Background
Snakes are legless reptiles. Some snakes kill their prey with poison, some by constriction.[1] Toussaint Gervais sees snakes around the St. Louis Cemetery 1 all the time, but most are not poisonous.[2]
Behind the scenes
Poisonous snakes are a reoccurring theme in through out many sierra games, particularly in fantasy and mystery games. See King's Quest, Quest for Glory, Conquests, Laura Bow, etc.