I 2'2 LYMPHATIC SYSTEM OF THE OX AND SHEEP 



along the medial surface of the medial chief digit, turns laterally above the fetlock joint, and is con- 

 nected with the corresponding lateral vein to form the plantar venous arch. From this the three 

 chief metatarsal veins ascend and to it come small veins from the rudimentary digits. 



The portal vein is formed usually by the confluence of two radicles, gastric 

 and mesenteric. It receives the gastro-duodenal vein and veins of the pancreas. 

 The gastric vein is the largest afl[iuent. It is formed by the junction of two trunks. 

 One of these, the right ruminal vein, receives the splenic vein. The other is a 

 short trunk which is formed by the confluence of the left ruminal and omaso- 

 abomasal veins; it receives the reticular vein. The anterior mesenteric vein is 

 formed by the confluence of three chief radicles which return the blood from the 

 entire intestine, with the exception of part of the duodenum and rectum; from 

 these the blood is conveyed by the gastro-duodenal and internal pudic veins. The 

 portal tributaries are in general satellites of the corresponding arteries. 



LYMPHATIC SYSTEM OF THE OX AND SHEEP 



The l3anph glands of the ox are in general less numerous but larger than those 

 of the horse; in some situations a single large gland occurs instead of a group of 

 small ones, as found in the latter animal. 



The thoracic duct arises from the cisterna chyli at the hiatus aorticus. In 

 some cases it remains single, as is most common in the horse, pursues a similar 

 course and opens into the origin of the anterior vena cava, or into the left common 

 jugular vein. But in many cases the duct divides into two branches which lie on 

 the right and left sides of the dorsal face of the aorta. The two ducts are united 

 by anastomotic branches and are embedded in fat. They usually unite about the 

 fifth thoracic vertebra. The terminal part is often ampullate, but the lymphatico- 

 venous opening is small. When single, the duct is 6-10 mm. in diameter. The 

 duct may receive efferent vessels from the intercostal, mediastinal, and bronchial 

 lymph glands. 



Many other variations have been described. In the anterior mediastinum there may be 

 three or even four ducts (with connecting branches), which usually unite just before the lym- 

 phatioo-venous opening, but may open separately. 



The cisterna chyU Hes in the hiatus aorticus, dorsal to the aorta and ventral 

 to the last thoracic and first lumbar vertcbrse. It receives the lumbar and intestinal 

 lymph trunks. It is very variable in form and is commonly about three-fourths 

 of an inch (1..5-2 cm.) wide. 



The intestinal trunk (Truncus intestinahs) is formed at the ventral face of the 

 posterior vena cava, just behind the dorsal border of the liver. It results from the 

 union of the common efferent vessels of the gastric and intestinal lymph glands. 



The trunk is a centimeter or less in diameter in the adult. It runs backward a short distance, 

 bends sharply dorsally between the aorta and vena cava, and unites (usually) with the IjMnbar 

 trunk to form the cisterna chyli. 



The lumbar tnink (Truncus lumbalis) is formed in the sublumbar region by 

 the confluence of efferent vessels from the iliac lymph glands. It concurs with the 

 intestinal trunk in the formation of the cisterna chyli. It receives efferent vessels 

 of the lumbar and renal lymph glands. The trunk is very variable in regard to 

 its mode of formation and two may be present. 



The mandibular lymph glands are usually two in number, one on each side. 

 The gland is situated between the sterno-cephalicus muscle and the ventral part of 

 the mandibular salivary gland, and is usually related dorsally to the external maxil- 

 lary vein. The gland is oval and is commonly about an inch and a half (ca. 3-4 cm.) 



