PSAMMOMATA (GRITTY TUMORS) OF THE BRAIN.
As already noted these sandy tumors are often the advanced stage of cholesteatomata, the abundance of the phosphate of lime leading to its precipitation in the neoplasm. The same cretaceous deposit often takes place in old standing tumors of other kinds, as in melanoma, and fibroma so that the sandy neoplasm may be looked upon as a calcareous degeneration of various forms of intracranial tumors. The same tendency to calcareous deposit is seen in the tuber cinereum (pineal body) of the healthy brain which has taken its name from the contained gritty matter. This tendency to the precipitation of earthy salts may be further recognized in the osteid tumors which occasionally grow from the dura mater.
The gritty tumors are especially found in the older horses in which the tendency is greatest to extension of ossification and calcic degenerations.
Like other tumors these may attain a considerable size before they give rise to any very appreciable symptoms, but having attained a given development—often the size of a walnut, they become the occasion of nervous irritation, delirium and disorder, as indicated under encephalic hyperæmia and inflammation, cholesteatomata, etc. There may, however, be drowsiness, stupor, coma, or paralysis as the exclusive symptom, or there may be spasms and convulsions.