phase i clinical trial: a clinical trial on a few persons to determine the safety of a new drug or invasive medical device; for drugs, dosage or toxicity limits should be obtained
clinical trial: a rigorously controlled test of a new drug or a new invasive medical device on human subjects; in the United States it is conducted under the direction of the FDA before being made available for general clinical use
flagellum: a lash-like appendage used for locomotion (e.g., in sperm cells and some bacteria and protozoa)