I looked at the notice. I wondered if I had time before my train left Philadelphia for Baltimore in one hour. That heart, ceiling high, occupied one corner of the large exhibition hall, and from wherever you stood in the hall you could hear its beating,…………… It was a popular exhibit, and sometimes, when there were too many children about, the entrance had to be roped off, as the children loved to race up down the blood vessels and match their cries to the heart’s beating