GENERAL C0N8IDEEATI0NS. 627 



lifw'^®? °^ *® branches from the cranial sinuses. The internal jugular arises at the 

 f^nlnl ■ '°™™^° laceruni, at a dilatation of the lateral sinus named the bulbus venm 

 iZIT^!if:,TA l^^^l^°J^<' subclavian vein. Lastly, the posterior jugular (or veriebral 

 TTll^t ^^f '^*\ «'e S'-^'^t complexus, and in relation with the cervical yertebr*, 

 ?.v th! n.^,-^ r, T *^,\^P™''1 ^ii"^es in tliis region, and which, in Solipeds, is received 

 by the occipital and vertebral veins. i" ' . 



ii, '^^^ i^P™r vena cava corresponds to the posterior vena cava of animals, and receives 

 the blood trom all the subdiaphragmatic veins. It originatea from the union of the 

 two commoji «2;ac wins, at the third lumbar articulation, and terminates in the right 

 auricle, in its course it receives the median sacral, lumbar, renal, suprarenal, inferior 

 phrenic, and right spermatic veins. The latter forms on the surface of the testicle, and at 

 the origm of tlie 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 porta:, which has the same disposition as in 

 animals. It begins by three branches : the great and small mesaraic and splenic veins. 

 ior affluents, it has the pancreatic and duodenal venules, and the right gastro-omental 

 vem. 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. 



FOUETH SECTION. 

 The Lymphatics. 



CHAPTEE I. 



GENERAL CONSIDERATIONS. 



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

 lympliatic or ahsorhent vessels are convergent canals with thin and transparent 

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

 and which, after traversing one or more ganglia (or glands) — glandiform 

 bodies placed on their course — enter the venous system by two trunks : the 

 thoracic duct and the great lymphatic vein. 



LTMPHATIC VESSELS. 



These canals resemble veins in so many points, as to merit the name of 

 white-hlood veins. Like these vessels, the lymphatics are directed from the 

 periphery to the centre of the circulatory apparatus ; like them, they are 

 nodulated cylindrical 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 apon- 

 euroses ; like the veins, also, the lymphatics terminate in two principal trunks 

 resembling the venae cavse ; and, finally, as the veins have three tunics, so 

 have the lymphatics, these not differing in any respect, except in being very 

 much thinner. 



In carrying this parallel still farther, we will find other analogies whose 

 existence was but little suspected until recently : the glands— those organs 

 which are apparently glandular, and seem to be proper to the lymphatic 

 system — are they not represented in the venous system by the liver — 



