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is the myeloid or giant celled variety. But the common 

 skin tumors do not in the least resemble this variety of 

 sarcoma. So far as I can see, there is only one point of re- 

 semblance between these skin tumors and the spindle-celled 

 sarcoma. The embryonal cells in the young skin tumor 

 may resemble the spindle cells of a sarcoma; but the tissues 

 surrounding these cells and the further development of the 

 cells in the fibroma prove conclusively that the young skin 

 tumors are not sarcomas. 



After the removal of one of these skin tumors, a peculiar 

 tumor may form in its place, which is nothing more or less 

 than an abnormal growth of granulation tissue, or " proud 

 flesh" as it is commonly called. These exuberant granula- 

 tion tumors occur in the following way : When the original 

 skin tumor is removed, the cavity must be filled up and 

 closed by granulation tissue, forming what is commonly 

 known as scar tissue. Layer after layer of embryonal 

 granulation cells are formed on the sides and bottom of the 

 wound, made by the excision of the original tumor. (Some- 

 times the original tumor drops out or is torn out leaving a 

 wound very similar to, but smaller than, the wound usually 

 made when the tumor is cut out.) The layers of granulation 

 cells are supplied with nutriment by the loops of capillary 

 blood vessels ; new capillary loops accompany the rapidly 

 growing, dividing embryonal granulation cells. But, before 

 the lips of the wound unite, there must be a formation of 

 epitiielium, either from the extension of the epithelial cells 

 on the edges of the wound or from the granulation cells. 

 When the epithelium is formed by neither of these pro- 

 cesses, we have, as a result, a growth of what is called exu- 

 berant granulations or " proud flesh." If the wound is 

 irritated by the animal's biting or rubbing it, and possibly 

 by the action of septic germs, this epithelial covering can 

 not be formed. In other words, periodic irritation will pre- 

 vent the healing of a wound and produce a granulation 

 tumor. 



Some sarcomas are composed largely of embryonal con- 



