Appearance of effusion material in the attic space correlated to an impaired Eustachian tube function. 
In adult Sprague-Dawley rats a dysfunction or a total blockade of the Eustachian tube was established by various experimental procedures.  The appearance of effusion material in the attic was subsequently considered to be evidence of incomplete ventilation of the middle ear cavity.  Though the salpingopharyngeus muscle (SPM) seemed to be the muscle which could open the Eustachian tube maximally, splitting of the soft palate and consequent interference with the tensor veli palatini muscle (TVPM) and the levator veli palatini muscle (LVPM)--but obviously not with the salpingopharyngeus muscle (SPM)--caused the effusion material to be produced in the middle ear cavity.  Neither blockade by about 80% of the tympanal orifice nor severing of the tendon of the tensor tympani muscle (TTM) close to the malleus produced any signs of effusion material whatsoever.  Our findings strongly suggest that the most important part of the Eustachian tube, as regards ventilation, is the nasopharyngeal portion, as a normally functioning TVPM and LVPM seems to be an absolute prerequisite to prevent effusion material from developing in the attic.