Found this scientific article on WIRED’s website very interesting – about how the horse works as a speed/endurance machine.
We definitely see latherin at work on endurance horses early in the training season – when they are still carrying some portion of their winter coats. And the blood supply available in the spleen is what makes it possible to trot a horse trained at sea level all the way up to High Camp from the valley floor at Squaw during Tevis.