at various points around its circumference. Such arteries may have a very short course through the red pulp or they may pursue very long courses. Upon entering the follicle, these arteries branch a number of times, the branches remaining together in a tight array of parallel arterioles along with capillaries formed from them, the whole bundle being enveloped by a reticular fiber sheath. There is thus formed an arteriolar-capillary bundle. The whole bundle may branch. From the sides, especially from its central end, arterioles and capillaries radiate out to all parts of the follicle to terminate in the marginal zone or in the follicle itself.