TUMORS. 395 



A papilloma consists of vascularized fibrous or areolar tissue 

 springing from a surface which is covered with epithelium. The 

 denser forms which occur e. g., upon the skin constitute "warts" ; 

 but much more delicate papillomata may spring from mucous mem- 

 branes, such as that of the bladder, and are then known as villous 

 tumors or villous papillomata. In many cases the denser forms of 

 papilloma appear to be hypertrophies due to irritation. But papil- 

 lomata which seem to be true neoplasms or tumors in the restricted 

 sense of that term hitherto employed appear to be among the possi- 

 bilities of morbid development. 



