General

The thoracic lymph nodes (Lnn. thoracis) are divided into the dorsal thoracic lymph centre (lymphocentrum thoracicum dorsale), which includes the intercostal lymph nodes (Lnn. intercostales) that are attached to the dorsal thoracic wall near the costovertebral joints, and the ventral thoracic lymph centre (lymphocentrum thoracicum ventrale), which includes the sternal lymph nodes (Lnn. sternales) that are attached to the ventral thoracic wall on the sternum, near the internal mammary artery and vein. In contrast to cattle (see Baum [6] pages 26 and 27), both of the lymph node groups are uncommon in the dog. The intercostal lymph nodes were absent in most dogs, and, when they were present, were always found to be a single lymph node on one side, while the sternal lymph nodes were usually only found as 1 lymph node on each side. Therefore, both groups should be addressed individually. The lymph nodes of the thoracic organs are also much less numerous than in cattle. In dogs, only the mediastinal and bronchial lymph centres (lymphocentrum mediastinale and bronchale) are found, with the former consisting only of a single group of lymph nodes, the cranial mediastinal lymph nodes (Lnn. mediastinales craniales).