Idea for anatomist prestige class features:
--If using "Heroes of Horror", the Archivist is also a likely, if not perfect, base class canidate.
--Anatomists who autopsy a humanoid or monstrous humanoid at least once per month get a +2 competence bonus to heal and poison use checks (+4 if they vivisect the subject instead). Bear in mind that vivisecting a sentient creature is considered an evil act. Anatomists with the backstab ability add a +1 bonus to their damage rolls (+2 if they have 10 or more levels in a class with the backstab ability) Because of their intricate understanding of anatomy and physiology, they also add +1 bonus to the save DC against poisons they use.
--Poison use is a class feature at lv. 1. Anatomists who choose to vivisect (or rarely, perform a exploratory surgery on ailing victims) frequently use paralyzing poisons as muscle relaxants. Neutral good characters can only use paralysis and sleep-inducing poisons on willing victims, or animals without affecting their alignment.
Yeah, that's all I have for now. You definitely need to figure out the prestige class features for the anatomists.