The art of preserving biological specimens started in 17th century. Preserving the tissue needs special care to prevent autolysis. The specimen is usually injected with formalin to prevent autolysis of the body. It is then submerged in a glass jar containing ethanol or isopropyl alcohol. Source: https://www.amnh.org/research/natural-science-collections-conservation/general-conservation/health-safety/fluid-preserved-specimens Image via: https://www.dreamstime.com/anatomical-human-specimens-formalin-anatomical-preserved-human-specimens-ugliness-anomalies-human-parts-body-preserved-image108299297