Get a look at what makes animals work with these gorgeous vintage anatomical illustrations.

1. Phormosoma indicum

These illustrations of a sea urchin appeared in the 1906 book Anatomie der Echinothuriden; the creature's outer layers appear to have been peeled away to reveal its inner workings. Volume 34 of Memoirs of the Museum of Comparative Zoölogy at Harvard College notes that "the color of this species is rather variable, ranging from yellow to dark brown, lighter above than below, and often with a reddish tinge." This species, and several others, are now included under the umbrella of Phormosoma placenta.

2. Cat Brain

As you might guess from its title, the 1882 book Anatomical technology as applied to the domestic cat tells you more than you could ever possibly want to know about the inner workings of felines. But though it might have shown you what a cat's brain looked like, it still couldn't tell you what was going on inside of it.

3. Green Frog

This gorgeous engraving appeared in Rösel von Rosenhof's Historia naturalis ranarum nostratium, which was devoted entirely to frogs and was published between 1753 and 1758. There are many species of green frog; this one might be of the genus Pelophylax, which is comprised of 25 species from Europe and Asia.

4. Xylocopa violacea

Xylocopa violacea, or the violet carpenter bee, is one of the largest bees in Europe. The illustration on the left, which appeared in the 1896 edition of Faune de France, shows the insect's head and mouthparts.

5. Eledone moschata

It's hard to tell from this illustration, which appeared in the 1890 book Atlas d'anatomie comparée des invertébrés, that what you're looking at is actually an octopus—the musky octopus, to be exact. The mollusk lives in the Mediterranean Sea.

6. Bat

This spooky-but-beautiful drawing of a bat's skeleton comes from Eduard Alton and Christian Heinrich Pander's 1821 book Die vergleichende Osteologie.

7. Anglerfish

I can't find any information about where this illustration—which appears to show three different species of female anglerfish—first appeared, or who drew it, but you can buy it for your wall right here. There are more than 200 species of anglerfish; to mate, the males latch on to the females and eventually fuse onto their bodies, providing sperm whenever she's ready to spawn.

8. Limulus polyphemus

You know Limulus polyphemus as an Atlantic horseshoe crab, but it's actually more closely related to arachnids than to crustaceans; the creatures, which have blue blood, are also captured and bled for biomedical purposes. This illustration is also from Atlas d'anatomie comparée des invertébrés; according to a translation of the text, Figure 2 shows a "Limulus whose dorsal integument have [been] removed to expose the heart and main arterial trunks dorsal."

9. Salamander

This flayed salamander appeared in the 1802 book Histoire naturelle, générale et particulière, des reptiles.

11. Horse Head

Much better than waking up to find a horse head in your bed is to examine this illustration, drawn by medical illustrator Hermann Dittrich, which details the musculature, bones, and ear mechanics of an equine. It appeared in Handbuch der Anatomie der Tiere für Künstler, which was published in 1898 and 1911 through 1925.

12. Turtle

This scary turtle illustration—which appears to show the animal's musculature, in addition to an empty shell—comes from the 1819 book Anatome testudinis Europaeae.