The first essay in Jonathan Gleason’s Field Guide to Falling Ill tells the story of his second cousins, two of his mother’s cousin’s children who died in early childhood of Tay-Sachs disease. Dr. Bernard Sachs, the neurologist who first noticed the symptoms of the disease in children in late-nineteenth-century New York, did not know how to treat it. “The families of the children he treated had come to him for help, for a cure, for relief,” Gleason writes.