The inventive cartoonist John Callahan died July 24 at the age of 59. Callahan was a quadriplegic as the result of a 1972 auto accident. He managed to draw by using his left hand to move his right hand around the paper. He often drew cartoons about disabilities, such as ''Don't worry, he won't get far on foot,'' which became the title of his autobiography. His work was adapted into two animated TV series, Pelswick, about a wheelchair-bound boy, and John Callahan's Quads.