Demonstrating the lymphatic system in rats with microinjection.

The lymphatic system plays an important role in human health and disease. In addition to a role in the immune response, the lymphatics can serve as a pathway for cancer metastasis. Visualizing the lymphatic system has been a difficult part of anatomic dissection studies. Anatomists have attempted to map the lymphatic system using various methods and materials; vivisection of dogs, injection of mercury into the skin and lymphatic vessel in cadavers, and injection of dye indirectly into the skin of dead and living specimens. In this study, we introduce a method of using a mixture of acrylic blue dye and hydrogen peroxide to visualize the lymphatic system in rats. The lymphatic vessels were cannulated with micropipettes, and radio-opaque orange lead oxide was selectively injected. The lymphatic system became visible from the dorsal side of the hand and foot, and distal region of the tail to their termination at the left and right subclavicular veins via lymph nodes. Cisterna chyli in the abdominal cavity and thoracic duct ran along with the aorta. The advantage of this technique is that lymph nodes as well as lymphatic channels could be recorded not only photographically but also radiographically. This microinjection technique is useful for demonstrating the lymphatic system in rats and may provide further information that will help in cancer metastasis research.