756 CIECULATOHY SYSTEM OF THE DOG 



The internal iliac vein corresponds in regard to its tributaries witii tiie branches 

 of the artery, except that it is not divided into parietal and visceral branches. 



The external iliac, femoral, and popliteal veins with their collateral tributaries 

 are satellites of the arteries. 



The anterior tibial vein is usually double, and the posterior tibial vein is very 

 small. 



The saphenous vein is the upward continuation of the medial plantar meta- 

 tarsal vein. It communicates by a large branch \vith the dorsal metatarsal vein, 

 and ascends the leg as a satellite of the saphenous artery and its plantar branch. 

 The recurrent tarsal vein is larger. It is formed at the lower part of the leg by the 

 union of dorsal metatarsal and lateral plantar metatarsal veins, crosses the lateral 

 surface of the leg obliquely upward and backward, ascends behind the gastrocnemius, 

 and joins the femoral vein. 



The metatarsal and digital veins resemble in general the corresponding vessels 

 of the forelimb. 



The Lymphatic System 



The cisterria chyli is relatively large and is fusiform; it is ventral to the last 

 thoracic and first lumbar vertebrae and is related ventro-medially to the aorta, 

 dorsally and laterally to the right crus of the diaphragm and the psoas minor. The 

 thoracic duct passes forward to the right of the aorta and ventral to the vena azygos 

 as far as the sixth thoracic vertebra; here it crosses to the left face of the oesophagus 

 and runs forward, turns ventrally at the thoracic inlet, and opens into the left 

 brachiocephalic or the common jugular vein. The duct may be single throughout, 

 but often divides anteriorly into two branches, which may then unite and form a 

 dilatation which receives the left tracheal duct and the vessels, from the forelimb. 

 Other variations occur and the primitive plexiform arrangement persists in varying 

 degree. The tracheal lymph ducts accompany the internal jugular veins. The 

 right duct opens into the right brachiocephalic vein. 



The mandibular lymph glands (Fig. 615) are commonly two or three in number 

 on each side, but as many as five have been observed. They are situated in the 

 angle between the masseter and the mandibular salivary gland, above and below 

 the external maxillary vein, and covered only by the skin and cutaneus muscle. 



A small round parotid lymph gland is situated superficially between the upper 

 part of the posterior border of the masseter and the parotid salivary gland or partly 

 or completely under cover of the latter. Exceptionally two or three may be present. 



The suprapharyngeal lymph glands, usually one on each side, lie dorsal to the 

 pharynx, under cover of the sterno-mastoideus and the mandibular salivary gland. 

 They are related deeply to the rectus capitis ventralis and the carotid artery, and 

 the anterior end is just behind the occipito-mandibularis (Fig. 433). Each is about 

 two inches (ca. 5 cm.) long in a good-sized dog. In a good many cases a second 

 gland is present. 



Anterior cervical lymph glands appear to be absent in the majority of subjects, 

 but in other cases small nodes may be present in relation to the anterior end of the 

 thyroid gland. It should be noted, however, that parathyroids may be mistaken 

 for lymph nodes unless a microscopic examination is made. Middle cervical 

 lymph glands are apparently not present, and the same is usually the case in regard 

 to the posterior cervical lymph glands ; but in some cases one or more of the latter 

 occur on the ventral face of tiie trachea near the thoracic inlet. 



The prescapular or superficial cervical lymph glands lie on the serratus ven- 

 tralis, at the anterior border of the supraspinatus, embedded in a mass of fat. Usu- 

 ally two are present on each side, but there may be three or only one. They are 

 oval aiad are about an inch long in a dog of medium size when two are present. 



