This form of disease is confined principally to children. Of thirty cases collected by Dr. P. H. Green, of London, all were between the ages of nineteen months and twelve years. =Adipose Tumors.= Under this name, has been described a peculiar and quite rare form of disease of the brain, in which either some portion of the brain itself, or growths attached to or imbedded within the cerebral substance, present a fatty appearance, which by some has been denominated _lardaceous degeneration_. The exterior of the tumor is smooth, of a yellow color, and the interior composed of adipose matter of ash color, and semi-solid consistency. =Cholesteroma.= This is another rare form of tumor of the brain, consisting of white pearl-like, glistening bodies, varying in size from that of a pea, to a walnut or small orange. They are found mostly at the back of the brain, and in the sub-arachnoid tissue. When examined chemically, the substance of these tumors is found to consist almost wholly of cholesterin. =Cartilaginous Tumors.= These are often spoken of as _scirrhus_ in their nature. They may be described as irregular in shape, sometimes lobulated, the interior yellowish in color, of a cartilaginous hardness, and arranged sometimes in streaks or bands, in other cases, in rounded masses. At a more advanced stage, from softening of the interior, cavities begin to form, which are filled with a semi-fluid or jelly-like substance. Death will generally ensue before this process is far advanced. =Calcareous or Bony Deposits.= _Osseous_ formations are not unfrequently found connected with the membranes of the brain, but rarely, if ever, with the brain substance. _Calcareous_ deposits, on the other hand, have been found in almost every part of the brain. In the brain of an idiot of sixteen, the pons Varolii, crura cerebri and cerebellum, contained so much earthy matter, as to give difficulty in cutting with a knife (_Sir E. Home_.) In the brain of a man who had long suffered from acute pain in the head, a hard plaster-like concretion was found as large as a filbert. These bodies are, therefore, not to be looked upon as genuine bony formations, but rather as an infiltration of chalky substance into the brain tissue. Of the same nature, are the calcareous deposits found in the pineal gland, which, although very constantly present after the age of eight or ten years, can hardly be considered as normal products, although it is well established that they exert no influence on the functions of the brain. =Encysted Tumors, Hydatids.= A variety of tumors of the encysted form have been found in the brain by different observers, varying in size from a pea, to that of an egg or orange. Their contents also, have presented a great degree of variation. While some have been filled with the cheesy substance of the ordinary steatome, others have contained blood, a jelly-like, or even a limpid watery fluid.