Actually, I shouldn’t have replied to you, but rather to the original post which made it sound like the source of analgesics was beaver butts.
Oddly, I had a beaver make a dam on my property last summer. It was the first time I’d seen one up close. I can see why their fur was so coveted, it looked like deep brown silk. So the anal gland oil is good for something anyway.
For your viewing pleasure:
"Grey Owl's Strange Guests"
(Native American adopts baby beaver)