APPENDIX. 



in from the atmosphere at every breath, that mysterious 

 change which prepares it to nourish every part of the 

 body. 



The arteries, which carry the blood from the heart to 

 all parts of the system, are divided into an infinite number 

 of ramifications ; and the branches from the same trunk are 

 frequently found to unite in their course, so that when by 

 any accident some are cut off or obstructed, the circula- 

 tion is still carried on by the others : a wise provision for 

 a most important purpose. 



As we have already explained under the article " Cir- 

 culation" the blood is carried to every part of the body 

 by the arteries, and again returned to the heart by the 

 veins, it being this continued circulation by which the 

 whole system is nourished and renovated, by the action 

 of these vessels. 



Absorbents. These constitute a distinct system of 

 vessels, which take up or carry away such portions of 

 the blood as are either not wanted for nourishment, or as 

 are useless, and to be cast out of the system in a state of 

 solution. These vessels are furnished with valves, like 

 the veins, and terminate in a common trunk called the 

 thoracic duct, w r hich pours its contents into a vein just 

 before it terminates in the right auricle of the heart. 

 This vein is called the subclavian, and the course of the 

 chyle through this duct has already been explained at 

 298, Fig. 74. 



Renovation and Decay. From the above observations, 

 it may be inferred that a system of deposition and removal 

 is continually going on within the living system ; that 

 the ramifications of the arterial system are constantly 

 renovating the different organs, while the absorbents are 

 as continually removing the worn-out materials thus de- 

 posited. 



It would appear, also, that the absorbent system, strictly 



What vessels carry the blood to all parts of the body ? What vessels re- 

 turn the blood to the heart? What are the absorbents? Where does the 

 thoracic duct discharge its contents? \Vh:tt is said of the renovation and 

 decay of the living system ? 



