download PDF version - Dr Harold Hillman

During the last two years, Mr. David Copestake and I have been looking at histoiogicalsections of brains and spinal cords of mice, rats, human beings, guinea pigs and rabbits, stainedby Davenport‟s (1934) modification of Ramon y Cajal‟s (1903) procedure. We examineddirectly only the tissue, named „neuroglia‟ by Virchow in 1846. We made the followingexperiments: (i) we followed the courses of the dendrites for hundreds of microns; (ii) we lookedfor the presence of knobs, granules, spheres, ovals, or deposits, indicating synapses, on thesurfaces of neuron cell bodies. We saw none; (iii) we saw no continuities between dendrites andany fibres ending on neuron cell bodies, usually called „presynaptic‟ fibres; (iv) we observed a1000 sites at which dendrites from different neurons apparently crossed, and then measured thevertical distances between the sets of two fibres. The fibres touched in only 11 out of the 1000crossings. In the other 989 pairs, the fibres were between 0.5 and 3.0 micrometers apart; a veryfew dendrites appeared to have swellings on them, but when we focussed on the swellings, theytuned out to be only bends of the dendrites.So far, we have been unable to obtain publication of these results. The main reasonsgiven were that “ synapses were not central to the interests of neurobiologists”, or that we hadnot used electron microscopy. We pointed out that anatomical synapses were described by lightmicroscopy over 50 years before they were seen by electron microscopy. Referees have usuallyneither sent our manuscript to referees, nor criticised our histology or microscopy.We urge colleagues to repeat these experiments.Mr. David Jarman and I were examining the history of neuroglia. We noticed that sinceLeeuwenhoek described fine granular material in 1684, it was seen several times in unfixed brainin the 19 th century. In 1827, Hodgkin and Lister described it briefly, when they examined thebrains using achromatic objectives, but they did not publish a definitive account of theseobservations. Hyden and Pigon (1960) using hand dissection, separated neuron cell bodies fromthe tissue surrounding them, which they called „neuroglial clumps‟. Mainly in the 1970s and1980s, at least 12 authors separated the clumps, photographed them, measured their oxygenuptake and enzyme activities, and published micrographs of them. Among these authors wereHyden, Hamberger, Hertz, Epstein, O‟Connor, Deutsch, Jarman and myself.32