TUMORS. 313 



may be flat, fusiform, spheroidal, or branched, and even 

 cvTmdricaA ; they may^hf. ninltimiclear and very large, or they may be 

 very small and spheroidal, resembling leucocytes. The fibril lar base- 

 ment substance may be present in such small quantity as entirely to es- 

 cape a superficial observation, covered as it may be by the abundant 

 cells ; or it may be so abundant as to give the tumor the general appear- 

 ance of a fibroma. It may be intimately intermingled with the cells in 

 fascicles, or it may be in large open-meshed networks, giving to the 

 tumor an alveolar appearance. The cells, however, always stand in an 

 intimate relationship to the basement substance, which they sometimes 

 reveal by fibrillar processes continuous with it. Blood-vessels also form 

 a constant and important structural element in these tumors, being in 

 some of them so predominating a factor that they give structural outline 

 and general character to the growth. They, too, as in the normal con- 

 nective tissue, are intimately associated with the basement substance and 

 with the tumor cells. 



Sarcomata are most frequently found in the skin, subcutaneous tis- 

 sue, fascia-, subserous connective tissue, the marrow or periosteum, and 

 in the choroid. They may also occur, though more rarely, in the dura 

 mater; brain and cord ; lymph-nodes; in the adventitia of blood-vessels, 

 and in nerve sheaths ; in subuiucous tissue ; in the uterus and ovary, 

 and~in the kidney. In the liver and lungs and heart they may occur by 

 metastasis. 



They are most common early in life. The cellular character, the 

 rapid growth, the vascularity and succulence of many forms, the marked 

 tendency to local recurrence, and the formation of metastases, stamp the 

 sarcomata, as malignant tumors. But in this they vary greatly ; while 

 some of the forms belong in every sense to the most malignant of tumors, 

 others grow slowly, are very dense, and may remain localized and harm- 

 less for years. Their tendencies in this respect will be mentioned under 

 the special forms. 



Intimately related as they are to the blood-vessels, metastasis is more 

 apt to occur through the blood than through the lymph channels, and 

 consequently adjacent lymph- nodes are much less apt to be involved than 

 in some other forms of tumor, notably the carcinomata. The richly cel- 

 lular and vascular forms of sarcoma are especially prone to haemorrhages, 

 degeneration, and ulceration. 



A single form of cells is often so predominant as to furnish a suitable 

 qualifying name for the tumor, but in many cases the cell form varies 

 greatly in the same growth. It may be said, in general, that there is a 

 tendency to reproduce in these tumors some of the special characteristics 

 of the tissues in which they originate. Thus, sarcomata of the bones are 

 apt to be osteo -sarcomata ; those of pigmented tissue, like the choroid, 

 are apt to be pigmented sarcomata. It will be more convenient for our 

 present purpose to describe briefly the more common forms one after 

 another than to attempt any systematic classification of them. It should 

 be remembered, however, that the various forms are not sharply defined, 



