Epithelial Cysts. 415 



to give rise to metastasis are explicable on meclianical grounds. 

 The cells of squamous epitheliomata are usually large cells and are 

 less easily displaced from their site of formation than many of the 

 smaller cells of the cylindrical cell and glandular types of cancers ; 

 and as a group all epithelial cells are larger and less easily dis- 

 placed than the small round cells of small round cell sarcoma. These 

 last mentioned growths have cells comparable to the small lympho- 

 cytes which are always and readily passing with the blood through- 

 out its entire capillary system. It amounts therefore to the general 

 rule that, whatever tumor cells may be able to gain entrance to some 

 small capillary blood vessels in the tissue in which they are growing, 

 the sarcoma cells have a better chance of convection than do the 

 epithelial cells. On the other hand sarcomas in their growth, direct- 

 ly from and in the connective tissue structures in which the blood- 

 vessels are distributed, are more favorably situated as early tumors 

 to gain access to these vessels than are the epithelial cells, which 

 primarily are separated from the blood stream not alone by the ves- 

 sel walls but by more or less connective tissue and by remnants, at 

 least, of a membrana propria. In their mode of growth cancers 

 primarily are more likely to gain entrance to the lymph spaces an 1 

 channels, and are therefore from the first more favorably situated 

 to follow this system provided the spaces and channels are of suf- 

 ficient calibre to allow the convection of the epithelial cells (as they 

 usually are, in comparison with the minute blood capillaries). Yet 

 granting such factors as these, as determining the usual course and 

 occurrence of metastasis, exceptions must arise and are constant'y 

 being seen. If a sarcoma grow in lymphatic tissue (a lymphosar- 

 coma for example) it is very likely, whatever the size of its cells, 

 to follow the lymph current to the neighboring nodes; and if in 

 some situation (as in stomach or intestinal wall where the larger 

 radicles of the portal vein are close to the cancerous growth start- 

 ing in the mucosa) the cancer cells be afforded easy access to 

 bloodvessels of sufficient calibre to accommodate their size they wiU 

 be found to give rise to hsematogenous metastasis (as the portal 

 convection of gastric cancer to the liver).] 



Epithelial Cysts, Dermoid Cysts, Odontomata, Mixed Teratomata. 



There are a number of tumor-like formations which, as hollow 

 epithelial lined sacs, limited to their place of development, originate 

 from embryonic cellular misplacements. These are cysts ( v kv<ttis. 

 vesicle) which arc not jiroduccd from mature glandular organs 



