ORGAN OF COKTI. 221 



though this view has not received the support of actual dem- 

 onstration, it affords an explanation, more or less plausible, 

 of the mechanism of audition, carried to the point of the 

 actual reception of impressions by the nerves. In view of 

 this, it is important to have a clear comprehension of the ar- 

 rangement of those parts which are supposed to receive the 

 sonorous vibrations ; and we shall, for the sake of simplicity, 

 eliminate from our description certain accessory structures, 

 the functions of which are obscure. 



In the quadrilateral canal, bathed in the endolymph, 

 throughout its entire spiral course, is an arrangement of pil- 

 lars, or rods, regular, like the strings of a harp in miniature, 

 which are supposed to repeat the varied vibrations of sound. 

 These are the pillars of Corti. 1 



The structures contained in the quadrilateral canal are so 

 delicate that their investigation presents great difficulty ; but 

 the arrangement of the pillars, or rods of Corti is pretty well 

 understood. These pillars are external and internal, with their 

 bases attached to the basilar membrane, and their summits 

 articulated above, so as to form a regular, spiral arcade, en- 

 closing a triangular space, which is bounded below by the 

 basilar membrane. The number of the elements of the or- 

 gan of Corti is estimated at about 3,500, for the outer, and 

 5,200, for the inner rods, the proportion of inner rods to the 

 outer being about three to two. 2 The relations of these 

 structures to the membranous labyrinth are seen in Fig. 16, 

 (19). In this figure, it is seen that the internal pillar, which 

 is the shorter of the two, is attached to the basilar membrane 

 just external to the point of entrance of the nerve into the 

 quadrilateral canal. The external pillar is longer, more deli- 

 cate and rounded, and is also attached to the basilar mem- 

 brane. The form of the pillars is more exactly shown in 



1 CORTI, Recherches sur Vorgane de Pome des mammiferes, 1851, p. 15, et seq. 



8 PRITCHARD, On the Structure and Functions of the Rods of the Cochlea in . 

 Man and other Mammals. Proceedings of the Royal Society, London, 1872, voL 

 xx., p. 371. 



