Microscopical focal destruction (tunnels) in exhumed human bones.

Abstract

This is a survey of microscopical focal destruction in exhumed human bones from several countries and burial times. The single change (destruction) seen in these bones contrasts with the sequence of changes in pathological processes (destruction, cellular infiltration, new bone formation and healing). The absence of cells stresses the importance of size and shape, in three dimensions, and contents of the destructive foci. Focal mineral redeposition (e.g. cuffing) is characteristic of most forms of tunnels, and is usually associated with focal loss of mineral and bone matrix, partial or whole. In one kind of foci/tunnels (Wedl's) redeposition is restricted to packed osteons. The accumulation of the waste products of the invading organism in the surrounding tissue may hinder or stop the growth of the organism and consequential bone destruction. Later the redeposited mineral may be leached out and the bone thus ‘returned to normal’ will allow further growth of the invader and renewed destruction. Desiccation after exhumation soon ‘fixes’ the redeposited mineral. Mineral redeposition is never found in pathological changes. Examination of transverse and longitudinal sections together with the comparison of the changes in the mid-zone of cortical bone with those in the inner and outer zones is helpful in understanding the progress of the changes. No invasion by organisms of the lamellar tissue from the osteon canals was seen although this must be the rule. The tunnels in bones and teeth are compared, and show that the contents are, with one exception, not related to any anatomical structure. There is only destruction, and no new bone can be laid down in these postmortem changes. One kind of focus/tunnel does not change into or overlap another. The results of experimental burials in garden soils were indecisive. Four kinds of such well-defined changes are described, but the examination of specimens from a wider range of provenances will almost certainly reveal others and may call for modifications of the conclusions of this paper. The cause of these changes is yet to be established; it is not physico-chemical, but is probably bacterial or fungal. Although the invasion must proceed from the cortical surfaces via the osteon canals, these canals persist in even the oldest specimens. These foci/tunnels probably occur in buried bones throughout the world where the inhumation environment is favourable. They have been reported from early geological periods, and in this study were found in pterodactyl bones from the Jurassic period about 190 million years ago. Complete packing of exhumed bone tissue with microscopical destructive foci/tunnels can completely obscure the pattern of pathological changes. The application of more sophisticated techniques would contribute to the fuller understanding of these changes and their causes.