178 



BLOOD AND LYMPH 



apparatus for pumping lymph. The lymph vessels are, 

 however, provided with valves which allow it to flow only 

 toward the veins. While the flow is irregular and slow the 

 pressure in the capillaries is sufficient to keep it in motion, 

 and the movements of muscles that press upon the tubes 

 also aid in driving it onward to the veins. 



Since the lymph is laden with waste, it will be recognized 

 that anjrthing which interferes with this flow is bound to 



disturb the health of the body 

 by the over-accumulation of 

 v.aste in the spaces. Muscular 

 exercise is necessary, since it 

 maintains the lymph flow. 



At irregular intervals the 

 tubes open into spongy bodies, 

 known as lymph glands or 

 nodes. These nodes are spongy 

 masses of fibers filled with cor- 

 puscles similar to the white cor- 

 puscles of the blood. They are 

 supposed to have two functions, 

 first, the removal of certain 

 wastes from the lymph, such 

 as bacteria, which the corpuscles 

 devour, arid second, the produc- 

 tion of the corpuscles them- 

 selves. In other words, these 

 glands filter the lymph as it 

 passes through them, and tend to remove harmful bac- 

 teria in this way. Occasionally these nodes become over- 

 charged ^Yith poisonous material, and break down, forming 

 abscesses or boils. 



Fig. 64— .V lymph node. 



