TUMORS. 



339 



A great practical difficulty in the description, and, to beginners, in 

 the recognition, of the carcinoniata and their varieties, lies in the great 

 diversity in shape which their cells present. It should be always borne 

 in mind that the shape of cells depends in part upon their inherited ten- 

 dencies in growth, which we cannot see under the microscope ; but to a 

 greater degree upon the varying conditions of nutriment and pressure 

 in which they are placed during life. In llio normal body these coudi- 



FIG. 185. CARCINOMA OF THE HAND. 

 This tumor is of the epitheliomatous type and presents a large, rough, ulcerated surface. 



tions conform to a certain standard, so that cells of a given kind at a 

 given stage of development are approximately similar. 



In tumors, however, the lawlessness and lack of fixed conditions in 

 growth are such that we may have many young and atypical so-called 

 indifferent forms of cells; while even the adult forms may depart widely 

 from normal shapes. Thus, in cylindrical-celled carcinoniata there are 

 many fully developed cells which are never cylindrical ; there are many 

 others not fully developed which are quite indifferent/ in form, looking 

 just like many other young cells. Finally, there may be in such tumors 

 inflammatory processes through which young connective-tissue cells are 

 formed, not to be distinguished individually from the atypical forms of 

 epithelium. Thus it is that there is no morphologically characteristic 

 (t cancer cell," as was formerly supposed. Some of them are typical and 

 some not, and the more typical may resemble normal epithelial cells, 



