Clockwerk lungs and stomach

The Clockwerk Lungs and Stomach were some of the Clockwerk parts that helped Clockwerk survive for hundreds of years.

History
Clockwerk replaced his organic lungs and stomach with mechanical ones to keep himself from aging.

Sly 2: Band of Thieves
They were given to Jean Bison, and were used by him to power his Iron Horse trains indefinitely, transporting illegal spice across North America.

After the two lungs were easily taken by Bentley and Sly, the stomach was bolted down, and was detached by the explosion from a bomb dropped from Bentley's RC chopper. They were later stolen back by Jean Bison and given to Arpeggio, then reassembled into the body of Clockwerk. They eventually faded into dust when Carmelita destroyed the Hate Chip.

Trivia

 * In real life, owls do not have technical stomachs, but rather they have a proventriculus which digests some of the food and a gizzard which grinds up the non-digestible parts.
 * Sly was, by his own admission, disturbed that out of all the Clockwerk parts, Jean Bison chose to take his stomach and lungs.
 * Despite the fact that lungs and stomachs perform different jobs, they look the same, or, at least very similar during gameplay. The stomach is also seen pumping.
 * On the other hand, the stomach looks different during the ending cutscene when Bentley carries it.