726 LYMPHATIC SYSTEM OF THE OX AND SHEEP 



The dorsal mediastinal lymph glands (Lgg. mediastinales dorsales) are situated 

 on each side of the thoracic aorta, in the fat which levels up the space between that 

 vessel and the bodies of the vertebrse. On the right side they lie chiefly dorsal to 

 the thoracic duct, and on the left side they are related to the vena: hemiazygos. 

 They are irregular in arrangement and their length varies from about half an inch 

 to an inch and a half (ca. 1-3.5 cm.). They are in series with the anterior medias- 

 tinal glands. 



Their afferent vessels come from the same parts as those of the intercostal 

 glands; also from the diaphragm, the mediastinum, the pericardium, the ribs, and 

 the intercostal lymph glands. The efferent vessels go chiefly to the thoracic duct 

 or join the common efferent duct of the posterior mediastinal glands. 



The ventral mediastinal lymph glands (Lgg. mediastinales ventrales) are 

 situated on the transversus thoracis muscle. Several (2-5) occur constantly in 

 the fat about the apex of the pericardium; they vary in length from about half an 

 inch to an inch or more (ca. 1-3 cm.). In some cases other glands are present 

 further forward. The afferent vessels come from the costal and mediastinal 

 pleura, the diaphragm, the pericardium, and the ribs. The efferent vessels usually 

 unite to form a trunk which goes to the anterior sternal lymph gland. Hsemolymph 

 glands may be present in this region. 



The anterior mediastinal lymph glands (Lgg. mediastinales craniales) are 

 situated in part at the thoracic inlet, in part along the oesophagus, trachea, anterior 

 vena cava, and brachiocephalic trunk. The former group comprises two to four 

 glands on either side, ventral to the trachea and oesophagus. Usually the largest 

 of these, which may be an inch or more (ca. 2-3 cm.) in length, lies along the origin 

 of the internal thoracic artery. The second group differs somewhat on the two sides. 

 On the right side there is usually a large gland, which may be two or three inches 

 (ca. 5-7 cm.) in length; it lies on the oesophagus and is crossed laterally by the 

 dorsal vein. Behind this there are commonly two or three glands on the oesophagus 

 or the longus colli, and in front two or three are placed similarly and on the trachea. 

 On the left side a variable number (2-7) are situated on the oesophagus, trachea, 

 brachiocephalic trunk, and anterior vena cava; glands may be between the vessels, 

 or between the vessels and the trachea, and escape superficial examination. Hsemo- 

 lymph glands are often present in the vicinity of these glands. The afferent vessels 

 come from the thoracic part of the oesophagus, trachea, and thymus; from the lungs, 

 pericardium, heart, costal and mediastinal pleura; from the intercostal glands of 

 the first four spaces and from the gland on the apical bronchus. In some cases these 

 glands receive also efferent vessels from the anterior sternal, left bronchial, and 

 other mediastinal glands. The efferent vessels for the most part go to the thoracic 

 duct, the right tracheal duct, and the costo-cervical glands. 



The posterior mediastinal lymph glands (Lgg. mediastinales caudales) are 

 situated along the oesophagus, from the aortic arch backward. The largest of these 

 may be eight inches (ca. 20 cm.) or more in length; its anterior part is dorsal to the 

 oesophagus, while posteriorly it lies in the angle between the' aorta and the diaphragm 

 (Fig. 389). But in some subjects there are two glands in place of this large one; in 

 these cases the additional posterior one is usually the smaller. Several other glands 

 of smaller size lie in front of the large one, in the angle between the aorta and the 

 oesophagus. In front of these there are usually two or three on the right side on the 

 aorta and the oesophagus.^ The afferent vessels come from the oesophagus, the 

 lungs, the pericardium, the mediastinum, the diaphragm, the peritoneum, the liver, 

 and the spleen. The efferent vessels unite to form a common trunk which joins the 

 thoracic duct. 



The diaphragmatic lymph glands (Lgg. diaphragmaticse) are small nodes which 

 may be present at the foramen venae cavse and the termination of the phrenic 

 1 These are termed by Baum the middle mediastinal lymph glands. 



