THE EAR OF MAN. I93 



An inspection of the Torpedo ear (Fig. i) shows it to 

 be composed of a number of more or less curved tubes, 

 three of which approach a semicircular form, and have 

 been on this account, since their discovery by Fallopius 

 in 1 561, called the semicircular canals. These three 

 canals project from the central sac of the ear in three 

 directions, and they lie approximately in the three planes 

 of space. These planes do not coincide with the sagittal, 

 horizontal and transverse planes of the body respec- 

 tively, nor do the planes of any of the canals of the 

 right side form continuations of the planes of the canals 

 of the left side, or vice versa. The importance of these 

 spacial relations will appear when we come to consider 

 the physiology of the organ. 



One of the canals projects forwards and outwards, and 

 is known as the anterior vertical canal (the terms supe- 

 rior and sagittal canal have also been applied to it), 

 another projects backwards and outwards, and is called 

 the posterior vertical canal (the terms inferior and fron- 

 tal have been given to it), while the third canal projects 

 outwards and downwards nearly in the horizontal plane, 

 and is called the external or the horizontal canal. 

 Although it is usually stated in the text-books, that 

 these canals occupy the three planes of space, and 

 although, if not stated directly, it is none the less implied, 

 that the canals also coincide with the three planes of 

 the vertebrate body, — the sagittal, frontal, and horizon- 

 tal respectively, — yet, we find that the very considerable 

 and universal deviation from this hypothetical condition 

 has been recognized by several investigators and the 

 important bearing of the facts on auditory physiology at 

 least in part recognized. I shall return to this further on. 



