THE KOJ^-CO^TAGIOUS DISEASES. 207 



lation with loss of many cells, as in degeneration, they 

 are called myxoma, or myeloid sarcoma, from their re- 

 semblance to bone-marrow. Sometimes the framework 

 contains black pigment or coloring matter; these are 

 called melano-sarcoma. 



Combinations of these and other names are used. 

 Ohrondroma means a tumor springing from cartilage; 

 osteoma, one springing from bone; myoma, springing 

 from muscle ; neuroma, nerve-tumor. Myxoma (mucous) 

 or myxo-sarcoma, is so called when degenerative changes 

 have produced a gelatinous substance resembling 

 mucous. 



Lipoma is one containing much fat. 



Sarcomas are composed of embryonic or newly 

 formed connective tissue cells, and may occur wherever 

 there is connective tissue. They may arise at any age, 

 but are most common in early life, while carcinomas sel- 

 dom occur before forty years of age. In carcinoma the 

 blood vessels are situated in the connective tissue frame- 

 work, in sarcoma they open directly into the growth, 

 and in their passage through the tumor the vessel walls 

 are formed by sarcomatous cells; therefore the cells 

 may easily fall into the current and be washed away 

 by the circulation. The veins may carry some of these 

 cells to the heart, and as the blood is sent through the 

 lungs the malignant cells may lodge in the capillary 

 network of vessels and produce secondary sarcoma. 

 Emboli, or blood-clots, may now be carried back to the 

 left side of the heart and sent through the general cir- 

 culation, and may lodge in the brain, liver, kidneys, 

 bone, etc., and produce secondary sarcoma. Sarcomas 



