364 THE FACULTY OF HEARING. 



tympanal membrane — receive vibratory impulses, as does the 

 cochlear pillar in the middle ear of birds or reptiles, or as the 

 ossicula of the mammal ear do. But while in the more developed 

 organs such vibrations are transferred to the auditory nerve only 

 after various intermediate changes, we here find the vibrations 

 directly transmitted from the tympanal membrane to the ganglion 

 (through the nerve rods above described), and thence as auditory 

 stimulus back through the nerve fibres to the central organ (brain.) 

 The analogy with higher organs of hearing is thus established, 

 though the scheme is simplified by omission of the arrangements 

 of the middle ear. 



In the case of the locust and cricket organ, the transmission of 

 vibration from the drum to the auditory stave is more indirect than 

 in the Acridia, and the mechanism is far more complex. The 

 nerve stimulus will be proportionately differentiated. In the 

 Acridia possibly simple perception of sound without difference of 

 quality or pitch, but in the cricket and locust which are endowed 

 with singing voice, variations of tone may be perceived. These 

 views are entertained by Professor Ranke, of Munich, 



About ten years ago Hensen examined the locust organ, and 

 made some comparisons with the auditory hairs and feelers of 

 Crustacea living in water. The result of recent investigations has 

 been to show that such bristles or hairs as in Crustacea, projecting 

 freely in the water, take up the undulatory impressions, and that 

 the nerves within them are brought into relation with some elastic 

 apparatus capable of being excited into vibration, and thus of 

 special sensation. 



Professor V. Graber, who has pursued the enquiry further than 

 any other investigator, rejects this theory of the auditory function 

 of the tympanal organ upon various grounds, (briefly given at the 

 end of this paper with the account of his experiments). 



Professor Oscar Schmidt has also given an account of the ' 

 anatomy of the organs, with some remarks upon their homologies 

 and general morphological character* 



