Hi Doc! Love reading your blog, I found you first through the Lucifer story (reminded me of a friend of mine actually) and then again through your mermaid post and have been hanging around ever since. I looked thru your archive but didn't find this question so hopefully it hasn't been asked before: what is it about horse anatomy that makes their legs so (seemingly) fragile? You'd think being as big as they are, they'd be more all-around solid. Thanks for reading, have a good one!
The horse, Equus caballus, is one of my favorite arguments against Intelligent Design. I’ve spoken before about why I no longer see them, but even as a student I would wonder why and how this species existed when there were apparently so many things that could go wrong with its own anatomy, especially next to something tough like a trusty cow.
I don’t know how it’s possible to believe in a benevolent, loving, wise creator when creatures like the horse come to exist.
So I’m going to use your question as an excuse to write a post that had been on my mind for a while:
Things That Are Wrong With Horses
The basic structure of a horse has a few significant design flaws.
Cannot vomit. This means that anything which would make another species sick enough to vomit results in a horse getting s distended stomach and colic, where the stomach can rupture and the horse can die. Also means symptoms of illness are hidden longer
The large bowel (hind gut) of the horse is fricking huge, but can actually displace itself and bend around the wrong way, resulting in obstruction, colic and death without surgical intervention. This can commonly happen after exertion (splenic contraction) and giving birth. Colic due to nephrosplenic entrapment is particularly common after the horse has an adrenaline release, which causes the spleen to temporarily contract, and this seems like a poor design to risk death every time you spook or go for a fast run, especially in a species known for spooking and running fast.
Giving birth is a fast and explosive affair in the horse. The whole pushing business should be over and done with in about 20 minutes, however this assumes that everything is lined up just right for a normal delivery. Foals are all long legs and necks, which are easy to get tangled or bent around the wrong way. A mare is strong enough to push her foal’s feet through her uterine wall, which is death all round.
Speaking of strength, sometimes horses will kick each other when they have attitude, and they can do so with enough strength to rupture each other’s spleens.
When galloping most horses, best studied in thoroughbreds because they are made to gallop on a regular basis, horses routinely bash their diaphragm with such force against their liver that their liver bruises.
Galloping also often makes their lungs bleed. That’s why racehorses have their head held up after a race, so you don’t see any blood come out their nose and disqualify them. Even horses that you don’t see bleed have evidence of pulmonary bleeding after a gallop if you scope them.
Their leg bones are actually pretty damn tough, but the ends are spindly little things compared to the mass of musculature up top. Their legs are subjected to huge biomechanical forces when a horse runs which can often subject them to ligament damage and lameness. A fractured leg bone can heal like any other, but if a horse can’t bear weight evenly on all four legs for an extended period of time (eg after a fracture) then they are at risk of laminitis.
Laminitis can cause the hoof to slough off. (Aaargh!) They can also get laminitis from eating a bit too well.
Speaking of eating, they can also get colic (and risk death) from eating not enough fiber or the wrong sort of plants or from eating too much dirt.
Oh, and just to mess with you, horses have a space in their head called a guttural pouch which seems to exist for no other reason as far as I can tell (okay, maybe it’s about heat regulation) other than to get fungal infections that eat through the exposed artery and cause the horse to die from blood loss through it’s nose.
And Bonus: Exquisite sensitivity to tetanus and vulnerability to Hendravirus
This list is by no means complete. I haven’t even touched on their anesthetics or drug reactions, but it’s a simple start.
