<lloween just behind us, it is the perfect time to talk about bones. Skeletons, our internal structure, are meant to be hidden, which makes them spooky to see. Whether in humans or animals, bones work with ligaments, tendons, and joints to fling our skeleton around. Besides motion they also protect internal organs with structures like our skull and rib cage.
Bones are largely made of collagen fibers strengthened by tiny inorganic crystals. Collagen is a fibrous protein which exists in a triple helical structure. At various points along a string of collagen there are attachment points for the bone mineral crystal, hydroxyapatite Ca10(PO4)6(OH)2. In the weight bearing bones cancellous (spongy) bone is found towards the ends to absorb as much tensile and compression stress as possible. Cortical (compact) bone is found in the middle creating the bone hollow to resist bending stress. The hard tissue protein of collagen stiffened by hydroxyapatite leaves a material that will outlast any organism’s soft tissue.
If you’re lucky enough to find a full skeleton, bones can capture a hidden story of why an animal died. For example, we found a deer with most of the bones intact, but many of its lower ribs were shattered along with its pelvic girdle. You can deduce that most likely a car slammed into the deer, critically injuring it. Another example was a decaying goose. As the bird’s tissue decomposed we could see its metacarpus, or terminal wing bone, was broken and healed horribly. Unable to migrate, cold, malnutrition and vulnerability to predators did the rest.
In our Arb collection, we have a few of these cases cleaned and viewable. Bones we collect are cleaned using demisted beetles, the same method used in natural history museums. These small beetles are detritivores, meaning they feed on the decaying tissue of dead animals, leaving behind spotless bones. Among the most shocking in our collection is a woodchuck skull with teeth that curl all the way under its jaw and slowly grew into its brain. . .
In the spirit of Halloween, venture through the Arb keeping an eye out for any eerie bones. Envision the story behind the bones and see a snippet of the Arb’s ghostly past.