STUDYING THE MUMMY OF PETOSIRIS
A PRELIMINARY REPORT
By Dr. Louis T. Kircos and Emily Teeter, Ph.D.
The University of Chicago
(This article originally appeared in The Oriental Institute News and Notes, No. 131, September-October 1991, and is made available electronically with the permission of the editor.)
On May 30th, at midnight, the mummy of Petosiris (OIM 269) traveled from the Egyptian gallery of The Oriental Institute to the University of Chicago Hospitals for a high-tech radiologic examination. This nighttime trip across Hyde Park marked the beginning of a new joint venture to examine and document the Egyptian mummies in the collection of The Oriental Institute.
Although the circumstances surrounding Petosiris's examination drew particular attention, the cooperation of the Department of Radiology in examining specimens from the OIM has been ongoing. In 1989, physicians and scientists from the Department of Radiology at the University of Chicago Hospitals x-rayed four mummies in the collection of The Oriental Institute Museum. This examination, performed in the museum conservation lab with portable equipment, was undertaken in preparation for future studies including CT (computed tomography) and MRI (magnetic resonance imaging). The results of the plain radiographs were helpful in documenting certain characteristics of the mummies. However, they did not provide conclusive evidence about some basic questions, even to the gender of one mummy. The macabre time for the transfer and work was not related to the mystique of mummies. It was purely practical: the CT scanners are used less at that time and we wanted to ensure that our work would not interfere with the use of the machines for hospital patients.
This year, museum conservator Laura D'Alessandro made arrangements with Dr. Louis Kircos, formerly Associate Professor of Radiology and Surgery, to continue the research project using sophisticated CT and MRI methods. To date, three of the mummies have been examined with CT scans and one with MRI. The Oriental Institute wishes to extend its deepest thanks to Dr. Kircos, technicians Edward Jones and Dale Eggleston, the Department of Radiology, and the administration of the University Hospitals for their cooperation in this research project.
Why study mummies?
Mummies are important documents which shed light upon many aspects of ancient Egyptian culture and history. They are primary records of the practical application of funerary beliefs, and poignant reminders of the ancient Egyptian quest for immortality. Artificial mummification was practiced from the 3rd Dynasty through the early Christian period. During this long period, there were many variations and modifications in the actual procedure. Ideally, one might be able to date a particular mummy by the form of mummification alone. For example, according to the tradition paradigm, in the New Kingdom the four major organs (stomach, liver, lungs and intestines) were removed from the body and after mummification they were placed in separate canopic jars. This practice was modified in the 21st Dynasty (ca. 1069 B.C.) when the mummified and wrapped organs were replaced in the body cavity. The New Kingdom technique of depositing the organs in canopic jars was revived in the 25th and 26th dynasties. After that period, the organs were most commonly placed alongside the wrapped legs of the mummy.
A difficulty with this standard outline of mummification practices for dating mummies is that there are many exceptions to this chronological outline. These variations may be due to local preferences, or perhaps to the whim of the individual embalmer. Therefore one must be cautious when assigning a date solely on the basis of the style of mummification.
Previous mummy studiesUntil recent years, the most common technique of studying mummies was to unwrap them and conduct an autopsy. This destroyed the record of the wrappings, and the original appearance of the mummy (figure 3). From 1898, x-rays have been employed to study mummies without unwrapping them. However, this technique has limitations, for although x-rays produce images of bones and hard structures, they are not sensitive to the presence of soft tissue and hence they can provide only a partial record of the mummification procedure. In the mid 1960s, CT (also referred to as CAT) scans were employed. This process gives far superior results and allows researchers to view the anatomy from a perspective not available previously. This is because the anatomy is imaged perpendicular to the long axis of the body producing tomograms (thin sections) with no vestige of underlying or overlying structure to obfuscate the anatomy. The CT images demonstrate both soft tissues such as muscle and fat as well as bone. Contiguous images can be stacked together to produce three-dimensional reconstructions.
An important feature of CT imaging is that the density of on an individual image is recorded.
The first mummy which we examined was that identified on its coffin as a man named "Petosiris." This mummy was purchased by James Henry Breasted during his honeymoon trip in 1894-5. According to the travel memoirs of the newly-wed Mrs. Breasted, her husband spent an entire day negotiating the price of a group of four mummies. When the purchase was made, he hired camels to carry the mummies to their dahabayia (sailboat) where mummies were stored in the honeymoon bedroom. This information provides amusing information about the purchase of the mummy, but really very little about the object itself. The name Petosiris, which is now associated with the mummy, is given twice on the coffin, sadly without any other titles or genealogical information.
The Oriental Institute's goals in examining the mummy include the basic verification of the gender of the mummy (if female, the mummy obviously was not that of the man Petosiris named on the coffin), any indications of the age at death or cause of death and the correspondence of the scientific information to information gleaned from the coffin of the mummy.
From a radiologic standpoint, the purpose in examining Petosiris with high resolution CT was similar. We wanted to verify/identify the sex and age at death of the mummy. Furthermore, from a forensic standpoint, we wanted to determine, if possible, any indications of disease or cause of death. The high-resolution techniques which we employed also enabled us to produce a three dimensional appearance of the facial skeleton. In the future we intend to produce the three-dimensional appearance of the soft tissue mask of the face and compare the materials used during the mummification process using quantitative CT techniques.
The high resolution CT techniques we employed were quantitative in the respect that the images are dimensionally accurate and that they enable comparison between the radiologic density of structures within a CT image, between CT images of the same study, and between CT images of different studies. The radiologic CT density is measured in Hounsfield units, after the Nobel laureate who is credited with discovering CT. CT studies are normalized with the CT number of water being established at zero. Densities greater than water have values more than zero (bone ranges from 200 to 2000 hu) and densities less than water have values less than zero (fat is -100 to -400).
We employed quantitative CT techniques in imaging the mummies of The Oriental Institute. For instance, the resin used in the mummification process has a CT number of -100 to -300. Although the cortex of many bones are intact with a CT number of about 1000 hu, the mummification process has eroded the mineralization, reducing the value to less than 100 hu. We also employed high resolution techniques (200 micron resolution) to the pubic synthesis, lumbar spine, and the facial skeleton, providing the foundation for further analysis and comparisons.
The style of mummification
The CT scan images provided much specific information about the style of mummification employed for Petosiris. The density readings of the images on the scans confirmed that the surface of Petosiris' skin was, as usual with ancient Egyptian mummies, smeared with resin before the first layer of wrappings was applied. It also appears that there are perhaps three intermediate layers of a resin-like substance between multiple layers of wrappings. The body of Petosiris is very shrunken, and the bulk of the mummy is copious layers of linen.
As was customary, the brain was removed during the mummification procedure. The lack of damage to the delicate sinus and orbital bones suggests that the brain was removed only after having been dissolved or cut into very small pieces. What appears to be a once liquid material, perhaps a resin, was poured into the skull where it solidified in the back of the skull (fig. 1). This is also well-attested by mummy autopsies. Attempts to restore a life-like appearance was achieved by packing the mouth with what may be linen impregnated with a resinous substance. Disks, which we assume on the basis of their density to be faience or stone, have been placed over each eyeball.
The major organs of the mummy were removed through a ragged embalming incision, roughly 6 inches long on the left side of the mummy, from the bottom edge of the rib cage down along the pelvic bone. A pad of linen (?) has been placed over the incision. Packets of material can be seen in the abdominal cavity. The convoluted twists of the material as well as the presence of hard inclusions (seen as bright white dots in the image), suggest that these structures are packets of linen wadding and other material, which have been placed in the body cavity to restore the fullness of the body's contour.
We have not yet been able to determine the absence or presence of the heart, although it was most commonly left in the body since it was related to the idea of revivification. As has been noted by radiologists who have previously worked with mummies, it is often so shrunken to be barely distinguishable. There are no amulets or other ornaments on or in the body cavity.
It is not uncommon for the genitalia of male mummies to be specially prepared to give them a lifelike or even exaggerated appearance. This practice is associated with the idea of rebirth in the afterlife and regeneration. According to ancient Egyptian mythology, Osiris, the god of the underworld, posthumously engendered his son Horus after his limbs were bound as a mummy by his faithful wife Isis. The most commonly attested method of continuing virility of male mummies was to wrap a reed or other support alongside the organ. With the mummy of Petosiris, we have encountered what appears to be a more elaborate process, the introduction of a resinous(?) substance into his penis. This process is not otherwise mentioned in the Egyptological literature. The suggestion that the material was injected is confirmed by the continuity of the material up into the floor of the pelvic cavity.
The study of Petosiris has only begun. Three dimensional reconstructions of the mummy will soon be produced. The Oriental Institute anticipates having the data examined by scholars of various disciplines who will be able to add observations from their own specialized fields. An Egyptological study of the coffins and cartonnage is underway, and those findings will be added to the medical conclusions in the effort to more precisely determine the period in which Petosiris lived.
A note on recent MRI examination of Egyptian Mummies
On June 21, 1991, the mummy of Meresamun (OIM 10707) was taken to the University of Chicago Hospitals for an examination using MRI (magnetic resonance imaging). Although various frequencies were employed, no images were produced due to the complete desiccation of the mummy's tissues.
Although there had been doubts about the effectiveness of MRI for mummy research, it was suggested that it be tried again with Meresamun, since the experiment would be conducted on a emphasizing the new state-of-the-art MRI machine. Unfortunately, no images were produced. MRI has been used for experimental mummy research (again with no results) in Minneapolis, Buffalo and other medical centers.
1. See News and Notes, no. 123 (March-April 1990) for a summary of the arrangements leading up to the present work.
2. For documentation of the earliest artificial mummification, see Zaki Iskander in J. Harris and E.F. Wente (editors), An X-Ray Atlas ofthe Royal Mummies (Chicago, 1980).
3. For a summary of the procedure, see Z. Iskander in J. Harris and E.F. Wente (editors), An X-Ray Atlas, 19-26; Alfred Lucas, Ancient Egyptian Materials and Industries (4th edition, London, 1962), 270326; Sue D'Auria et al, (editors) Mummies and Magic (Boston, 1988), 14-19.
4. Derek Notman et al., "Modem Imaging and Endoscopic Biopsy Techniques in Egyptian Mummies" American Journal of Roentgenology 150 (January, 1988): 94.
6. Attested in "several" of the mummies CT scanned by Myron Marx and Sue D'Auria for the Museum of Fine Arts, Boston, (personal communication from Dr. Marx); Sue D'Auria, Myron Marx "CT Examination of Eleven Egyptian Mummies" Radiographics vol. 6 no. 2, March, 1986, 324; D'Auria et al, (editors) Mummies and Magic, 22 1; Adian and Eva Cockburn (editors) Mummies, Disease and Ancient Culture (Cambridge, 1980), 55.
Revised: July 30, 2007