82 PHYSIOLOGY. 



diaphragm forms a membranous partition between it and 

 the cavity of the abdomen. It is conical in shape, with its 

 apex above, where, indeed, it is so contracted, that there is 

 barely room in the aperture to contain the tubes which go 

 to the lungs and stomach, and for the larger blood-vessels 

 that go and come from the heart. 



Thorax or chest ; a, the sternum ; b, 6, the spine ; c, c, the ribs, the 

 cartilages being in front. 



37. The ribs are 24 in number,- twelve on each side, of 

 which/ the seven upper are united to the sternum by car- 

 tilage, and are called true rib&Ahe cartilages of the other 

 five are united with each other, and are not attached to the 

 sternum ; these are called false ribsfc all of them are con- 

 nected behind to the spinal column. The ribs increase in 

 length as far as the seventh, by which the cavity of the 

 chest is enlarged ; from the seventh, they successively dimin- 

 ish in length, thus diminishing the cavity. The direction 



