THE BODY.] 



PHYSIOLOGY, 



17 



good way from it. The opening between the two jaws 

 is the gap or gape of the mouth, which as you know 

 can be opened or shut at pleasure. If you try it on 

 yourself you will find that, as in the rabbit, it is the 

 lower jaw which moves when you open or shut your 

 mouth. The upper jaw does not move at all except 

 when your whole head moves. Underneath the skull 

 at the top of the neck the mouth narrows into the 

 thtoat, into the upper part of which the cavity of the 

 nose opens. So that there are two ways into the 

 throat, one through the mouth and the other through 

 the nose (Fig. 2). 



At the back of the skull you will see a rounded 

 opening, and if you put a bodkin through this opening 

 you will find it leads into a large hollow space in the 

 inside of the skull. In the living rabbit this hollow 

 space is filled up with the brain. The skull, in fact, 

 is a box of bone to hold the brain, a bony brain-case. 

 This bony case fits on to the top of the vertebrae of the 

 neck in such a way that the round :^d opening we 

 spoke of just now is placed exactly over the top of 

 the tunnel or canal formed by the rings or arches of 

 the vertebrae. If you were to put a wire through the 

 arch of the lowest vertebra, you might push it up 

 through the canal formed by the arches of all the 

 vertebrae, right into the brain cavity. In fact the 

 brain-case and the row of arches of tlie vertebrae 

 form together one canal, which is a narrow tube in the 

 back and in the neck, but swells out in the head into 

 a wide rounded space (Fig. 2, A and B, (7.5.) During 

 life this canal is filled with a peculiar white delicate 

 material, which is called nervous matter. The 

 rounded mass of this material which fills up the cavity 



