CONNECTIVE TISSUE 



515 



of in bundles, and individual fibres branch and join each other ; 

 when one is cut its ends are pulled apart, showing that the fibre 



pundle of 



— ¥vhite fibrtJ 



— ijeJlo*/ fibres 



Fig. 400. 



-Fibrous connective tissue, areolar, from subcutaneous tissue of rabbit, 



X 300. — From Thomson. 



was under tension. The chief cells of areolar tissue are the fibro- 

 blasts, or fibrocytes, in the restricted sense, which spin outside 

 themselves masses of cytoplasm 

 which develops into the white 

 fibres. The direction of the 

 fibres is to some extent deter- 

 mined by any tension in the 

 ground substance, so that on 

 the whole they are formed in 

 the way most useful to resist 

 the stresses to which the tissue 

 is exposed. This is the immedi- 

 ate explanation of why con- 

 nective tissue is functionally 

 adapted to its purpose. Fibro- 

 cytes are flattened, with two 

 or three pointed processes, and 

 are stationary. The other chief 

 type of cell in areolar tissue, the 

 histiocyte, is not a mechanocyte 

 but an amoebocyte. It is able 



to move and ingest foreign particles, and is then called a 



macrophage. Other types of cell are present in smaller numbers. 



The other types of connective tissue may all be looked on as 



derived from areolar tissue by modification of its cells, its fibres 



Fig. 401. — Part of one of the fat bodies 

 of a frog, compressed and magni- 

 fied, showing fat cells with fat 

 globules in various stages. 



/.g., Fat globules; mm., nuclei. 



