TUMORS. 



315 



posed or arranged in large meshes resembling alveoli. In many cases, so 

 small is the quantity of intercellular substances that it is difficult of detec- 

 tion without special modes of preparation. These tumors often contain 



FIG. 152. SMALL ROUND-CELLED SARCOMA. 

 From a raetastatic tumor in the lungs. 



many blood-vessels, and may be very soft and succulent. Their growth 

 is sometimes rapid and they are oftenverv jjufl.lipna.Trf-.. 

 ~~ Titey most frequently occur in the connective, tissue of the muscles 

 and fasXiai, in bouepand" in lymph -nodes (Jympho-sarcoma). They also 

 occur in the internal organs, not infrequently in the brain, associated 

 with glioma as glio-sarcoma. 



2. In the large round-celled sarcomata (Fig. 154) the cells vary in 

 size, but are usually very much larger than in the last variety. Their 

 nuclei are usually large and contain prominent nucleoli. They, too, are 

 often very vascular, and contain a variable quantity of basement sub- 



FIG. 153. MELANO-SARCOMA OF THE SKIN, FUNGOID IN SHAPE. 

 A small nodule showing local extension is seen in the subcutaneous tissue beneath. 



stance. They are occasionally alveolar in character. They are, as a 

 rule, less soft and malignant than the small-celled varieties. 



Melano-Sarcoma. These tumors consist most frequently of polyhedral 

 cells of various sizes. They are characterized by the presence in the 

 cells, and less frequently in the intercellular substance, of larger and 

 smaller particles of brown or black pjgoufint (Fig. 155). The pigment 

 is usually quite irregularly distributed~m patches or streaks. They arise 

 most frequently in the skin (Fig. 153) and in the choroid. Pigmented 



