Caleb, turning on the Bubble Machine Every Wednesday Caleb and his mom get in the car at their home south of Atlanta, Georgia, and drive 75 miles to McKenna Farms, in Dallas, Georgia. There, Caleb, a sweet eleven-year-old with dark red hair and freckles, spends an hour in hippotherapy.   Then they drive the 75 miles home.   It’s a long trip that uses a lot of gas money. It’s also a trip that makes a world of difference for Caleb and his family, starting with that two-to-three hour trip home through Atlanta traffic. Like many children with autism, Caleb bangs his head because the sensory receptors in his brain are unable to filter incoming sensory information, and he is overwhelmed. Head banging is a way to stop the overload. When he is not consistently in hippotherapy   his head banging becomes much worse . That happened this winter, once when his grandmother was in the hospital in critical condition and again when his therapist was ill . It's both frightening