<prompt> Body cavity which is opened first on post moem examinationHeadNeckThoraxabdomen  <response>: Routinely thorax is the first cavity most commonly opened on PM examination. In aspyxial deaths, dissection of the head is recommended prior to body because a bloodless field . In case of poisoning: After the opening of the skull we may immediately smell the presence of volatile, poisonous substances e.g., ethanol, cyanide, solvents, etc. without competing odours from thoracic and abdominal cavity 