23 



The glands are situated between the hind quarters of the udder and the 

 ventral surface of the pelvis but at some little distance, 12 cm. more or less, 

 from it, Pis. IX, X. Of the three glands shown in PL IX, Fig. 2, the largest 

 one was 5.5 cm. long and 3.5 cm. wide. (Average size, 6-10 cm. long by 

 1-4 cm. wide by f-1.5 cm. thick, Baum.) The supramammary lymph 

 glands, in many cases at least, may be readily palpated in the healthy dairy 

 cow. 



The thoracic duct. In all mammals, so far as known, except the New World 

 monkeys, the lymphatic system communicates with the venous system 

 by two main trunks, the thoracic duct and the right lymphatic duct (or 

 right tracheal duct). The thoracic duct opens into the veins at, or close 

 to, the angle of junction of the left external jugular and axillary veins, Pis. 

 VI, VII. The right lymphatic duct (or right tracheal duct) opens at a 

 corresponding point or points, on the right side. The thoracic duct begins 

 at the cisterna chyli which is situated between the aorta and the right crus 

 of the diaphragm at the first and second lumbar vertebrae. The duct 

 passes through the hiatus aorticus of the diaphragm into the right pleural 

 cavity, PI. IV, 35. It extends forward between the aorta and the vena 

 azygos to the fifth, sixth or seventh thoracic vertebra where it inclines 

 ventrally, and crosses obliquely over to the left side of the oesophagus and 

 trachea, PI. VII, 29. From here the duct extends along the left side of the 

 oesophagus to the inlet of the thorax where it inclines ventrally and opens 

 by one or more orifices into the veins at, or near, the junction of the left 

 external jugular and the axillary veins, PI. VII, 28. The thoracic duct 

 drains approximately three fourths of the body, viz., the hind quarters, the 

 abdominal viscera, portions of the thoracic viscera, the left side of the head 

 and neck and the left thoracic limb. The remainder of the body is drained 

 by the right lymphatic duct. 



