Preserved Materials - FAQ

Preserved Materials

Leave specimens in shipping bags/containers until use.

As long as the original container seal is unbroken, specimens will remain usable indefinitely. If the seal on the specimen bag has been broken during transit, the shelf life is affected only slightly. Just close the bag with a rubber band or some other type of closure. Keep tightly sealed. Exposure to air will not cause decay, but specimens will gradually dry out. Between classroom sessions, return specimens to tightly closed plastic bag or airtight container.

If specimens are to be dissected over an extended period of time, they can be remoistened with NASCO–Guard® Humectant Fluid (item numbers SB17218M, SB12631M, SB32395M, or SB32396M).

No, do NOT add water. Do NOT add formaldehyde or any other preservative to NASCO–Guard® specimens. Your specimens are completely preserved and the addition of water or other preservatives might have undesirable effects on the specimens.

Specimens may occasionally have an odor common to the animal itself (i.e. fish). Since there is no chemical odor, large capacity ventilation systems are not necessary when using NASCO–Guard® preserved materials. However, because specimens may have been originally fixed with formaldehyde or glutaraldehyde by some of our collectors, a trace may remain. Individuals who are sensitive to these chemicals should take the usual precautions when handling specimens.

NASCO-Guard® specimens are biodegradable. They are suited for burial in an approved sanitary landfill or for incineration. Ambient fluids may be safely disposed via city sewers.

Depending on the size of the shell, you can use a scalpel, hacksaw, or coping saw (item numbers SB15423M 5" bone-cutting shears or SB07832M 6" bone-cutting shears). A general classroom tool kit is also available from Nasco (item number 9703612).

Professional collectors provide some of the items (i.e. grasshoppers and earthworms). Some specimens are byproduct from stockyards (i.e. cow eyes, fetal pigs). Some are from the food industry (i.e. bullfrogs, perch). Cats are obtained from Humane Societies after euthanasia.


This is a unique, patented process for preserving specimens. Most NASCO–Guard® specimens are originally fixed in a 3.7% formaldehyde solution, which is still the best animal tissue fixative known. In the NASCO-Guard® process, skilled technicians remove the formaldehyde fixative in a series of water baths, then perfuse the specimens with propylene glycol until tissue fluids contain at least 25% glycol; this inhibits the growth of decay organisms by raising the osmotic pressure of the specimens. Propylene glycol also acts as a humectant to insure moist specimens, and it lowers the vapor pressure of residual formaldehyde, thus markedly reducing the concentration of formaldehyde fumes in the lab. Perfusion also washes away water-soluble carbohydrates and proteins, which could nourish decay organisms. Residual formaldehyde is further reduced as it reacts with propylene glycol to form hemiacetals and acetals, which have a very low order of toxicity. Large embalmed mammals may contain trace amounts of phenol.

Click here to download the NASCO–Guard® Safety Data Sheet (SDS).


  • Single injection - means the arteries have been injected with red latex.
  • Double injection - means the arteries have been injected with red latex and the veins have been injected with blue latex.
  • Triple injection - means red latex in the arteries, blue latex in the veins, plus the hepatic portal system has been injected with yellow latex.