Biological preservation of dead animals involves treating organisms with specific substances to halt decay. Its primary purpose is to maintain the structural integrity of tissues and organs for long-term study, display, and historical records. Preserved specimens are invaluable resources for researchers to investigate anatomy, evolutionary changes, and biodiversity.
Common Liquids for Preservation
Formaldehyde, typically used as an aqueous solution known as formalin, is widely employed for initial tissue fixation. Formalin is a solution of formaldehyde gas in water, often with a small amount of methanol as a stabilizer. For most preservation purposes, a 10% formalin solution is used, containing approximately 3.7% to 4% formaldehyde. It is commonly injected into or specimens immersed in it for long-term storage.
Ethanol is frequently used for the long-term storage of biological specimens after initial fixation. It functions by dehydrating tissues, removing water that is essential for decomposition. A common concentration for long-term storage is 70% ethanol, which effectively inhibits microbial growth and helps tissues maintain their shape. For specific applications like DNA analysis, higher concentrations are preferred to thoroughly dehydrate samples.
Isopropyl alcohol serves as an alternative to ethanol, particularly when ethanol is less accessible. While it can be used for preserving smaller specimens, it is generally less suitable for long-term scientific collections than ethanol. This is because it can cause greater specimen shrinkage and other undesirable physical changes.
Glycerin is used in preservation, often in combination with other chemicals. Its role is to maintain tissue flexibility and prevent desiccation. Glycerin is known for its penetrating and plasticizing abilities, contributing to the pliability of preserved tissues. It possesses hygroscopic properties, meaning it draws water, which contributes to its antiseptic action.
The Science Behind Liquid Preservation
Liquids used in biological preservation inhibit the biological processes that lead to decomposition. These chemicals primarily prevent the growth of bacteria and fungi, which are significant agents of decay. They also inactivate the specimen’s own enzymes, which would otherwise cause cellular self-destruction, a process known as autolysis.
Formaldehyde achieves preservation primarily through a process called fixation, which involves protein denaturation and cross-linking. Formaldehyde molecules react with proteins within the tissue, forming stable chemical bonds. These cross-links stabilize cellular structures and make the proteins resistant to enzymatic breakdown and microbial attack. This chemical alteration creates a rigid internal “skeleton” that maintains the tissue’s physical toughness and structural integrity.
Alcohols, such as ethanol and isopropyl alcohol, preserve by dehydrating the specimen. These alcohols are hygroscopic, drawing water out of tissues. Water is essential for most decomposition processes, including enzymatic activity and microbial proliferation. By replacing water within cells and tissues with alcohol, they create an environment unsuitable for decay, preserving the specimen’s shape and internal structures.
These chemical actions maintain the specimen’s original shape, size, and internal structures over extended periods. The stabilization of proteins and the removal of water prevent the degradation that would otherwise distort or destroy the specimen. This allows for detailed anatomical and morphological studies years after initial preservation.
Preserving Specimens: Methods and Safety
Liquid preservation typically begins with an initial fixation step. Specimens are injected with or immersed in a fixative solution, commonly formalin, shortly after death to halt rapid decomposition. After this initial treatment, the specimen is usually transferred to a long-term storage solution, often an alcohol like 70% ethanol. This multi-step process ensures thorough penetration and stabilization of tissues.
Preserved specimens are widely used across various institutions. Natural history museums house collections for research and public display, documenting biodiversity and historical changes. University biology laboratories utilize these specimens for dissection and anatomical study, providing hands-on learning experiences for students. Medical schools also rely on preserved cadavers and organs for anatomical instruction.
Handling preservation chemicals necessitates strict safety precautions due to their hazardous nature. Formaldehyde is a known carcinogen and can cause skin irritation, respiratory issues, and allergic reactions. Proper ventilation, such as working in a fume hood, is essential to minimize inhalation exposure. Personal protective equipment (PPE) like chemical-resistant gloves, eye protection, and laboratory coats must be worn to prevent skin and eye contact.
Proper disposal and storage of these chemicals are crucial for environmental safety and regulatory compliance. Flammable materials like ethanol require storage in locked, fire-safe cabinets, and all chemicals should be disposed of according to hazardous waste guidelines. Regulations and guidelines ensure safe handling and use, protecting personnel and the environment.