THE VIBRATORY SENSE 



filaments. This organ of the lateral line is an auditory 

 apparatus of simplified structure which spreads out in 

 length instead of being arranged in a compact mass, 

 and communicates with the external world through 

 all the orifices with which the scales dependent upon 

 it are pierced. The size of the nerve is evidence of 

 the importance of the part it plays. And this nerve, 

 originating in the brain close to the auditory nerve, 

 shows a real community of connection and function 

 with that nerve. The lateral line, like the ear, is the 

 seat of a vibratory sensitivity. 



Fig. 50. — Simplified and enlarged representation of a section through 

 a scale of the lateral line of a Red-eye, showing the tube which 

 passes obliquely through the scale and opens, on the one hand, 

 outwards, and, on the other, into the longitudinal canal inside the 

 creature. Linear magnification, 30 times. 



Its mode of functioning is to be understood from 

 the manner of its construction. The holes which open 

 outwards receive the concussions which pass through 

 it directly from the surrounding water. They trans- 

 mit them to the mucous liquid with which the tubes 

 to which they give access are filled. As this liquid 

 also bathes the sensorial centres inside the apparatus, 

 the vibrations directly affect the filaments whose 

 business it is to receive them on the sensitive elements. 

 They are thus perceived. 



This remarkable arrangement is peculiar to fishes; 



the species which do not have it, or in which it is 



limited, are in the minority. We also find it frequently 



in the bodies of the young Batrachians. Its presence 



271 



