CHAPTER VII. 

 THE LYMPHATIC SYSTEM. 



Tx the main the lymphatic system consists of a series of ves- 

 sels or channels distributed throughout the entire organism and 

 serving chiefly for draining away superfluous fluids in the 

 tissues and returning them into the blood. 



The fluid contained in these channels is the lymph. 



The absorptive action of the lymphatics, as in the intestinal 

 walls and the removal of substances introduced hypodermi- 

 cally, is allied to their drainage function. In some situations, 

 as in the cornea and bone, lymph-channels afford the only 

 passages by which fluids can permeate the tissues for the 

 purpose of nourishing them. 



In the course of lymphatic vessels are also interposed gland- 

 ular structures, which among other functions have the power 

 of arresting noxious and toxic bodies in the lymphatic circu- 

 lation. 



The morphologic elements of the lymphatic system may be 

 stated to be lymph-spaces and origins, lymphatic vessels, 

 lymphoid tissue, and lymphatic glands. 



Lymph-spaces : The interstices or empty spaces in tissues, 

 especially connective tissues, form cavities which may contain 

 lymph and communicate directly or indirectly with lymphatic 

 vessels. Cell-spaces, the intervals between (connective-tissue) 

 cells and their processes and the walls of the cavities or 

 lacunae in which they are situated (as in bone and the cornea), 

 often afford sufficient room for the passage of lymph. In 

 some instances separations or fissures in tissues form lymph- 

 spaces, without any specialization of the walls; in other cases 

 the walls of the spaces are lined partially or whollv with 

 flattened connective-tissue cells or endothelium. The lacunae 

 and canal iculi of bone, the cell-spaces and channels in the 

 cornea, the minute intervals between the prickle-cells of the 

 epidermis, form communicating passages by which lymph can 



