520 



THE RABBIT 



CHAP. 



arising from the wall of the tympanic cavity and inserted on 

 to the manubrium of the malleus. 



The study of development indicates that the malleus corresponds to 

 Ihe articular part of Meckel's cartilage of lower Vertebrates, and the 

 incus to the quadrate (p. 44) : the articulation of the bony mandible 



l''iG. 133. — Diagram of the mammalian bony labyrinthj tympanic cavity, and external 

 auditory passage. 

 Cch. bony cochlea ; E, Eustachian tube ; Ex, external auditory passage ; L. bony 

 semicircular canals ; M, tympanic membrane ; N. auditory nerve ; OK stapes ; 

 O^. incus ; C^. malleus. (After Headley.) 



with the squamosal in Mammals has rendered these parts unnecessary 

 for their original purpose, and they have undergone a change of function, 

 forming an accessory part of the auditory apparatus. 



Urinogenital Organs. — -The kidneys (Fig. 125, k) are of a 

 somewhat compressed, oval shape, with a notch or kilns on 

 the inner side. They are in close contact with the dorsal 

 wall of the abdominal cavity, the right being somewhat in 

 advance of the left. Towards the hilus, the tubules of 



