TUMORS. 



E INFLAMMATORY new formations are very unstable and 

 1 when their cause, usually some irritation, is removed they will 

 have a strong tendency to return to a healthy standard or condi- 

 tion. The non-inflammatory have great independence, grow by an 

 inherent activity of their own, and are constantly tending to become 

 removed farther and farther from a healthy condition. Their 

 general tendency is to increase in size, although after a time they 

 may remain permanent. To this class belong the new formations, 

 known as tumors. A tumor is many times pathological simply be- 

 cause its sp'ecific elements occur in a place where they do not nor- 

 mally belong. Virchow calls a tumor composed of but one tissue 

 "histioid," when composed of several tissues "organoid." When 

 in addition to the latter there are organ-like tissues "systematoid." 



If a new formation occurs in a tissue agreeing with it in struc- 

 ture it is said to be "homologous." If unlike it, it is "heterolo- 

 gous." 



All of the pathological elements found in a new formation, in- 

 cluding the cells, nuclei, matrix, vessels, etc., are prototypes of 

 those found in the normal tissues, only undergoing change and de- 

 struction more readily. 



The cells of these growths are reproduced most frequently by 

 cell division, the nucleus dividing first, followed by a division of the 

 formed part of the cell. This has been observed to occur in a very 

 few seconds. Sometimes the nucleus alone will divide, these nuclei 

 thus formed dividing again and again, until one cell may possess in 

 this way from four to twenty or more nuclei. 



These 'cells are known as the "giant," "mother," or " myeloid " 

 cells. They are found normally in the medullary substance of bone. 



Pathological cells, then, come from pre-existing cells, and when 

 newly formed are usually small and round, having a nucleus or com- 

 posed of nucleus matter alone, simple undifferentiated protoplasmic 



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