LAMINA SPIRALIS OF THE COCHLEA. 1>8V 



on the membnine Jurin;^ vibration. Kolliker, af^ain, believes 

 that from the almost mathematical re^nilarity with which they 

 are arranged along the vestibular surface of the lamina spiralis, 

 the.se peculiar terminations of the cochlear nerves are the 

 structures which distinguish the pitch, timbre, and strength 

 of sounds, through the medium of the water of the labyrinth 

 and the fenestra oval is. 



From comparative anatomy it would appear that the 

 vestibule is that part of the organ by means of which any 

 sound, or series or combination of sounds, is heard merely as 

 ncdse. The simplest form of ear, which consists of a vesti- 

 bule only, probably enables the sensorium merely to become 

 cognisant of sound, irrespective of the pitch or harmony of its 

 constituent tones. 



In regard to the semi-circular canals, it appeare probable 

 from their intimate cormection with the vestibule, that they, 

 like it, have to do with sound merely as novie, and that their 

 function, therefore, is of secondary importance in the liigher 

 forms of the organ. 



Dr. Thomas Young, with his usual sagacity, considered 

 the cochlea as a " micrometer of sound." Kolliker, as already 

 stated, has put forward a similar idea, based on his know- 

 ledge of the structures just described. His conception, how- 

 ever, appears to be so far unsatisfactory, inasmuch as he 

 considers the rods of Corti to be merely the extremities of the 

 cochlear nerves ; and it wants that completeness which it 

 woulil have, had he been able to admit those rods to be a 

 series of acoustic arrangements, as they are believed to be by 

 their discoverer. 



The hypothesis presents a more satisfactoiy form if we 

 assume that each of the rods of Corti, or that groups of these 

 rods are so organised and arranged as to act or vibrate as 

 acoustic apparatuses appended to the (wtremities of the coch- 

 lear nenes. Ejich rod, or group of rmls, may be so constituted 



