170 GLIMPSES OF NATURE. 



of the ailment resides in the semicircular canals we 

 have been discussing. A study of disease, therefore, 

 tends to confirm what experiment suggests ; and the 

 conclusion we arrive at is that the canals in question, 

 formerly regarded as part and parcel of the hearing- 

 sense, are really the organs of a new sense that of 

 motion. They give us information about the nature 

 of the rotations of the head, and it is quite possible 

 their sphere of usefulness extends even beyond this 

 limit. 



We see in these curious canals tubes which contain 

 fluid a condition suggestive enough, in a common 

 way, of an apparatus to record changes of level. 

 This fluid acts against delicate hairs when rotation 

 occurs, and probably in this way communicates to the 

 nerves of the canals an impulse which, in the brain, 

 becomes translated into a sensation of motion. The 

 turning of the head to right and left seems a small 

 thing indeed, viewed from the ordinary standpoint. 

 But if what has here been recorded is correct, it is 

 obvious our knowledge of how far and in what direction 

 we have made that movement is due to these curious 

 canals of the ear. They are organs of sense which 

 minister to our safe conduct as we move through space, 

 and as we pass sorrowing or rejoicing through the 

 world's pastures. 



