224 MARINE BIOLOGICAL LABORATORY. 



for it can be clearly shown that during the wounded 

 state the bird is still able to equilibrate itself under 

 certain conditions, and those conditions involve calling 

 into use the tactile sense. The sensation of giddiness 

 produced by injury to or destruction of the canals is 

 due not to the injury of the ampullar sense-organs, but 

 either to a disturbance of the centre of equilibration 

 in the brain by mechanical injury to the cells of this 

 centre, or to the cessation of the perceptions arising in 

 part from the functional activity of the auditory mech- 

 anism. It has been observed that a pigeon operated 

 on by canal section or destruction can, and usually does, 

 steady itself and properly direct and execute coordinated 

 movements, the moment its sense of sight is aided by 

 the tactile sense sufficiently to enable it to form a cor- 

 rect judgment of its position in space and its relation 

 to surrounding objects. 



Now, barring nausea or other nervous disturbance 

 accompanying section among the warm-blooded animals, 

 it is plainly true that the animal's failure to coordinate 

 its movements lies in the fact that it forms false judg- 

 ments of its spacial relations on an insufficient basis 

 sense-perception, the constant stream of auditory im- 

 pressions having been cut off, even in the milder 

 experiments, by the disturbance of the pressure equi- 

 librium of the endolymphatic fluid. 



On the basis of the evidence which had been pro- 

 duced by the advocates of this doctrine, Milne-Edwards 

 disposed of the kinetic and statical theories of the 

 equilibration functions of the semicircular canals in 

 jthe following words : " Mais les hypotheses propos^es 



