I belive he is refering to what as know in english as your diaphragm... no not the female condom! it's a large muscle near your stomach which is also responsible for controling breathing If I'm not mistaken... ah! here we go!
1) A muscular membranous partition separating the abdominal and thoracic cavities and functioning in respiration. Also called midriff. <---!
2) A membranous part that divides or separates.
3) A thin disk, especially in a microphone or telephone receiver, that vibrates in response to sound waves to produce electric signals, or that vibrates in response to electric signals to produce sound waves.
4) A contraceptive device consisting of a thin flexible disk, usually made of rubber, that is designed to cover the uterine cervix to prevent the entry of sperm during sexual intercourse. (YIKES! not that one!)
5) A disk having a fixed or variable opening used to restrict the amount of light traversing a lens or optical system.
"It was me, peering through the looking-glass"