Under the Microscope: The Formation of Adipocere

 

Most of the discussion concerning the definitions of death belongs to the field of legal medicine and even that of ethics, rather than forensic pathology. Notwithstanding this, a quick review of this complex problem is appropriate here, as when we come to describe the various post-mortem phenomena, some appreciation is necessary of the zero point from which such changes are timed. It is conventional to describe two types of death:

     somatic death, in which the person irreversibly loses its sentient personality, being unconscious, unable to be aware of (or to communicate with) its environment, and unable to appreciate any sensory stimuli or to initiate any volunrary movement. Reflex nervous activity may, however, persist, and circulatory and respiratory functions continue either spontaneously or with artificial support so that the tissues and cells of the body, other than those already damaged in the central nervous system, are alive and functioning.

 

     cellular death, in which the tissues and their constituent cells are dead - that is, they no longer function or have metabolic activity, primarily aerobic respiration. Cellular death follows the ischaemia and anoxia inevitably consequent upon cardiorespiratory failure, but it is a process rather than an event, except in the exceptionally rare circumstance of almost instantaneous total bodily destruction, such as filling into molten metal or a nuclear explosion. Even fragmentation of a body by a bomb does not kill all cells instantly. Different tissues die at different rates, the cerebral cortex being vulnerable to only a few minutes' anoxia, whereas connective tissues and even muscle survive for many hours, even days after the cessation of the circulation.

An important and relatively common post-mortem change is the formation of adipocere, a waxy substance derived from the body fat. In most instances the change  of adipocere is partial and irregular, though occasionally  almost the whole body may be affected. In small amounts, adipocere is more common than usually thought in buried or concealed corpses. It is caused by hydrolysis and hydrogenation of adipose tissue, leading to the formation of a greasy or waxy substance if of recent origin. After months or years have passed, adipocere becomes brittle and chalky. The colour can vary from dead white, through pinkish, to a grey or greenish-grey. The substance itself is off-white, but standing with blood or products of decomposition can give it the red or greenish hues. The chemistry of adipocere has been studied extensively. It contains palmitic, oleic and stearic fatty acids together with some glycerol, though the latter may have been leached out in older adipocere. These form a matrix for remnants of tissue fibres, nerves and muscles, which give some slight strength to the fats.

The formation of adipocere, as an alternative to total putrefaction, requires certain environmental conditions. A body left exposed in air, unless the conditions are conducive to mummification, will undergo moist putrefaction if  the temperature remains above about 5-8°C. In burials, immersion in water, and in incarceration in vaults and crypts, adipocere often forms to a greater or lesser extent. It is usually taught that moisture is necessary for the process, and it is undoubtedly a fact that most adipocere formation occurs in immersed bodies and those in wet graves and damp vaults. Numerous cases have been described, however, in which dry concealment also led to adipocere formation and here it must be assumed that the original internal body water was sufficient for the hydrolysis to proceed. It is said that some warmth is necessary for adipocere formation, but the process seems to occur even in deep graves and in cold water. The frequency with which adipocere forms may be gauged by the observations of those who have exhumed old cemeteries and vaults, as well as the victims of wartime  slaughter.

The process is more than a biochemical curiosity as, once it  is formed, adipocere may persist for decades or even centuries.  The usual dissolution of putrefaction is replaced by a permanent firm cast of the fatty tissues and, although distorted compared to the immediate post-mortem shape, it allows the form of the body and sometimes even of the facial features to be retained in recognizable form. Injuries, especially bullet holes, may be preserved in a remarkable fashion. Though adipocere mainly affects the subcutaneous fat, it may also preserve the omental, mesenteric and perirenal adipose deposits; in addition, organs containing fat through pathological or degenerative processes may be preserved by adipocere forming in their parenchyma.

There seems little reason to doubt that hydrolysis of  body fat begins soon after death, as crystals of fatty acids  have been found in infant bodies lying in water for only a - week. This process is usually overtaken by liqueing putrefaction, however, which allows the fat, especially in obese  persons, to collect as extracellular pools and pockets of triglycerides in the body cavities. If the putrefactive process is slowed by burial or immersion, then hydrolysis and hydrogenation can outpace putrefaction. In addition, adipocere formation actually inhibits putrefaction, as the increasing acidity of tissues and the dehydration caused by the consumption of water in hydrolysis slow the growth and spread of the usual putrefactive organisms. The point at which adipocere becomes visible to the naked eye varies greatly, but it has been observed as early as 3 weeks, though 3 months is a more typical period.

Even within a coffin or other place of sequestration, there may be several different 'mini-environments'. One end of the body may be putrefied or skeletalized, whilst other parts may be mummified or in adipocere. Certain areas tend to develop adipocere, such as the cheeks, orbits, chest, abdominal wall and buttocks. Only rarely is the face preserved well enough by adipocere to be genuinely recognizable, as disintegration of the eye globes and shrinkage of the tissues around the nose and mouth obscure the most characteristic features.

The third type of long-term change after death is mummification; a drying of the tissues in place of liquefying putrefaction. Like the other modes of decomposition, this can be partial and can coexist with them in different areas of the same body. It is, however, more likely than the others to extend over the whole corpse. Mummification can only occur in a dry environment, which is usually but not exclusively, also a warm place. Mummification can occur in freezing conditions, partly because of the dryness of the air and partly because of the inhibition of bacterial growth. The most widely known forms of mummification are those in hot, desert zones. The process of artificial mummification practised for millennia in Egypt was an imitative process founded on the natural mummification of bodies in predynastic times. The essential requirement for mummification is a dry environment, preferably with a moving air current. If sterility of the tissues can be attained, as in a newborn baby, then putrefaction is held at bay whilst drying occurs. The skin and underlying tissues are hard, making autopsy dissection difficult. The condition of the internal organs is variable, depending partly on the length of time since death. They may be partly dried, partly putrefied - and adipocere is not uncommon. In fact, slight adipocere formation is common in mummification, and perhaps the two are related in that the utilization of body water to hydrolyse fat in turn helps to dehydrate the tissues. The major factor, however, is evaporation from the surface in dry conditions.

Most experienced forensic pathologists are familiar with the mummified fetus or newborn infant, concealed in domestic circumstances, such as a house loft, where complete mummification has taken place. With small bodies such as these, evaporation is faster and more complete, and may extend to all organs, especially as there would have been no invasion of putrefactive micro-organisms from the gut. The timing of mummification is not well documented, as most mummified corpses have been concealed so well that discovery does not occur until long after the process has reached its maximum effect. It certainly takes some weeks and the early stages are often mixed with a degree of putrefactive change, especially in the internal organs.

After complete drying has taken place, the body may remain in that state for many years. Eventually, mould formation and physical deterioration progress, the dried tissues becoming split and powdery and gradually disintegrating. This process is usually hastened by animal predation. Even in the shelter of a barn or house, moths, beetles, mice and rats will wreak damage on the corpse. It will eventually skeletalize though tough, leathery shreds of skin, tendon and ligament may persist for many years.

 Mummification allows major injuries to be preserved, though as in the putrefied body, the detection of bruises and abrasion may be difficult or impossible to differentiate from discoloration, artefacts and fungal damage.

 

Acknowledgements:

www.politie.nl  Politiekorpschef  @Janny Knol©

www.aived.nl    AIVD – @Erik Akerboom ©

www.politie.nl WEB Politie - @Henk van Essen©

https://www.police-nationale.interieur.gouv.fr/ @ Stephane Folcher ©

 

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