TUMORS OF THE BRAIN AND ITS MEMBRANES. 263 



aries. They sometimes start from the brain itself, sometimes from the 

 dura mater and cranial bones, or they develop originally from the 

 external soft parts of the skull and neighboring cavities, especially in 

 the orbit, and thence press into the skull. On the other hand, it rarely 

 happens that carcinoma occurring in the brain perforates the meninges 

 and cranial bones. There is usually only one carcinomatous tumor of 

 the brain, and this is generally located in the cerebrum ; where there 

 have been several, they have occasionally been found symmetrically 

 located on the two sides of the brain. Cerebral carcinomata, which 

 may attain the size of the fist, never suppurate unless they perforate 

 outwardly ; on the other hand, they readily undergo partial retrogres- 

 sive metamorphosis, become yellow and cheesy in the middle, shrink, 

 and thus cause umbilicated depressions on the surface of the brain, if 

 the cancer had advanced so far. 



Sarcomata occur as often as carcinomata in the brain. They are 

 often attached to the meninges, and the tumors of this variety, at the 

 base of the brain, usually attain greater size than those of the dura 

 mater that covers the convexity. (Just as often sarcomata are em- 

 bedded in the midst of the brain-substance, in the majority of cases in 

 the cerebrum.) They form round or lobulated tumors, from the size of 

 a hazel-nut to that of a good-sized apple ; their cut surface is smooth, 

 dirty white, or grayish red ; they are usually soft, even medullary, more 

 rarely hard and fibrous. Occasionally they contain cavities filled with 

 fluid. Sarcomata consist chiefly of spindle-shaped cells, arranged in 

 filamentary striae. They differ from cancer, and especially from glioma, 

 not only in being sharply bounded, but in being often surrounded by a 

 vascular envelope, from which they can be turned out. Small lumps 

 of carbonate of lime not unfrequently occur in sarcoma of the dura 

 mater ; on rubbing the tumor between the fingers, these lumps cause 

 a sandy feel. Virchow has designated tumors, containing numbers 

 of the chalky lumps, as psammonea, or sand-tumors. Then* mode of 

 origin is not yet exactly known. 



Myxomata consist of mucous tissue that is, of variously-formed 

 cells, embedded in a homogeneous, mucous, hyaline, intercellular sub- 

 stance. They are not very rare in the brain. Like sarcomata, they 

 are located most frequently, but not exclusively, in the medullary sub- 

 stance of the cerebrum, where they generally appear as circumscribed 

 tumors, more rarely as infiltrations of soft gelatinous substance. The 

 tissue of myxoma is somewhat translucent, and of a weak yellowish 

 or red color, but may acquire a varied hue from extravasated blood. 

 Myxomata also correspond with sarcomata in regard to the size they 

 may attain ; and, between these two forms of tumors, there are all 

 possible grades of transformations (gelatinous sarcoma). 

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