ABSORPTION. 37 



alimentary canal, and as they converge, unite with the splenic vein to form 

 \\\z portal vein, which enters the liver (Fig. 5). 



As the digested mass of food, the chyme, passes through the alimentary 

 canal, a large portion of it disappears; the veins absorb water, albuminose, 

 glucose, and inorganic salts, and convey them directly into the liver; the 

 blood of the portal vein being especially rich in these substances. 



At times, after the ingestion of large quantities of oleaginous food, the 

 blood vessels take up, in addition, a certain quantity of fatty matter ; but 

 this is not usually the case ; the fats being absorbed by special vessels, the 

 lymphatics or lacteals. 



General Anatomy of the Lymphatic System. The lymphatics 

 constitute a system of minute, delicate, transparent vessels, which, having 

 their origin at the periphery of the body, pass forward toward the centre 

 and empty into the veins at the base of the neck, by means of the thoracic 

 duct. In their course they pass through small ovoid bodies, the lymphatic 

 glands. 



Origin of the Lymphatics. The lymphatic vessels arise in several 

 distinct ways : I . In lymph spaces or juice canals. Throughout the con- 

 nective tissues of the body are found numbers of small, irregular, stellate 

 spaces, which communicate freely with each other, and represent the 

 ultimate radicles of the lymphatic vessels. They frequently contain lymph 

 corpuscles. These spaces communicate with the lymph trunks, through the 

 medium of the plexuses of lymph capillaries, which are much larger than 

 capillary blood vessels, and are lined with endothelial cells with sinuous 

 margins. 2. In openings on the surface of serous membranes. The sur- 

 faces of the serous membranes are covered with a layer of endothelial cells. 

 At intervals between these cells are found openings the stomata. These 

 stomata communicate directly, through short canals, with the lymph capil- 

 laries. The serous cavities may be thus regarded as large lymph spaces. 

 3. In perivascular lymph spaces. In the brain and spinal cord the capil- 

 lary blood vessels are surrounded by a sheath, formed of endothelial cells, 

 and which contains lymph. This space is in free communication with the 

 lymphatics. By this means the blood vessel is bathed by the lymph stream. 



The lymphatic vessels of the small intestine (the lacteals] arise within the 

 villous processes which project from the inner surface of the intestine 

 throughout its entire extent. The wall of the villus is formed by an eleva- 

 tion of the basement membrane, and covered by a layer of columnar 

 epithelial cells. The basis of the villus consists of adenoid tissue, fine 

 plexus of blood vessels, unstriped muscular fibres and the lacteal vessel. 

 The adenoid tissue consists of a number of intercommunicating spaces, 



