72 CLINICAL APPLIED ANATOMY. 



parts ; hence, organs far removed from the primary seat of 

 disease rapidly become infected with secondary deposits. While, 

 however, it is true that sarcomata are chiefly disseminated by 

 the blood stream, it is also true that a considerable number are 

 also spread by the lymphatic system, for sarcomata of periosteum, 

 bone, tonsil, testis, ovary, parotid and skin, as well as all 

 melanomata, frequently give rise to secondary deposits in 

 lymphatic glands. 



EPITHELIAL TUMOURS. 



Epithelium occurs on the surface of the body, covering the 

 skin and the appendages thereto, and lining mucous mem- 

 branes, or, deeply, as a lining to the secreting portion and ducts 

 of glands. 



TUMOURS ARISING FROM SURFACE EPITHELIUM. 



Papillomata, or warts. These, the common, innocent epi- 

 thelial tumours occur on the skin, but particularly on those 

 parts which are liable to be irritated or infected ; therefore they 

 are common about the hands, the glans penis, prepuce, vulva, and 

 surrounding skin. The crops of warts so frequent on the fingers 

 are due to the exposed position of these organs, and therefore 

 their constant liability to be irritated and infected. 



There are two surfaces covered by stratified epithelium other 

 than the skin which may give origin to warts. The first is the 

 dorsum of the tongue, on which papillomatous tumours are by 

 no means infrequently seen, and are again as a rule the outcome 

 of irritation and infection. The second is the true vocal cord, 

 where again papillomata, sometimes multiple, are frequent. 

 Their occasional disappearance after tracheotomy in children may 

 be in part due to the rest given to the larynx. 



Epitheliomata. An epithelioma is a squamous-celled carci- 

 noma, and therefore may arise on any surface covered by a 

 stratified epithelium. It is undoubtedly true that epithelioma 



