No, it's not their brain. The "guttural pouch" inside horses' heads was discovered in 1764, but no one knew what it was for.
Some scientists believed that it worked as a sound amplifier. Others thought it might act as a voice resonator or even a floatation device.
Scientists at the University of Saskatchewan in Saskatoon, Canada, determined that the guttural pouch actually acts as a radiator! It works to cool horses' blood when they are running to prevent heat stroke or seizures.
Why do horses have an air-filled sac inside their heads
"And God took a handful of southernly wind, blew His breath over it and created the horse."
~ Bedouin Legend
The highest prized horse race in the world is the Dubai World Cup in Japan which has a purse of $2.4 million.