THE BODY.] 



PHYSIOLOGY, 



IS 



turned to the front towards the cavity of the trunk, 

 and it is the row of vertebral bodies which you feel 

 as a hard ridge when you pass your fingers down 

 the back of the abdomen. The arches are at the 

 back of the bodies, so you cannot feel them in the 

 abdomen; but if you turn the rabbit on its belly 

 and pass your finger down its back, you will feel 

 through the skin (and you can feel the same on 

 your owrn body) a sharp edge, formed by what 

 are called the spines, i.e. the uneven tips of the 

 arches of the vertebrae (Fig. 2) all the way down 

 the baclc. 



So that what we really have in the trunk is this. 

 In front a large cavity, containing the viscera, and 

 surrounded in the upper part or thorax by hoops 

 of bonej but not (or only slightly) in the lower part 

 or abdomen; behind, a much smaller long narrow 

 cavity 01 canal formed by the arches of the vertebrae, 

 and theiefore surrounded by bone all the way along, 

 and coEtaining we shall presently see what ; and 

 between these two cavities, separating the one from 

 the other, a solid pillar formed by the bodies of the 

 vertebrae. So that if you were to take a cross slice, 

 or transverse section as it is called, of the rabbit 

 across the chest, you would get something Hke what 

 is represented in Fig. 2, C, where C.S. is the narrow 

 canal of the arches and where the broad cavity of the 

 ch^t containing the heart H is enclosed in the ribs 

 re^hing from the vertebra behind to the sternum 

 in. front. Both cavities are covered up on the out- 

 side with muscles, blood-vessels, nerves, connective, 

 aiki skin, just as in the leg. 



10. We have now to consider the head and neck. 



