Soft Tissue Preservation
The human body contains many types of soft tissue: skin, organs, muscles, etc. These tissues are made of cells and when a person dies their cells die, too. Cells undergo a process known as autolysis where enzymes within the cell are released and the cells break down. In addition, bacteria, fungi, insects, and scavengers also act upon the body to help break it down and recycle it back into the ecosystem. Even bone contains cells that decompose along with the rest of the body leaving behind only the sturdy mineral component of bone.
In some instances, however, soft tissue may be preserved. Natural forms of mummified can be caused by environmental conditions such as desiccation (hot, dry conditions like "Ginger") and extreme cold (like "Otzi the Ice Man"). Preservation can also be caused by chemical means such as tannins (like the "Bog Bodies") and saponification (the chemical conversion of fat tissue into a waxy-like substance, like the "Soap Lady"). All these methods may preserve skin and sometimes organs. Man-made preservation also exists and is seen most commonly today through embalming.
The remains recovered from 218 Arch Street present a range of preservation: some bones are badly deteriorated while others are in very good shape. One individual has a preserved lung and another organ that may be a liver. But what has been truly remarkable are the large number of preserved brains. A final tally is underway to determine what percentage of individuals have brain material. In may cases the skull is intact and the brain is inside where it will stay as there is no way to remove it without damaging the skull or the brain material. The brain in this image, however, is from a broken cranium. All the preserved brains have shrunk to a fraction of their original size.