By S. Milius Air sacs bulging from a horse's hearing system may solve the mystery of how such an athletic animal cools its brain during exercise without the standard anatomical gadgetry, argues an international team of researchers. In gazelles, cheetahs, dogs, and a herd of other zoological athletes, brain cooling depends on a structure called the carotid rete mirabile, explains Keith E. Baptiste of the Danish Veterinary Laboratory in Copenhagen. In the rete, hot blood surging from the heart via the carotid artery flows into smaller arteries surrounded by cool blood returning from the nose and face.
Horses lack a fete.
Never mind that horses don't vocalize, hear, or swim better than animals without pouches. Analyzing the pouches in discarded carcasses gave Baptiste the cooling idea. Finally he persuaded the University of Saskatchewan in Saskatoon to let a research team implant sensors into arteries in live horses. The project struck some prominent veterinarians as a waste of funds, but the school consented as long as the first horse yielded good data. A dozen bystanders gathered around a barn treadmill when Baptiste tested a little gray Arabian named Dusk.