ABSTRACT
The choroid plexus of the cat, rabbit and rat have been investigated by means of scanning elecron microscopy. The surface appearance of choroid plexus of these animals exhibited pleomorphism. The free surface of epithelial cells are covered with dense microvilli, single long cilium, clusters of cilia, bulbous protrusions and flower-like structure. They are scattered throughout the ventricular surface of the choroid plexus. High magnification scanning electron microscopy reveals that the population of microvilli consist of slender finger-like microvilli and microvilli with the bleb-like protrusion. Flower-like structure is the clusters of microvilli. On the surface of the choroid plexus of these animals, the Kolmer cells were observed. According to the number of processes, the Kolmer cells of cat, rabbit and rat may be divided into four main types. The ultra-architectural organization of choroid plexus of the cat, rabbit and rat is quite similar, but the number of bulbous protrusions in the cat and clusters of cilia in the rat occurs more.