io6 



ELEMENTS OF PHYSIOLOGY 



179. We may say, then, that lymph is nearly the same 

 as the blood without the red corpuscles. Did you ever 

 see any lymph ? Certainly you have seen it, many times. 

 Whenever there is a blister in the skin from friction, or 

 from a burn, the lymph collects. Sometimes when the 

 skin is grazed, but no blood vessel touched, the lymph 

 may exude. 



180. The Origin and Course of the Lymphatics. Unlike 

 the blood vessels, the lymphatics, or the tubes which carry 



the lymph, have a beginning. The blood 

 vessels do not begin, but make a never- 

 ending circle. The lymphatics begin in 

 open ends between the capillaries and the 

 cells, or among the cells themselves (Fig. 97). 

 It will be interesting to learn how they 

 lead the lymph back to the circulation, and 

 what makes it flow, for surely there is no 

 heart for the lymph as there is for the 

 blood. When the lymph once enters the 

 open end of the lymphatic, it does not 

 return to the blood, but continues to move 

 slowly or at intervals through the lymphatics 

 on its return to the blood system (Fig. 98). 

 Small lymphatics come together and form 

 larger ones. They continue to unite and 

 form larger ones, until finally the lymphatics 

 from nearly the entire body unite into one 

 FIG. 98. The i ar pre tube, which passes up through the 



larger Lympha- * 



tics of the Front abdomen and thorax, and pours the lymph 

 of the Right Arm. into t ^ Q venous system beneath the. collar 



g; lymphatic glands. . . ,, . .. . .. 



bone near the neck. This largest of all 

 lymphatics is called the thoracic duct. 



181. The Thoracic Duct is about the size of a goose quill, 

 and empties into the venous system just where the large 

 vein from the left side of the head (the left jugular vein) 



