Distribution of colloidal carbon in lymph nodes of mice injected by different routes

Systemic distribution of colloidal carbon injected by different routes was examined microscopically at 24 hr postinjection, After intravenous injection, carbon was mildly distributed in postcapillary venules of systemic lymph nodes, in addition to heavy deposition in the liver, spleen and bone marrow. Carbon was deposited also in lymphatic sinuses of mediastinal and pancreatic lymph nodes, indicating redistribution through the lymphatic route. In other extravascular injection routes, carbon was distributed predominantly in the lymphatic sinus, follicle and paracortex of regional lymph nodes draining from the injected sites, while a systemic distribution of a smaller amount was observed also in distally located nodes, liver, spleen or bone marrow. Distribution at postcapillary venules was observed also after intraperitoneal injection when the dose was increased. It was noted that different lymph nodes was involved according to the site of subcutaneous injection, either ventral or dorsal. After intradermal injection at the rightforefootpad, carbon was distributed more extensively in reticular tissues than injection at the leftforefootpad.