The earliest mention of a cell sheath enveloping the body of the neurons in sensory ganglia is probably the following description by Valentin: "Sowohl die Kugeln der Be­ legungsformation 1 , als die Primitivfasem, werden von eigenthi. imlichen, sie isolirenden Scheiden umgeben, welche aile Stufen der Dicke von einer fast gar nicht mehr wahr­ nehrnbaren Zartheit bis zu einer ziemlich bedeutenden Starke durchlaufen. Diese Hill­ len sind aber immer zellgewebeartiger Natur" (1836, p 162). In some illustrations of the above mentioned paper the nuclei of the satellite cells adjacent to the surface of the nerve cell body, both in the trigeminal ganglion and in the ganglia of the vegeta­ tive nervous system, are clearly shown (Fig. lA). The author, however, miSinterpreted these nuclei as pigment granules (Pigmentkorperchen). A little later, Remak (1838) denied the existence of the perineuronal cell sheath. This prompted a ready reply from Valentin (1839), who offered a more detailed description of the perineuronal cell sheath, illustrated it with new drawings (Fig. IB), and gave a correct interpreta­ tion of the nuclei. In fact, he wrote: Fig. lA-B. Nerve cell bodies of sympathetic ganglia with the nuclei of the satellite cells on the neuronal surface. Redrawn from Valentin, A, 1836, B, 1839.