The secrets of embalming human bodies
Pictured here is a complete set of canopic jars dating back to c. 900 B.C.E. These jars were used by the ancient Egyptians to store and preserve the organs of their owner for the afterlife. There were four Canopic jars, each for the storage of the four major organs: the stomach, intestines, lungs, and liver. These were thought to be needed in the afterlife.
History of Embalming
Embalming is the act of preserving human remains by treating them with chemicals to lower the rate of decomposition. Its intention is to keep them suitable for public display at funerals and can preserve bodies for several years. Some of the earliest descriptions of embalming came from the Egyptians since they are credited with the development of the first recorded embalming. Due to their religious laws, anyone who died in their land was embalmed before given a proper burial. Herodotus, a Greek historian, described three different embalming methods that were available to Egyptians in the fifth century B.C.E.
The most complex embalming technique involved the removal of all brain tissue from the nostrils, eviscerating the internal organs through an incision in the lower back, and anointing the interior of the body cavity before closing the incision. This cut was then covered with beeswax to make it more subtle. Afterwards, the Egyptians would use a mixture called natron to dehydrate the body before the remains were wrapped in many layers of linen cloths and resins as part of the mummification process. The natron mixture consisted of sodium chloride, sodium sulfate, sodium carbonate, potassium nitrate, and sodium nitrate.
The second embalming method involved injecting cedarwood oil into body cavities, like the anus, and stoppering the opening. The external body was then treated with natron for dehydration of the body. After a certain amount of time, the cedarwood oil was drained which now contained the dissolved internal organs. The body would ultimately be reduced to just preserved skin and bones.
The cheapest embalming method that the Egyptians used involved cleansing the body, drying it with natron, and then simply wrapping it with linen.
Leonardo da Vinci's anatomical studies of the shoulder created between 1510 and 1511.
In the fifteenth century, interest in body preservation peaked primarily due to the desire to learn more about human anatomy. Leonardo da Vinci described a method of venous injection to preserve the cadavers he was studying. These early embalming fluids contained mixtures of turpentine, camphor, lavender oil, vermilion (also known as mercury sulfide), wine, rosin, and saltpeter. By the late 1600s, Gabriel Clauderus, a German physician, published a book describing an embalming method using "balsamic spirit" that was synthesized by dissolving one pound of tartar cream and a half-pound of salammoniac in six pounds of water. This mixture would then be injected into the body where it would remain for six weeks, after which the body would be placed in the sun to dry. By the beginning of the 19th century, embalming was becoming increasingly popular in the United States, especially since it became the norm to have a proper mourning period before interment.
In 1850, a patent was granted for the refrigeration of corpses. Although this effectively delayed the decomposition process, it was useless in destroying harmful bacteria. As smallpox, diphtheria, and other epidemics began to spread, sanitation was of upmost importance. Therefore, other patents were issued for embalming fluid formulations for use as a disinfectant and body preservative. These fluids contained salts of heavy metals to inhibit bacterial growth.
The Rise of Formaldehyde and Its Mechanism in Preserving Bodies
By the early 1900s, laws prohibiting the use of metal salts in embalming were passed. Formaldehyde soon became the compound of choice and continues to be the most common preservative in embalming fluids. In the late 1800s, German physician Ferdinand Blum was working with a 4% aqueous solution of formaldehyde when he discovered that his wet fingers became stiff. This was the beginning of the widespread use of formaldehyde as a cell preservative. Reasons for its popularity today include its low cost, availability, and simplicity of use. It also provides good cell preservation under a variety of pH conditions.
This image demonstrates the reactions of formaldehyde in the body. Methylene glycol is formed by the reaction of formaldehyde and water. Formaldehyde dehydrogenase is an enzyme that converts formaldehyde into formic acid.
Formaldehyde preserves tissues by forming cross-links between proteins to create a stable matrix. Although this exact mechanism is not well known, it is thought that once a formaldehyde molecule reacts with a protein, it will remain there until it reacts with a second protein. The small size of the formaldehyde molecule allows for rapid tissue penetration, which reduces the self-destruction of cells and tissues after death.
In aqueous solutions, formaldehyde undergoes two reactions. The first involves the formation of methylene glycol that also preserves tissues. In the second reaction, formaldehyde reacts with oxygen to yield formic acid, which having too much of leads to the presence of "formaldehyde pigments" on the body. Methanol, methyl salicylate, and and other buffers are added to embalming fluids to prevent excess formic acid formation.
The pH of blood also plays a critical role in the embalming process. After death, the pH of the blood becomes 10 times more acidic due to the build-up of lactic acid and carbonic acid during rigor mortis. This period of increased acidity lasts for about 48 hours after death and is the time when embalming typically occurs. A neutral or slightly alkaline embalming fluid is required to neutralize the acidic blood and optimize cell fixation. Boric acid combined with borax (also called sodium tetraborate) or sodium bicarbonate combined with dibasic sodium phosphate are among the more common buffer pairs used in formaldehyde-based embalming fluids to ensure an appropriate body fluid pH.
Health and Environmental Concerns of Embalming
Various health concerns are associated with exposure to embalming fluids. Formaldehyde has long been presumed to be a carcinogen and to cause "occupational asthma" and dermatitis. Formaldehyde also tends to dry out tissue and result in a grey coloration of the skin. Glutaraldehyde was first used as a formaldehyde substitute in 1955. This dialdehyde was found to react with tissue proteins in a manner similar to formaldehyde, although without significant tissue dehydration. Despite both compounds preserving tissue in similar ways, there are several major differences. Protein binding with glutaraldehyde is considerably higher since there are a greater number of protein cross-links present. Additionally, glutaraldehyde diffuses and penetrates into tissue more evenly than formaldehyde. Therefore, the body is more likely to retain its natural texture and a more natural and even coloration is produced. It firms the body tissue more easily and is a more effective disinfectant. Despite these advantages, formaldehyde is still the embalming fluid of choice in the United States. Some reasons for this include it being a well-accepted standard in the embalming industry as well as it being about six times less expensive than glutaraldehyde.
Ham Down Woodland Natural Burial Ground in the United Kingdom is just one example of many eco-friendly burial locations across the world. The bodies are buried in biodegradable coffins that nourish the trees planted right over the deceased's grave.
Original Photo by Bob Ford and licensed under CC BY-SA 2.0.
Embalming dead bodies also takes a surprisingly heavy toll on the environment. The aforementioned toxic chemicals involved in embalming bodies leaches into the air and soil. More than 800,000 gallons of formaldehyde are estimated to seep into the ground each year in the United States alone. Multiple greener forms of burial exist, such as placing the body into a pod that eventually turns into a tree or sealing your ashes in a concrete ball that goes deep into the ocean to feed coral reefs. Other methods that do not involve embalming include getting buried in a wood-only casket and using alkaline hydrolysis. In the latter, the body is placed in a pressure vessel that is filled with a mixture of water and lye (concentrated potassium hydroxide) and is heated to about 160 degrees Celsius (320 degrees Fahrenheit) at a higher pressure to prevent boiling. After approximately five hours, the body is broken down into its chemical components (proteins, sugars, and salts). The remaining bone can be crushed and its ashes then given to the next of kin of the deceased. The green-brown tinted liquid can then be disposed of or used in a garden. Despite formaldehyde's predominance in the embalming industry, more research needs to be done into using other chemicals that are both safe for the mortician and the environment.
