482 ORGANIC SENSATIONS 



a wheel-like rotation of the eye about its axis when the head is bent to one 

 side or the other. This is not caused by the nerves which convey muscular 

 sensations, for the same rotation appears when the whole body is inclined one 

 way or the other without bending the head or neck. When, for example, a 

 person lying horizontally on his back turns his head to the right his eyes turn 

 to the left, while with the same rotation of the head in a standing position no 

 rotation of the eyes takes place. Such phenomena appear, therefore, to de- 

 pend upon the changed position of the head with reference to the line of 

 gravity. Since they are very different in character from those aroused from 

 the semicircular canals, we should probably not go far astray in assuming 

 that they are mediated by the otolith sacs, that is, that the latter furnish 

 impressions which inform us of the direction of the line of gravity. 



These impressions do not figure prominently except under circumstances 

 which exclude the ordinary visual, motor and tactual impressions, as for example 

 in diving. It is said that many deaf-and-dumb persons lose all sense of direc- 

 tion when the body is submerged (James), also that such persons have great 

 difficulty in standing on one leg, and when the eyes are closed find it quite impos- 

 sible. We may 'suppose that in these persons the otolith sacs have undergone 

 pathological changes. 



The dizziness produced by sending an electric current transversely through 

 the head is also thought to be due to stimulation of the labyrinth. When the 

 current is closed the person feels as if the head and entire body were inclined 

 toward the cathode; when it is opened one has the sensation of falling toward 

 the anode. 



From the observations and experiments here presented it appears quite 

 probable that the labyrinth is a peripheral organ which reflexly regulates 

 various finely graduated movements especially of the eyes and of the head, and 

 in general is of considerable importance for the tonus and functional capac- 

 ity of the skeletal muscles. If the conclusion is correct that conscious im- 

 pressions as to the position of the head and orientation of the body are 

 obtained from the labyrinth, it ought to be regarded also as an actual sense 

 organ analogous to the organs of the motor sensations. That these impres- 

 sions are usually indistinct says nothing against their occurrence, for super- 

 ficially considered, the sensations aroused through the nerves of the tendons, 

 joints and muscles, in spite of their demonstrably great importance, appear 

 to us much less vividly than the sensations which proceed from sense organs 

 stimulated by external agencies. 



REFERENCES. St. von Stein, " Die Lehre von den Funktionen der einzelnen 

 Teile des Ohrlabyrinthes," Jena, 1894. J. R. Ewald, " Physiologische Unter- 

 suchungen iiber das Endorgan des Nervus octavus," Wiesbaden, 1892. J. Breuer, 

 Wiener Sitzungsber., November, 1903. 



