THE CHEST. 



167 



CHAPTER. VI. 

 THE CHEST. 



a 'i hii first lib. 



h 'i hu caiiilrtges of the eleven hindermost, or false ribs, connected together, and uniting with 

 that oi the seventh or last true rib. 



c The breast-bone. 



d The top, or point, oi" the withers, which are formed by the lengthened spinous, or upright 

 processes of the ten or eleven first bones of the back. The bones of the back are 

 eighteen in number. 



e The ribs, usually eighteen on each side ; the seven first united to the breast-bone by car- 

 tilage ; the cartilages of the remaining eleven united to each other, as at 6. 



/ That portion of the spine where the loins commence, and composed of five bones. 



g The bones forming the hip, or haunch, and into the hole at the bottom of which the head 

 of the thigh-bone is received. 



h The portion of the spine belonging to the haunch, and consisting of five pieces. 



t The bones of the tail, usually fifteen in number. 



The chest, in the horizontal position in which it is placed in the cut, is of a some- 

 what oval figure, with its extremities truncated. The spine is its roof; the sternum, 

 or breast, its floor; the ribs, its sides; the trachea, oesophagus, and great blood- 

 vessels passing through its anterior extremity and the diaphragm, being its posterior. 

 It is contracted in front, broad and deep towards the central boundary, and again 

 contracted posteriorly. It encloses the heart and the lungs, the origin of the arterial, 

 and the termination of the venous trunks and the collected vessels of the absorbents. 

 The windpipe penetrates into it, and the oesophagus traverses its whole extent. 



A cavity whose contents are thus important should be securely defended. The 

 roof is not composed of one unyielding prolongation of bone, which might possibly 

 have been strong enough, yet would have subjected it to a thousand rude and danger- 

 ous shocks ; but there is a curiously-contrived series of bones, knit together by strong 

 ligaments and dense cartilaginous substance, forming so many joints, each possessed 

 but of little individual motion, but the whole united and constituting a column of 

 such exquisitely-contrived flexibility and strength, that all concussion is avoided, and 

 no external violence or weight can injure that which it protects. It is supported 

 chiefly by the anterior extremities, and beautiful are the contrivances adopted to 

 prevent injurious connexion. There is no inflexible bony union between the shoulders 

 and the chest; but while the spine is formed to neutralise much of the concussion 

 that might be received — w hile the elastic connexions between the vertebrae of the 

 back, alternately aff'ording a yielding resistance to the shock, and recjaining their 

 natural situation when the external force is removed, go far, by this playful motion, 

 to render harmless the rudest motion — there is a provision made by the attachment 

 of the shoulder-blade to the chest calculated to prevent the possibility of any rude 

 concussion reaching the thorax.* 



* " Had," says Mr. Percivall, " the entire rib been one solid piece of bone, a violent blow 

 might have broken it to pieces. On the other hand, had the ribs been composed from end to 



