[Confusion of "the interstitial cells of Cajal"]

What did SR Cajal described as the interstitial cells? The structure of the nerve plexuses in the guinea-pig small intestine stained by the Champy-Maillet (ZIO) method was investigated by light microscopy and transmission electron microscopy. Scanning electron microscopic examination of the nerve elements in various layers of the intestinal wall was also performed. Results indicated that the peripheral innervation consisted of autonomic groundplexus in which neuronal processes ran along a glial-cell framework. Projections of all the neurons formed a network of bundles, while being separated from each other and not making any interconnection. The glial cells enclosed and supported these bundles of neuronal projections. In the light microscopy of the ZIO stained specimen, amalgamation of glial cells and neuronal projections frequently occurred. They represented the structure described by Cajal as interstitial cells. The so-called interstitial cells of Cajal which many histologists looked for in the earlier half of the 20th century were not true cells but these stained structural artefacts of the autonomic groundplexus and/or nearby cellular elements. The interstitial cells defined by later authors including many electron microscopists from 1960s to 1980s were another type of cells such as fibroblast-like cells. For references, see Kobayashi et al.: Arch. Histol. Cytol. 52: 267-286, 1989.