CONNECTIVE TISSUE. 39 



round, ovoid, oblong, fusiform, or irregularly rec- 

 tangular, often sending off branches which seem 

 to be connected with the branches of neighboring 

 cells. Sometimes the thin cell-body sends off one 

 or more delicate wing-like processes at varying 

 angles. These cells may have one or more nuclei ; 

 they lie in the interstices of the fibres, which they 

 often enwrap with their delicate bodies. The form 

 which they assume in the different varieties of con- 

 nective tissue would seem to be largely dependent 

 upon the varying conditions of pressure to which 

 they are subjected by the adjacent fibres. These 

 flattened connective-tissue cells in many parts of 

 the body may, and in certain parts constantly do, 

 contain pigment granules. 



In certain parts of the body the connective tissue 

 presents free surfaces, lining more or less well-defined 

 closed spaces or cavities, or free surfaces which are 

 movable over one another, as in the great serous 

 cavities, in the blood- and lymph-channels, tendon- 

 sheaths, etc. In these cases the flat connective- 

 tissue cells usually undergo some modification in 

 their form, character, and relations to one another, 

 and are called endothelial cells or endothelium. 



Finally, in certain parts of the body, usually in 

 the vicinity of blood-vessels, are found irregular- 

 shaped granular cells, not usually flat, and of vary- 

 ing size and form, called plasma cells, which resemble 

 in many respects cells found in the embryo. 



