The lesions consist of hemorrhages recognizable by gross and microscopic examination. The capillaries and veins are congested and thrombosed. Their endothelial cells are swollen. Arterioles are generally little affected. Though hemorrhages and thromboses are usually seen together in the nodes, they have been observed occurring independently. They are both probably secondary to endothelial changes. The lesions are not dependent on the amount of preexisting inflammation in the nodes.

Endothelial changes, hemorrhages and thromboses were usually noted in the regional nodes when positive Shwartzman reactions had been elicited in prepared skin by intravenous injection of the bacterial filtrate. However, these lesions in many instances were observed under similar conditions in these nodes even when the Shwartzman reaction in the skin was negative. It appears that lymph nodes are more susceptible to the production of the Shwartzman phenomenon than the skin sites which they drain.

A single intralymphatic or intradermal injection of the bacterial filtrates used in this study, even in high concentrations, does not produce in adjacent lymph nodes the characteristic changes noted when this preparatory injection is followed by a subsequent intravenous injection of the filtrate.

Single intravenous injections also are not productive of hemorrhage and thrombosis in lymph nodes.