"When relaxed, it can stretch to a surprisingly large size. I'll demonstrate that later. It relaxes in two ways. The body, without conscious control, relaxes it when pressure is applied. Its owner can also tighten or relax it. With proper training, the owner can develop near total control. Black has had that training, Kitten has not." Rob nodded his understanding. "Black has been trained to relax. Kitten, we'll have to coax. A couple of inches inside is a second sphincter. A backup, so to speak, that assists keeping feces inside until it's appropriate to evacuate it. This one we have less control of, but again, with proper training, it can...