264: DISEASES OF THE BRAIN. 



Oliomata result from a local proliferation of the neuroglia, or con- 

 nective tissue of the brain, at the expense of its nervous elements. 

 Microscopically they consist of roundish nuclei, distributed through a 

 finely-reticulated basement substance. By the naked eye they are 

 distinguishable from not forming circumscribed tumors, but passing 

 gradually into the healthy brain-tissue ; also from the fact that they 

 never pass from the brain to its membranes. (Jliomata may attain the 

 size of a fist ; they most frequently originate from the medullary sub- 

 stance of the cerebrum. Haemorrhages into or partial retrogression 

 of glioma may take place after precedent fatty degeneration of its ele- 

 ments. The consistence of these tumors varies between that of a me- 

 dullary cancer and of healthy brain. The cut surface varies in color 

 from whitish yellow to bright grayish red, and usually shows a number 

 of cut vessels. Formerly glioma was regarded as infiltrated cancer, 

 and, as it occurs chiefly in young persons, or, at least, in those under 

 forty years of age, we see why it was said that cancer of the brain 

 has been observed at all ages. 



Cholesteatomata, or pearl tumors, are rare. They sometimes start 

 from the cranial bones, at others from the meninges, again they de- 

 velop in the brain itself. They form irregular tumors, of variable size, 

 of a pearly lustre ; they are enclosed by a delicate membrane, and con- 

 sist of concentric layers of epidermic cells. 



Lipomata, as small lobulated tumors, starting from the dura mater, 

 cysts filled with fluid, or fat and hairs, and cystoid neoplasia, with 

 cauliflower excrescences from the walls, belong to the rarities, and 

 have more pathologiccnanatomical than clinical interest. 



Tubercles of the brain are the most frequent form of cerebral tu- 

 mors. Usually we find only one collection of tubercles, occasionally 

 two, more rarely a greater number. The size varies from that of a 

 hemp-seed to that of a cherry, or, in rare cases, to that of a hen's egg. 

 They are located most frequently in the cerebellum or cerebrum, more 

 rarely in the mesencephalon. Tubercles of the brain form irregular, 

 roundish, non-vascular tumors, of a yellow, dry, and cheesy character. 

 They are sometimes surrounded by a layer of loose connective tissue, 

 which separates them from neighboring parts of the brain ; sometimes 

 the main portion of the yellow nodule gradually passes into the brain- 

 substance as a gray-white, slightly-translucent, narrow margin, consist- 

 ing of young tubercle elements. In the latter case the tubercle has 

 been growing till death ; in the former, where it can be readily turned 

 out of its capsule, growth has ceased long before death. From soft- 

 ening of its centre, the tubercle nodule is occasionally transformed into 

 a vomica, filled with tubercle pus. 



Syphilomata only rarely occur in the brain in the form of nodules 



