200 



INTRODUCTION TO NEUROLOGY 



In the human body the cochlear and vestibular nerves are 

 very intimately associated, but the embryological studies of 



Fig. 95. Diagram of the acoustico-lateral system of nerves with their 

 peripheral end-organs, as seen from the right side, in a fish, the common 

 silver-sides, Menidia (X 9). The relations here figured were recon- 

 structed from serial sections by projection upon the sagittal plane. For 

 the relations between the acoustico-lateral nerves and the other systems 

 of nerves in this fish, see the more detailed chart from which this was drawn 

 off, in the Journal of Comparative Neurology, vol. ix, 1899, plate 15; cf. 

 also Fig. 65, p. 149, of this book. The dotted outline represents the posi- 

 tion of the brain, the lateral line canals are shaded with cross-hatching, the 

 internal ear is stippled, and the nerves are drawn in black. The organs 

 of the lateral line system are drawn as black disks when naked on the 

 surface of the skin, and as black circles when lying in the canals. NAA, 

 Anterior nasal aperture; NAP, posterior nasal aperture; N OL, olfactory 

 nerve; N OPT, optic nerve; RAA, nerve of superior ampulla; RAE, nerve 

 of lateral ampulla; RAP, nerve of inferior ampulla; R BUG, ram us bucca- 

 lis of facial nerve; RL, nerve of the lagena (rudimentary spiral organ); 

 RLAT, ram us lateralis of the vagus; ROS, ramus ophthalmicus super- 

 ficialis of the facial nerve; R MAN EX, ramus mandibularis externus of 

 the facial nerve; R SAC, nerve of the sacculus; RU, nerve of the utriculus; 

 T, acoustico-lateral area. (After Herrick, from Wood's Reference Hand- 

 book of the Medical Sciences.) 



Streeter and others have made it plain that these two nerves are 

 really more distinct than was formerly supposed. The periph- 



