150 



STUDIES IN PHYSIOLOGY 



finally enter a duct of considerable size (the tho-rac'ic duct) 



which carries the lymph 

 up ward -from the abdomi- 

 -/ nal cavity, through the 

 chest or thoracic cavity 

 (see Fig. 58, a, 6). The 

 thoracic duct finally emp- 

 ties the lymph into a 

 branch of the superior 

 vena cava on the- left side 

 of the neck (Fig. 58,/), 

 and in this way the liquid 

 that has soaked out from 

 the blood is restored to 

 the circulation. A smaller 

 duct drains off portions 

 of the right side of the 

 trunk into a right branch 

 of the superior vena cava 

 (Fig. 58, 7i), and at vari- 

 ous other points in the 

 body lymphatics empty 

 into blood vessels. 



Throughout the course 

 of the lymphatics are 

 found valves much like 

 those in the veins (Fig. 

 59). These prevent the 

 FIG. 58. -The Thoracic Duct. lymph from taking a 



a,b = thoracic duct. backward course. Small 



c = opening of duct into veins. swellings (lymphatic 



d lymphatic nodes in lumbar re- 7 N ,> ~ -, 



gion. nodes) are likewise found 



f, g, h = superior vena cava and its at frequent intervals 



branches. /T7 ,. ~~ x mi 



1 = part of rib. ( Fl g- 59 ); Their P rmcl ' 



pal function is supposed 

 to be that of forming new white corpuscles. They also 



