THE COXXF.CTTVE TISSUES 



89 



appearance is that of a minute amount of cytoplasm shrunken 

 down around a nucleus. Somewhat similar cells with more coarsely- 

 granular or vacuolated cytoplasm have been designated ''clas- 

 mocytes" (Ran\'ier). By some these are believed to be of leucocyte- 

 origin, by others to be an earlier stage in the development of the 

 fixed connective-tissue cell. 



{b) Plasfua Cells.- — -These cells occur mainly near the smaller 

 blood-vessels. Their protoplasm is finely granular and stains with 

 basic aniline dyes. They frequently contain vacuoles. Their 

 nuclei are small, spherical and usually excentric. Small plasma cells 



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^ji.: 





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Fig. ^t,. — Section of Human Cornea cut Tangential to Surface. X350. (Technic 

 9, p. loi.) Connective-tissue Cell Spaces (Lacunae) and Anastomosing Canaliculi, 

 white; Intercellular Substance (Ground Substance and Fibres), dark. 



are about the size of leucocytes, which they closely resemble. Large 

 plasma cells are larger than leucocytes and richer in protoplasm. 

 Some consider them as derived from leucocytes, others as a modified 

 form of the ordinary fixed connective-tissue cell. 



(c) Mast cells are spherical or irregular-shaped cells, found like 

 the preceding in the neighborhood of the blood-vessels. Their proto- 

 plasm contains coarse granules which stain intensely with basic 

 aniline dyes (Fig. 31). They are believed by some investigators to 

 be connected \^ith the formation of fat; by others to represent a 

 stage in the development of the fixed connective-tissue cell. 



(d) Clasmatocytes . — These are large, mostly spindle shaped cells 

 with granular protoplasm. 



Connective- tissue cells may be pigmented (Fig. 35). In suck 

 cells the cytoplasm is more or less filled with brown or black pigment 



