62 



Further Observations on the Effects which take place from the De- 

 struction of the Membrana Tympani of the Ear; with an Account of 

 an Operation for the Removal of a particular Species of Deafness. 

 By Mr. Astley Cooper. Communicated by Everard Home, Esq. 

 F.R.S. Read June 25, 1801. [Phil. Trans. 1801, p. 435.] 



The former part of this paper may be considered as a continuation 

 of a preceding one by the same author, printed in the last volume of 

 the Philosophical Transactions, and contains an enumeration of many 

 more facts and circumstances, from which we gather that an aper- 

 ture in the Membrana Tympani does not essentially diminish the 

 power of the ear, and that even a complete destruction of that mem- 

 brane is not followed by total deafness. 



The causes by which it may be injured are here further inquired 

 into, and are found chiefly to be a suppuration in the Meatus Audi- 

 torius, and any kind of external violence ; such as blows on the side 

 of the head, the forcible introduction of extraneous substances into 

 the ear, &c. 



Mr, Cooper proceeds next to describe the remedy he has, in con- 

 sequence of his repeated observations that an aperture in the Mem- 

 brana Tympani does not injure the ear, thought fit to apply to one 

 particular species of deafness; namely, that which arises from an 

 obstruction in the Eustachian tube. After enumerating the causes 

 which most frequently produce these obstructions, such as colds, 

 which often affect the parts contiguous to the orifice of this tube, 

 ulcers in the throat, extravasation of blood, and uncommon strictures 

 in the tube, the author proceeds to describe his operation, which con- 

 sists simply in puncturing the membrane, with very little pain to the 

 patient, and with instant relief to the disorder. 



Several cases are described in which the operation has proved suc- 

 cessful. 



The criteria are next mentioned by which it may be known whether 

 this tube be closed or open : and lastly, those kinds of deafness are 

 enumerated in which the operation is not likely to produce any salu- 

 tary effect. These are, when the auditory nerve is affected ; when 

 there is any alteration in the contents of the labyrinth ; and when 

 in general any derangement takes place which does not immediately 

 affect the Eustachian tube. 



The Croonian Lecture. On the Power of the Eye to adjust itself to 

 different Distances, when deprived of the Crystalline Lens. By 

 Everard Home, Esq. F.R.S. Read November 5, 1801. [Phil. 

 Trans. 1802, p. 1.] 



Its object is to state some facts and observations in support of an 

 opinion advanced by the author in a former Lecture, that the ad- 

 justment of the eye to see objects at different distances does not de- 

 pend upon any internal changes in the crystalline lens. 



Before he proceeds, Mr. Home pays a due tribute of praise and 



