There may be an answer at last. Keeping a cool head while setting a brisk pace comes naturally to horses. But until recently, no one knew how they did it. But horses don't, says Keith Baptiste, a large-animal veterinarian now at the Danish Veterinary Laboratory in Copenhagen, Denmark. Horses need something special to do the same function.
Horses do have that special something.
It's a pair of pint-sized bags of air lying right under the braincase. When the artery carrying blood to the brain runs up the backside of those air sacs, the blood inside the artery cools off, report Baptiste and his colleagues at University of Saskatchewan in Saskatoon, Saskatchewan. Benjamin is one of the horses that Keith Baptiste studied to understand how their brains cool. Their study appears in the Jan. 27 issue of the journal Nature . Although people have known for centuries that horses had such air bags, called guttural pouches, no one was sure what the pouches were for.