1906.] Observations on the Labyrinth of Certain Animals. 287 



largest of the canals. It measures 6 - 5 mm. from limb to limb internally, and 

 7*5 mm. externally. The height of the vertex of the canal from the vestibule 

 is 6 mm., and the diameter of the canal itself at the vertex is - 75 mm. 



The posterior canal lies in a plane almost at right-angles to that of the 

 superior canal. It is somewhat smaller than the latter. Its diameter, 

 measured internally, is 5*5 mm. in length, and measured externally is rather 

 less than 7'5 mm. The height of the vertex of the canal above the 

 vestibule is 5'5 mm. and the diameter of the canal itself at the vertex 

 is - 5 mm. 



Unfortunately the horizontal canal was broken in the process of 

 preparation, but it was noticed that it was distinctly smaller than either 

 of the other two. The plane of this canal is relatively low and, indeed, at 

 its posterior extremity it appears to open into the ampulla of the posterior 

 canal. This low level of the plane of the horizontal canal is very common 

 among mammals, and in none of the mammals examined by the writer 

 is the plane of the canal so high relative to the posterior canal as in 

 the monkeys and in man. In the two latter the space enclosed by the curve 

 of the posterior canal is almost bisected by the plane of the horizontal 

 canal. 



The perilymphatic space is almost entirely absent from the canals of the 

 lion, indeed it can only be seen in the angles formed by the ampullae of the 

 canals with the canals themselves. This feature is common to the carnivora 

 that have been examined with the single exception of the seal. In the 

 latter the space is well marked. 



The length of the whole labyrinth of the lion is 17 mm. The cochlear 

 portion is large relative to that portion formed by the vestibule and canals. 

 In this respect the lion resembles the cat and other carnivora. A condition 

 exactly the reverse of this is found in the lemur. 



The angles which the planes of the canals form with one another are 

 rather large in the lion. That is to say, the canals diverge widely from one 

 another, much more so than in man. This divergence of the canals is 

 greater in the lemur than in any animal which I have yet examined. 



The Labyrinth of the Indian Gazelle (Gazella Bennetti). (Plate 16, fig. 2.) 

 The membranous labyrinth of the Indian gazelle resembles that of the 

 other ungulates in its general outline. There are, however, some unexpected 

 differences. 



The organ measures 14 mm. in extreme length from the outermost point 

 on the vertex of the posterior canal to the innermost point on the lowest 

 whorl of the cochlea. The diameter of the lowest whorl of the cochlea is 



