484 COMPARATIVE PHYSIOLOGY. 



now treat of the functions of a portion of the ear, according to 

 our present classification. 



HAVE THE SEMICIRCULAR CANALS A CO-ORDINAT- 

 ING FUNCTION? 



Physiologists have as yet been unable to assign to the semi- 

 circular canals a function in hearing, and upon certain results, 

 partly of disease but chiefly of experiment, it has been con- 

 cluded, though somewhat dubiously, that they are concerned 

 with those sensations that conduce to or are essential to main- 

 tenance of the sense of equilibrium ; in a word, that they are 

 the organs of that sense in the same way that the eye is the 

 organ of vision. 



Until further evidence is forthcoming, we are not incUned 

 to give assent to the existence of any mechanism in the semi- 

 circular canals, affording sensory data so entirely different 

 from those furnished by other recognized (and unrecognized) 

 sense-organs, that upon them alone, or in a manner entirely 

 their own, arises a consciousness of equilibrium. We are in- 

 clined to regard the latter as depending upon the fusion in con- 

 sciousness of a vast complex of sensations ; and that upon the 

 whole being there represented, or a portion wanting, depends 

 either the preservation of equilibrium, or a partial or entire loss 

 of the same. Nevertheless, it is highly probable that sensory 

 impulses of a very important character, in addition to such as 

 are essential for hearing, may proceed from the semicircular 

 canals, and indeed other parts of the labyrinth of the ear. 



FORCED MOVEMENTS. 



When certain portions of the ibrain of the mammal have 

 been injured, movements of a special character result, and, inas- 

 much as they are not voluntary, in the ordinary sense at least, 

 have been spoken of as forced or compulsory. The movements 

 may be classified according as they are around the long, the 

 vertical or the transverse axis of the body of the animal. Hence 

 there are "circus " movements, when the creature simply turns 

 about in a circle, " rolling " movements, etc. These and others 

 may be toward or from the side of injury. While in some 

 cases there may be a certain amount of muscular weakness in 

 consequence of the injury, which may, in part, account for the 



