On the basis of the findings on the relationship between tubal muscles and the Eustachian tube as described in the previous report, the actions of various tubal muscles on the Eustachian tube are discussed, and the observations carried out by the methods described below on the movements in vivo of the naso-haryngeal orifice at the time of phonation and of swallowing reveaied the following results. 1. Observations were carried out with the use of a nasopharyngoscope. 2. Observations were done on the patients who underwent the radical operation for the cancer of maxillar sinus. As the inferior nasal concha was already removed at the time of the operation, it was possible to insert a small nasal mirror into the posterior nasal cavity of the operated side to catch the whole view around the tubal orifice of healty side. 3. For the children over 5-6 years old with cleft palate, observations were carried out directly on the pharyngeal orifice through the mouth cavity (motion pictures were taken in this instance). At a result it has been found that the nasopharyngeal orifice of the tube is widened because the posterior lip and the mucous membrane of the base of the Eustachian tube move slightly outward at the time of swallowing. In anatomically summarizing these observations the author arrived at the following conclusions. At the time of swallowing the tensor muscle of the palate dilates the Eustachian tube at the points near the middle part and the anterior part of the tube. The levator palatini muscle assists the opening action of the tensor muscle by fixing or by drawing the base of the tube slightly toward the inferior-interior side. The salpingopharyngeus muscle or the salpingopharyngeal fold, being drawn inward by the cephalopharyngeal muscle and pahryngopalatine muscle and widening the nasopharygeal orified, assists the dilatating action of the tensor muscles. When the muscles are relaxed, the Eustachian tube is closed probably by the elasticity of the lateral cartilaginous lamina and by the pressure of the tissues surrounding the tube.