384 



Tumors. 



the papilla and their overlying epithehum. The physiological 

 prototype of this combination of tissue and its source of develop- 

 ment are in fact the epithelial-covered papillae of the skin, but 

 in their pathological proliferation the quantitive relations be- 

 tween the two forms of tissue are very irregular. In some 

 tumors the connective tissue growth is so predominant that the 

 tumor practically consists of thick clumps of this tissue covered 

 only^ by a thin layer of epithelium rather stretched over the mass 



Fig. 112. 

 Cutaneous papillomatosis of beef. 



than growing with it (for which reason some authors prefer to 

 speak of such a specimen as fibroma papillare), the superficial 

 papillary structure being only recognizable under the micro- 

 scope. In other instances the fibrous tissue of the base of the 

 tumor sends out long branched villous processes, or may undergo 

 changes which give it a soft, oedematous or very vascular appear- 

 ance ; and again the keratous epithelium may form so thick a 

 laver as to throw the connective tissue substructure into insig- 

 nificance. Different types of these iibroepithelial autoblastomata 

 may be distinguished by taking such features into consideration. 



