On April 10, 1901, Duncan MacDougall, together with four other doctors, were waiting for six people to die. In a hospital in Dorchester, Massachusetts, the patient’s entire bed was placed on an industrial-sized Fairbanks scale that was sensitive within two-tenths of an ounce (5.6 grams). After a few hours waiting, when the patients died, something strange happened.

An illustration entitled Death of the Good Old Man found in Robert Blair’s The Grave, A Poem, drawn by William Blake and engraved by Luigi Schiavonetti.

As soon as they died, the scales dropped. The conclusion was that a human soul left the body and registered the loss of 21 grams. Repeating the experiment with dogs resulted in no loss of weight, indicating that dogs have no soul to lose.

Since the soul was material, MacDougall reasoned that we should be able to measure it. Four years later, the New York Times reported in a front page story that MacDougall tried to take X-rays of the soul escaping the body at the moment of death. Then MacDougall died in 1920 at the age of 54, leaving behind many questions.

Following the publication of these experiments, both in the popular media as well as in academic journals, his colleague physician Augustus Clarke criticised the experiments. Clarke argued that the loss of 21 grams could be accounted for by expiration. Clarke noted that at the time of death – as the lungs are no longer cooling blood – there is a sudden rise in body temperature, causing a subsequent rise in evaporative sweating. Since dogs do not have sweat glands and, therefore cannot lose weight in this manner, Clarke argued that the experiments were flawed.

There was evidence to suggest that MacDougall knew of alternate interpretation to his experiments beforehand. The idea of measuring is as old as science itself. Medical historian M. D. Grmek wrote about one of the great scientists, Santorio Santorio (1561-1636), who diligently weighed and measured everything. In particular he weighed all the food and drink that he ingested. He also measured all that came out the other end – faeces and urine. For every eight pounds (3.6kg) he consumed, Santorio found that he only excreted three pounds (1.3kg). Five pounds (2.26kg) of food and drink could not be accounted for.

The problem with science is that it is necessarily finicky with details and the problem with belief is that it is necessarily not

It was not until 1862 that the infamous hygienist Max von Pettenkoffer constructed an insulated room designed to measure the exact amount of heat the body generated. As a hygienist, promoting good sewage and public health approach to health, Max von Pettenkoffer designed a machine – respiration calorimenter – to measure heat given off by the body’s chemical reactions and physical changes expended by a person at rest, standing and walking.

All the evidence was already there to suggest that our metabolism generates evaporative loss of weight. And MacDougall knew this. In his original paper, he reports that: “He [dying patient] lost weight slowly at the rate of one ounce per hour due to evaporation of moisture in respiration and evaporation of sweat.”

But he also addressed this loss as an explanation for the loss of weight when the patients died: “This loss of weight could not be due to evaporation of respiratory moisture and sweat, because… this loss was sudden and large…”

True science is through experimentation. MacDougall’s theory was that there had to be “continuity” in life after death – a soul – was part of this experimentation. But it also assumes that we know when people die. As strange as this question seems, it is by no means an easy definition.

Our definition of death is a legal rather than a biological definition. In medicine it is a prognosis (predicting) rather than a diagnosis (confirming). Although having no brain or heart activity protects surgeons from liability when they are harvesting organs for transplantation, the first heart transplant in the US was threatened by legal suit. This does not explain what death is. The Catholic Church has a definition of death as indicated by petrification; hence the waiting before burial. But this method is clumsy.

British researcher Sam Parnia argues that many people who are actually dead from heart attacks or blood loss could be resuscitated up to 24 hours after they die. Parnia has been studying those who have no heart beat and no detectable brain activity for periods of time. While in this state they are given names of cities and when – and sometimes, if – they recover, patients are asked to ‘randomly’ name cities.They found that the patients are more likely to choose the same cities that they were exposed to while unconscious. It seems that when we are dead we are still aware, although not conscious.

As with the MacDougall study, there is a problem of small samples. But such problems can be overcome with better research design.

Weighing the soul might be complicated if we do not know when we actually die. There is increasing interest in both defining death and capturing the process. But evidence is scant and the methods used leave room for many errors and misinterpretations. Many reports exist of unsubstantiated experiments – Konstantin Korotkov, Eugenyus Kugis, Vitaliy Khromova and others – that purport to repeat MacDougall’s findings. But none are published in scientific journals.

We have a great interest in ‘proving’ things. The problem with science is that it is necessarily finicky with details and the problem with belief is that it is necessarily not. And never the twain shall meet.

Mario Garrett was born in Malta and is currently a professor of gerontology at San Diego State University in California, US.