288 



Birds, as is commonly known, have no effective 

 movement in the vertebrae of the body whilst the 

 numerous vertebrae of the neck are very moveable. 

 We should explain the S S actions of the neck in 

 the following manner : Supposing the body ver- 

 tebrae of a man to be thus solidified, there would be 

 one of the motive connections of the arms, viz., 

 that with the body, unprovided with a diagonal 

 counteracting basis. This basis, as it exists, 

 brings the legs and arms into connection, and both 

 are then brought into a central line by the neck S. 

 Possibly the extra S in the neck of birds (one or 

 more above the number in quadrupeds and man) 

 (§ 85) supplies this loss, and there is still the same 

 double action on a bird's wing as on the arms of a 

 man. 



A bird cannot, we think, keep its head steady 

 when walking on the ground, without stretching 

 the neck. May it be that, the body, being then 

 confined to one plane, and the lower S of the neck 

 having no means of adjusting the excentric move- 

 ments of the neck-root, these movements must be 

 communicated to the head. If the neck be stretch- 

 ed, the action of this S is reduced as much as 

 possible. 



The spring collected in the wing and the double 



