458 DISSECTION OF THE PIGEON. 



forceps the outer spongy layer of bone, until the shape of the 

 organ can be clearly seen. 



a. The anterior vertical semicircular canal lies, in the 



natural position of the parts, close alongside the 

 posterior border of the optic lobe and the side of 

 the cerebellum. 



b. The posterior vertical semicircular canal lies 



almost immediately below the anterior vertical 

 canal. 



c. The horizontal semicircular canal lies opposite the 



lower border of the optic lobe and the hinder end 

 of the cerebellum. 



The three semicircular canals, as in other 

 vertebrates, are in planes each at right angles to 

 the other two. 



