TUMORS. 



383 



first appears as little solid columns of epithelial cells, which spring 

 from the epithelium covering the part and penetrate the underlying 



FIG. 350. 





Section of mammary gland in a state of involution. (Altmann.) From a woman, aged 

 thirty-two, fourteen months after functional activity had ceased. 



tissues (see Fig. 181). These columns subsequently become hollowed 

 to form tubes or sacs lined with secreting epithelium. In carci- 



FIG. 351. 



Infiltrating adenoma of the rectum. (Hansemann.) The figure represents alveoli of atypical 

 character, differing greatly from the normal glandular structures of that part of the body. 

 The section does not include the infiltrating portion of the growth. 



nomata the embryonic state of gland-formation is simulated by the 

 growth, so that a carcinoma may be considered as formed upon the 



