What about when the horse is sleeping?
I guess when the horse lays down the pumping force from the heart is enough to pump the blood back. Much less gravity to work against
then you dont need that much circulation.
See https://news.ycombinator.com/item?id=48247471
alt Hacker News
I guess when the horse lays down the pumping force from the heart is enough to pump the blood back. Much less gravity to work against