Description: Segment 1 Intertitles explain that cilia protect the nose, nasal sinuses, middle ear and lungs. An animation shows how cilia work in the respiratory system. A diagram is shown of the anatomy of the respiratory system in the human head. Ciliary action in the mouth of a frog is shown. Ciliary action in an oyster is shown, as well as in slow motion. Mucous membranes from a rabbit's trachea are shown. The intertitles explain that cilia are extremely susceptible to changes of medium. They are then placed in a variety of solutions, including chlorine and ammonium carbonate. Time start: 00:00:00:00 Time end: 00:05:48:21 Length: 00:05:48:21 Segment 2 Cilia are placed in a variety of solutions including lactic acid, glycerine, sodium bicarbonate, carbon dioxide and chloroform, and the effects of the solutions commented on. The ejection of lamp black from the eustachian tube of a frog is shown. Ciliary action in the trachea of a cat is shown. A microscopic view of the movement of cilia is shown, with drops of oil as indicators of movement. Time start: 00:05:48:21 Time end: 00:11:21:12 Length: 00:05:32:16