THE LYMPHATICS. 713 



number. The anterior jugular — the smallest — descends beneath the superficial cervical aponeu- 

 rosis, in front of the sterno-mastoideus muscle, and enters the subclavian vein. The external 

 jugular commences by the union of the facial and temporal veins ; in its disposition it resembles 

 the jugular of the Horse, and would be a complete representative if deprived of the branches 

 from the cranial sinuses. The internal jugular arises at the posterior foramen lacerum, at a 

 dilatation of the lateral sinus named the bulbus venoe jugularis, and passes to the subclavian 

 vein. Lastly, the posterior jugular (or vertebral vein) situated beneath the complexus muscle, 

 and in relation with the cervical vertebrae, carries the blood from the spinal sinuses in this 

 region, and which, in Solipeds, is received by the occipital and vertebral veins. 



The inferior vena cava corresponds to the posterior vena cava of animals, and receives the 

 blood from all the sub-diaphragmatic veins. It originates from the union of the two common 

 iliac veins, at the third lumbar articulation, and terminates in the right auricle. In its course 

 it receives the median sacral, lumbar, renal, supra-renal, inferior phrenic, and right spermatic 

 veins. The latter forms on the surface of the testicle, and at the origin of the cord, a rich 

 network — the spermatic plexus; on the abdominal portion of the cord it constitutes the 

 pampiniform plexus. 



The vena cava also receives the vena portce, which has the same disposition as in animals. 

 It begins by three branches — the great and small mesenteric and splenic veins. For affluents, 

 it has the pancreatic and duodenal venules, and the right gastro-omental vein. It passes 

 behind the pancreas, and not through that gland, as in the Horse. 



The veins of the abdominal limb are divided into deep and superficial. The first terminate 

 by forming the femoral vein, which, in joining the vessels of the pelvis, constitutes the common 

 iliac vein. The superficial veins commence by a network on the dorsum of the foot, which 

 gives origin to the two saphenas— external and internal. 



FOURTH SECTION. 

 THE LYMPHATICS. 



CHAPTER I. 



General Considerations. 



Charged with the absorption and transport of the chyle and lymph, the 

 lymphatic or absorbent vessels are convergent canals with thin and transparent 

 walls, which originate in the texture of organs by fine reticulated radicles ; these, 

 after passing through one or more glands — glandiform bodies placed on their 

 course — enter the venous system by two trunks — the thoracic duct and the great 

 lymphatic vein. 



Lymphatic Vessels. 



These vessels resemble veins in so many points, as to merit the name of ivhite- 

 blood veins. Like these vessels, the lymphatics are directed from the periphery 

 to the centre of the circulatory apparatus ; hke them, they are nodulated cylin- 

 drical tubes ; internally, and at those points where they outwardly appear to 

 be constricted, they show numerous valves which look towards the heart. Like 

 the veins, again, they separate into two orders of canals — the ones deep-seated, 

 lodged in the vasculo-nervous intermuscular sheaths ; the others superficial, 

 situated on the surface of containing aponeuroses. Like the veins, also, the 

 lymphatics terminate in two principal trunks resembling the venas cavEe ; and, 



