Inclusion bodies of the epithelium of the urinary bladder in the rhesus monkey

Inclusion bodies observed by light microscopy in the superficial epithelial cells of the urinary bladder of the rhesus monkey have been examined by electron microscopy. The inclusions varied from focal aggregates of fibrils in their least differentiated form to mature, paranuclear inclusion bodies 3 × 5 μ in size composed of orderly arranged fibrillar structures. The fibrils comprising the inclusions were indistinguishable from cytoplasmic tonofilaments. The significance of the inclusions remains obscure in the absence of known physiologic alteration.