Decomposition, the enemy of anatomy and embalming and the case of the exploding pope

In this blog post our Senior Research Fellow, Professor Ken Donaldson, explores decomposition, embalming and what happens when embalming goes wrong.

Anatomy, the study of the structure of living bodies has, at its centre, a contradiction. To minutely study the body it has to be cut up i.e. dissected. However, dissection cannot be carried out on living bodies and so anatomical dissection is carried out on dead bodies, but dead bodies quickly start to decompose and lose their structure. The solution to this contradiction is preservation, commonly called ‘fixation’ by anatomists. Fixation of the body, or a part of it (usually called a specimen) causes the dead tissues to be preserved (fixed) in a form that is as close as possible to that of the living body but, importantly, the fixed tissue does not decompose. We have specimens in the Surgeons Hall Museums that were fixed in Edinburgh as long ago as the late the 18th century and are still preserved in the form that that they were in on the day the person died all these years ago. Fixation is more or less permanent and the fixed body or tissue can then be studied at leisure by the anatomist or displayed in a museum.

Image of a human lung fixed in the Surgeons Hall Museums almost 100 years ago, showing a structure that is perfectly preserved by the fixation process. The layer of light tissue surrounding the dark lung tissue is a tumour called a mesothelioma.

Life and death at the tissue level

The tissues of the body are alive as a consequence of a huge number of chemical reactions that occur in the cells that comprise them; together these chemical reactions are called metabolism. are Metabolism requires oxygen and nutrients and these are delivered to tissues by the blood and so, as soon as someone dies and the heart stops pumping blood to the tissues and they are deprived of oxygen and nutrients, the cells and tissues start to die. Dead tissue soon starts to decompose by two processes – autolysis and putrefaction. Autolysis is a process whereby the components of cells, called enzymes, digest the cells and so break down the tissue; no microbes are involved in autolysis. In putrefaction the microbes in the air settle in the dead tissue and those in the bowel, mouth etc. also grow and destroy the tissues.  

Cooling versus fixation

An autopsy is dissection for the determination of death, rather than for educational or research purposes. For autopsy, the processes of autolysis and putrefaction can be kept at bay, in the short term, by keeping the body cold, just as meat kept in a fridge is prevented from going off. So if someone dies, the body can be kept cold in special fridges, until the following day or even a couple of days, and still be satisfactorily autopsied. However, even at cool temperatures, autolysis and putrefaction still proceed, only at a slower pace than occurs at warmer temperatures. So for permanent preservation or for proper anatomical dissection, fixation is carried out by pumping a liquid ‘fixative’ through the blood system and by immersion of the body in the fixative. This has the effect of stopping both autolysis and putrefaction in their tracks, for good. A common component of fixatives is formaldehyde, a gas that when dissolved in water makes a solution called formalin. If tissues are exposed to formalin, it immediately destroys enzymes so stopping autolysis; it also kills bacteria, so preventing putrefaction. 


There is another situation where chemicals are used to treat dead bodies and it is called embalming. Embalming is not a method used for anatomical preservation, only for cosmetic purposes in funeral parlours when viewing of the body is to take place. A well-preserved body is required for viewing and so the aim of embalming is purely cosmetic, to make the body acceptable for viewing  i.e. lifelike. In contrast to an embalmed body, there is no attempt to make a body fixed for anatomical dissection look as if it is alive and in general they do not look alive although they are identifiably human bodies.  On its own, embalming is not necessarily permanent, but may only slow down the decomposition process.

Gases released during decomposition

If there is no fixation or embalming of the corpse, then decomposition proceeds and the processes of autolysis and putrefaction give rise to gases. These are principally carbon dioxide and methane, but also very strong and unpleasant smelling gases such as hydrogen sulphide, cadaverine and putrescine. These give decomposing bodies a characteristic putrid smell that can be used to train dogs to detect them for forensic purposes. Fixation prevents the formation of these gases of course, but if there is no fixation and decomposition proceeds, these gases can produce a bloated appearance in the decomposing corpse.

The exploding pope

Pius XII. Michael Pitcairn, Public domain, via Wikimedia Commons

When embalming goes wrong it shows the powerful production of gases during decomposition. In a very famous case, this occurred when Pope Pius XII died in Rome on October 11th, 1958.  As is normally the case with popes, there was to be a large funeral with viewing, requiring the body to be embalmed to preserve it during the viewing process. In accordance with tradition, the papal physician Riccardo Galeazzi-Lisi was responsible for the embalming. Known to be an incompetent physician, Galeazzi-Lisi showed himself to be as bad at embalming as he was in normal medical matters and he botched the embalming. He used a technique that involved soaking the body with oils, then wrapping it tightly in cellophane sheets. Although it was in line with Pius’s wishes to be buried ‘as God had made him’, you may spot the mistake in that the internal organs were not preserved in this approach. Inevitably autolysis, plus putrefaction caused by the gut bacteria, were soon generating large amounts of gas inside the body. This was exacerbated by the failure to refrigerate the body in the unseasonably hot weather.  Over the 4 day course of the viewing and funeral ceremony, the Pope’s chest ‘exploded’ due to build-up of gas in the chest cavity, then the nose and fingers fell off and the body turned a greenish black colour. The smell was so sickening that some guards fainted and guarding could only be made bearable by changing the guard every 15 minutes. Galeazzi-Lisi was humiliated and was eventually banned from the Vatican forever.

It is likely that ‘exploding’ corpses were rather common in past times, when timely burial or efficient embalming could hardly be relied on. In fact, William the Conqueror underwent the same ignominious fate as Pius. He died in 1087 and his body was poorly embalmed, then underwent a long journey between death and burial. Inevitably decomposition with gas production occurred and as he was being lowered into his grave, his body exploded, the foul-smelling gas that was released making the crowd scatter and bringing the ceremony to an early and humiliating end.  

Modern anatomical labs and anatomical museums, where fixed human body parts are on display, like The Surgeons’ Hall Museums, do not have an unpleasant smell. Decomposition is the enemy of anatomy and all human tissue preserved in these settings is well fixed.  Such specimens will be maintained in their original form, displaying their anatomical features for generations to come.

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