40 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



hearing ability of birds, as is well known, is scarcely inferior to that 

 of the most highly developed mammals. We are therefore not only 

 at liberty to assume, but we are forced to conclude that the hearing 

 apparatus of the promammalians, whatever they were, must liave 

 already reached a comparatively high state of development and was 

 a delicate one before they passed into the mammalian stage, with 

 both quadrate and articular still functioning as suspensoria and not 

 as auditory bones, else they could not have been their forerunners. 



Bearing in mind, then, the delicacy of this mechanism, with its 

 chain of bones, one end of which was fixed in the fenestra ovalis 

 and the other in the eardrum, and whose efficiency in performing 

 the function for which it was especially evolved through untold 

 preceding generations, was largely dependent upon its mobility and 

 power to respond to the most delicate impressions made upon the 

 eardrum, what may be asked would have been the result of any 

 interference, however slight, with the free movement of any of these 

 elements within their respective and prescribed arcs ? 



If one were to ask any physician who has had the least experience 

 in treating diseases of the ear about such an interference, he would 

 be compelled to reply that it would invariably result in permanent 

 deafness or complete loss of hearing. Any thickening of the mucous 

 membrane through inflammatory processes produces serious impair- 

 ment of the hearing apparatus by reason of limiting or restricting 

 the free movement of the ear bones. Even occlusion of the eustachian 

 tube, by means of v/hich the equalization of the density or rarity of 

 the air in the tympanic chamber is maintained, results in deafness. 

 Yet we are called upon to believe that a clums}^ quadrate, in its sup- 

 posedly new function could have impinged with impunity upon the 

 delicately movable stapes, without producing an impairment of the 

 hearing which could have had no other result than the extinction of 

 the animal. 



Gregory goes even so far as to picture a second eardrum, located 

 in advance of the old one, and attached to the articular and quad- 

 rate, which in turn acted upon the stapes, both functioning at the 

 same time.^ If any such device ever existed in any mammal, it is 

 indeed strange that embryology should not give us the faintest hint 

 or clue, nor furnish the first scintilla of evidence of its former pres- 

 ence. As regards Gregory's repl}^ to Gadow's objection, the question 

 is not what may or may not have constituted a ''train of bones," 

 morphologically or othel'^^'•ise, but Jiow could the quadrate have heen 

 intercalated functionaUy in an already delicately movable chain of bones 

 without destroying or a-ifecting the movement of the stapes ? As a reply 

 to this question it is a failure. Since an impossi])ility can not be 

 explained otherwise than as a thing that can not be done, we must 



1 Journal of Morphology, vol. 24, 1913, p. 34, fig. 23. 



