In 1756 they were seen for the first time at the base of the rider, surrounding the carotid artery that goes to the brain, with two bags of air. Each has between 300 and 500 ml of air and so far they did not know what they were for.
Canadian Keith Baptiste suggested that they were mechanisms of temperature control in the blood and has now demonstrated the above. He applied probes to measure blood temperature to several horses and observed that between the inlet and outlet of the bag the temperature of blood circulating to the brain decreased by two degrees.
Other good racers cool the blood heated by exercise through networks of small capillaries, but horses have no capillary system. However, if they do not want to die they have to cool the blood that goes to the brain.
This discovery will help to better understand the biology of animals similar to horses, even though it remains to be clarified the operation of air bags.