46 VERTEBEATA: MAMMALIA. 



which originate in the mucous membrane of the intestines, and which, 

 after passing through and being more or less modified by the mesen- 

 teric glands, open into an organ called the thoracic duct. 



This duct, which begins in the abdomen, carries the chyle, which is 

 constantly becoming more and more like blood, and pours it into the 

 left sub-clavian vein, which is one of the great branches that lead 

 directly to the heart. 



The absorption of chyle by a certain kind of vessels has 

 just been alluded to ; and we may properly notice here 

 the vessels which constitute the true Absorbent system. 

 While absorption of a certain kind as described on 

 page 10 is carried on by various tissues, the walls of the 

 stomach, walls of the intestines, and blood-vessels, there 

 are in all the Vertebrates, except the Amphioxus (Fig. 

 352), special organs of absorption, which we will now 

 briefly describe. 



Besides the capillaries, already referred to, and the veins 

 which they open into on the one hand, and the arteries 

 which they open into on the other, there are, in all parts 

 of the body which have ordinary capillaries excepting 

 only the brain and spinal cord, eyeball, cartilages, tendons, 

 and, possibly, the bones other vessels or capillaries called 

 absorbents or lymphatics. The Lymphatic or Absorbent 

 system consists of vessels which originate in the tissues, in 

 excessively minute roots or tubes, and which open only into 

 trunks which bear fluid away from them there are no 

 vessels to bring anything to the absorbents. They are 

 filled with a liquid known as lymph, and which is slightly 

 yellowish or transparent ; or milky, as in that part of the 

 system known as the lacteals or chyliferous vessels. They 

 often anastomose or unite with one another along their 

 course ; and at intervals they enter certain bodies called 

 lymphatic glands, from which they emerge as new trunks 

 and continue onward as before. 



