LAMINA SPIRALIS OF THE COCHLEA. 287 



on the membrane during vibration. Kolliker, again, believes 

 that from the almost mathematical regularity with which they 

 are arranged along the vestibular surface of the lamina spiralis, 

 these 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 ovalis. 



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 

 noise. 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 appears probable 

 from their intimate connection with the vestibule, that they, 

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

 function, therefore, is of secondary importance in the higher 

 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 

 would 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 satisfactory 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 extremities of the coch- 

 lear nerves. Each rod, or group of rods, may be so constituted 



