Every time I try Google searching some images of large mammal anatomy for drawing I end up seeing a couple of really good break down images floating around that are usually un-sourced, but look like they come from the same collection.
After about 5 seconds of searching I found out they were from a Veterinary Anatomy collection (from Handbuch der Anatomie der Tiere für Künstler)
held online at the University of Wisconsin. Source: digicoll.library.wisc.edu/Scie…
I feel like sharing this because I'm happy that I've finally figured out where they're from and where to get hi-res images.
There isn't a lot of species variety, but they have the most popular animals, and the images are very detailed and big and helpful for all you animal-drawing folks who can't remember what muscles exist and stuff. Also there's a book in Additional Resources that you can read if you like reading and stuff. Libraries are great.