HYPERTROPHY, HYPERPLASIA, METAPLASIA, REGENERATION. 103 



it is the cells alone which take the initiative, the formation of intercel- 

 lular substance being always secondary to the formation of the cells and 

 always occurring under their influence. 



Xew connective-tissue cells may be formed by mitosis, either from 

 older connective-tissue cells, or, as now seems certain, from the endothe- a LJi 

 limn <>!' the, blood-vessels and possibly from the so-called "plasma cells." l ,-.. 

 In either case the cell about to divide shows an increase in the size 

 of the body, which becomes more granular; the nucleus divides by 

 mitosis, segmentation of the cytoplasm following. This process may be 

 repeated so that many cells are derived from one, separated at first by 



FIG. 34. REGENERATION OF CONNECTIVE TISSUE. 



Showing ttbroblasts with a few new-formed intercellular fibrils between them. The vessels have 

 thin walls, and a few leucocytes have passed through them into the tissue. A mitotic figure is shown in the 

 left lower portion. 



n small amount of homogeneous intercellular substance. These cells, 

 at first more or less spheroidal in form, may become larger, and poly- 

 hedral or elongated. Little by little, fine fibrils appear between the 

 cells, sometimes apparently as extensions of their cytoplasm, sometimes 

 along their sides in the homogeneous material in which they lie. Such 



1 PLASMA CELLS. It is believed by many that the so-called plasma cells are fre- 

 quently and largely concerned in the formation of new fibrous tissue. Plasma cells 

 are rounded or polyhedral or elongated, depending upon their situation, and vary in 



usually excentric and commonly shows several irregular groupings of chromatin masses 

 just beneath the membrane. The body of the plasma cell is especially characterized 

 by the staining of its protoplasm by basic anilin dyes the polychrome methylene blue 

 of Unna, for example. The staining is commonly less intense near the nucleus and is 

 otherwise frequently uneven. 



Such cells occur normally in the bone marrow, spleen, lymph nodes, and gastro- 

 intestinal mucosa of man, and may be found under various pathological conditions, 

 especially in hyperplasia and the new formation of fibrous tissue. It is believed by 

 man}' observers that plasma cells are direct derivatives of the small mononuclear 

 lymphocytes, and that when these gather in the tissue by emigration they may either 

 undergo degeneration and destruction, or, on the other hand, that they may become 

 connective-tissue cells and share as fibroblasts in the formation of fibrillar stroma. The 

 origin and significance of "plasma cells" is not yet altogether clear, and we must refer 

 to larger works for further data. See "Critical Summary of Recent Literature," by 

 William*, American Journal of the Medical Sciences, vol. cxix.. p. 702, 1900. 



