The brak'lul was a Klingon term for a characteristic redundancy in Klingon physiology. All vital bodily functions were protected by a redundant organ or system. Klingons possessed two livers, an eight-chambered heart, 23 ribs, two stomachs, three lungs (TNG: "Ethics"; VOY: "Lineage") and a double-lined neural pia mater. This allowed Klingons to survive injuries that normally killed other humanoids. Some scientists, such as Doctor Toby Russell, believed it to be a good design in practice, but also noted that the extra redundancy meant there was also much more chance for a system to fail or cause problems.