Preserved bullfrogs for dissection and biology studies. The bullfrog presents a larger alternative to the grassfrog—facilitating a study of general vertebrate anatomy and of that specific to the Amphibia. Measurements from nose to cloaca. Flinn-Preferred™ preserved specimens are safe, non-toxic alternatives to formaldehyde preparations. These specimens retain a more lifelike and natural appearance and have not been exposed to formaldehyde at any point. Look for the Flinn-Preferred™ symbol!