286 



February 17, 1853. 

 J. P. GASSIOT, Esq., V.P., in the Chair. 



A paper was read, entitled " On the Muscles which open the 

 Eustachian Tube." By Joseph Toynbee, M.D., F.R.S. Received 

 February 2, 1853. 



The author compaences by alluding to the opinion generally held 

 by anatomists, viz. that the guttural orifice of the Eustachian tube 

 is always open, and that the air in the tympanum is constantly con- 

 tinuous with that in the cavity of the fauces. An examination of 

 the guttural orifice of the tube in man and other animals has led the 

 author to conclude, that, except during muscular action, this orifice 

 is always closed, and that the tympanum forms a cavity distinct and 

 isolated from the outer air. The muscles which open the Eustachian 

 tube in man are the tensor and levator palati, and it is by their ac- 

 tion during the process of deglutition that the tubes are ordinarily 

 opened. That the act of swallowing is the means whereby the Eu- 

 stachian tubes are opened, is shown by some experiments of which 

 the following may be cited. If the mouth and nose be closed during 

 the act of swallowing the saliva, a sensation of fulness or distension 

 is produced in the ears ; this sensation arises from the air, which is 

 slightly compressed in the fauces, passing into and distending the 

 tympanic cavities : upon removing the hand from the nose, it will be 

 observed that this feeling of pressure in the ears does not disappear, 

 but it remains until the act of deglutition is again performed while 

 the nose is not closed. In this experiment the Eustachian tubes 

 w^ere opened during each act of deglutition; during the first act, 

 while they were open, air w^as forced into the ca\dty of the tympanum 

 by the contraction of the muscles of the fauces and pharynx, and the 

 guttural orifices of the tubes remained closed until the second act of 

 swallowing, which opened the tubes and allowed the air to escape. 

 That the act of deglutition opens the Eustachian tubes, was infen^ed 

 also from the custom usually adopted of swallowing while the de- 

 scent in a diving-bell is performed ; by this act the condensed air is 

 allowed to enter the tympanum, and the sensation of pain and pres- 

 sure in the ears is removed or entirely avoided. 



The author gives an account of the Eustachian tube and its 

 muscles in Mammalia, Birds and Reptiles. In some mammalia the 

 muscles opening the tubes appertain, as in man, to the palate, in 

 others this function is performed by the superior constrictor muscles 

 of the pharynx. In Birds it is shown that there is a single mem- 

 branous tube into which the two osseous tubes open ; this mem- 

 branous tube is situated between and is intimately adherent to the 

 inner surface of each pterj^goid muscle, and by these muscles the 

 tube is opened. The conclusion to which the author arrives re- 

 specting the influence of the closed Eustachian tubes is, that the 

 function of hearing is best carried on while the tympanum is a closed 

 cavity, and that the analogy usually cited as existing between the 

 ordinary musical instrument, the drum and the tympanum, to the 

 effect, that in each it is requisite for the air within to communicate 



