Visualization of the primo vascular system in the skin lymph vessel between inguinal lymph node and axillary lymph node. (a) A schematic diagram of large caliber lymphatic system in a rat. (b) Axillary and inguinal lymph nodes and the lymph vessel between them. Alcian blue was injected into the inguinal lymph node and it flowed up to the axillary lymph. (c) Magnified view of the rectangular area in (b). A primo vessel stained by Alcian blue was visualized in the lymph vessel (the fuzzy milky white tissue).