Flexibility of Thiel's embalmed cadavers: the explanation is probably in the muscles.

Introduction: The flexibility of cadavers conserved using Thiel's embalming method remains unexplained. We aimed to perform microscopic comparison of muscle and tendon fibres from fresh cadavers (FC), formaldehyde-preserved cadavers (FPC) and cadavers conserved by Thiel's method (TC).

Methods: Muscle and tendon biopsies performed on FC, FPC and TC were conditioned and stained by Masson's trichrome, Sirius red and Ramon y Cajal, then studied under optical microscope. Alignment and integrity of the muscle and tendon fibres were studied.

Results: We observed a modification of the muscle fibres in all specimens from TC, regardless of the type of staining used. The muscle fibres taken from FC and FPC were relatively well conserved, both in terms of alignment and integrity. We did not observe any modification of collagen in either muscle or tendon fibres.

Conclusions: The considerable fragmentation of the muscle proteins, probably caused by certain corrosive chemicals, (e.g. boric acid) present in Thiel's embalming solution, could explain the suppleness of the TC. However, we cannot exclude the possibility of alterations in tendon or muscle collagen, since the experimental methods we used, did not allow for the study of collagen ultrastructure.