✓ Oral mucosa was transplanted into the brains of 50 baby rats; in 45, viable growth was demonstrated when the animals were sacrificed 1 to 24 months later. The transplants showed stratified squamous, cuboidal, and transitional-like epithelium plus secondary changes such as cholesterol clefts, calcification, and in one case, lamellar bone. The tumors had an unpredictable growth rate. The histological characteristics were those of epidermoids, dermoids, craniopharyngiomas, or Rathke cleft cysts, and suggested a common histogenesis.