<;n HISTOLOGY. 



Thev seem to be in no way connected with the general nutritive 

 condition of the animal. It is interesting to note that they have 

 been found in equal abundance in bats before and after the 

 winter sleep (Ballowitz). Like plasma cells, the mast cells are 

 found usually in the neighborhood of blood-vessels. They are 

 found also tinder epithelial surfaces, iu the smooth muscles, mam- 

 mary gland, and testicle. Many authors claim that the two are 

 identical, and the differences in staining reaction they consider 

 to be dependent on a chemical or functional condition. Some 

 trace their origin from leucocytes; others assert that they are 

 true elements and essential constituents of connective tissue : 

 .-till others regard them as products of pathological change. 



;>. Clasmatocytes are large spindle-shaped or stellate cells, 

 with long, irregular processes, which may be torn or cast off 

 and be found as separate masses near the cell. Ranvier claims 

 that they arise from leucocytes, and that in inflammation of a 

 tissue, for example, they may again become leucocytes and form 

 pus. They stain well with methyl-violet 5 B. 



Truly there is little known, and nothing with certainty, con- 

 cerning this whole group of granular cells. Up to the present 

 time their origin and their function are by no means clearly 

 understood, nor, indeed, do we know in what relation the three 

 kinds of cells stand to one another. 



(c] Wandering cells (Fig. 29) are really not connective- 

 ti.-sue cells, but leucocytes which by "diapedesis" have wan- 

 dered through the walls of the smaller blood-vessels into the 

 surrounding connective tissue. They are not characteristic for 

 connective tissue, since they are found also (e.g.) in epithelium; 

 but they occur in greater quantities in the former than in any 

 other tissue. They possess the power of amreboid movement, 

 and wander freely between the constituents of other tissues. 



Wandering cells may undergo division in the connective 

 tisHi- and increase there. Thev have, in common with leu- 

 cocytes, the power of taking up certain materials (e.g., bacteria), 

 which they either assimilate or render innocuous to the organ- 

 ism i. e., they play the part of phagocytes (Metchnikow). 



It has been observed that young fixed cells which arise from 



