THE LYMPH VESSELS AND GLANDS 623 



metatarsal vein is larger than the preceding. It passes superficially over the 

 outer face of the hock and is continued by the recurrent tarsal vein. 



The digital veins differ from those of the fore limb chiefly in that the dorsal 

 vein is large and the plantar absent or small. 



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

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

 The gastric vein is the largest affluent. It is formed by the junction of three veins, 

 the left of which receives the splenic vein. The anterior mesenteric vein is also 

 formed by the confluence of three radicles; it usually receives the small posterior 

 mesenteric vein. The portal tributaries are in general satellites of the correspond- 

 ing arteries. 



The Lymph Vessels and Glands 



The thoracic duct arises from a small cisterna chyli and is very variable. It is 

 exceptional to find a single trunk throughout, as is often the case in the horse. The 

 duct is largely covered by fat and small lymph glands. There are often two ducts, 

 one on either side of the aorta, which may join at a variable point or terminate close 

 together at the junctions of the jugular and brachial veins. In other cases the duct 

 is single for a varialjle distance, then bifurcates or divides into three or four branches, 

 which are often connected by plexiform anastomoses. 



The efferent vessels from the intestine converge to a large trunk which ac- 

 companies the anterior mesenteric artery and vein. It passes below the pancreas 

 and receives usually a large tluct which is formed ])y efferent vessels from the stom- 

 ach, liver, and spleen; this duct sometimes opens directly into the cisterna. The 

 gastro-intestinal trunk receives the collecting duct (truncus lumbalis) of the lumbar 

 lymph vessels, forms a bend around the right renal vessels, and joins the cisterna. 



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

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

 smaller ones, as found in the latt(n- animal. 



The submaxillary lymph glands are usually two in numl^er, right and left; 

 each is situated under the external maxillary vein between the submaxillary sali- 

 vary gland and the sterno-cephalicus muscle. Usually one or two haemolymph 

 glands are near it. There is generally a small gland on the deep face of the 

 anterior part of the submaxillary salivary gland, and small nodes may be found 

 further forward in the submaxillary space. 



A large subparotid lymph gland lies on the postero-superior part of the 

 masseter muscle, ])artly under cover of the upper end of the parotid gland. 

 Several htTpmolym]:)h glands lie on its deep face. 



The pharyngeal lymph glands number two or three on each side. Of these, two 

 large suprapharyngeal glands (Lg. retropharyngeales) are situated about an inch 

 apart between the dorsal wall of the pharynx and the ventral straight muscles 

 (Figs. 281, 365). These are two to three inches long. Enlargement of them is 

 likely to cause difficulty in swallowing and in respiration. Behind these are 

 several hsemolymph glands. An atlantal gland is situated below the wing of the 

 atlas on the spinal accessory nerve. It is discoid, oval in outline, and may be 

 an inch and a half or more in length. It is partly covered by the upper end 

 of the sul)maxillary salivary gland. 



A smaller lymph gland (parapharyngeal) is usually found along the lower 

 border of the carotid artery {i. e., ventral to the atlantal gland) on the lateral 

 wall of the pharynx and under cover of the submaxillary salivary gland or at 

 its posterior border. 



Two or three smaH anterior cervical lymph glands commonly lie along the 

 carotid artery a little further back. 



