THE PROPRIO-CEPTIVE MECHANISM 



057 



The extirpation of one labyrinth in an animal immediately affects 

 the resting attitude of the animal, and also its movements in spaje. 

 In the frog, the head is inclined to the side of the lesion. In swimming, 

 the operated side is lower in the water, with an abduction and exten- 

 sion of the limbs of the opposite side, particularly the fore-limb. 



In the pigeon, destruction of the membranous labyrinth produces 

 marked disturbances of equilibration. The bird is unable to rest 

 quietly, and is continuously performing inco-ordinate movements. 

 After a time these pass off, and it learns to a certain extent to co- 

 ordinate its movements by means of sight and touch. 



FIG. 384. EFFECT OF DESTRUCTION OF LABI'IUXTH ON 



IX A Pi?, EOS. 



Extirpation of one labyrinth produces a loss of tone on the opposite 

 side of the body. When only one canal is put out of action, oscillatory 

 movements of the head are produced in the plane corresponding to 

 the damaged canal (Fig. 384). The same results hold for mammals, 

 but the canals are not so accessible as those of the pigeon. 



The canals have been stimulated experimentally, chiefly the 

 external canal, owing to its greater accessibility. By plugging. one 

 end of the canal behind an artificial opening, and introducing into it 

 a syringe, it has been shown that pressure on the ampulla causes a 

 deviation of the eyes to the opposite side, with nystagmus when the 

 eyes looked to the same side of the body. Rarefaction produced an 

 opposite result a deviation of the eyes to the same side of the body, 

 and a nystagmus when the eyes turned towards the opposite side of 

 the body 



Like results have been obtained upon the human subject in 

 cases of middle-ear disease where suppuration has produced a fistulous 

 opening into the external canals. 



42 



