Why 11 Million Embalmed Specimens Are Stored In The Field Museum's Basement

From Bonnethead sharks to Komodo dragons, more than 11 million fluid-preserved specimens reside in the basement of Chicago's Field Museum. This includes 883 frogs. But why keep them all, and why store them in liquid?

Think of it as a living library. These wet specimens maintain their shape and, in many cases, their DNA, offering researchers a near-live view into the past. Each jar is like a book, ready to be opened and studied, sometimes even revealing new species right on the shelves. However, preparing these specimens is no simple task. The Field Museum painstakingly preserves them to ensure they last for centuries.

Specimens come from donations or strategic field collections. For example, researchers might humanely collect a common water snake, carefully preserving its DNA for future study. DNA extraction, a step introduced in the 1990s, is crucial for modern research. Scientists use sanitized tools to collect tissue samples, ensuring they avoid contamination. Sarah, one of the museum’s researchers, uses scissors and forceps to take samples from fresh specimens, first burning away any random DNA on the tools to prevent mixing. She takes samples from inside the snake to avoid damaging its external appearance, ensuring future researchers can still study the specimen’s physical characteristics.

The preservation process involves formalin, which freezes tissues in time, much like embalming a person. Formalin fixes the tissues, keeping them intact for centuries. Sarah positions the specimens carefully to preserve their anatomical features. For snakes, this might involve displaying their hemipenes, making it easy to determine the sex without opening the jar.

After the formalin treatment, specimens soak in alcohol baths for long-term preservation. This switch is safer for researchers and keeps the specimens stable. Alcohol is less toxic than formalin and helps maintain the specimen’s structure and appearance. Larger specimens, like the Komodo dragon, release debris and oils that can discolor the alcohol, but this doesn’t affect the preservation quality.

Some specimens undergo a different process called clearing and staining to highlight their bones and cartilage. This method makes the specimens transparent and dyes their cartilage blue and bones red, providing a detailed view for microscopic study. The clearing process involves using an enzyme called trypsin to digest proteins while leaving the collagen intact. This process, which can take from a few days to a month, results in specimens that look almost alien but offer unparalleled insights into their anatomy.

The Field Museum's collection is meticulously organized, much like a library. Each specimen has an ID number and a specific place on the shelves, ensuring that they can be found when needed. Some specimens have been waiting decades for someone to unlock their secrets, like the spider-tailed horned viper. Originally collected in the 1960s, this specimen was thought to have a deformity, but in the early 2000s, it was identified as a new species, Pseudocerastes urarachnoides.

Old specimens hold immense value, sometimes requiring special techniques to extract viable DNA. For instance, heating and digesting the tissue can help pull DNA away from the formalin, though success rates vary. Sarah’s techniques have made it possible to retrieve DNA from specimens over a century old, providing invaluable genetic information.

The Field Museum’s collection is not just a static archive but a dynamic resource for ongoing scientific discovery. Researchers like Sarah rely on both new and old specimens to study changes in species over time, examining how habitat alterations have impacted biodiversity. Each specimen tells a story, contributing to our understanding of evolution, ecology, and environmental changes.

In preserving these specimens, the Field Museum ensures they don't just die in vain—they live on, advancing science forever. Like library books, these jars may sit untouched for years, but each has the potential to change our scientific knowledge profoundly. Specimens in this living library offer a window into the natural world, helping researchers unlock the mysteries of life, both past and present.

Ultimately, the Field Museum’s dedication to preserving these specimens in fluid ensures that they remain a vital resource for generations of scientists. Each jar is a testament to the meticulous care and scientific curiosity that drives the quest for knowledge, making the Field Museum’s collection an invaluable treasure trove of biological diversity.