264 THE PIGEON 



jaw raised, the quadrates swing round and the pterygoids and palatines slide 

 forward along the basi- sphenoidal rostrum. 



The qtiadrate (the suspensorium) bears the articular surface for the lower jaw ; 

 it is a stout triradiate and movable bone, and it is articulated with the squamosal, 

 the quadrato-jugal, and the pterygoid. 



Each ramus of the lower jaw is composed of jive bones, namely, the articular, 

 angular, supra-angular, splenial (along the inner side of the middle portion of 

 the ramus), and dentary. The dentary forms the distal half of the ramus ; and 

 the two dentaries are fused in front at the symphysis. 



The upper and lower Jaais are without teeth, but have horny sheaths. There 

 is only one auditory ossicle, the columelJu. In the floor of the mouth is the hyoid, 

 which is partly ossified and partly cartilaginous. {See Fig. 91, p. 262.) 



The Nervous System. 



The Brain. 



Remove the roof of the cranium (frontals and parietals) by carefully paring 

 oft' the bone, and take away the sides, piece by piece, so as to expose the brain. 

 Notice the spongy nature of the bone. 



Note and draw the following parts :— 



The large cerebral hemispheres overlie the thalamencephaloii and reach the 

 cerebellum, hence the large optic lobes are displaced and lateral in position. 

 The olfactory lobes are very small, poorly developed. The large cerebellum is 

 grooved transversely, and is divided into a median lobe and two small lateral 

 lobes (flocculi). The medulla oblongata is largely overlapped and hidden by 

 the cerebellum, and descends almost verticallv from it. 



