264 PRACTICAL ANATOMY. 



the spine freely communicate with one another; they are 

 very abundant, and are divided into the veins of the 

 cord, those of the bodies of the vertebrae, those of the 

 meninges of the cord, and the external veins. 



LYMPHATICS. 



Lymphatics, or absorbent vessels, are found in all the 

 tissues of the body except the cartilage, epidermic struc- 

 tures, cornea, and white matter of the brain and cord. 

 Tney are delicate, transparent vessels, and have three 

 coats, an outer areolar, middle fibro-muscular, and inner 

 epithelial. They are abundantly supplied with valves. 

 The origin of the lymphatic vessels has been an open 

 question. Most probably they begin in intercellular 

 spaces, which, by communicating, become lymph-sinuses. 

 These sinuses are lined by cells at first irregularly placed, 

 then pavement in character, showing, however, here and 

 there openings between the cells called the stomata. 

 These minute capillaries communicate freely, forming a 

 plexiform anastomosis, from which the lymphatic vessel 

 proper starts. Scattered along the course of the lym- 

 phatics are a great number of ovoidal solid bodies, vary- 

 ing in size from a small pea to an almond. These are 

 the lymphatic glands. On section they are seen to be 

 formed of, first, an outer, fibrous capsule, which sends 

 inward a number of septa that divide the gland into 

 alveoli, which constitute the cortical portion. It is 

 light in color and deficient at the hilum, a linear 

 depression at one part of the gland, at which the blood- 

 vessels enter and pass out. The medullary portion is 

 dark in color and granular in appearance. The lym- 

 phatic that leaves the gland is called the efferent. It 

 passes out through the hilum, and is connected with the 

 medullary portion. The afferent vessels, those which 



