334 COMPARISON BETWEEN THE ABSORBENTS AND VEINS. 



large venous trunks. Like the veins, also, the absorbents are 

 divided, into two portions or couches ; a superficial set of ves- 

 sels which are extensively spread immediately under the skin, 

 and accompany in general the superficial veins of the limbs ; 

 and into a deep-seated or profound, which accompany the deep- 

 seated arteries and veins. Like the veins, too, the absorbent 

 vessels are provided abundantly with valves. 

 Here the analogy ceases between the two systems of vessels. 

 The absorbents differ from the veins, in having their course 

 interrupted from time to time, by the lymphatic glands ; by the 

 mode in which they run, not uniting successively into branches 

 and into trunks like the veins, but each running as it were an 

 independent course from their origin to near their termination, 

 and not enlarging much in diameter, though they anastomose 

 frequently with each other. The fluid which circulates in the 

 veins, is yet, though in a diminished degree, under the influence 

 of the heart (vis a tergo) ; the fluid of the absorbent vessels, 

 appears to be exclusively under the influence of the walls of the 

 vessels themselves. The origin of the veins have been clearly 

 shown by the microscope, to be from the arteries through the 

 intervention of the capillary vessels ; whilst the origin of the 

 absorbents though yet involved in much obscurity, on account of 

 their tenuity and the transparency of the fluids which they 

 carry, is believed to be wholly different. 



The absorbents which originate in the Lower Extremities 

 and the Cavity of the Abdomen, unite and form a large trunk 

 called the Thoracic Duct, which proceeds through the thorax, 

 and terminates in the left Subclavian Fein, at its junction 

 with the Internal Jugular. Those of the Left Upper Extre- 

 mity, the Left Side of the Head, and the contiguous parts, 

 form a trunk which terminates in the same place. While the 

 remaining absorbents, or those of the Right Upper Extremity 

 and the Right Side of the Head, fyc., also form a trunk which 

 terminates in the corresponding part of the Right Subclavian 

 Vein. 



The absorbent vessels of middle size, which arise from 

 the union of the small vessels, and unite to form the larger, in 



