i2o 4 THE EAR. 



ally into two portions, the " hearing labyrinth " and the " muscular-tone 

 labyrinth," the former consisting of the cochlea, and the latter of the 

 semicircular canals, and the structures in the vestibule. After many 

 experiments, he concluded that all the muscles of the body are kept 

 in a state of tone by means of the labyrinth, and that injury to it most 

 affects those muscles whose movements are most delicate, such as those 

 of the eye and larynx. After plugging the canals, abnormal flaccidity 

 of all the muscles ensued. He further states that if the labyrinth of 

 an animal be injured, and the animal be then killed, the usual rigor 

 mortis does not, in most cases, occur. In some cases, however, it 

 appeared to come on earlier. While Ewald thus relates the labyrinth 

 to muscular tonicity, he does not deny that sound-waves stimulate the 

 nerve-endings, and he suggests that in this way rhythmic movements 

 of the muscles, as in dancing to music, may be facilitated. 



In 1883, Sewall 1 carried out instructive experiments on carti- 

 laginous fishes. The animals selected were young sharks and skates. 

 He found that merely cutting through all the canals on one side pro- 

 duces no disturbance of equilibrium. The same negative result follows 

 section of the vertical canals on both sides. On injuring the utricle 

 and removing the otoliths, there was occasionally no disturbance of 

 equilibrium ; but in the majority of instances it was observed that 

 the fishes dived and swam downwards in circles towards the injured 

 side. The surest way, however, of producing disturbance of equilibrium 

 was to injure the saccule, when the fish kept swimming round in a 

 circle in the vertical plane. Operations on the ampullae gave somewhat 

 ambiguous, though generally positive, results. Thus, injury to the 

 anterior vertical ampulla tended to produce rotation in the long axis 

 of the body, while similar injury to the longitudinal ampulla tended to 

 produce somersault movements. When the nerve supplying a horizontal 

 ampulla was cut, there was no disturbance of equilibrium. 



In the larger sharks serious injuries to the labyrinth often produced 

 little or no disturbance of equilibrium ; but the most common results 

 were nystagmus and vomiting. Sewall cautiously concludes that the 

 results of experiments are not sufficient to justify the opinion that the 

 labyrinth is the peripheral organ of equilibrium. 



It is remarkable that Steiner 2 came to the conclusion that in the 

 dog-fish the canals had nothing to do with equilibrium, while we have 

 seen that Lee obtained remarkable positive results (p. 1203). In another 

 research, Lee 3 found that, after cutting the auditory nerve in dog-fish 

 on one side, rolling movements round the longitudinal axis towards the 

 injured side occurred. Somersault movements were absent. On cutting 

 the auditory nerves on both sides, the sense of statical equilibrium was 

 lost, and the animal lay on its back, belly, or side indifferently, and 

 swam in these positions. On stimulating the ampulla of the anterior 

 canal, an upward rotation of the eye on the same side, and a downward 

 rotation on the opposite side, were noticed. On dividing the nerve to 

 this ampulla, the opposite effect was produced on the eyes, and if both 

 nerves were cut the fish dived downwards. On cutting the nerves to 

 the posterior ampulla on both sides, the fish swam upwards near 

 the surface, sometimes even putting its head out of the water. 



1 Journ. Physiol., Cambridge and London, vol. iv. p. 339. 



2 Deutsche met I. TVehnschr., Leipzig, 1889, No. 47. 



3 Journ. Physiol., Cambridge and London, 1894, vol. xv. 



