io8 



ELEMENTS OF PHYSIOLOGY 



ting horse, or in a jolting vehicle, the lymph is moved be- 

 yond the valves at every jolt, and its circulation aided. 



183, The' secret of the powerful effect of muscular work 

 upon the health lies chiefly in the great aid that it gives 

 the lymphatic and venous circulations. The 

 importance of an active lymphatic circulation 

 is seen when we remember that the blood 

 does not make its exchange directly with the 

 cells of the tissues, but with the lymph, and 

 the lymph makes the exchanges with the 

 tissue cells. 



184. The Lymphatic Glands. Along the 

 course of the lymphatics, numerous enlarge- 

 ments occur called lymph nodes or lymph 

 glands (Fig. 101). They 

 consist of a connective 

 tissue framework, the 

 meshes of which are 

 crowded with lymph cells. 

 The lymph in its course 

 must filter through these 

 clusters of cells, and, in 

 doing so, is purified; for 

 the node cells take up 

 impurities in the lymph, 

 and work over and change 

 The cells in these nodes 

 multiply, and some of them are taken up 

 by the lymph and carried into the blood 

 to become those remarkable little bodies, 

 the white blood corpuscles. It is a curi- 

 ous fact that the older white corpuscles 

 are broken up in the lymph nodes, and their remains are 

 absorbed by the newly formed white corpuscles, just as the 

 latter absorb germs and other foreign particles that may 



FIG. loo. A Full 

 Lymphatic with 

 its Valves dis- 

 tended. 



their nature. 



FIG. 101. Lymphatic 

 Gland. 



Showing valved lymphatics 

 entering and leaving it. 



