282 ASTONISHMENT. Chap. XII. 



They are highly characteristic of the expression of sur- 

 prise or astonishment. Each eyebrow, when raised, be- 

 comes also, as Duchenne remarks, 4 more arched than it 

 was before. 



The cause of the mouth being opened when astonish- 

 ment is felt, is a much more complex affair; and several 

 causes apparently concur in leading to this movement. 

 It has often been supposed 5 that the sense of hearing 

 is thus rendered more acute; but I have watched per- 

 sons listening intently to a slight noise, the nature and 

 source of which they knew perfectly, and they did not 

 open their mouths. Therefore I at one time imagined 

 that the open mouth might aid in distinguishing the 

 direction whence a sound proceeded, by giving another 

 channel for its entrance into the ear through the eu- 

 stachian tube, But Dr. W. Ogle 6 has been so kind as to 

 search the best recent authorities on the functions of the 

 eustachian tube, and he informs me that it is almost 

 conclusively proved that it remains closed except during 

 the act of deglutition; and that in persons in whom the 

 tube remains abnormally open, the sense of hearing, as 

 far as external sounds are concerned, is by no means 

 improved; on the contrary, it is impaired by the respira- 

 tory sounds being rendered more distinct. If a watch 

 be placed within the mouth, but not allowed to touch 

 the sides, the ticking is heard much less plainly than 

 when held outside. In persons in whom from disease 

 or a cold the eustachian tube is permanently or tempo- 

 rarily closed, the sense of hearing is injured; but this may 



4 ' Mecanisme de la Physionomie,' Album, p. 6. 



See, for instance, Dr. Piderit (' Mimik und Physiog"- 

 nomik,' s. 88), who has a good discussion on the expression 

 of surprise. 



6 Dr. Murie has also given me information leading" to 

 the same conclusion, derived in part from comparative 

 anatomy. 



