L 



44o 



nuition occurring in tho l)riiiii ami cniiiiuiii, tlu; foniiur may be traced 

 to an arrest or imj)erfeftion in the ihivclopment of part of tbe walls 

 of the visceral cavity, more particularly of the two anterior luanchial 

 arches and the fissure between them. The incomplete condition of 

 the chain of ossicula, and part of the bony wall of the tympanum, 

 is attributable mainly to the defective development of the first bran- 

 chial arch; the want of the tympanic ring and auditory process, and 

 the consequent absence of bony meatus, to the deficient development 

 of the second branchial arch. The same observations rendered it 

 probable, that the closed condition uf the meatus proceeds from a 

 preternatural increase of that deposit in the outer part of the fii-st 

 branchial fissure, wliich, in the course of natural development, forms 

 the founilation of the septum of the mcmbrana tympani, and thus 

 separates the cavity of the tympanum and Eustachian tube on the 

 inside from the meatus on the outside of this the fii'st branchial fissure. 

 The malformation of the softer part of the meatus extemus, and of 

 the auricle, is connected with a defect in the development of the 

 integumental parts of the first and second branchial arches, which 

 constitutes the latest series of changes occurring in the parts under 

 consideration, and, accordingly, is more frequently defective than 

 the others. The very peculiar form of the face, resulting from the 

 undeveloped condition of its maxillary, zygomatic, and malar por- 

 tions, together with the existence of cleft palate, to a slight degree, 

 in two of the individuals described, appeared to the author to 

 establish still more fully the relation subsisting between the origin 

 of the malformation of the auricle, meatus, and tjTnpanum, and the 

 incomplete development of the anterior part of the transitory bran- 

 chial apparatus of the fa'tus. 



The third part of the paper contained an account of a series of 

 ex])criments performed on the state of hearing in the malformed indi- 

 viduals, and in other persons having the external meatus artificially 

 plugged. In all the three malformed individuals, the hearing was 

 such that they coidd carry on a conversation with others who spoke 

 slowly and articulately to them, and in one only was there any degree 

 of difficulty in this ; and yet, in all of them, sounds must have been 

 communicated to the ear entirely through the bones of the head. In 

 ordinary persons, it is weU known, that all sounds wliich are trans- 

 mitted directly by contact of the sounding body with the hard parts 

 of the head, are heard with greater intensity when the external ears 

 are closed ; but in them the most complete plugging or obliteration 

 of the meatus does not reduce the car to the condition of that oman 



