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.