TUMORS. 363 



territory which it occupies, but the more central portions also grow. 

 After a certain stage of growth has been attained the older portion- 

 of the tumor are liable to undergo degenerations or necrosis. 



It is evident, from the structure of this variety of sarcoma, that 

 it must be very prone to suffer metastasis. This may take place 

 through the lymphatics of the surrounding tissues, favored by the 

 infiltrating qualities of the growth ; or it may take place through 

 the bloodvessels, some of the cells finding their way through the 

 thin walls of the vessels in the tumor itself, or into the lumina 

 of larger vessels through an infiltration of their walls. In either 



FIG. 326. 



Small round-cell sarcoma of the pelvis, infiltrating dense fibrous tissue. 



of these ways a generalization of the growth may take place, sec- 

 ondary nodules appearing in many parts of the body. 



Round-cell sarcomata of this type are liable to arise in the 

 connective fibrous tissue between the muscles, in the fasciae, etc. 

 They also find their origin in the skin, testis, and ovary. They 

 arc among the most malignant of the sarcomata, growing rapidly, 

 infiltrating their surroundings, and undergoing metastasis. 



b. LYMPHOSARCOMA. This variety of sarcoma differs only 

 slightly in structure from the small round-cell form in possessing 

 a somewhat more elaborate stroma, a term which could hardly be 

 applied to the small amount of intercellular substance found in the 

 latter. In the lymphosarcomata the cells closely resemble those of the 

 small round-cell variety of sarcoma, but they lie loosely aggregated 

 in the meshes of a reticulum of fibres, many of which constitute the 

 processes of stellate cells penetrating the substance of the growth 



