Preserved skin structure of a recently found fifteenth-century mummy in Daejeon, Korea

Abstract

Recently published reports on Korea's medieval mummies have been regarded as an invaluable source for studies into the physical characteristics of medieval Koreans. However, even though the mummified tissues have been investigated histologically on various previous occasions, there are many unanswered questions relating to their tissue preservation. The aim of this study was to obtain new data on the ultramicroscopic characteristics of the mummified skin of a fifteenth-century mummy found recently in Daejeon--one of the oldest ever found in Korea. Electron microscopy revealed that much of the epidermis had decayed; what remained of the dermis was filled with collagen fibres and melanin granules or invading bacterial spores present within the mummified epidermis. Considering the histological characteristics shared by naturally formed mummies in different parts of the world, we concluded that the ultramicroscopic patterns of the Daejeon mummy were more comparable with those naturally formed mummies than with artificially formed ones. This is the first full description of the morphological characteristics of the skin collected from this recently found medieval mummy from Daejeon, South Korea.

Fig. 1

(A) The mummy we investigated previously (Shin et al. 2003a) was found in Yangju, Korea (rectangle marked ‘a’). The current case was found in Daejeon, Korea (rectangle marked ‘b’). (B) Face of the mummy. Note that white coating materials (arrows) were observed on the skin.

Fig. 2

Comparison of the skin structure collected from an adult individual (A,B) and the fifteenth-century mummy (C,D). Both sections were stained with haematoxylin–eosin. Comparing the relative ratio of epidermis (asterisks) and dermis (D) with that of normal skin tissue (A,B), mummified skin exhibited an epidermis with remarkably decreased thickness, whereas the thickness of the dermis had not changed as much (C,D). Melanin granules were observed in the basal layer of epidermis (the region within the white dotted line in B) in modern adult skin, while black granules (arrows in D), which also seem to be melanin granules, were localized within the presumptive remaining epidermis of the mummified skin. Bars, 50 µm.

Fig. 3

Comparison of skin collected from a modern adult individual (A) and the fifteenth-century mummy (B–D). (A,B) Sections stained by Masson’s trichrome techniques. (A) The dermis (D) was stained green owing to the presence of collagen fibres. (B) The dermis of the mummified skin was also intensely stained green by Masson’s trichrome method; red staining due to the presence of cytoplasm, which could be observed in epidermis (Epi) in A, could not be localized in B. (C) Silver staining for reticular fibres was negative in the mummified skin tissue. (D) Magnified image of silver staining. Melanin pigments (indicated by arrows) are present in the epidermis (Epi). (E) Fontana-Masson staining for melanin pigments (indicated by white open arrows) in the epidermis (Epi) overlying the much thicker dermis (D). (F) Orcein staining for elastic fibres. Dark brown-staining structures for elastic fibres were not detected. Bars, 50 µm.

Fig. 4

SEM observation on the surface of the skin. (A) A white coating was present on the surface of the epidermis. (B) After the tissue was washed using sonication, the underlying keratinized epithelium was exposed, in which we could clearly observe keratinized scales (asterisks). (C–E) Images of the surface coat on the epidermis, magnified sequentially. The surface coating material was observed to be composed of crystaline debris. Bars: A–C,) 100 µm; D, 50 µm; E, 5 µm.

Fig. 5

(A) Use of EDS to analyse the coating substance found on the surface of the epidermis. (B) Relative percentage weight of the materials in the debris. Sodium (Na), potassium (K) and calcium (Ca) were detected.

Fig. 6

SEM data showing holes for hair shafts (asterisk) on the surface of the skin, which was washed with sonicator treatment. Bar, 200 µm.

Fig. 7

(A) SEM data on the lateral cut surface of the skin sample. Thread-like structures, which seem to be collagen fibres, filled the dermis. Asterisk indicates the epidermis. (B) Magnified image of presumptive collagen fibres in the dermis. Bars: A, 500 µm; B, 30 µm.

Fig. 8

(A,B) SEM data on collagen fibres within the region that might be filled with dense connective tissue. The collagen fibres were aligned in parallel. (B) Magnified image of A. In B, the mummified collagen fibres showed a ‘banding pattern’ (arrows), which resembles those observed in the collagen fibres within dermis from living mouse. (C,D) SEM data on collagen fibres within the mummified dermis in which loose connective tissue might be present. The collagen fibres were loosely arranged in various directions. (D) Magnified image of C. Banding patterns (arrows in D) in the collagen fibres were also identified. Bars: A, 4 µm; B, 1 µm; C, 2 µm; D, 1 µm.

Fig. 9

(A,B) TEM data on the presence of melanin pigment in the epidermis of mummified skin. (B) Magnified image of epidermis in A. In A, a number of melanin granules (asterisks in B) were aggregated within the remaining epidermis (Epi) in which epithelial cells were not clearly discernible, even though the keratinized layers (Kr) were visible on the surface of the skin epithelium. D, dermis. Bar, 2 µm.