Hemal Lymph Nodes
I cannot say with certainty that hemal lymph nodes occur in dogs, but if they do, they are rare. In my extensive research into the canine lymphatic system, which included hundreds of dogs (or at least parts of them), I noticed only 3 lymph nodes of unknown origin, as they were dark in colour. Two of these lymph nodes of unknown origin were located on the cervical trachea, and 1 was located on the aortic arch. Two of these lymph nodes were examined under a microscope, and they did not appear to be hemal lymph nodes. One of these microscopically examined nodes was determined to be a lymph node with numerous pigment cells resulting from hemorrhage in the drainage area, and the other was a strongly anthracotic lymph node. The third case involved a lymph node that was also identified as a possible hemal lymph node due to its external appearance (scarlet red to dark red in colour). When it was injected to confirm the diagnosis, no efferent vessels were found, suggesting that it was, in fact, a hemal lymph node. Because of the injection, however, the node could not be microscopically examined.