EOUND-CELL SARCOMATA. 151 



having its cells partially converted by fatty infiltration into fat- 

 cells. This transformation is always restricted to a limited 

 number of the elements present ; inasmuch however as the 

 altered cells arrest attention by their lustre and their size, it may 

 very readily seem as though the vast majority, if not all, of 

 the sarcoma-cells had been converted into fat-cells. The resem- 

 blance to genuine adipose tissue does not go very far ; the lack of 

 uniformity in the infiltration, and the promiscuous assemblage of 

 very large and very small fat-cells, which are never united into 

 clusters, make it impossible to confound these tumours with 

 lipomata. 



The irqjxomatous sarcoma (s. myxomatodes). Small portions 

 of mucous tissue are not unfrequehtly found embedded here and 

 there in the substance of round-cell sarcomata. Such islets 

 betray themselves even to the unaided eye by their transparent, 

 jelly-like, tremulous consistency ; the microscope usually demon- 

 strates an abundant proportion of mucous basis-substance, with 

 a great number of round-cells wdiich do not anastomose with 

 one another, embedded in it. Mucous softening" of the basis- 

 substance may justly be regarded as a secondary metamorphosis 

 to which all round-cell sarcomata are liable. The possibility of 

 tliis change occurring at an early period in their development, 

 and its extension through large portions of a tumour, justifies 

 the term " myxomatous sarcoma." ^ay, the mucous tissue may 

 so exceed the proper structure of the tumour in amount, that we 

 might be led to think of a true myxoma, but for the presence of 

 some few unaltered portions ; these, and more particularly the 

 youngest products at the periphery of the tumour, and its striking 

 metastases, place its sarcomatous nature beyond the possibility of 

 question. The extremely rapid rate of growth which is charac- 

 teristic of myxomatous sarcomata might be inferred from the 

 fact that m.ucus, owing to its capacity for swelling by imbibition, 

 takes up a volume disproportionately greater than that occupied 

 by the scanty intercellular substance of the sarcoma. 



Mucous metamorphosis and fatty infiltration often co-exist ; 

 such tumours are peculiarly prone to assume a colossal size. 



The lax connective tissue of the extremities and the subperi- 

 toneal connective tissue are the seats of election of the mucous 

 variety of sarcoma. 



The large-celled round-cell sarcoma is distinguished by the 



