POSITION OP THE SKULL ON THE SPINE. 207 



To this is attached the round head of the shoulder bone. 

 To prevent this from falling forward, the collar bone 

 runs from the sternum to the point of the shoulder on both 

 sides, and thus separates the shoulders and keeps them 

 securely in their position. This completes the whole 

 skeleton. 



Emily. I think you remarked when entering on the 

 subject of the bones, that many of the inferior animals 

 possess a skeleton, though it is different in some respects 

 from that of man. Wherein does this difference con- 

 sist ? 



Dr. B. Chiefly in the want of certain parts, for the 

 only ones which they all have in common, are the skull 

 and spinal column. The whales and porpoises have no 

 lower extremities; and. in the snakes and fishes, we find 

 neither upper nor lower extremities ; neither thorax, nor 

 pelvis. The higher order of quadrupeds, such as the 

 apes and monkeys, possess a skeleton which in the gen- 

 eral arrangement of its parts, very nearly resembles 

 man's ; but there are still some very important charac- 

 ters in the latter, which clearly distinguish it from all 

 others. 



In the first place, we can see throughout its whole con- 

 formation a constant adherence to that plan of construc- 

 tion and disposition of the parts, which is best adapted to 

 the erect stature. The position of the head on the 

 spine affords a strong proof, of how the principle of the 

 erect position predominates through the whole structure. 

 The human skull is connected with the spine nearly in 

 the centre of its base, and is slightly inclined to prepon- 

 derate forward, yet it is so nearly balanced, that but little 

 muscular exertion is necessary to keep it in equilibrium. 

 In all other animals on the contrary, the skull is connec- 

 ted with the spine, at its back part ; it projects very little 

 behind, almost the whole base being in front of the spine. 

 Now, this arrangement requires for the support and mo- 

 tions of the head, a large mass of muscles on the back 

 of the neck, and particularly a powerful ligament, the 

 rudiments of which only are found in man, 



