TUMOES. 



499 



f. i., the derma of the skin, and by degrees entirely replaces it. 

 The fibrous structure of such tumors is sometimes very faintly 

 marked ; but their comparatively slight degree of malignity 

 is recognized by the presence of a finely granular basis-sub- 

 stance between the homogeneous plastids, which, of the size of 

 nuclei, are scattered at regular intervals. Sometimes these 

 tumors are lobate or nodular, and covered with a richly pig- 

 mented rete mucosum (mole, naevus). With advancing age or 



FIG. 198. MELANOTIC GLOBO- AND SPINDLE-MYELOMA OF THE CHOROID. 



L, group of globular pigmented plastids ; f, delicate fibrous connective tissue at the 

 periphery of the tumor; Jf, haematoblasts ; P, pigment cluster ; V, vitreous body. Magnified 

 600 diameters. 



improper treatment they readily assume the character of malig- 

 nant myeloma. (See Fig. 199.) 



fb) Myxo-myeloma is constructed on the plan of myxomatous 

 tissue i. e.j a delicate fibrous reticulum contains in its meshes 

 plastids in different stages of development; but they are^far 





