CONCOCTION. [Lesson xxxvm. ( 



cnyle, being more and more diluted and blended 

 \viih abundance of lymph from the glands through 

 which it passes, and from other sources, approaches 

 still nearer to the nature of our animal juices, and 

 consequently becomes more fit for nutrition. 



The chyle is pushed from its reservoir into a 

 narrow transparent pipe, called the thoracic duct, 

 which climbs in a perpendicular direction by the 

 side of the back-bone, from the loins up to the 

 collar-bone, and opens into the subclavian vein : 

 where, by the peculiar arrangement of several 

 small valves, the chyle mingles gently with the 

 blood after it has been thoroughly elaborated ; and 

 attenuated with lymph from every part of the 

 thorax, or great cavity of the breast, and is from 

 thence soon conveyed to the heart. 



Thus we may perceive, that by a wonderful me- 

 chanism, a large quantity of chyle and lymph is 

 forced upwards, in a perpendicular course, through 

 a thin slender pipe ; but lo render this more plain, 

 the following pariiculars must be attended to: 

 First, to the progress of the chyle, urged forward 

 and continued from the ante edent action of the 

 intestines, and the beating of the mesenteric arte- 

 ries. Secondly, to the motion of the diaphragm 

 and lungs, in respiration, pressing the thoracic 

 duct that lies under them, whilst the thorax, rising 

 and falling:, resists their action, whereby the duct 

 is squeezed between two contrary forces, and the 

 liquor which it contains pushed upwards. Thirdly, 

 this duct runs close by the side of the great artery 

 (called by anatomists, the superior portion of the 



descending 



