Orbicularis Oris 



103 



tion is likely to be associated with imperfect development of the 

 tympanic end of the first post- 

 oral cleft. Sometimes the 

 tubercles join over and hide 

 the meatus ; sometimes there 

 is neither meatus nor pinna. 

 On the other hand, by a sort of 

 carelessness, or, possibly, over- 

 zeal, on the part of Nature, 

 a supplementary pinna, or an 

 attempt at one, is sometimes 

 developed at the end of one of 

 the lower clefts. 



The Eustachian tube and 

 tympanum ' are developed in 

 connection with the inner end 

 of the first post-oral cleft, while 

 the meatus externus and pinna 



are formed On the OUtside, the Rudimentary pinna developed at dorsal end of 



membranatympani being inter- third branchial deft. (BLAND BUTTON.) 

 posed between them. (Quain.) 



THE MOUTH 



The lips consist of striated fibres of the orbicularis and other 

 muscles covered on the outside by skin, and on the dental aspect by 

 mucous membrane which is continuous with that of the gums and 

 mouth. This entire mucous surface is covered with squamous epithe- 

 lium. Where the membrane is reflected from the middle line of the 

 upper and lower jaw to the lip, a prominent fold or frcenum occurs, 

 that of the upper lip being well-marked. Beneath the mucous mem- 

 brane of the lips racemose labial glands are placed ; and, should the 

 orifice of one of them be occluded, a labial cyst occurs ; sometimes 

 the glands become the seat of suppuration. 



The orbicularis oris, a sphincter of striated fibres, consists of a 

 semi-elliptical portion in each lip ; the fibres of each piece blend and 

 cross at the corners of the mouth, where they join other muscles of 

 expression ; they become continuous externally with the anterior part 

 of the buccinator. 



The orbicularis arranges the lips in whistling, and when the facial 

 nerve, which supplies it, is paralysed (p. 67) all efforts in that direction 

 are attended with characteristic failure. Contraction of the separate 

 halves of the muscle may spoil the plastic operation in hare-lip ; it 

 was to check this strain upon the wound that hare-lip pins were 

 formerly so much used. The employment of abundant fine sutures 



