Warning, NOT FOR THE SQUEAMISH
What's in John's Freezer is a blog by a research veterinarian specializing in morphology of large animals who, as a result, works at a lab with a freezer full of huge dead animals that eventually get dissected in the name of research (in an intro posts he says he never discusses their sources for their research subjects for various reasons but being a legitimate research facility, they are all legal sources. Probably a fair guess that most are from zoos). He talks about the specimens, and posts photos of them.
This photo is just mind boggling. I'm normally pretty squeamish myself, but from a "holy crap, I never even THOUGHT about that, at that scale, that is amazing!" perspective this was...amazing.
Elephant intestines.
You've been warned
ETA: And, there's actually a whole documentary series on the subject in the UK,
Inside Nature's Giants