The boy, whose parents have asked that he not be identified, climbed over a box on top of a 3.5ft railing and fell 18ft on to the concrete floor of the enclosure which houses seven gorillas (right).
Binta Jua, who was carrying her own infant on her back, cradled the boy in her arms (centre)and took him to a door where zoo keepers and paramedics could attend to him. Water was sprayed on the other gorillas to keep them away.
Binti Jua, (far right) whose name is Swahili for "Daughter of Sunshine," is a Western Lowland gorilla. Because she was raised by humans, she had to be taught nurturing skills, using ape-like stuffed toys, when she gave birth, 17 months ago.
The boy initially was considered critical, but "his condition has improved, which is good news," said a spokesman for Loyola University Medical Center in Maywood. Photographs: AP