While it may seem as if the animals he used were literally alive, the specimens were likely dead and in some sort of alcohol for conservation, very likely used, cleaned, stored and reused.
Though he documented much of his life and work in writing, Palissy kept much of the specifics of his life-casting process secret. Based on the methods of fellow French artisans who also employed this technique, it’s likely that he kept a menagerie of specimens in jars in his workshop. Once it was time to cast a subject, it was customary to dip the creature in vinegar or urine, coat it in a greasy substance, then position it on a bed of plaster, arranged in a striking, lively pose. The final step would have been covering—as in, suffocating—the specimen with additional plaster.
While it may seem as if the animals he used were literally alive, the specimens were likely dead and in some sort of alcohol for conservation, very likely used, cleaned, stored and reused.
Sadly, it wasn't the case with this gentleman.
Ooops! Ok, maybe I shouldn't have scanned through it. That's pretty terrible then.