288 



Dr. A. A. Gray. 



[Jan. 26, 



7 mm., while that of the second whorl is 3-5 mm. The diameter of the tube 

 of the cochlea immediately in front of the round window is also 3 - 5 mm., 

 the scala tympani showing a marked bulging downwards similar to that 

 found in other ungulates and in most of the mammals. The slant height 

 of the cochlea measured from the upper margin of the round window to 

 the apex of the organ is 5"75 mm. The aqueduct of the cochlea is quite 

 unlike that of any of the mammals which I have hitherto examined. 

 Instead of being comparatively straight, as in its near ally the antelope, it 

 is sharply curved. A large vein accompanies the aqueduct out of the 

 cochlea and, to judge from the photograph, the blood is carried away from 

 the cochlea by this vein. This disposition of the veins of the organ is 

 different from that of the arteries, which are supplied by the internal 

 auditory artery which enters the labyrinth by way of the internal auditory 

 meatus. 



Tlie shape of the cochlea differs in no way from the general type of the 

 ungulates, that is to say, it is of the flattened type. It consists of two and 

 a-half turns. 



The vestibule of the Indian gazelle is also like that of the other ungulates. 

 It measures 3"75 mm. in its longest diameter and does not contain any 

 otoliths of a size sufficient to be recognised by the naked eye. The oval 

 window measures 2 "75 mm. in its longest axis. 



The semicircular canals of the Indian gazelle differ from those of the 

 other ungulates in one important respect. The perilymphatic space is much 

 more marked than in either the antelope, the sheep, or the pig. In the last- 

 mentioned this space does exist throughout the whole length of the canals, 

 but is so small that at parts it can hardly be seen ; in the sheep and 

 antelope it cannot be seen at all in a large portion of the length of the 

 canals. In the gazelle, however, the space can be traced easily round the 

 whole course of all the canals. It is not so large as in man, the monkeys, 

 the seal or the sloth. In their general appearance the canals show much 

 the same features as those of the other ungulates, apart from the fact of the 

 large perilymphatic space. They are regularly curved in outline, the pig 

 being the one exception to this rule in the ungulates. 



The diameter of the superior canal, measured internally, is 4 - 75 mm., while 

 externally the diameter is 6 mm. The height of the vertex of the canal 

 above the vestibule is 6 mm. and the diameter of the canal itself at the 

 vertex is 1 mm. The posterior canal measures 4 mm. in its internal, and 

 rather more than 6 mm. in its external diameter. The height of the vertex 

 of the posterior canal above the vestibule is 5 mm. and the diameter of the 

 canal itself at the vertex is 1 mm. The external canal measures 3 - 5 mm. in 



